Name: vector competence analyses on aedes aegypti mosquitoes using zika virus
Uploaded: 2020-05-31T14:00:00.000+00:00
Duration: 10 min 35 s
Description: Watch this Scientific Journal Video about Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus at JoVE.com

We acknowledge the staff of the World Reference Center for Emerging Viruses and Arboviruses (WRCEVA): Dr. Robert Tesh, Hilda Guzman, Dr. Kenneth Plante, Dr. Jessica Plante, Dionna Scharton, and Divya Mirchandani, for their tireless work in curating and providing many of the viral strains used for our and other groups&#8217; vector competence experiments. The presented work was funded by the McLaughlin Fellowship Fund (SRA) and NIH grants AI120942 and AI121452.

All procedures performed in these protocols were performed in full compliance with protocols approved&#160;by the Institutional Biosafety Committee and the Institutional Animal Care and Use Committee of the University of Texas Medical Branch at Galveston.
1. Amplify ZIKV in Vero cells
<ol>
	<li>Grow Vero cells (CCL-81 or VeroE6) in Dulbecco&#8217;s modification of Eagle&#8217;s minimal essential medium (DMEM) supplemented with 10% v/v heat-inactivated fetal bovine serum (FBS), and 1% (v/v) penicillin-streptomycin (100 U/mL and 100 &#956;g/mL, respectively) in a humidified 37 &#176;C incubator with 5% CO2 to between 80&#8722;90% confluency in a 150 cm2 tissue culture flask.</li>
	<li>In a biosafety cabinet (BSC), remove the medium and dispose of in either 10% bleach or a working dilution of dual quaternary ammonium (Table of Materials). Immediately inoculate the monolayer with 1 mL of viral stock, aiming for 0.1&#8722;1 infectious viral particle per cell. Agitate the flask immediately such that the inoculum contacts the monolayer in its entirety.</li>
	<li>Top up the medium to a volume of 5 mL using DMEM supplemented with 2% v/v heat-inactivated FBS, and 1% (v/v) penicillin-streptomycin. Then move the flask into the humidified 37 &#176;C incubator with 5% CO2 for 60 min.</li>
	<li>Remove the flask from the incubator and bring it into a BSC. Add additional medium to a total volume of 15 mL using DMEM supplemented with 2% v/v heat-inactivated FBS, and 1% (v/v) penicillin-streptomycin. Move the flask into a humidified 37 &#176;C incubator with 5% CO2.</li>
	<li>Examine the flask daily under phase contrast microscopy for evidence of cytopathic effects (CPE). Proceed to the viral harvest (step 1.7) when only approximately 40&#8722;50% of the cells remain in the monolayer, generally 3&#8722;5 days postinfection depending on the strain of ZIKV being utilized.</li>
	<li>Aspirate the supernatant and place in a 50 mL conical vial. Clarify the supernatant of cellular debris by centrifugation (3,500 x g for 20 min). 
	NOTE: If multiple flasks were infected identically, supernatants from multiple flasks can be combined into 50 mL conical tubes.</li>
	<li>Remove the supernatant from the 50 mL conical tube to a fresh one, taking care not to disrupt the pellet. Supplement the supernatant with heat-inactivated FBS to a final concentration of 30% (v/v). Aliquot this mixture into individual screw cap tubes and freeze at -80 &#176;C until use.</li>
</ol>
2. Preparation of artificial bloodmeals
<ol>
	<li>On the day mosquitoes are to be exposed to infectious bloodmeals, turn on the power source (Table of Materials) in an arthropod containment facility such that the feeding units (Table of Materials) are preheated by the time the mosquitoes are prepared for exposure.</li>
	<li>Prepare artificial bloodmeals using one of the methods described below.
	<ol>
		<li>Method 1: Combine freshly harvested (within a week) citrated or heparinized human blood purchased commercially 1:1 v/v with viral stock (prepared as described in section 1). 
		NOTE: This method is contingent on the absence of any antibodies to the virus/virus family being present in the blood.</li>
		<li>If absence of antibodies cannot be confirmed or the blood source is known to have prior flavivirus exposure, wash and manually pack erythrocytes.
		<ol>
			<li>In a BSC, add 30 mL of whole human blood to a 50 mL conical tube and top up to 50 mL with phosphate buffered saline (PBS).</li>
			<li>Centrifuge at 3,500 x g for 20 min.</li>
			<li>Aspirate the supernatant either by gently pouring into a tray pan containing either 10% bleach or working dilution of dual quaternary ammonium, taking care to not discard the erythrocyte pellet.</li>
			<li>Add 10 mL of PBS and gently tap the bottom of the conical tube against the bottom of the BSC such that the erythrocyte pellet has been reconstituted. Bring the volume of the suspension up to 50 mL with PBS. Mix by gentle inversion.</li>
			<li>Repeat steps 2.2.2.1&#8722;2.2.2.4 a total of 4&#8722;6x. Confirm that the supernatant is clear or only slightly pink and no longer opaque. Remove all the supernatant using a serological pipette. Resuspend the erythrocyte pellet in 1&#8722;2 mL of PBS.</li>
			<li>Assemble the bloodmeal: 350 &#956;L of packed erythrocytes, 100 &#956;L of 10% sucrose, 200 &#956;L of heat-inactivated FBS, 900 &#956;M recombinant ATP, and 2 mL of appropriately diluted virus stock using DMEM supplemented with 2% v/v heat-inactivated FBS, and 1% (v/v) penicillin-streptomycin.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Overlay a standard 3 mL reservoir unit (Table of Materials) with the skin of an uninfected mouse (other options include paraffin film, collagenous membranes, or sausage casing).</li>
	<li>Place the covered reservoir on white paper towels. Add ~2 mL of infectious bloodmeal to the reservoir 1 mL at a time. Inspect the towel underneath the feeder for any evidence of leakage. If leaks are present, recover the bloodmeal from the feeders and discard the covers. Seal the feeders with plugs. Once again confirm that no leaks are present.</li>
</ol>
3. Backtitration of bloodmeals/plaque assay
<ol>
	<li>Using the remaining volume of the prepared bloodmeal, perform a 10x serial dilution series (i.e., 6 dilutions, ranging from diluted 10x to 1,000,000x) using DMEM supplemented with 2% v/v heat-inactivated FBS, and 1% (v/v) penicillin-streptomycin.</li>
	<li>Aliquot 100 &#181;L of the dilutions into the wells of 24 or 12 well plates from the most dilute to most concentrated.</li>
	<li>Incubate for 1 h in a 37 &#176;C, 5% CO2 incubator.</li>
	<li>At the end of the 1 h incubation period, bring the plates back into the BSC and add 1 mL or 2 mL of methylcellulose overlay to the 24 well or 12 well plates, correspondingly.</li>
	<li>Place overlayed plates back in a 37 &#176;C, 5% CO2 incubator and incubate for 3&#8722;7 days (virus strain-dependent).</li>
	<li>Following incubation, remove the plates from the incubator and bring into the BSC. Discard the methylcellulose overlay into a tray pan containing 10% bleach or dual quaternary ammonium disinfectant.</li>
	<li>Wash each well 2x with PBS, discarding the wash into a tray pan containing 10% bleach or dual quaternary ammonium.</li>
	<li>Add ~1 mL of methanol:acetone (1:1 v:v) and allow the cells to fix onto plate for at least 30 min in the BSC at room temperature (RT). Discard methanol:acetone according to institutional policy on organic waste.</li>
	<li>Visualize ZIKV using one of two methods described below.
	<ol>
		<li>Following the removal of methanol:acetone, stain immediately with a crystal violet solution (0.25% w/v in 30% methanol) for 5 min. Rinse 2x in tap water and leave to dry, then directly visualize by eye for evidence of plaques or destruction of monolayer.</li>
		<li>Alternatively, perform focus forming assay.
		<ol>
			<li>Allow the plates to air dry until no organic fixative remains. 
			NOTE: This should take ~2&#8722;3 h outside of the BSC but can be accelerated by air-drying in a BSC or chemical fume hood.</li>
			<li>Wash each well 3x for 15 min each in nonsterile PBS (Mg2+ and Ca2+ free) on an orbital plate rocker. Remove PBS and add 1 mL of blocking solution (PBS + 3% FBS) to each well and rock for 15 min at RT.</li>
			<li>Add 100 &#956;L per well of &#945;-ZIKV or &#945;-flavivirus primary antibody (e.g., flavivirus group hybridoma D1-4G2-4-15 [4G2]) at a 1:2,000 dilution in blocking solution. Incubate with rocking for a minimum of 4 h (preferably overnight, not exceeding 18 h) at RT.</li>
			<li>Remove the primary antibody and wash 3x for 15 min each with PBS (Mg2+ and Ca2+ free) on an orbital plate rocker.</li>
			<li>Add 100 &#181;L per well of the secondary antibody (goat &#945; mouse HRP-labeled) diluted 1:2,000 in blocking buffer. Incubate with rocking for 1 h at RT.</li>
			<li>Wash 3x for 15 min each with PBS (Mg2+ and Ca2+ free) on an orbital plate rocker.</li>
			<li>Aliquot 100 &#181;L of substrate development reagent (Table of Materials) per well. Rock plates at RT for 15 min.</li>
			<li>Halt the reaction upon development of foci/plaques by removing the substrate and rinsing the plates 2x with tap water. Pour off tap water and allow the plates to air dry before quantifying.</li>
			<li>Count viral foci to determine the number of FFU present in the given sample.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
4. Administration of bloodmeals
<ol>
	<li>Use Ae. aegypti mosquitoes 2&#8722;4 days post eclosion. Sort female mosquitoes into 0.5 L cardboard cartons with screened lids and deprive them of sugar (generally 36&#8722;48 h prior to the infectious bloodmeal). Provide ad libitum water via water-saturated cotton balls.</li>
	<li>Remove the water-saturated cotton balls on the morning that the mosquitoes will be exposed to the infectious bloodmeal.</li>
	<li>Attach reservoirs containing artificial bloodmeals to feeding unit leads within a clear plastic glove box.</li>
	<li>Within the glovebox, place a 0.5 L cardboard carton with a screened lid, containing 50&#8722;100 starved Ae. aegypti mosquitoes, underneath the feeding unit attached to the reservoir. 
	NOTE: Appropriately starved mosquitoes will generally feed within 20 min. Feeding can be prolonged as needed to increase sample size in slower populations, although this should not extend beyond 60 min, because (ZIKV) viral titer can decrease within the feeder after ~60 min.</li>
	<li>Upon completion of feeding, remove the reservoir and immerse in freshly made 10% bleach.</li>
	<li>Cold-anesthetize mosquitoes by incubation for 30 s at -20 &#176;C or for 5 min in a refrigerator.</li>
	<li>Within the glovebox, pour the mosquitoes into a Petri dish on ice. Count and sort the engorged females from unengorged mosquitoes. Dispose of the unengorged mosquitoes by immersion in a 50 mL tube conical tube filled with 70% ethanol. While the mosquitoes are still anesthetized, pour them back into the 0.5 L cardboard carton and quickly cover with the screen and lid. Trim excess screen mesh off of the carton and secure the mesh with tape.</li>
	<li>Add a cotton ball saturated with sterile filtered 10% aqueous sucrose to the screen of each carton. Place all mosquito cartons in a large plastic secondary container with a damp sponge to maintain humidity.</li>
	<li>Place secondary container containing cartons of mosquitoes into an incubator with a temperature of 27 &#177; 1 &#176;C (or as appropriate to simulate conditions in region of interest) with 80% &#177; 10% relative humidity and a 16:8 light:dark cycle). Maintain the mosquitoes with ad libitum access to 10% sucrose until completion of the experiments.</li>
</ol>
5. Sample acquisition and processing
<ol>
	<li>On specified days postfeeding, aspirate a predetermined number of mosquitoes from the appropriate cartons using a mechanical aspirator within a glovebox. Cap the collection tube with a cotton round after the requisite number of mosquitoes is acquired.</li>
	<li>Cold-anesthetize mosquitoes by incubation for 30 seconds at -20 &#176;C or for 5 minutes at 4 &#176;C.</li>
	<li>Within the glovebox, pour the mosquitoes into a Petri dish on ice. Using two pairs of forceps, remove all six of each mosquito&#8217;s legs and place in a prelabeled 2 mL round bottom microcentrifuge tube containing a sterilized stainless steel ball bearing (7/32&#8221;) and 500 &#956;L of mosquito collection media (MCM) composed of DMEM, 2% FBS, 1% penicillin-streptomycin, and 2.5 &#956;g/mL amphotericin.</li>
	<li>Gently place the mosquito onto a drop of mineral oil to restrain it, taking care to not allow any contact between the oil and the mosquito&#8217;s head and proboscis.</li>
	<li>Insert the mosquito proboscis into a 10 &#956;L pipette tip filled with 10 &#956;L of heat-inactivated FBS. 
	NOTE: Alternatively, the pipette can be filled with sucrose, blood, or mineral oil. The oil allows for direct visualization of saliva bubbles via light microscopy.</li>
	<li>Allow the mosquito to salivate for 30 min. Eject the micropipette tip containing FBS + saliva into a microcentrifuge tube containing 100 &#956;L of MCM, then place the carcass into a separate 2 mL round bottom microcentrifuge tube containing a sterilized steel ball bearing and 500 &#956;L of MCM. Ensure that the tubes used for the bodies, legs, and saliva are labeled so that it is clear all three samples originated from the same mosquito.</li>
	<li>While the mosquito(s) are salivating, perform steps 5.3&#8722;5.5 on the remaining mosquitoes.</li>
	<li>Transport the tubes containing the bodies and legs to a bead milling tissue homogenization device contained within a BSC. Triturate all body and leg samples at 26 Hz for 5 min to liberate viral particles into the supernatant. Clarify all samples by centrifugation at 200 x g for 5 min to pellet cellular debris. 
	NOTE: At this point, samples can be frozen at -80 &#176;C, or assayed immediately.</li>
</ol>
6. Detection of ZIKV by infectious assay
<ol>
	<li>In a BSC, prepare 24 well tissue culture plates with Vero cells (105 cells per well) 24 h prior to the onset of the infectious assay. Label each well with the identity of a single mosquito/sample.</li>
	<li>If samples were frozen at -80 &#176;C, allow to thaw.</li>
	<li>Remove the media from the Vero cell plates prior to inoculation with samples one plate at a time.</li>
	<li>For samples containing bodies or legs, carefully aliquot 100 &#956;L of clarified supernatant into each well, taking care not to disturb the mosquito cell debris from the pellet. 
	NOTE: Saliva samples can be diluted 1:1 (v/v) with MCM prior to inoculation onto cells to conserve samples for later titration, if necessary.</li>
	<li>Move the plates into a 37 &#176;C, 5% CO2 incubator and incubate for 1 h.</li>
	<li>Return the plates to the BSC and add ~1 mL of methylcellulose overlay to each well. Place the overlayed plates back in a 37 &#176;C, 5% CO2 incubator and incubate for 3&#8722;7 days (virus/strain-dependent).</li>
	<li>Perform fixation and visualization as described in steps 3.6&#8722;3.9.</li>
	<li>Regarding scoring via a focus forming assay, quantify the positive wells by examination under a light microscope. Detection of intracytoplasmic staining of cells in a well indicates the presence of virus. Samples are scored solely as focus-positive or -negative.</li>
</ol>

<ol>
	<li>Azar, S. R., Weaver, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vector+Competence:+What+Has+Zika+Virus+Taught+Us.">Vector Competence: What Has Zika Virus Taught Us.</a> Viruses. 11 (9), 867 (2019).</li><li>Souza-Neto, J. A., Powell, J. R., Bonizzoni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aedes+aegypti+vector+competence+studies:+A+review.">Aedes aegypti vector competence studies: A review.</a> Infection, Genetics and Evolution. 67, 191-209 (2019).</li><li>Smith, D. R., Adams, A. P., Kenney, J. L., Wang, E., Weaver, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Venezuelan+Equine+Encephalitis+Virus+in+the+Mosquito+Vector+Aedes+taeniorhynchus:+Infection+Initiated+by+a+Small+Number+of+Susceptible+Epithelial+Cells+and+a+Population+Bottleneck.">Venezuelan Equine Encephalitis Virus in the Mosquito Vector Aedes taeniorhynchus: Infection Initiated by a Small Number of Susceptible Epithelial Cells and a Population Bottleneck.</a> Virology. 372 (1), 176-186 (2008).</li><li>Forrester, N. L., Coffey, L. L., Weaver, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arboviral+bottlenecks+and+challenges+to+maintaining+diversity+and+fitness+during+mosquito+transmission.">Arboviral bottlenecks and challenges to maintaining diversity and fitness during mosquito transmission.</a> Viruses. 6 (10), 3991-4004 (2014).</li><li>Kramer, L. D., Ciota, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissecting+vectorial+capacity+for+mosquito-borne+viruses.">Dissecting vectorial capacity for mosquito-borne viruses.</a> Current Opinion in Virology. 15, 112-118 (2015).</li><li>Kramer, L. D., Hardy, J. L., Presser, S. B., Houk, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissemination+Barriers+for+Western+Equine+Encephalomyelitis+Virus+in+Culex+tarsalis+infected+after+Ingestion+of+Low+Viral+Doses.">Dissemination Barriers for Western Equine Encephalomyelitis Virus in Culex tarsalis infected after Ingestion of Low Viral Doses.</a> American Journal of Tropical Medicine and Hygiene. 30 (1), 190-197 (1981).</li><li>Lounibos, L. P., Kramer, L. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Invasiveness+of+Aedes+aegypti+and+Aedes+albopictus+and+Vectorial+Capacity+for+Chikungunya+Virus.">Invasiveness of Aedes aegypti and Aedes albopictus and Vectorial Capacity for Chikungunya Virus.</a> The Journal of Infectious Diseases. 214, 453-458 (2016).</li><li>Heitmann, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Forced+Salivation+as+a+Method+to+Analyze+Vector+Competence+of+Mosquitoes.">Forced Salivation as a Method to Analyze Vector Competence of Mosquitoes.</a> Journal of Visualized Experiments. (138), e57980 (2018).</li><li>Beerntsen, B. T., James, A. A., Christensen, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+of+Mosquito+Vector+Competence.">Genetics of Mosquito Vector Competence.</a> Microbiology and Molecular Biology Reviews. 64 (1), 115-137 (2000).</li><li>Guo, X. X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culex+pipiens+quinquefasciatus:+a+potential+vector+to+transmit+Zika+virus.">Culex pipiens quinquefasciatus: a potential vector to transmit Zika virus.</a> Emerging Microbes &amp; Infections. 5 (9), 102 (2016).</li><li>Secundino, N. F. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zika+virus+transmission+to+mouse+ear+by+mosquito+bite:+a+laboratory+model+that+replicates+the+natural+transmission+process.">Zika virus transmission to mouse ear by mosquito bite: a laboratory model that replicates the natural transmission process.</a> Parasites &amp; Vectors. 10 (1), 346 (2017).</li><li>Smith, D. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Venezuelan+Equine+Encephalitis+Virus+Transmission+and+Effect+on+Pathogenesis.">Venezuelan Equine Encephalitis Virus Transmission and Effect on Pathogenesis.</a> Emerging Infectious Diseases. 12 (8), 1190-1196 (2006).</li><li>Lazear, H. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Mouse+Model+of+Zika+Virus+Pathogenesis.">A Mouse Model of Zika Virus Pathogenesis.</a> Cell Host Microbe. 19 (5), 720-730 (2016).</li><li>Morrison, T. E., Diamond, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+Models+of+Zika+Virus+Infection,+Pathogenesis,+and+Immunity.">Animal Models of Zika Virus Infection, Pathogenesis, and Immunity.</a> Journal of Virology. 91 (8), 9-17 (2017).</li><li>Reynolds, E. S., Hart, C. E., Hermance, M. E., Brining, D. L., Thangamani, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Overview+of+Animal+Models+for+Arthropod-Borne+Viruses.">An Overview of Animal Models for Arthropod-Borne Viruses.</a> Comparative Medicine. 67 (3), 232-241 (2017).</li><li>Rossi, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+Novel+Murine+Model+to+Study+Zika+Virus.">Characterization of a Novel Murine Model to Study Zika Virus.</a> American Journal of Tropical Medicine and Hygiene. 94 (6), 1362-1369 (2016).</li><li>Styer, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquitoes+inoculate+high+doses+of+West+Nile+virus+as+they+probe+and+feed+on+live+hosts.">Mosquitoes inoculate high doses of West Nile virus as they probe and feed on live hosts.</a> PLoS Pathogens. 3 (9), 1262-1270 (2007).</li><li>Azar, S. R., Diaz-Gonzalez, E. E., Danis-Lonzano, R., Fernandez-Salas, I., Weaver, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Naturally+infected+Aedes+aegypti+collected+during+a+Zika+virus+outbreak+have+viral+titres+consistent+with+transmission.">Naturally infected Aedes aegypti collected during a Zika virus outbreak have viral titres consistent with transmission.</a> Emerging Microbes &amp; Infections. 8 (1), 242-244 (2019).</li><li>Dzul-Manzanilla, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+vertical+transmission+and+co-circulation+of+chikungunya+and+dengue+viruses+in+field+populations+of+Aedes+aegypti+(L.)+from+Guerrero,+Mexico.">Evidence of vertical transmission and co-circulation of chikungunya and dengue viruses in field populations of Aedes aegypti (L.) from Guerrero, Mexico.</a> Transactions of the Royal Society of Tropical Medicine and Hygiene. 110 (2), 141-144 (2016).</li><li>Grard, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zika+virus+in+Gabon+(Central+Africa)+&#8211;+2007:+a+new+threat+from+Aedes+albopictus.">Zika virus in Gabon (Central Africa) &#8211; 2007: a new threat from Aedes albopictus.</a> PLoS Neglected Tropical Diseases. 8 (2), 2681 (2014).</li><li>Grubaugh, N. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic+epidemiology+reveals+multiple+introductions+of+Zika+virus+into+the+United+States.">Genomic epidemiology reveals multiple introductions of Zika virus into the United States.</a> Nature. 546 (7658), 401-405 (2017).</li><li>Guerbois, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outbreak+of+Zika+Virus+Infection,+Chiapas+State,+Mexico,+2015,+and+First+Confirmed+Transmission+by+Aedes+aegyti+Mosquitoes+in+the+America.">Outbreak of Zika Virus Infection, Chiapas State, Mexico, 2015, and First Confirmed Transmission by Aedes aegyti Mosquitoes in the America.</a> The Journal of Infectious Diseases. 214 (9), 1349-1356 (2016).</li><li>Lundstrom, J. O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sindbis+virus+polyarthritis+outbreak+signalled+by+virus+prevalence+in+the+mosquito+vectors.">Sindbis virus polyarthritis outbreak signalled by virus prevalence in the mosquito vectors.</a> PLoS Neglected Tropical Diseases. 13 (8), 0007702 (2019).</li><li>Miller, B. R., Monath, T. P., Tabachnik, W. J., Ezike, V. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemic+yellow+fever+caused+by+an+incompetent+mosquito+vector.">Epidemic yellow fever caused by an incompetent mosquito vector.</a> Tropical Medicine and Parasitology. 40 (4), 396-399 (1989).</li><li>Brown, H. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effectiveness+of+Mosquito+Traps+in+Measuring+Species+Abundance+and+Composition.">Effectiveness of Mosquito Traps in Measuring Species Abundance and Composition.</a> Journal of Medical Entomology. 45 (3), 517-521 (2008).</li><li>Gorsich, E. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+assessment+of+adult+mosquito+trapping+methods+to+estimate+spatial+patterns+of+abundance+and+community+composition+in+southern+Africa.">A comparative assessment of adult mosquito trapping methods to estimate spatial patterns of abundance and community composition in southern Africa.</a> Parasites &amp; Vectors. 12 (1), 462 (2019).</li><li>Azar, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ZIKV+Demonstrates+Minimal+Pathologic+Effects+and+Mosquito+Infectivity+in+Viremic+Cynomolgus+Macaques.">ZIKV Demonstrates Minimal Pathologic Effects and Mosquito Infectivity in Viremic Cynomolgus Macaques.</a> Viruses. 10 (11), 661 (2018).</li><li>Azar, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+Vector+Competency+of+Aedes+albopictus+Populations+from+the+Americas+for+Zika+Virus.">Differential Vector Competency of Aedes albopictus Populations from the Americas for Zika Virus.</a> American Journal of Tropical Medicine and Hygiene. 97 (2), 330-339 (2017).</li><li>Hanley, K. A., Azar, S. R., Campos, R. K., Vasilakis, N., Rossi, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Support+for+the+Transmission-Clearance+Trade-Off+Hypothesis+from+a+Study+of+Zika+Virus+Delivered+by+Mosquito+Bite+to+Mice.">Support for the Transmission-Clearance Trade-Off Hypothesis from a Study of Zika Virus Delivered by Mosquito Bite to Mice.</a> Viruses. 11 (11), 1072 (2019).</li><li>Hart, C. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zika+Virus+Vector+Competency+of+Mosquitoes,+Gulf+Coast,+United+States.">Zika Virus Vector Competency of Mosquitoes, Gulf Coast, United States.</a> Emerging Infectious Diseases. 23 (3), 559-560 (2017).</li><li>Karna, A. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colonized+Sabethes+cyaneus,+a+Sylvatic+New+World+Mosquito+Species,+Shows+a+Low+Vector+Competence+for+Zika+Virus+Relative+to+Aedes+aegypti.">Colonized Sabethes cyaneus, a Sylvatic New World Mosquito Species, Shows a Low Vector Competence for Zika Virus Relative to Aedes aegypti.</a> Viruses. 10 (8), 434 (2018).</li><li>Roundy, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+in+Aedes+aegypti+Mosquito+Competence+for+Zika+Virus+Transmission.">Variation in Aedes aegypti Mosquito Competence for Zika Virus Transmission.</a> Emerging Infectious Diseases. 23 (4), 625-632 (2017).</li><li>Wilson, A. J., Harrup, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reproducibility+and+relevance+in+insect-arbovirus+infection+studies.">Reproducibility and relevance in insect-arbovirus infection studies.</a> Current Opinion in Insect Science. 28, 105-112 (2018).</li><li>Hagan, R. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dehydration+prompts+increased+activity+and+blood+feeding+by+mosquitoes.">Dehydration prompts increased activity and blood feeding by mosquitoes.</a> Scientific Reports. 8 (1), 6804 (2018).</li><li>Guo, X. X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+Feeding+Patterns+of+Mosquitoes+in+a+Rural+Malaria-Endemic+Region+in+Hainan+Island,+China.">Host Feeding Patterns of Mosquitoes in a Rural Malaria-Endemic Region in Hainan Island, China.</a> Journal of the American Mosquito Control Association. 30 (4), 309-311 (2014).</li><li>Kuno, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+history+of+laboratory+breeding+of+Aedes+aegypti+(Diptera:+Culicidae)+focusing+on+the+origins+and+use+of+selected+strains.">Early history of laboratory breeding of Aedes aegypti (Diptera: Culicidae) focusing on the origins and use of selected strains.</a> Journal of Medical Entomology. 47 (6), 957-971 (2010).</li><li>Mayilsamy, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extremely+Long+Viability+of+Aedes+aegypti+(Diptera:+Culicidae)+Eggs+Stored+Under+Normal+Room+Condition.">Extremely Long Viability of Aedes aegypti (Diptera: Culicidae) Eggs Stored Under Normal Room Condition.</a> Journal of Medical Entomology. 56 (3), 878-880 (2019).</li><li>Althouse, B. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+for+Zika+Virus+to+Establish+a+Sylvatic+Transmission+Cycle+in+the+Americas.">Potential for Zika Virus to Establish a Sylvatic Transmission Cycle in the Americas.</a> PLoS Neglected Tropical Diseases. 10 (12), 0002055 (2016).</li><li>Vasilakis, N., Cardosa, J., Hanley, K. A., Holmes, E. C., Weaver, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fever+from+the+forest:+prospects+for+the+continued+emergence+of+sylvatic+dengue+virus+and+its+impact+on+public+health.">Fever from the forest: prospects for the continued emergence of sylvatic dengue virus and its impact on public health.</a> Nature Reviews Microbiology. 9 (7), 532-541 (2011).</li><li>Vasilakis, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+of+ancestral+sylvatic+dengue-2+viruses+to+re-emerge.">Potential of ancestral sylvatic dengue-2 viruses to re-emerge.</a> Virology. 358 (2), 402-412 (2007).</li></ol>

The authors have nothing to disclose.

The methods described here provide a generalized workflow to conduct vector competence analyses. As a general framework, many of these methodologies are conserved throughout the literature. However, there is substantial room for modifications (reviewed in Azar and Weaver1). Virus (e.g., viral lineage, storage of challenge virus, viral passage history), entomology (e.g., laboratory colonization of mosquito populations, innate immunity, the mosquito microbiome/virome), and experimental variables (e....

Vector competence is defined as the ability at the level of species, population, and even an individual, of a given arthropod such as a mosquito, tick, or phlebotomine sand fly, to acquire and transmit an agent biologically with replication or development in the arthropod1,2. With respect to mosquitoes and arthropod-borne viruses (i.e., arboviruses), the agent is imbibed from a viremic host by a female mosquito. Following ingestion, the virus must productively infect one of a small population of midgut epithelial cells3, overcoming various physiological obstacles such as proteolytic degradation by digestive enzymes, the presence of the microbiota (midgut infection barrier, or MIB), and the secreted peritrophic matrix. Infection of the midgut epithelium must be followed by replication of the virus and eventual escape from the midgut into the mosquito&#8217;s open circulatory system, or hemolymph, which represents the onset of a disseminated infection overcoming the midgut escape barrier (MEB). At this point the virus can establish infections of secondary tissues (e.g., nerves, muscles, and fat bodies) and continue to replicate, although such secondary replication may not be strictly necessary for the virus to infect the acinar cells of the salivary glands (overcoming the salivary gland infection barrier). Egress from the salivary gland acinar cells into their apical cavities and then movement into the salivary duct enables inoculation of the virus into subsequent hosts on biting, and completes the transmission cycle1,2,4,5,6,7.
Given this well-characterized and generally conserved mechanism of spread within a mosquito vector, laboratory vector competence assessments are often methodologically similar, although differences in protocols do exist1,2. Generally, after oral virus exposure, mosquitoes are dissected so that individual tissues such as the midgut, legs, ovaries, or salivary glands can be assayed for viral infection, disseminated infection, disseminated infection/potential transovarial transmission, and disseminated infection/potential transmission competence, respectively8. The mere presence of a virus in the salivary glands, however, is not definitive evidence of transmission capability, given evidence of a salivary gland escape/egress barrier (SGEB) in some vector/virus combinations1,2,4,5,7,9. The standard method to prove transmission competence remains mosquito transmission to a susceptible animal10,11,12. However, given that for many arboviruses this necessitates the use of immunocompromised murine models13,14,15,16, this method is often cost-prohibitive. A commonly used alternative is the collection of the mosquito saliva, which can be analyzed by reverse transcription-polymerase chain reaction (RT-PCR) or an infectious assay to demonstrate the presence of the viral genome or infectious particles, respectively. It is worth noting that such in vitro saliva collection methods may overestimate12 or underestimate17 the amount of virus deposited during in vivo feeding, indicating that such data must be interpreted with caution. Nonetheless, the in vitro method is highly valuable when analyzed from the perspective of the mere presence of virus in the saliva, indicating transmission potential.
Two major approaches exist for determining the role of mosquito vectors in arboviral disease outbreaks. The first method involves field surveillance, in which mosquitoes are collected in the context of active transmission18,19,20,21,22,23,24. However, given that infection rates are typically quite low (e.g., the estimated 0.061% infection rate of mosquitoes in areas of active Zika virus (ZIKV) circulation in the United States21), incrimination of potential vector species can be heavily biased by trapping methodology25,26 and random chance (e.g., sampling one infected individual out of 1,600 uninfected)21. Taking this into account, a given study may not acquire sufficient mosquitoes in both raw numbers or species diversity to accurately sample mosquitoes involved in transmission. In contrast, vector competence analyses are undertaken in a laboratory setting, allowing for strict control of parameters such as oral dose. Although not fully capable of representing the true complexity of mosquito infection and transmission capability in a field setting, these laboratory assessments remain powerful tools in the field of arbovirology.
Based on various vector competence analyses with ZIKV in several mosquito species, populations, and methods27,28,29,30,31,32, as well as a recent review of vector competence assessments1, we describe here several of the protocols associated with a typical vector competence workflow. In these experiments, three Ae. aegypti populations from the Americas (the city of Salvador, Brazil; the Dominican Republic; and the lower Rio Grande Valley, TX, USA) were exposed to a single strain of ZIKV (Mex 1-7, GenBank Accession: KX247632.1) at 4, 5, or 6 log10 focus-forming units (FFU)/mL doses by way of artificial bloodmeals. Subsequently, they were analyzed for evidence of infection, disseminated infection, and transmission competence after various times of extrinsic incubation (2, 4, 7, 10, and 14 days) by means of dissection and a cell culture-based infectious assay. Although the present workflow/protocols are optimized for ZIKV, many elements are directly translatable to other mosquito-borne arboviruses in arthropod containment and biosafety levels 2 and 3 (ACL/BSL2 or ACL/BSL3).

<table><tbody><tr><td>3mL Standard Reservoir</td><td>R37P30</td><td>Hemotek Ltd</td><td>Insectary Equipment</td></tr><tr><td>7/32&quot; Stainless Steel 440 Grade C Balls</td><td>4RJH9</td><td>Grainger</td><td>Grinding Media</td></tr><tr><td>Acetone, Histological Grade, Fisher Chemicals, Poly Bottle, 4L, 4/Case</td><td>A16-P4</td><td>FisherScientific</td><td>Fixative</td></tr><tr><td>Adenosine 5&#039;-triphospate disodium salt hydrat, microbial, BioReagent, suitable for cell culture</td><td>A6419-1G</td><td>MilliporeSigma</td><td>Reagent</td></tr><tr><td>Anti-Flavivirus Group Antigen Antibody, clone D1-4G2-4-15</td><td>MAB10216</td><td>MilliporeSigma</td><td>Primary Antibody for focus forming assay</td></tr><tr><td>Anti-Mouse IgG (H+L) Antibody, Human Serum Adsorbed and Peroxidase-Labeled, 1.0mL/Bottle</td><td>5450-0011</td><td>KPL/Seracare</td><td>Secondary Antibody for focus forming assay</td></tr><tr><td>Bleach</td><td>NC0427256</td><td>FisherScientific</td><td>Decontamination</td></tr><tr><td>Corning, Cell Culture Treated Flasks, 150cm2, Vented Cap, Case of 50</td><td>10-126-34</td><td>FisherScientific</td><td>Cell culture consumable</td></tr><tr><td>Costar Cell Culture Plates, 24-well, 5/bag, 100/case, Corning</td><td>07-200-740</td><td>FisherScientific</td><td>Cell culture consumable</td></tr><tr><td>Costar Cell Culture Plates, 96-well, 5/bag, 100/case, Corning</td><td>07-200-91</td><td>FisherScientific</td><td>Cell culture consumable</td></tr><tr><td>Crystal Violet</td><td>C0775-100G</td><td>MilliporeSigma</td><td>Stain</td></tr><tr><td>Eppendorf Snap Cap Microcentrifuge Safe-Lock 2mL Tubes, 500/Case</td><td>05-402-7</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon 15mL Conical Centrigue Tubes</td><td>14-959-70C</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon 50mL Conical Centrigue Tubes</td><td>14-959-49A</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon Disposable Polystyrene Serological 10mL Pipets, 200/Case</td><td>13-675-20</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon Disposable Polystyrene Serological 1mL Pipets, 1000/Case</td><td>13-675-15B</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon Disposable Polystyrene Serological 25mL Pipets, 200/Case</td><td>13-675-30</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon Disposable Polystyrene Serological 5mL Pipets, 200/Case</td><td>13-675-22</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Falcon Standard Tissue Culture Dishes</td><td>08-772B</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Fetal Bovine Serum-Premium, 500mL</td><td>S11150</td><td>Atlanta Biologicals</td><td>Cell culture reagent</td></tr><tr><td>Fisherbrand Economy Plain Glass Microscope Slides</td><td>12-550-A3</td><td>FisherScientific</td><td>Immobilization of Mosquitos</td></tr><tr><td>FU1 Feeder</td><td>FU1-0</td><td>Hemotek Ltd</td><td>Insectary Equipment; feeding units</td></tr><tr><td>Gibco DPBS with Calcium and Magnesium, 10 x 500mL Bottles</td><td>140-040-182</td><td>FisherScientific</td><td>Cell culture reagent</td></tr><tr><td>Gibco Fungizone, Amphotericin B, 250&amp;mu;g/mL, 50mL/Bottle</td><td>15-290-026</td><td>Fisher Scientific</td><td>Cell culture reagent</td></tr><tr><td>Gibco Penicillin-Streptomycin (10,000 U/mL), 100mL/Bottle, 20 Bottles/Case</td><td>15-140-163</td><td>FisherScientific</td><td>Cell culture reagent</td></tr><tr><td>Gibco, Tryptsin-EDTA (.25%), Phenol red, 20 x 100mL Bottles</td><td>25-200-114</td><td>FisherScientific</td><td>Cell culture reagent</td></tr><tr><td>Gibcom DMEM, High Glucose, 10 x 500mL Bottles</td><td>11-965-118</td><td>FisherScientific</td><td>Cell culture reagent</td></tr><tr><td>Human Blood, Unspecified Gender, Na-Citrate, 1 Unit</td><td>7203706</td><td>Lampire</td><td>Bloodmeal preparation</td></tr><tr><td>InsectaVac Aspirator</td><td>2809B</td><td>Bioquip</td><td>Insectary Equipment</td></tr><tr><td>Methanol, Certified ACS, Fisher Chemicals, Amber Glass Bottle, 4L, 4/Case</td><td>A412-4</td><td>FisherScientific</td><td>Fixative</td></tr><tr><td>Methyl cellulose, viscosity: 3,500-5,600 cP, 2 % in water(20 &amp;deg;C), 250g/Bottle</td><td>M0512-250G</td><td>MilliporeSigma</td><td>Cell culture reagent</td></tr><tr><td>Micro-chem Plus Disinfectant Detergent</td><td>C849T34</td><td>Thomas Scientific</td><td>Decontamination; working dilution of dual quaternary ammonium</td></tr><tr><td>Mineral Oil, BioReagent, for molecular biology</td><td>M5904-5X5ML</td><td>MilliporeSigma</td><td>Immobilization of Mosquitos</td></tr><tr><td>O-rings</td><td>OR37-25</td><td>Hemotek Ltd</td><td>Insectary Equipment</td></tr><tr><td>Plastic Plugs</td><td>PP5-250</td><td>Hemotek Ltd</td><td>Insectary Equipment</td></tr><tr><td>PS6 Power Unit (110-120V)</td><td>PS6120</td><td>Hemotek Ltd</td><td>Insectary Equipment; power source</td></tr><tr><td>Rubis Forceps, Offset blades, superfine points</td><td>4525</td><td>Bioquip</td><td>Insectary Equipment</td></tr><tr><td>Sarstedt Inc, 2mL Screw Cap Microtube, Conical Bottom, O-ring Cap, Sterile, 1000/Case</td><td>50-809-242</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>Sucrose, BioUltra, for molecular biology</td><td>84097-250G</td><td>MilliporeSigma</td><td>Reagent</td></tr><tr><td>ThermoScientific, ART Barrier Low Retention 1000&amp;mu;L Pipette Tips, 100 tips/Rack, 8 Racks/Pack, 4 Packs/Case</td><td>21-402-487</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>ThermoScientific, ART Barrier Low Retention 200&amp;mu;L Pipette Tips, 96 tips/Rack, 10 Racks/Pack, 5 Packs/Case</td><td>21-402-486</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>ThermoScientific, ART Barrier Low Retention 20&amp;mu;L Pipette Tips, 96 tips/Rack, 10 Racks/Pack, 5 Packs/Case</td><td>21-402-484</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>ThermoScientific, ART Barrier Low Retention, Extended Reach 10&amp;mu;L Pipette Tips, 96 tips/Rack, 10 Racks/Pack, 5 Packs/Case</td><td>21-402-482</td><td>FisherScientific</td><td>Plastic consumable</td></tr><tr><td>TissueLyser II</td><td>85300</td><td>QIAGEN</td><td>Homogenization</td></tr><tr><td>TrueBlue Peroxidase Substrate Kit, 200mL</td><td>5510-0030</td><td>Seracare</td><td>Developing solution for focus forming assay</td></tr><tr><td>Vero</td><td>CCL-81</td><td>American Type Culture Collection</td><td>Mammalian cell line to amplify virus and conduct infectious assay</td></tr><tr><td>Vero C1008 [Vero 76, clone E6, Vero E6]</td><td>CRL-1586</td><td>American Type Culture Collection</td><td>Mammalian cell line to amplify virus and conduct infectious assay</td></tr></tbody></table>

vector competence analyses on aedes aegypti mosquitoes using zika virus

The procedures presented describe a generalized methodology to infect Aedes aegypti mosquitoes with Zika virus under laboratory conditions to determine the rate of infection, disseminated infection, and potential transmission of the virus in the mosquito population in question. These procedures are widely utilized with various modifications in vector competence evaluations globally. They are important in determining the potential role that a given mosquito (i.e., species, population, individual) may play in the transmission of a given agent.

Three populations of Ae. aegypti from the Americas (Salvador, Brazil; the Dominican Republic; and the Rio Grande Valley, TX, USA) were exposed to an outbreak strain of ZIKV from the Americas (ZIKV Mex 1-7, Chiapas State, Mexico, 2015) over a range of bloodmeal titers (4, 5, and 6 log10 FFU/mL) presented in a washed human erythrocyte-based artificial bloodmeal. At days 2, 4, 7, 10, and 14 postinfection, subsets of mosquitoes were processed to determine infection, dissemination, and potential transmissi...

Watch this Scientific Journal Video about Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus at JoVE.com

Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus

The presented protocol can determine the vector competence of Aedes aegypti mosquito populations for a given virus, such as Zika, in a containment setting.

Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus

The procedures presented describe a generalized methodology to infect Aedes aegypti mosquitoes with Zika virus under laboratory conditions to determine ...

vector-competence-analyses-on-aedes-aegypti-mosquitoes-using-zika

Universidad de Cartagena UDEC

Research

JoVE Journal

Immunology and Infection

2.9K Views.  University of Texas Medical Branch. The presented protocol can determine the vector competence of Aedes aegypti mosquito populations for a given virus, such as Zika, in a containment setting.

Video: Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus

Embryo Microinjection Techniques for Efficient Site-Specific Mutagenesis in Culex quinquefasciatus

Culex quinquefasciatus is a vector of a diverse range of vector-borne diseases such as avian malaria, West Nile virus (WNV), Japanese encephalitis, Eastern equine encephalitis, lymphatic filariasis, and Saint Louis encephalitis. Notably, avian malaria has played a major role in the extinction of numerous endemic island bird species, while WNV has become an important vector-borne disease in the United States. To gain further insight into C. quinquefasciatus biology and expand their genetic control toolbox, we need to develop more efficient and affordable methods for genome engineering in this species. However, some biological traits unique to Culex mosquitoes, particularly their egg rafts, have made it difficult to perform microinjection procedures required for genome engineering. To address these challenges, we have developed an optimized embryo microinjection protocol that focuses on mitigating the technical obstacles associated with the unique characteristics of Culex mosquitoes. These procedures demonstrate optimized methods for egg collection, egg raft separation and other handling procedures essential for successful microinjection in C. quinquefasciatus. When coupled with the CRISPR/Cas9 genome editing technology, these procedures allow us to achieve site-specific, efficient and heritable germline mutations, which are required to perform advanced genome engineering and develop genetic control technologies in this important, but currently understudied, disease vector.

Embryo Microinjection Techniques for Efficient Site-Specific Mutagenesis in Culex quinquefasciatus

This protocol describes microinjection procedures for Culex quinquefasciatus embryos that are optimized to work with CRISPR/Cas9 gene editing tools. This technique can efficiently generate site-specific, heritable, germline mutations that can be used for building genetic technologies in this understudied disease vector.

Culex quinquefasciatus is a vector of a diverse range of vector-borne diseases such as avian malaria, West Nile virus (WNV), Japanese encephalitis, ...

Genetics

Genome Editing in the Yellow Fever Mosquito Aedes aegypti using CRISPR-Cas9

The emergence of the clustered, regularly interspersed, short palindromic repeats (CRISPR)-Cas9 technology has revolutionized the genetic engineering field and opened the doors for precise genome editing in multiple species, including non-model organisms. In the mosquito Aedes aegypti, loss-of-function mutations and DNA insertions have been accomplished with this technology. Here, we describe a detailed protocol for genome editing through embryonic microinjection in the mosquito A. aegypti using the CRISPR-Cas9 technology, focusing on both the generation of gene knockout and knockin lines. In this protocol, quartz needles are filled with a mixture of guide RNA, recombinant Cas9, and a plasmid containing a DNA cassette encoding a gene for a fluorescent marker, if gene knockin is desired. Embryos at the preblastoderm stage are lined up onto a strip of double-sided sticky tape placed onto a coverslip, which is subsequently mounted onto a glass slide. With the help of a microinjector, the needles are inserted gently into the posterior end of the embryos and a small volume of the CRISPR mixture is dispensed. When the embryos are hatched, the larvae are checked under the fluorescent scope, and the pupae are sex-sorted and separated in different cages. Once the adults emerge, these are reciprocally crossed with wild-type individuals, blood-fed, and placed for egg laying. Once these eggs are hatched, the fluorescent larvae collected represent individuals with stable insertion of the DNA cassette into their genome. These larvae are then grown to the adult stage, outcrossed to wild-type individuals, and then further assessed through molecular techniques to confirm that the exact sequence of the DNA cassette is present at the desired site of the mosquito genome. Homozygous lines can also be obtained by following the provided pipeline of crossing schema and molecular screening of the mutations.

Here, we describe a detailed protocol for genome editing through embryonic microinjection in the mosquito A. aegypti using the CRISPR-Cas9 technology.

The emergence of the clustered, regularly interspersed, short palindromic repeats (CRISPR)-Cas9 technology has revolutionized the genetic engineering ...

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV is an RNA virus of the Flaviviridae family. ZIKV is mainly transmitted by mosquitoes, but can also be spread by maternal to fetal vertical transmission as well as sexual contact. To date, there are no reliable treatment or vaccine options available to protect those infected by the virus. The development of a reproducible, effective Zika virus infectious cell culture system is critical for studying the molecular mechanisms of ZIKV replication as well as drug and vaccine development. In this regard, a protocol describing a mammalian cell-based in vitro Zika virus culture system for viral production and growth analysis is reported here. Details on the formation of plaques by Zika virus on a cell monolayer and plaque assay for measuring viral titer are presented. Viral genome replication kinetics and double-stranded RNA genome replicatory intermediates are determined. This culture platform was utilized to screen against a library of a small set of cytokines resulting in the identification of interferon-&#945; (IFN-&#945;), IFN-&#946; and IFN-&#947; as potent inhibitors of Zika viral growth. In summary, an in vitro infectious Zika viral culture system and various virological assays are demonstrated in this study, which has the potential to greatly benefit the research community in elucidating further the mechanisms of viral pathogenesis and the evolution of viral virulence. Antiviral IFN-alpha can further be evaluated as a prophylactic, post-exposure prophylactic, and treatment option for Zika virus infections in high-risk populations, including infected pregnant women.

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV), an emerging pathogen, is linked to fetal developmental abnormalities and microcephaly. The establishment of an effective infectious cell culture system is crucial for studies of ZIKV replication as well as vaccine and drug development. In this study, various virological assays pertaining to ZIKV are illustrated and discussed.

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV ...

Rescue and Characterization of Recombinant Virus from a New World Zika Virus Infectious Clone

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral evolution. Here we describe the construction of an infectious clone for Zika virus (ZIKV), which is currently causing an explosive outbreak in the Americas. To prevent toxicity to bacteria that is commonly observed with flavivirus-derived plasmids, we generated a two-plasmid system which separates the genome at the NS1 gene and is more stable than full-length constructs that could not be successfully recovered without mutations. After digestion and ligation to join the two fragments, full-length viral RNA can be generated by in vitro transcription with T7 RNA polymerase. Following electroporation of transcribed RNA into cells, virus was recovered that exhibited similar in vitro growth kinetics and in vivo virulence and infection phenotypes in mice and mosquitoes, respectively.

This protocol describes the recovery of infectious Zika virus from a two-plasmid infectious cDNA clone.

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral ...

Quantification of Antibody-dependent Enhancement of the Zika Virus in Primary Human Cells

The recent emergence of the flavivirus Zika and neurological complications, such as Guillain-Barr&#233; syndrome and microcephaly in infants, has brought serious public safety concerns. Among the risk factors, antibody-dependent enhancement (ADE) poses the most significant threat, as the recent re-emergence of the Zika virus (ZIKV) is primarily in areas where the population has been exposed and is in a state of pre-immunity to other closely related flaviviruses, especially dengue virus (DENV). Here, we describe a protocol for quantifying the effect of human serum antibodies against DENV on ZIKV infection in primary human cells or cell lines.

We describe a method to evaluate the effect of pre-existing immunity against dengue virus on the Zika virus infection by using human serum, primary human cells, and infection quantification by quantitative real-time polymerase chain reaction.

The recent emergence of the flavivirus Zika and neurological complications, such as Guillain-Barr&#233; syndrome and microcephaly in infants, has brought ...

Experimental Viral Infection in Adult Mosquitoes by Oral Feeding and Microinjection

Mosquito-borne viruses (MBVs), which are infectious pathogens to vertebrates, are spread by many mosquito species, posing a severe threat to public health. Once ingested, the viruses must overcome the mosquito midgut barrier to reach the hemolymph, from where they might potentially spread to the salivary glands. When a mosquito bites, these viruses are spread to new vertebrate hosts. Similarly, the mosquito may pick up different viruses. In general, only a tiny portion of viruses may enter the salivary glands via the gut. The transmission efficiency of these viruses to the glands is be affected by the two physical barriers found in different mosquito species: midgut barriers and salivary glands barriers. This protocol presents a method for virus detection in salivary glands of Aedes aegypti&#39;s&#160;following oral feeding and intrathoracic injection infection. Furthermore, determining whether the guts and/or salivary glands hinder viral spread can aid in the risk assessments of MBVs transmitted by Aedes aegypti.

This methodology, which included oral feeding and intrathoracic injection infection, could effectively assess the influence of midgut and/or salivary gland barriers on arbovirus infection.

Mosquito-borne viruses (MBVs), which are infectious pathogens to vertebrates, are spread by many mosquito species, posing a severe threat to public ...

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, chikungunya and Zika. Wolbachia-infected mosquitoes can be released into the field to either reduce population sizes through incompatible matings or to transform populations with mosquitoes that are refractory to virus transmission. For these strategies to succeed, the mosquitoes released into the field from the laboratory must be competitive with native mosquitoes. However, maintaining mosquitoes in the laboratory can result in inbreeding, genetic drift and laboratory adaptation which can reduce their fitness in the field and may confound the results of experiments. To test the suitability of different Wolbachia infections for deployment in the field, it is necessary to maintain mosquitoes in a controlled laboratory environment across multiple generations. We describe a simple protocol for maintaining Ae. aegypti mosquitoes in the laboratory, which is suitable for both Wolbachia-infected and wild-type mosquitoes. The methods minimize laboratory adaptation and implement outcrossing to increase the relevance of experiments to field mosquitoes. Additionally, colonies are maintained under optimal conditions to maximize their fitness for open field releases.

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes infected with Wolbachia are being released into natural populations to suppress the transmission of arboviruses. We describe methods to rear Ae. aegypti with Wolbachia infections in the laboratory for experiments and field release, taking precautions to minimize laboratory adaptation and selection.

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, ...

Biology

Forced Salivation As a Method to Analyze Vector Competence of Mosquitoes

Vector competence is defined as the potential of a mosquito species to transmit a mosquito-borne virus (mobovirus) to a vertebrate host. Viable virus particles are transmitted during a blood meal via the saliva of an infected mosquito. Forced salivation assays allow determining the vector potential on the basis of single mosquitoes, avoiding the use of animal experiments. The method is suitable to analyze a large number of mosquitoes in one experiment within a short period of time. Forced salivation assays were used to analyze 856 individual mosquitoes trapped in Germany, including two different Culex pipiens pipiens biotypes, Culex torrentium as well as Aedes albopictus, which were experimentally infected with Zika virus (ZIKV) and incubated at 18 &#176;C or 27 &#176;C for two and three weeks. The results indicated the lack of vector competence of the different Culex taxa for ZIKV. In contrast, Aedes albopictus was susceptible to ZIKV, but only at 27 &#176;C, with transmission rates similar to an Aedes aegypti laboratory colony tested in parallel.

For efficient control of mosquito borne virus transmission, the knowledge of the vector potential of respective mosquitoes is of particular interest. We describe forced salivation as a method to analyze vector competence of Aedes albopictus and three different Culex taxa for the transmission of Zika virus.

Vector competence is defined as the potential of a mosquito species to transmit a mosquito-borne virus (mobovirus) to a vertebrate host. Viable virus ...

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male Aedes aegypti Mosquitoes

The success of sterile or incompatible insect technique-based population suppression programs depends on the ability of released males to compete for wild-type females and induce sterility in the target population. Hence, laboratory assessment of male mating competitiveness is essential for evaluating the release strain&#8217;s fitness before field release. Conventionally, such an assay is performed by determining the proportion of viable eggs produced by the females after being simultaneously exposed to two sets of males (wild-type and release strains) for copulation. However, this process is time-consuming and laborious due to the need to first blood-feed the females for egg production and then hatch and enumerate the hatched eggs to determine egg viability.&#160;
Moreover, this method cannot discern the degree of competitiveness between two sterile or Wolbachia-infected mosquito lines as wild-type female mosquitoes will only produce non-viable eggs upon mating with both. To circumvent these limitations, this paper describes a more direct method of measuring male mosquito mating competitiveness in laboratory settings using the fluorescent dye, rhodamine B (RhB), which can be used to mark males by feeding them in sucrose solution containing RhB. After the mating assay, the presence of fluorescing sperms in the spermathecae of a female can be used to determine her mating partner. This method is cost-effective, reduces the experimental time by 90% and allows comparison of mating fitness between two sterile or Wolbachia-infected lines.&#160;

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male Aedes aegypti Mosquitoes

Here, we present a protocol for studying mating competitiveness of male Aedes aegypti using fluorescent dye as a marker. Female mosquitoes are exposed to both marked and unmarked males for copulation. Post mating, their spermathecae are examined under a fluorescence microscope to determine their mating partner.

The success of sterile or incompatible insect technique-based population suppression programs depends on the ability of released males to compete for ...

Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes

With the broad application of sequencing technologies, many novel virus-like sequences have been discovered in arthropods, including mosquitoes. The two main categories of these new mosquito-associated viruses are &#34;mosquito-borne viruses (MBVs)&#34; and &#34;mosquito-specific viruses (MSVs)&#34;. These novel viruses might be pathogenic to both vertebrates and mosquitoes, or they could just be symbiotic with mosquitoes. Entity viruses are essential to confirm the biological characters of these viruses. Thus, a detailed protocol has been described here for virus isolation and amplification from field-collected mosquitoes. First, the mosquito samples were prepared as supernatants of mosquito homogenates. After centrifugation twice, the supernatants were then inoculated into either mosquito cell line C6/36 or vertebrate cell line BHK-21 for virus amplification. After 7 days, the supernatants were collected as the P1 supernatants and stored at -80 &#176;C. Next, P1 supernatants were passaged twice more in C6/36 or BHK-21 cells while the cell status was being checked daily. When cytopathogenic effect (CPE) on the cells was discovered, these supernatants were collected and used to identify viruses. This protocol serves as the foundation for future research on mosquito-associated viruses, including MBVs and MSVs.

Numerous novel virus-like sequences have been found in mosquitoes due to the extensive use of sequencing technologies. We provide an effective procedure for isolating and amplifying viruses using vertebrate and mosquito cell lines, which might serve as the basis for future studies on mosquito-associated viruses, including mosquito-borne and mosquito-specific viruses.

With the broad application of sequencing technologies, many novel virus-like sequences have been discovered in arthropods, including mosquitoes. The two ...

Vector Competence Analyses on Aedes aegypti Mosquitoes using Zika Virus

Summary

Explore More Videos

Chapters in this video

Embryo Microinjection Techniques for Efficient Site-Specific Mutagenesis in Culex quinquefasciatus

Genome Editing in the Yellow Fever Mosquito Aedes aegypti using CRISPR-Cas9

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Rescue and Characterization of Recombinant Virus from a New World Zika Virus Infectious Clone

Quantification of Antibody-dependent Enhancement of the Zika Virus in Primary Human Cells

Experimental Viral Infection in Adult Mosquitoes by Oral Feeding and Microinjection

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Forced Salivation As a Method to Analyze Vector Competence of Mosquitoes

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male Aedes aegypti Mosquitoes

Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes