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Effect of repeat human blood feeding on Wolbachia density and dengue virus infection in Aedes aegypti.

Amuzu HE, Simmons CP, McGraw EA - Parasit Vectors (2015)

Bottom Line: The Wolbachia infected Aedes aegypti mosquito line was used for the study.All groups were orally infected with DENV-2 and then their midguts and salivary glands were dissected 10-11 days post infection.RNA/DNA was simultaneously extracted from each tissue and subsequently used for DENV RNA copies and Wolbachia density quantification, respectively.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Monash University, Clayton, Melbourne, Victoria, Australia. hilaria.amuzu@monash.edu.

ABSTRACT

Background: The introduction of the endosymbiotic bacterium, Wolbachia into Aedes aegypti populations is a novel approach to reduce disease transmission. The presence of Wolbachia limits the ability of the mosquito to transmit dengue virus (DENV) and the strength of this effect appears to correlate with Wolbachia densities in the mosquito. There is also some evidence that Wolbachia densities may increase following the consumption of a bloodmeal. Here we have examined whether multiple blood feeds lead to increases in density or associated changes in Wolbachia-mediated blocking of DENV.

Methods: The Wolbachia infected Aedes aegypti mosquito line was used for the study. There were three treatment groups; a non-blood fed control, a second group fed once and a third group fed twice on human blood. All groups were orally infected with DENV-2 and then their midguts and salivary glands were dissected 10-11 days post infection. RNA/DNA was simultaneously extracted from each tissue and subsequently used for DENV RNA copies and Wolbachia density quantification, respectively.

Results: We found variation between replicate vector competence experiments and no clear evidence that Wolbachia numbers increased in either the salivary glands or remainder of the body with feeding and hence saw no corresponding improvements in DENV blocking.

Conclusions: Aedes aegypti are "sip" feeders returning often to obtain bloodmeals and hence it is important to assess whether repeat blood feeding improved the efficacy of Wolbachia-based DENV blocking. Our work suggests in the laboratory context when Wolbachia densities are high that repeat feeding does not improve blocking and hence this ability should likely be stable with respect to feeding cycle in the field.

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Related in: MedlinePlus

Wolbachia density in wMel.F mosquito midguts. In replicate A, midgut Wolbachia density in wMel.F mosquitoes decreased in mosquitoes fed twice on human bloodmeal (Fed 2x) before being challenged with DENV-2 compared to those which were not blood fed (Unfed) (P = 0.002) and those fed only once on human blood (Fed 1x) (P = 0.03). However in replicate B, there was no significant change in Wolbachia density across treatment groups. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical groups. Error bars are standard error of the mean of 14-21individual midguts.
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Fig5: Wolbachia density in wMel.F mosquito midguts. In replicate A, midgut Wolbachia density in wMel.F mosquitoes decreased in mosquitoes fed twice on human bloodmeal (Fed 2x) before being challenged with DENV-2 compared to those which were not blood fed (Unfed) (P = 0.002) and those fed only once on human blood (Fed 1x) (P = 0.03). However in replicate B, there was no significant change in Wolbachia density across treatment groups. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical groups. Error bars are standard error of the mean of 14-21individual midguts.

Mentions: Repeat blood feeding did not significantly affect DENV RNA copies in the midgut of wMel.F infected mosquitoes in replicate A (Figure 4A) and in replicate B (Figure 4B), DENV infection rates were lower, making comparisons of viral RNA concentration difficult to assess. There were no consistent effects of blood feeding on wMel density in the midgut, but there was an unexpected significant decrease in Wolbachia density after the second bloodmeal compared with controls and those fed one time for replicate A (Figure 5A) but not replicate B (Figure 5B). This effect was also observed in wFlu from Ae. fluviatilis where the midgut Wolbachia density of blood fed individuals were consistently lower compared to sugar-fed females [36]. Surprisingly, this change did not have an effect on DENV infection or RNA copies in the wMel.F midgut. It should be determined if there is a threshold Wolbachia density in mosquitoes below which viral blocking is interrupted or if densities in only a limited set of tissues are predictive of blocking ability. Repeat feeding had no consistent effect on DENV RNA copies in the midgut of Wildtype mosquitoes (Figure 4).Figure 4


Effect of repeat human blood feeding on Wolbachia density and dengue virus infection in Aedes aegypti.

Amuzu HE, Simmons CP, McGraw EA - Parasit Vectors (2015)

Wolbachia density in wMel.F mosquito midguts. In replicate A, midgut Wolbachia density in wMel.F mosquitoes decreased in mosquitoes fed twice on human bloodmeal (Fed 2x) before being challenged with DENV-2 compared to those which were not blood fed (Unfed) (P = 0.002) and those fed only once on human blood (Fed 1x) (P = 0.03). However in replicate B, there was no significant change in Wolbachia density across treatment groups. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical groups. Error bars are standard error of the mean of 14-21individual midguts.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4413987&req=5

Fig5: Wolbachia density in wMel.F mosquito midguts. In replicate A, midgut Wolbachia density in wMel.F mosquitoes decreased in mosquitoes fed twice on human bloodmeal (Fed 2x) before being challenged with DENV-2 compared to those which were not blood fed (Unfed) (P = 0.002) and those fed only once on human blood (Fed 1x) (P = 0.03). However in replicate B, there was no significant change in Wolbachia density across treatment groups. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical groups. Error bars are standard error of the mean of 14-21individual midguts.
Mentions: Repeat blood feeding did not significantly affect DENV RNA copies in the midgut of wMel.F infected mosquitoes in replicate A (Figure 4A) and in replicate B (Figure 4B), DENV infection rates were lower, making comparisons of viral RNA concentration difficult to assess. There were no consistent effects of blood feeding on wMel density in the midgut, but there was an unexpected significant decrease in Wolbachia density after the second bloodmeal compared with controls and those fed one time for replicate A (Figure 5A) but not replicate B (Figure 5B). This effect was also observed in wFlu from Ae. fluviatilis where the midgut Wolbachia density of blood fed individuals were consistently lower compared to sugar-fed females [36]. Surprisingly, this change did not have an effect on DENV infection or RNA copies in the wMel.F midgut. It should be determined if there is a threshold Wolbachia density in mosquitoes below which viral blocking is interrupted or if densities in only a limited set of tissues are predictive of blocking ability. Repeat feeding had no consistent effect on DENV RNA copies in the midgut of Wildtype mosquitoes (Figure 4).Figure 4

Bottom Line: The Wolbachia infected Aedes aegypti mosquito line was used for the study.All groups were orally infected with DENV-2 and then their midguts and salivary glands were dissected 10-11 days post infection.RNA/DNA was simultaneously extracted from each tissue and subsequently used for DENV RNA copies and Wolbachia density quantification, respectively.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Monash University, Clayton, Melbourne, Victoria, Australia. hilaria.amuzu@monash.edu.

ABSTRACT

Background: The introduction of the endosymbiotic bacterium, Wolbachia into Aedes aegypti populations is a novel approach to reduce disease transmission. The presence of Wolbachia limits the ability of the mosquito to transmit dengue virus (DENV) and the strength of this effect appears to correlate with Wolbachia densities in the mosquito. There is also some evidence that Wolbachia densities may increase following the consumption of a bloodmeal. Here we have examined whether multiple blood feeds lead to increases in density or associated changes in Wolbachia-mediated blocking of DENV.

Methods: The Wolbachia infected Aedes aegypti mosquito line was used for the study. There were three treatment groups; a non-blood fed control, a second group fed once and a third group fed twice on human blood. All groups were orally infected with DENV-2 and then their midguts and salivary glands were dissected 10-11 days post infection. RNA/DNA was simultaneously extracted from each tissue and subsequently used for DENV RNA copies and Wolbachia density quantification, respectively.

Results: We found variation between replicate vector competence experiments and no clear evidence that Wolbachia numbers increased in either the salivary glands or remainder of the body with feeding and hence saw no corresponding improvements in DENV blocking.

Conclusions: Aedes aegypti are "sip" feeders returning often to obtain bloodmeals and hence it is important to assess whether repeat blood feeding improved the efficacy of Wolbachia-based DENV blocking. Our work suggests in the laboratory context when Wolbachia densities are high that repeat feeding does not improve blocking and hence this ability should likely be stable with respect to feeding cycle in the field.

Show MeSH
Related in: MedlinePlus