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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 salivary glands. wMel.F mosquitoes fed once and twice on human bloodmeals (Fed 1x and Fed 2x) prior to being challenged with DENV-2 did not have a significant change in Wolbachia density in both replicates A and B compared to the Unfed controls which were not blood fed. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical group. Error bars are standard error of the mean of 11–19 salivary glands.
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Fig3: Wolbachia density in wMel.F mosquito salivary glands. wMel.F mosquitoes fed once and twice on human bloodmeals (Fed 1x and Fed 2x) prior to being challenged with DENV-2 did not have a significant change in Wolbachia density in both replicates A and B compared to the Unfed controls which were not blood fed. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical group. Error bars are standard error of the mean of 11–19 salivary glands.

Mentions: There was little (Figure 2A) to no (Figure 2B) DENV infection of the salivary glands in the presence of wMel making it difficult to assess the effects of repeat feeding for this tissue. In replicate A, however, where DENV was present, wMel.F mosquitoes that fed twice exhibited greater inhibition than the controls (Figure 2A). Regardless, Wolbachia densities did not increase with repeat blood feeding in either replicate experiment (Figure 3A, B). Hence the complete inhibition of DENV after the second feed in replicate A may not be explained by Wolbachia density. It is possible that immunity of the mosquito may have been improved by availability of nutrients through blood feeding [34,35] but this is not consistent with the lack of an effect in the Wildtype (Figure 2B). Alternatively, the positive result in replicate A may be due to a synergy between Wolbachia and blood feeding or be an artefact of small sample sizes.Figure 2


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 salivary glands. wMel.F mosquitoes fed once and twice on human bloodmeals (Fed 1x and Fed 2x) prior to being challenged with DENV-2 did not have a significant change in Wolbachia density in both replicates A and B compared to the Unfed controls which were not blood fed. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical group. Error bars are standard error of the mean of 11–19 salivary glands.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: Wolbachia density in wMel.F mosquito salivary glands. wMel.F mosquitoes fed once and twice on human bloodmeals (Fed 1x and Fed 2x) prior to being challenged with DENV-2 did not have a significant change in Wolbachia density in both replicates A and B compared to the Unfed controls which were not blood fed. Y-axis shows ratio of wsp/Rps17. Letters represent distinct statistical group. Error bars are standard error of the mean of 11–19 salivary glands.
Mentions: There was little (Figure 2A) to no (Figure 2B) DENV infection of the salivary glands in the presence of wMel making it difficult to assess the effects of repeat feeding for this tissue. In replicate A, however, where DENV was present, wMel.F mosquitoes that fed twice exhibited greater inhibition than the controls (Figure 2A). Regardless, Wolbachia densities did not increase with repeat blood feeding in either replicate experiment (Figure 3A, B). Hence the complete inhibition of DENV after the second feed in replicate A may not be explained by Wolbachia density. It is possible that immunity of the mosquito may have been improved by availability of nutrients through blood feeding [34,35] but this is not consistent with the lack of an effect in the Wildtype (Figure 2B). Alternatively, the positive result in replicate A may be due to a synergy between Wolbachia and blood feeding or be an artefact of small sample sizes.Figure 2

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