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Review 1: "Two Mosquito Salivary Antigens Demonstrate Promise as Biomarkers of Recent Exposure to P. Falciparum Infected Mosquito Bites"

Reviewers found the article to be compelling, highlighting the importance of finding new biomarkers for malaria surveillance, particularly in low-transmission settings.

Published onJun 18, 2024
Review 1: "Two Mosquito Salivary Antigens Demonstrate Promise as Biomarkers of Recent Exposure to P. Falciparum Infected Mosquito Bites"
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Two mosquito salivary antigens demonstrate promise as biomarkers of recent exposure to P. falciparum infected mosquito bites
Two mosquito salivary antigens demonstrate promise as biomarkers of recent exposure to P. falciparum infected mosquito bites
Description

Abstract Background Measuring malaria transmission intensity using the traditional entomological inoculation rate is difficult. Antibody responses to mosquito salivary proteins such as SG6 have previously been used as biomarkers of exposure to Anopheles mosquito bites. Here, we investigate four mosquito salivary proteins as potential biomarkers of human exposure to mosquitoes infected with P. falciparum: mosGILT, SAMSP1, AgSAP, and AgTRIO.Methods We tested population-level human immune responses in longitudinal and cross-sectional plasma samples from individuals with known P. falciparum infection from low and moderate transmission areas in Senegal using a multiplexed magnetic bead-based assay.Results AgSAP and AgTRIO were the best indicators of recent exposure to infected mosquitoes. Antibody responses to AgSAP, in a moderate endemic area, and to AgTRIO in both low and moderate endemic areas, were significantly higher than responses in a healthy non-endemic control cohort (p-values = 0.0245, 0.0064, and <0.0001 respectively). No antibody responses significantly differed between the low and moderate transmission area, or between equivalent groups during and outside the malaria transmission seasons. For AgSAP and AgTRIO, reactivity peaked 2-4 weeks after clinical P. falciparum infection and declined 3 months after infection.Discussion Reactivity to both AgSAP and AgTRIO peaked after infection and did not differ seasonally nor between areas of low and moderate transmission, suggesting reactivity is likely reflective of exposure to infectious mosquitos or recent biting rather than general mosquito exposure. Kinetics suggest reactivity is relatively short-lived. AgSAP and AgTRIO are promising candidates to incorporate into multiplexed assays for serosurveillance of population-level changes in P. falciparum-infected mosquito exposure.

RR:C19 Evidence Scale rating by reviewer:

  • Strong. The main study claims are very well-justified by the data and analytic methods used. There is little room for doubt that the study produced has very similar results and conclusions as compared with the hypothetical ideal study. The study’s main claims should be considered conclusive and actionable without reservation.

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Review: Measuring malaria transmission intensity using the traditional entomological inoculation rate is difficult, hence using antibody responses to mosquito salivary proteins as biomarkers of exposure to Anopheles mosquito bites is a viable alternative. Mosquito salivary proteins biomarkers in a multiplex approach can also be used in disease surveillance at community level and potentially in different disease transmission settings.

The manuscript is well written and very informative. It provides good arguments in supporting the use of biomarkers in estimating exposure to infectious mosquito bite. The multiplex approach with the possibility of adding more markers is appealing and allows flexibility.  This ventures into an exciting area to be explored and used in disease surveillance at population/community level, both pre-and post intervention.

The methods used are clear and the presentation is logical.

Overall the conclusions and main claims are substantiated by the evidence presented.

Below are very minor comments on the manuscript and I recommend accepting this interesting manuscript for publication. 

  1. On the limitations, maybe include a strong justification for the sample size which in this case was small particularly in Senegal with 164 samples where 33 were from the low transmission area of Thiès. 

  2. The moderate to weak correlation between plasma and DBS results, are they not due to sample size? Will the results be different with larger sample size? 

  3. The authors should also consider adding a small explanation in the selection of the 4 markers tested. Are these the only ones associated with increasing Plasmodium infection (3) and decreasing Plasmodium infection (1). Was it not possible to compare two in each category?

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Two mosquito salivary antigens show exciting potential as biomarkers for recent exposure to P. falciparum-infected mosquito bites https://www-krogercomfeedback.com