Human exposure to Anopheles farauti bites in the Solomon Islands is not associated with IgG antibody response to the gSG6 salivary protein of Anopheles gambiae

Pollard, Edgar J.M., Patterson, Catriona, Russell, Tanya L., Apairamo, Alan, Oscar, Jance, Arcà, Bruno, Drakeley, Chris, and Burkot, Thomas R. (2019) Human exposure to Anopheles farauti bites in the Solomon Islands is not associated with IgG antibody response to the gSG6 salivary protein of Anopheles gambiae. Malaria Journal, 18. 334.

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Abstract

Background:

Mosquito saliva elicits immune responses in humans following mosquito blood feeding. Detection of human antibodies recognizing the Anopheles gambiae salivary gland protein 6 (gSG6) or the gSG6-P1 peptide in residents of Africa, South America and Southeast Asia suggested the potential for these antibodies to serve as a universal marker to estimate human biting rates. Validating the utility of this approach requires concurrent comparisons of anopheline biting rates with antibodies to the gSG6 protein to determine the sensitivity and specificity of the assay for monitoring changes in vector populations. This study investigated whether seroprevalence of anti-gSG6 antibodies in humans reflected the relative exposure to Anopheles farauti bites in the Solomon Islands as estimated from sympatric human landing catches.

Methods:

Human biting rates by An. farauti were estimated by landing catches at 10 sampling sites in each of 4 villages during the wet and dry seasons. Human serum samples from these same villages were also collected during the wet and dry seasons and analysed for antibody recognition of the gSG6 antigen by the Luminex xMAP© platform. Antibody titres and prevalence were compared to HLCs at the sampling sites nearest to participants’ residences for utility of anti-gSG6 antibodies to estimate human exposure to anopheline bites.

Results:

In this study in the Solomon Islands only 11% of people had very high anti-gSG6 antibody titres, while other individuals did not recognize gSG6 despite nightly exposures of up to 190 bites by An. farauti. Despite clear spatial differences in the human biting rates within and among villages, associations between anti-gSG6 antibody titres and biting rates were not found.

Conclusions:

Few studies to date have concurrently measured anopheline biting rates and the prevalence of human antibodies to gSG6. The lack of association between anti-gSG6 antibody titres and concurrently measured human biting rates suggests that the assay for human anti-gSG6 antibodies lacks sufficient sensitivity to be a biomarker of An. farauti exposure at an epidemiologically relevant scale. These findings imply that an improvement in the sensitivity of serology to monitor changes in anopheline biting exposure may require the use of saliva antigens from local anophelines, and this may be especially true for species more distantly related to the African malaria vector An. gambiae.

Item ID: 60532
Item Type: Article (Research - C1)
ISSN: 1475-2875
Keywords: gSG6, Human biting rate, Anopheles farauti, Saliva antigens
Copyright Information: © The Author(s) 2019. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Funders: Bill and Melinda Gates Foundation (BMGF), National Institutes of Health (NIH), Australian Institute of Tropical Health and Medicine (AITHM), Global Good Fund I, Rotarians Against Malaria (RAM)
Projects and Grants: BMGF Grant No. 45114, NIH subaward U19AI08986, AITHM Capacity Building grant number 15032
Research Data: https://doi.org/10.25903/5d4a47cbf1df2
Date Deposited: 09 Oct 2019 03:58
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111799 Public Health and Health Services not elsewhere classified @ 100%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920404 Disease Distribution and Transmission (incl. Surveillance and Response) @ 100%
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