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

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.

IgG antibody response against Anopheles salivary gland proteins in asymptomatic Plasmodium infections in Narino, Colombia

“…In the same way, Pollard et al suggested that the antibodies to the gSG6-P1 peptide in the Colombian population may represent exposure to An. punctimacula, which is a member of the Anopheles subgenus or could hypothetically represent exposure to minor vectors in the country [31]. Thus, the current results suggest that the gSG6-P1 peptide could be a useful marker for malaria risk in areas of Colombia where mosquitoes belonging to subgenus other than Nyssorhynchus are present.…”

The changing epidemiology of Plasmodium vivax: Insights from conventional and novel surveillance tools

“…Antibody responses against the Anopheles gambiae salivary gland protein gSG6 or the synthetic peptide gSG6-P1 have been correlated with mosquito exposure [ 94 , 102 ]. While these serological markers have been successfully validated at multiple sites in Africa, Asia, and Southeast Asia, other studies suggest that anti-gSG6 targets of local anopheline vectors are more reliable for estimating transmission intensity [ 103 – 106 ].…”

IgG Antibody Responses to the Aedes albopictus 34k2 Salivary Protein as Novel Candidate Marker of Human Exposure to the Tiger Mosquito

“…IgG responses to the Anopheles gambiae gSG6 or the gSG6-P1 peptide have been widely validated as marker of human exposure to Afrotropical malaria vectors in different epidemiological settings in Western and Eastern African countries (Poinsignon et al, 2008 ; Drame et al, 2010 ; Rizzo et al, 2011b ; Badu et al, 2012 ; Stone et al, 2012 ; Proietti et al, 2013 ; Yman et al, 2016 ). Moreover, the same antigens have been successfully employed for Asian malaria vectors (Ya-Umphan et al, 2017 ) and may be of some use with Polynesian (Idris et al, 2017 ; Pollard et al, 2019 ) and American Old World anophelines (Montiel et al, 2020 ). For Aedes mosquitoes some promising indications have been obtained with the Nterm-34kDa peptide, which is designed on the culicine-specific Ae.…”