Human IgG responses to Aedes mosquito salivary peptide Nterm-34kDa and its comparison to Anopheles salivary antigen (gSG6-P1) IgG responses measured among individuals living in Lower Moshi, Tanzania

Abstract

Background The level of human exposure to arbovirus vectors, the Aedes mosquitoes, is mainly assessed by entomological methods which are labour intensive, difficult to sustain at a large scale and are affected if transmission and exposure levels are low. Alternatively, serological biomarkers which detect levels of human exposure to mosquito bites may complement the existing epidemiologic tools as they seem cost-effective, simple, rapid, and sensitive. This study explored human IgG responses to an Aedes mosquito salivary gland peptide Nterm-34kDa in Lower Moshi, a highland area with evidence of circulating arboviruses and compared the Aedes IgG responses to Anopheles mosquitoes’ salivary antigen (GSG6-P1) IgG responses. Methods Three cross-sectional surveys were conducted in 2019: during the first dry season in March, at the end of the rainy season in June and during the second dry season in September in five villages located in Lower Moshi. Blood samples were collected from enrolled participants above six months of age (age span: 7 months to 94 years) and analysed for the presence of anti-Nterm-34kDa IgG antibodies. Possible associations between Nterm-34kDa seroprevalence and participants’ characteristics were determined. Levels of IgG responses and seroprevalence were correlated and compared to the already measured IgG responses and seroprevalence of Anopheles mosquitoes’ salivary antigen, GSG6-P1. Results During the first dry season, Nterm-34kDa seroprevalence was 34.1% and significantly increased at the end of the rainy season to 45.3% (Chi square (χ2) = 6.42 p = 0.011). During the second dry season, the seroprevalence significantly declined to 26.5% (χ2 = 15.12 p<0.001). During the rainy season, seroprevalence was significantly higher among residents of Oria village (adjusted odds ratio (AOR) = 2.86; 95% CI = 1.0–7.8; p = 0.041) compared to Newland. Moreover, during the rainy season, the risk of exposure was significantly lower among individuals aged between 16 and 30 years (AOR = 0.25; 95% CI = 0.1 = 0.9; p = 0.036) compared to individuals aged between 0 and 5 years. There was weak to moderate negative correlation between N-term 34kDa IgG and gSG6-P1 antigens. N-term 34kDa seroprevalence were higher compared to gSG6-P1 seroprevalence. Conclusion The findings of this study support that IgG antibody responses towards the Aedes mosquito salivary peptide Nterm-34kDa are detectable among individuals living in lower Moshi and vary with season and geographical area. More individuals are exposed to Aedes mosquito bites than Anopheles mosquito and those exposed to Aedes bites are not necessarily exposed to Anopheles mosquitoes.

Little disease but lots of bites: social, urbanistic, mobility, and entomological risk factors of human exposure toAedes aegyptiin South Texas, U.S.

“…aegypti bites indicating that younger people were more likely to be bitten than older people. In previous studies, age has been a contributor to bite exposure levels, though the directionality of the relationship varied among studies (32,44,54). Doucoure and colleagues (44) propose three hypotheses to understand the difference in exposure between adults and children: 1) antibody response is directly correlated to the bites received, 2) children have stronger reactions to bites than adults, or 3) adults experience desensitization to bites.…”

“…aegypti bites indicating that younger people were more likely to be bitten than older people. In previous studies, age has been a contributor to bite exposure levels, though the directionality of the relationship varied among studies (32,44,54).…”

“…A mixed model was chosen to account for the potential lack of spatial independence (i.e., individuals nested within households and households nested within communities). While both linear mixed models (32,43) and GLMMs (44)(45)(46) have been used in similar serological-biomarker studies, we chose a Gaussian GLMM because they are an ideal tool for analyzing normal data whose independence is constrained by different factors (e.g., spatial or temporal) and that are modeled as random effects (47,48) in our study.…”

“…Other studies have showed mixed results in terms of SES variables and bite exposure. For example, one SES variable, occupation type, has been associated with exposure previously (32) while education level has been shown to have no effect on exposure (54). In our study, age was negatively associated with exposure to Ae.…”

Antibodies to Aedes spp. salivary proteins: a systematic review and pooled analysis

“…Studies measuring antibody to MSP have revealed the impact of factors such as urbanization/agriculture, season, and climate on the level of mosquito bite exposure (21, 28). Furthermore, these measurements have been used to assess how subject age influences the immunoglobulin response to MSP (16,19,20,22,26,27,(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41). Additionally, due to the immunomodulatory effects of MSP, antibody responses have been investigated for vaccine development (42).…”