Immunological surveillance using gSG6-P1 biomarker reveals spatio-temporal dynamics of Anopheles exposure and gaps in malaria risk assessment

Abstract

Malaria risk assessment often relies on the entomological inoculation rate (EIR), which quantifies infectious bites per person over time. However, this approach does not account for human behavioral variability, limiting its effectiveness in accurately reflecting malaria risk at the population level. Recent studies have attempted to estimate mosquito-bite risk through the measurement of antibody responses to Anopheles salivary peptides. However, this approach has yet to be applied to evaluate malaria transmission risks along the Thailand-Cambodia border. This study aims to employ an immune biomarker for Anopheles salivary peptide (anti-gSG6-P1) to identify key risk factors associated with exposure to Anopheles mosquitoes in Sisaket Province, a region bordering Thailand and Cambodia. Blood samples from the same set of 184 participants were collected via finger prick during each season: rainy (August 2022), cool-dry (December 2022), and hot-dry (April 2023). Anti-gSG6-P1 antibody levels were quantified using enzyme-linked immunosorbent assay (ELISA). Factor Analysis of Mixed Data (FAMD) revealed that seasonality exerts the strongest influence on antibody levels. This pattern was likely driven by human activities, particularly the frequency of rubber tapping activity in the rubber plantation area where Anopheles species, especially Anopheles dirus, are present. While this study successfully identifies seasonality and human factors as critical influences on antibody responses, it also highlights gaps in understanding the kinetics of anti-salivary peptide responses to Anopheles bites, particularly in species with low salivary peptides sequence similarity to that of Anopheles gambiae. These findings emphasize the need for the development of new serological tools tailored to malaria vectors in the Greater Mekong Subregion to enhance malaria risk assessment and improve vector control strategies.