Thongpoon S.Roobsoong W.Nguitragool W.Chotirat S.Tsuboi T.Takashima E.Cui L.Ishino T.Tachibana M.Miura K.Sattabongkot J.Mahidol University2024-02-272024-02-272024-02-14The Journal of infectious diseases Vol.229 No.2 (2024) , 567-575https://repository.li.mahidol.ac.th/handle/123456789/97340BACKGROUND: Human immunity triggered by natural malaria infections impedes parasite transmission from humans to mosquitoes, leading to interest in transmission-blocking vaccines. However, immunity characteristics, especially strain specificity, remain largely unexplored. We investigated naturally acquired transmission-blocking immunity (TBI) against Plasmodium vivax, a major malaria parasite. METHODS: Using the direct membrane-feeding assay, we assessed TBI in plasma samples and examined the role of antibodies by removing immunoglobulins through protein G/L adsorption before mosquito feeding. Strain specificity was evaluated by conducting a direct membrane-feeding assay with plasma exchange. RESULTS: Blood samples from 47 patients with P vivax were evaluated, with 37 plasma samples successfully infecting mosquitoes. Among these, 26 showed inhibition before immunoglobulin depletion. Despite substantial immunoglobulin removal, 4 samples still exhibited notable inhibition, while 22 had reduced blocking activity. Testing against heterologous strains revealed some plasma samples with broad TBI and others with strain-specific TBI. CONCLUSIONS: Our findings indicate that naturally acquired TBI is mainly mediated by antibodies, with possible contributions from other serum factors. The transmission-blocking activity of plasma samples varied by the tested parasite strain, suggesting single polymorphic or multiple targets for naturally acquired TBI. These observations improve understanding of immunity against P vivax and hold implications for transmission-blocking vaccine development.MedicineArticleSCOPUS10.1093/infdis/jiad4692-s2.0-851853443131537661337943633