Controlled human infection with Plasmodium falciparum-infected mosquito bites elicits antibodies against mosquito salivary protein SG1L3.

Two monoclonal antibodies from a human volunteer recognize the surface of Plasmodium falciparum sporozoites but target the mosquito salivary protein SG1L3, not CSP.

• Why it matters: Antibodies to non-CSP sporozoite surface antigens are poorly characterized, limiting understanding of early malaria immunity and potential serological markers of mosquito exposure.
• What they did: Single B cells were isolated from a volunteer immunized by Plasmodium falciparum-infected mosquito bites, yielding two non-CSP-binding mAbs; immunoprecipitation plus mass spectrometry identified SG1L3 as the target.
• The result: Recombinant SG1L3 binds sporozoites, but SG1L3-specific mAbs and polyclonal antibodies (including rabbit antisera) fail to block liver-stage infection in vitro; Burkina Faso residents with intense Anopheles exposure show SG1L3 antibodies with titers increasing with age.