(2nd Place) Warmer temperatures speed up the age-dependent decline of humoral immunity in mosquitoes

Insects mount a multifaceted immune response to infection. A key humoral immune response is melanization, where melanin molecules are deposited on the surface of pathogens in a manner that encases and isolates them. Another key humoral response is lysis, where antimicrobial peptides disrupt pathogen membranes. The strength of the humoral immune response is altered by both insect age and by environmental temperature, but how these two factors interact to shape humoral immunity is unknown. Here, we investigated how warmer temperatures, older ages, and their interaction alter the humoral immune response in the African malaria mosquito, Anopheles gambiae. We reared mosquitoes at 27ºC, 30ºC, and 32ºC and evaluated the melanization and lytic responses of adult females at each temperature in four age groups (1-day, 5-day, 10-day, and 15 days old), under four immune treatments (naïve, injured, E. coli-infected, and M. luteus-infected). We biochemically quantified the melanization potential of hemolymph and visualized melanin deposition in the dorsal abdomen. We assessed the lytic immune response by quantifying the strength of the antimicrobial activity of hemolymph using a zone of inhibition assay. Individually, warmer temperatures and older ages weakened the melanization immune response, reducing the melanization potential of hemolymph and melanin deposition in the dorsal abdominal wall. Together, warmer temperatures accelerated the age-dependent decline in the melanization immune response. Preliminary data also suggest that warmer temperatures and older ages negatively impact the mosquito’s lytic immune response, and at warmer temperatures, age-dependent dysregulation and decline in immunity may be accelerated.