Does antibody binding to diverse antigens predict future infection?

Summary We studied diverse antigen binding in hosts and the outcome of parasitism. We used captive‐bred F 1 descendants of feral rock pigeons ( C olumba livia) challenged with blood‐feeding flies ( H ippoboscidae) and a protozoan parasite ( H aemoproteus). Enzyme‐linked immunosorbent assays ( ELISA s) and immunoblots were used to test (i) whether pre‐infection I g Y antigen binding predicts parasite fitness and (ii) whether antigen binding changes after infection. Assays used extracts from three pigeon parasites (northern fowl mite, S almonella bacteria and avian pox virus), as well as nonparasitic molecules from cattle, chicken and keyhole limpet. Binding to hippoboscid and S . enterica extracts were predictive of hippoboscid fly fitness. Binding to extracts from hippoboscids, pox virus and nonparasitic organisms was predictive of H aemoproteus infection levels. Antigen binding to all extracts increased after parasite challenge, despite the fact that birds were only exposed to flies and H aemoproteus. Immunoblots suggested innate I g binding to parasite‐associated molecular markers and revealed that new antigens were bound in extracts after infection. These data suggest that host antibody binding to diverse antigens predicts parasite fitness even when the antigens are not related to the infecting parasite. We discuss the implications of these data for the study of host–parasite immunological interaction.