D3331: Analyzing the effects of Borrelia recurrentis infection on the body louse immune system

Invading bacterial pathogens are known to trigger immune responses in their insect hosts. Diverse immune responses have been characterized in model insects such as Drosophila melanogaster as well as in major vectors such a mosquitoes. However, minimal research has been conducted on the immune system of the human body louse (Pediculus humanus humanus) in response to bacterial challenge. More specifically, there is no prior research on the effect of the human pathogen Borrelia recurrentis, responsible for louse-borne relapsing fever, on the body louse immune system. We addressed this gap in knowledge by orally administering varying concentrations of B. recurrentis to body lice via an in vitro feeding system and analyzing the expression of antimicrobial peptide genes, genes involved in reactive oxygen species production, and genes involved in melanization, nodulation, and encapsulation. Our results identify genes that are induced in response to B. recurrentis as well as genes that are suppressed by infection. These findings have implications for understanding pathogen transmission by the body louse, which remains a neglected vector.