Impact of the blood meal on humoral immunity and microbiota in the gut of female Culicoides sonorensis

Authors: Nayduch, Dana; ERRAM, DINESH - Kansas State University; LEE, MATTHEW - Former ARS Employee; ZUREK, L - Kansas State University; SASKI, CHRISTOPHER - Clemson University

Submitted to: Veterinaria Italiana
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2015
Publication Date: 12/31/2015
Publication URL: http://handle.nal.usda.gov/10113/61860
Citation: Nayduch, D., Erram, D., Lee, M.B., Zurek, L., Saski, C. 2015. Impact of the blood meal on humoral immunity and microbiota in the gut of female Culicoides sonorensis. Veterinaria Italiana. 51:385-392. doi:10.12834/VetIt.495.2397.2.

Interpretive Summary: Although Culicoides sonorensis is an important vector of orbiviruses that cause significant disease in domestic and wild ruminants in the USA, little is known about factors contributing to midge vector competence, or their permissiveness in harboring and disseminating these pathogens. In other insects such as mosquitoes, tripartite interactions between the immune response, microorganisms and ingested pathogens (such as viruses) within the midge’s gut directly impact pathogen survival and therefore transmission potential. We recently described an expressed gene set (transcriptome) for the midge C. sonorensis, and identified components of the midge immune response. Further we looked at the expression profiles of these immune-related genes across several dietary states (unfed, blood or sugar fed). Blood feeding altered the expression of several humoral immune components of the Imd, REDOX and JAK/STAT pathways. In particular, genes for immune effectors such as antimicrobial peptides (AMPs) were in particular highly induced. Blood feeding also stimulates proliferation and diversification of bacterial populations colonizing the gut of female midges. Thus, we infer that changes in immune gene expression, especially bacteria-killing molecules like AMPs, resulted due to fluctuations in gut microbiota. Diet alone can indirectly (via microbiota) impact gut immune status and therefore should be carefully considered in subsequent studies assessing vector competence in biting midges.

Technical Abstract: Although Culicoides sonorensis is an important vector of orbiviruses that cause significant disease in domestic and wild ruminants in the USA, little is known about factors contributing to midge vector competence. In other vectors such as mosquitoes, interactions between the humoral immune response, microbiota and ingested pathogens within the vector gut directly impact pathogen survival and therefore vectoring potential. We recently described components of the humoral immune response in the reference transcriptome for adult female C. sonorensis and analyzed their temporal expression profiles across several dietary states (unfed, blood or sugar fed). Blood feeding altered the transcription of several humoral immune components of the Imd, REDOX and JAK/STAT pathways, and genes for immune effectors such as antimicrobial peptides were in particular highly induced. Since blood feeding also stimulated proliferation and diversification of bacterial populations colonizing the gut of female midges, we infer that changes in immune gene expression were a result of fluctuations in gut microbiota. Thus, diet can indirectly (via microbiota) impact gut immune status and therefore should be carefully considered in subsequent studies assessing vector competence in biting midges.