Effects of ingested vertebrate-derived factors on insect immune responses

• Ingested blood-derived factors can alter the immune response of insect vectors.
• Factors released by hemoglobin digestion can limit the growth of pathogens.
• Pathogen-derived factors can signal in the insect midgut to alter immunity.
• Human chitotriosidase can alter the peritrophic matrix of insects.
• Human insulin, IGF-1, and TGF-β1 signal in the insect midgut to alter immunity.

During the process of blood feeding insect vectors are exposed to an array of vertebrate-derived blood factors ranging from byproducts of blood meal digestion to naturally occurring products in the blood including growth hormones, cytokines and factors derived from blood-borne pathogens themselves. In this review, we examine the ability of these ingested vertebrate blood factors to alter the innate pathogen defenses of insect vectors. The ability of these factors to modify the immune responses of insect vectors offers new intriguing targets for blocking or reducing transmission of human disease-causing pathogens.