Resisting an invasion: A review of the triatomine vector (Kissing bug) defense strategies against a Trypanosoma sp infection.

Triatomines are an important group of insects in the Americas. They serve as transmission vectors for Trypanosoma cruzi, the etiologic agent responsible for the deadly Chagas disease in humans. The digenetic parasite has a complex life cycle, alternating between mammalian and insect hosts, facing different environments. In the insect vector, the metacyclic trypomastigote (non-replicative) and epimastigote (replicative) stages face a set of insect-mediated environmental changes, such as intestinal pH, body temperature, nutrient availability, and vector immune response. These insects have the ability to differentiate between self and non-self-particles using their innate immune system. This immune system comprises physical barriers, cellular responses (phagocytosis, nodules and encapsulation), humoral factors, including effector mechanisms (antimicrobial peptides and prophenoloxidase cascade) and the intestinal microbiota. Here, we consolidate and synthesize the available literature to describe the defense mechanisms deployed by the triatomine vector against the parasite, as documented in recent years, the possible mechanisms developed by the parasite to protect against the insect's specific microenvironment and innate immune responses, and future perspectives on the Triatomine-Trypanosome interaction.