The developmental forms of African trypanosomes exhibit multiple physiological differences (4), including nondividing stages, variation in the acyl-anchored surface protein and amino acid identity of GPI-anchored surface protein (5,6), differential rates of endocytosis (7) and motility (8), and differences in mitochondrial structure and function (9,10). One potential source of new therapeutic agents is the vast and diverse biological repertoire of antimicrobial peptides (AMPs) (11). These small, typically cationic molecules are ubiquitous components of the innate immune system of metazoans and as such have evolved simple

biochemical mechanisms of find more target cell specificity. The mode of action of many AMPs involves increasing the permeability of the cell membrane, often through the formation of transmembrane pores (11). Conventional AMPs with trypanocidal activity have been EPZ6438 identified in multiple phyla, including humans (12), and are specifically involved in the insect vector’s immune response to African trypanosomes

(13–19) (Table 1). The unsatisfactory state of pharmacological intervention strategies for HAT has prompted the identification of natural products and synthetic peptides that exhibit trypanocidal activity (20–22) (Table 1). Additionally, trypanocidal peptides with unconventional modes of action have been identified from unusual sources, including neuropeptides (23) and secretory signal peptides (24) (Table 1). Antimicrobial peptides and synthetic derivatives with activity against the related kinetoplast organisms Trypanosoma cruzi and Leishmania spp. have been identified and are described in a recent review by McGwire and Kulkarni (25). Here, I limit discussion to the African trypanosomes, specifically the role of AMPs in the insect vector immune response to

African trypanosomes, the characteristics of trypanocidal peptides identified to date and the mechanisms of unconventional trypanocidal mafosfamide peptides from unusual sources. A role for AMPs in the immune response of the insect vector has been well established. Perhaps surprisingly, only a small percentage (<5–17%) of tsetse are infected in endemic areas (26), only a small number of trypanosomes within a bloodmeal successfully develop into insect stage procyclic forms (PC) (27) and a large portion of tsetse eliminate the parasites entirely at around day 3 post-infection (28). Additionally, some tsetse species, i.e. Glossina pallidipes and Glossina palpalis palpalis, are more refractory to African trypanosome infection than the main vector Glossina morsitans. The innate immune response has been implicated in preventing or limiting the establishment of gut infections (13,16).