Proopiomelanocortin-derived peptides as tools of immune evasion for the human trematode Schistosoma mansoni.

Schistosomes are digenetic trematodes which share their life cycle between a definitive (vertebrate) and an intermediate (invertebrate) host. Their survival is highly dependent on their ability to reduce significantly the efficiency of the host defences. We have previously demonstrated the presence of POMC derived peptides (ACTH, alpha-MSH, beta-endorphin) in all stages of Schistosoma mansoni life cycle. Given the immunomodulatory properties of these peptides in vertebrates and invertebrates it has been postulated that they might be implicated in parasite immune evasion. We report the release of these neuropeptides during the cycle, associated with the inhibition by these peptides of the locomotory activity of immunocytes from both hosts, the hamster Mesocricetus auratus and the freshwater snail B. glabrata. The implication of these common signals in this new strategy of parasite adaptation is discussed.