Salivary proteins of sand flies and the immune aspects of Leishmania transmission

Sand flies serve as the vectors of leishmaniasis and their saliva was shown to affect the outcome of Leishmania infection by immunomodulation of the host. On the other hand, sand fly saliva contains a large scale of farmacologically active proteins that are strongly immunogenous for bitten hosts and specific anti-saliva immunity initiated by repeated sand fly feeding provides protection against Leishmania infection. Specific cell-mediated immunity was shown to be the core of the protectivity; however, our data suggests that the protective immunity has certain limitations. In mice bitten by sand flies for prolonged periods, we observed the desenzitization in term of abrogation of the protective immunity. Thus, we can speculate that the protective effect of immunity is linked solely with the short-term exposure. Nevertheless, our experiments showed that this aspect is also conditioned by the immediate infection after the protective short-term immunization. Taken together, it seems that these limitations may explain the circulation of leishmaniasis in endemic areas, even though humans and animals are frequently immunized by bites of uninfected sand flies. Repeated sand fly feeding on various hosts also promotes production of anti-saliva antibodies that reflect the intensity of exposure. We..