Binding of Leishmania infantum Lipophosphoglycan to the Midgut Is Not Sufficient To Define Vector Competence in Lutzomyia longipalpis Sand Flies

Abstract

It is well established that the presence of LPG is sufficient to define the vector competence of restrictive sand fly vectors with respect to Leishmania parasites. However, the permissiveness of other sand flies with respect to multiple Leishmania species suggests that other factors might define vector competence for these vectors. In this study, we investigated the underpinnings of Leishmania infantum survival and development in its natural vector, Lutzomyia longipalpis . We found that LPG-mediated midgut binding persists in late-stage parasites. This observation is of relevance for the understanding of vector-parasite molecular interactions and suggests that only a subset of infective metacyclic-stage parasites (metacyclics) lose their ability to attach to the midgut, with implications for parasite transmission dynamics. However, our data also demonstrate that LPG is not a determining factor in Leishmania infantum retention in the midgut of Lutzomyia longipalpis , a permissive vector. Rather, LPG appears to be more important in protecting some parasite strains from the toxic environment generated during blood meal digestion in the insect gut. Thus, the relevance of LPG in parasite development in permissive vectors appears to be a complex issue and should be investigated on a strain-specific basis.