Abstract:
Trichomonas vaginalis is a flagellated protozoan parasite that causes trichomoniasis, the world most common non-viral sexually transmitted infection. Although infections may be asymptomatic, trichomoniasis has been associated with an increased risk of cervical and prostate cancers, pre-term delivery and low birth weight infants and has been implicated as a risk factor for acquisition of the human immunodeficiency virus. As an obligate extracellular protozoan parasite, adherence to the vaginal epithelial cells is critical in order to establish and maintain infection. Nevertheless, the biochemical processes behind T. vaginalis infection and its interaction with the vaginal microbiota are still not well defined. The draft genome sequence of T. vaginalis strain G3 identified nine NlpC/P60-like members (Clan CA, family C40). The NlpC/P60 proteins define a superfamily with diverse enzymatic functions, where the majority of the members are cell-wall hydrolases. Since T. vaginalis does not have a cell wall, investigating origins and whether the NlpC/P60 genes are functional and aiding parasite infection became the main focus of this research. Bioinformatics analyses of the nine NlpC/P60 genes in T. vaginalis revealed that these genes were acquired via lateral gene transfer (LGT) from bacteria and belong to the P60-like family. To investigate the function of the NlpC/P60 family of proteins in T. vaginalis, two members were expressed, purified and crystallised with their threedimensional structure determined at resolutions of 1.2 Å and 2.3 Å, by X-ray diffraction. The enzymatic activity of three NlpC/P60 enzymes in T. vaginalis was characterised in a peptidoglycan cleavage assay, revealing these members to be active D, L-endopeptidases. The gene expression analysis showed that all genes are up-regulated when in contact with host microbiota. Further analyses revealed the NlpC proteins to be located in different cellular compartments and parasite transfectants to possess a really strong phenotype with bacteriolytic activity. Overall these results suggest that T. vaginalis is using the LGT acquired genes against the vaginal microbiota. This work sheds light into the interaction of T. vaginalis and the host microbiota, highlighting the role of new molecules that are possibly involved in the parasite pathogenesis. Understanding how T. vaginalis interact in the vaginal ecosystem and the discovery of molecules involved in these interactions can be of potential use to develop vaccines and drugs in the future.