Identification of feline <i>Tritrichomonas foetus</i> surface epitopes: Putative targets for development of a novel diagnostic test for feline trichomonosis

BACKGROUND: Tritrichomonas foetus (T. foetus) is a flagellated protozoa that infects the distal ileum and proximal colon of domestic cats and also induces reproductive failure in cattle. Although feline trichomonosis is recognized to have a global prevalence of up to 30%, it still poses a diagnostic and therapeutic challenge to veterinarians; thus, there is a need for both improved diagnostics and therapeutics. Despite differing organ tropism between genotypes, evidence exists for conserved virulence factors between feline and bovine T. foetus. Two epitopes (1.15 and 1.17) of the bovine T. foetus glycosylated surface antigen 1.15-1.17 have been found to facilitate adhesion and cytotoxicity towards bovine urogenital epithelium. Although epitope 1.15 has been previously identified in feline isolates, conservation and function of epitope 1.17 has not yet been evaluated.

METHODS: Western blotting and indirect immunofluorescence were used to identify the presence of 1.15-1.17 in feline T. foetus isolates. One bovine T. foetus and one feline Pentatrichomonas hominis (a non-pathogenic feline trichomonad) isolate were used as positive and negative controls for all assays. Validated co-culture assays with in vitro porcine jejunal epithelial cell (IPEC-J2) cultures were used to determine the role this antigen plays in mediating adherence and cytotoxicity to the intestinal epithelium. Confluent epithelial cells were infected with feline T. foetus either treated with 1) isotype control or 2) 1:100 monoclonal antibody, and co-cultured for either 6 (i.e. adhesion assays) or 24 hours (i.e. cytotoxicity studies).

RESULTS: Presence and surface localization of both epitopes in feline T. foetus isolates was confirmed via western blotting, immunofluorescence and flow cytometry. Co-culture adhesion and cytotoxicity assays showed that epitopes 1.15 and 1.17 were either found to decrease or have no role in adhesion of T. foetus to intestinal epithelial cells.

CONCLUSIONS: Discovery of this antigen in feline T. foetus provides continued evidence that similarities exist between the bovine and feline genotypes. Although the role of 1.15-1.17 differs in feline versus bovine T. foetus in vitro, the conservation of expression across isolates and surface location of these epitopes are ideal characteristics for engineering a novel diagnostic assay for detection of whole organism trichomonads in fecal samples.