Evaluation of surface antigen TF1.17 in feline Tritrichomonas foetus isolates

Abstract

Tritrichomonas foetus (T. foetus) is a flagellated protozoa that infects the distal ileum and proximal colon of domestic cats, as well as the urogenital tract of cattle. Feline trichomonosis is recognized as a prevalent cause of chronic diarrhea in cats worldwide. The suspected route of transmission is fecal-oral, with cats in densely crowded environments at highest risk for infection. Thus, the recommended strategy for minimizing spread of infection is to identify and isolate T. foetus-positive cats from the general population. Rapid identification of infected cats can be challenging due to the inability to accurately and quickly detect the organism in samples at point of care facilities. Thus, identification of targets for use in development of a novel diagnostic test, as well as a vaccine or therapy for T. foetus infection is a significant area of research. Despite a difference in organ tropism between T. foetus genotypes, evidence exists for conserved virulence factors between feline and bovine T. foetus. The bovine T. foetus surface antigen, TF1.17, is an adhesin that is conserved across isolates. Vaccination with the purified antigen results in amelioration of cytopathogenicity and more rapid clearance of infection in cattle. We previously showed that three feline isolates of T. foetus were positive for TF1.17 antigen so we further hypothesized that TF1.17 is conserved across feline T. foetus isolates and that this antigen would represent an attractive target for development of a novel diagnostic test or therapy for feline trichomonosis. In these studies, we used monoclonal antibodies previously generated against 1.15 and 1.17 epitopes of the bovine T. foetus TF1.17 antigen, to evaluate for the presence and role of TF1.17 in the cytopathogenicity of feline T. foetus. A previously validated in vitro co-culture approach was used to model feline T. foetus infection. Immunoblotting, immunofluorescence assays, and flow cytometric analysis confirmed the presence and surface localization of antigen TF1.17 across all feline T. foetus isolates tested. Antigen TF1.17 was notably absent in the presumably nonpathogenic intestinal trichomonad, Pentatrichomonas hominis, a parasite that can be confused microscopically with T. foetus. Similar to bovine trichomoniasis, TF1.17 was found to promote T. foetus adhesion to the intestinal epithelium. These results support further characterization and development of the TF1.17 antigen as a possible target for the diagnosis and prevention of feline T. foetus infection.

Keywords: 1.15–1.17; Adhesion; Epithelium; Epitopes; Protozoa; Tritrichomonas foetus.