A novel surface protein of Trichomonas vaginalis is regulated independently by low iron and contact with vaginal epithelial cells

An IgA mAb called 6B8 was isolated from a library of mAbs reactive to surface proteins of T. vaginalis. The 6B8 mAb recognized a 44-kDa protein (TV44) by immunoblot analysis, and a full-length cDNA clone encoded a protein of 438 amino acids. Southern analysis revealed the gene (tv44) of T. vaginalis to be single copy. The tv44 gene was down-regulated at both the transcriptional and translational levels in iron-depleted trichomonads as well as in parasites after contact with immortalized MS-74 vaginal epithelial cells (VECs). Immunofluorescence on non-permeabilized organisms confirmed surface localization of TV44, and the intensity of fluorescence was reduced after parasite adherence to VECs. Lastly, an identical protein and gene were present in Tritrichomonas foetus and Trichomonas tenax.This is the first report of a T. vaginalis gene (tv44) encoding a surface protein (TV44) reactive with an IgA mAb, and both gene and protein were conserved in human and bovine trichomonads. Further, TV44 is independently down-regulated in expression and surface placement by iron and contact with VECs. TV44 is another member of T. vaginalis genes that are regulated by at least two independent signaling mechanisms involving iron and contact with VECs.The amitochondriate protist Trichomonas vaginalis is responsible for the number one incidence of sexually transmitted disease (STD) worldwide with ~9 million new cases of vaginitis in the US and 250 million cases worldwide [1-3]. There are serious health consequences for women, including adverse pregnancy outcomes, risk for cervical cancer, pelvic inflammatory disease, infertility, and infection by other STD agents [4-8]. Symptomatic women may experience foul-smelling discharge, severe irritation, and abdominal pain while some men will have a non-gonococcal, non-chlamydial urethritis. Trichomonosis is now appreciated to increase the portal of entry and exit for HIV [9,10], and the disproportionate incidence of this STD among American mino