Epitopes of the Highly Immunogenic Trichomonas vaginalis α-Actinin Are Serodiagnostic Targets for Both Women and Men

Abstract

There is a need for a point-of-care serodiagnostic test for women and men for sexually transmitted infections (STIs) caused by Trichomonas vaginalis. Sera from women with this STI and sera from men that were analyzed in studies showing a relationship between serostatus and prostate cancer are highly seropositive in response to trichomonad ␣-actinin and its truncated protein (ACT-P2) (positive control sera). Epitope mapping experiments showed that positive control sera from women had antibodies to 13 distinct epitopes, 5 of which were detected by positive control sera from men. Sera from women and men that were unreactive with ␣-actinin (negative control sera) failed to detect any of the epitopes or other ␣-actinin amino acid sequences. The T. vaginalis ␣-actinin amino acid sequence and the sequences of the epitopes showed little or no identity with those of other proteins of microbial pathogens or the human ␣-actinin 1 (HuACTN1) homolog. Immunoassays such as dot blot, immunoblot, and enzyme-linked immunosorbent assays were used. Positive control sera did not detect HuACTN1 in immunoassays, and the range of levels of identity of ␣-actinin epitopes with HuACTN1 was 0% to 50%. Comparison of the T. vaginalis ␣-actinin epitopes with proteins in data banks, such as Tritrichomonas suis, Candida albicans, and Saccharomyces cerevisiae proteins, gave a range of identity levels of 0% to 22%. Specific 15-mer peptide epitopes of ␣-actinin with low to no identity with other proteins were synthesized and were reactive with positive control sera only. These findings identify epitopes of ␣-actinin as candidate serodiagnostic targets and suggest strongly that a highly seropositive reaction to ␣-actinin suggests exposure to T. vaginalis.T richomonas vaginalis is the most common nonviral causative agent for sexually transmitted infections (STIs). The adverse consequences for the health of women have been well documented (1, 2). Although in the literature it is routinely reported that men infected by their partners resolve their infections, there is neither experimental evidence nor clinical studies proving this. Reports have shown the expression of numerous virulence factors that permit this ancient protist to survive in the changing host environment of the female urogenital region (3-18). Iron is an important modulator of upregulation and downregulation of the expression of virulence genes (8,(19)(20)(21)(22)(23)(24)(25). Key steps for host colonization result from overcoming the urogenital mucous layer (18) in preparation for specific cytoadherence to vaginal epithelial cells (7,9,11,22,24). The intimacy of the host-parasite relationship during colonization and infection is exceedingly complex, as evidenced by the large number of proteinases (4,11,15,26) and the secretion by trichomonads of large amounts of putrescine for spermine uptake and back-conversion to spermidine (13,26). This coating of T. vaginalis by polyamines and host macromolecules affects levels of cytoadherence and cytotoxicity (3, 13).More recently, epidemiologic...

Persistence of Trichomonas vaginalis serostatus in men over time

“…Men with scores ≥3+ were considered seropositive and those with scores ≤2+ were considered seronegative, consistent with the most recent analysis of Tv infection and PCa [6]. Sera with scores ≥3+ are also known to have antibodies to numerous trichomonad proteins by immunoblotting of total Tv proteins [16]. …”

“…This assay detects IgG antibodies against recombinant Tv α-actinin protein [5, 16]. We ran baseline and repeat plasma samples for each participant in duplicate in the same batch.…”

“…We obtained negative control sera (scores ≤2+) from individuals without a history of Tv or other STIs, and positive control sera (scores ≥3+) from patients with Tv infection [17]. Negative control sera had no detectable reactivity to trichomonad proteins blotted onto nitrocellulose after SDS-PAGE of total Tv proteins and immunoblotting, whereas positive control sera readily detected trichomonad proteins by immunoblotting [16, 18]. Sera with scores of 1+ or 2+ gave non-specific reactions above baseline by ELISA.…”

Trichomonas vaginalis infection and risk of prostate cancer: associations by disease aggressiveness and race/ethnicity in the PLCO Trial

“…We obtained control specimens with scores ≤2+ from individuals without a history of T. vaginalis or other STIs, and specimens with scores ≥3+ from patients with known T. vaginalis infection [18]. Specimens with scores ≥2+ had no detectable reactivity to trichomonad proteins blotted onto nitrocellulose after SDS-PAGE of total T. vaginalis proteins and immunoblotting, whereas those with scores ≥3+ readily detected trichomonad proteins [19, 20]. Specimens with scores of 1+ and 2+ exhibited non-specific reactions above baseline by ELISA.…”

Comparison between mixed lysate antigen and α-actinin antigen in ELISA for serodiagnosis of trichomoniasis

“…Recently, several candidate antigens, such as specific 15-mer peptide epitopes of α-actinin, TvMP50 metalloproteinase, glycolipid, have been suggested for the serodiagnosis of T. vaginalis infection [12][13][14]. The development of an appropriate antigen for ELISA is needed for serodiagnosis to facilitate epidemiological studies on the association of trichomoniasis with other diseases including prostate cancer.…”