Monoclonal antibody to a major surface glycoprotein immunogen differentiates isolates and subpopulations of Trichomonas vaginalis

Abstract

To produce monoclonal antibodies (MAbs) to highly immunogenic membrane proteins of Trichomonas vaginalis NYH286, the sera of subcutaneously infected BALB/c mice were first monitored for antibody to trichomonad surface proteins. The sera possessed antibody to one major surface protein by 7 days and antibody to numerous other trichomonad membrane proteins by 4 weeks postinfection. A hybridoma was then generated that synthesized an MAb, designated C20A3, which reacted to a parasite-derived glycoprotein possessing a molecular weight of 267,000 (267K glycoprotein). The immunogen corresponded to the single high-molecularweight immunogenic surface protein recognized by 7-day mouse antisera. The MAb differentiated T. vaginalis isolates by a whole-cell enzyme-linked immunosorbent assay and by indirect immunofluorescence, using either fixed or live organisms. All isolates, however, possessed C20A3-reactive material when tested by enzyme-linked immunosorbent assay, using detergent extracts of the isolates incubated with MAb-coated microtiter well plates. The epitope was accessible to antibody binding on live T. vaginalis organisms expressing the major immunogen, and the 267K glycoprotein was readily removed from the parasite membranes by trypsinizing the intact trichomonads. The antigen incorporated radiolabeled glucose, mannose, and acetate. Also, an unlabeled 267K glycoprotein on nitrocellulose blots was detected by '25I-concanavalin A and 1251-wheat germ agglutinin, confirming the glycoprotein nature of the immunogen. Finally, of seven isolates used in this study, one possessed a cross-reactive 170K, rather than 267K, antigen. The data reinforce the idea that antigenic heterogeneity among T. vaginalis isolates may be a function of the presence or absence of high-molecular-weight glycoprotein immunogens from trichomonal membranes.

Trichomonas vaginalis phenotypic variation occurs only among trichomonads infected with the double-stranded RNA virus.

“…The loss of viral dsRNA and the concomitant absence of the surface disposition of specific immunogens (Table 11) strengthens the likelihood of involvement of the virus in the sequestration of immunogens into trichomonal membranes. This is further reinforced by the detection of intrinsically labeled but not extrinsically labeled immunogen in the cytoplasm of negative phenotype trichomonads of isolates (2,4) and supopulations of isolates (3). Loss of virus, therefore, prevents expression of the C20A3 mAb-reactive immunogen on the parasite surface.…”

“…$ Metronidazole-resistant isolate. disposition of prominent immunogens (1)(2)(3). This capability is lost upon in vitro cultivation of most clinical isolates of T. vaginalis along with loss of the dsRNA (Tables I and II).…”

“…We do not know the mechanism(s) by which the dsRNA within certain T. vaginalis may regulate or influence the surface expression of certain immunogens such as those recognized by the mAbs (2,3). The loss of viral dsRNA and the concomitant absence of the surface disposition of specific immunogens (Table 11) strengthens the likelihood of involvement of the virus in the sequestration of immunogens into trichomonal membranes.…”

“…Trichomonas vaginalis is a major sexually transmitted parasite that inhabits primarily the vaginal tract of women. Very little is known about precise virulence factors of the pathogenic human trichomonads, although recent reports (1)(2)(3) indicate that the ability of these parasites to undergo phenotypic variation may be related to expression of certain virulence attributes . For example, parasites that lacked a repertoire of major immunogens on their surface (negative phenotype) displayed enhanced cytadherence and killing of host cells (3).…”

Antigenic variation of a cysteine-rich protein in Giardia lamblia.

“…Certain isolates of Trichomonas vaginalis are able to alternate between two different phenotypes (27), an ability that is associated with the presence of a dsRNA virus (28) . This phenomenon is clearly different from antigenic variation in G. lamblia in a number of ways : (a) the repertoire of surface antigens in Giardia appears extensive and reversion back to expression of CRP170 has not been observed (Nash, T. E., et al, submitted for publication) ; (b) the WB isolate used for these studies does not possess the dsRNA virus (Wang, C. C., personal communication) that is present in some isolates of Giardia (29); (c) in phenotypic variants of T. vaginalis, the previous surface antigen, while not present on the surface, is present in whole cell lysate (27).…”