Monoclonal antibody to a major glycoprotein immunogen mediates differential complement-independent lysis of Trichomonas vaginalis

Abstract

An immunoglobulin G type 2a (IgG2a) monoclonal antibody (MAb), designated C20A3, which reacts with a highly immunogenic trichomonad membrane glycoprotein (approximately 270,000 daltons), produced complement-independent cytolysis of Trichomonas vaginalis organisms. Time- and temperature-dependent lysis of parasites was observed following incubation of washed, live T. vaginalis with certain concentrations of C20A3 IgG. Differential killing of trichomonal isolates and clones of a given isolate by C20A3 was dependent on the presence of the glycoprotein antigen on the parasite surface.

Phenotypes and protein-epitope phenotypic variation among fresh isolates of Trichomonas vaginalis

“…Test procedures were the same as described elsewhere (7), except that peroxidase-conjugated goat anti-human IgG or anti-mouse IgG were used as needed for the second type of antibody. dependent cytotoxicity (6) and resistance to antibody killing (5). It was necessary to evaluate many fresh isolates in order to confirm the results of these earlier studies performed primarily with isolates grown long term (7,8).…”

“…The phenotypes of Trichomonas vaginalis isolates, as defined by indirect immunofluorescence (IF) assay with monoclonal antibodies (MAbs) on the basis of the presence on (positive [Pos] phenotype) or absence (negative [Neg] phenotype) of key immunogens from trichomonal membranes (5)(6)(7)(8), may represent an important virulence determinant. It is interesting that trichomonads which are Neg phenotype still synthesize the molecule and can become Pos phenotype (7,8).…”

Relatedness of structures of a major immunogen in Trichomonas vaginalis isolates

“…Our initial attempts to raise monoclonal antibodies (MAbs) toward these immunogens resulted in almost all of the MAbs being directed toward one particular molecule, and all of approximately 40 hybridomas selected for future work produced MAbs which had identical epitope specificities (10). Interestingly, when a MAb called C20A3 was tested cytofluorometrically to examine trichomonal populations, two types of T. iaginalis isolates were resolved (8)(9)(10). These early observations have been supported by more recent studies with fresh in vivo isolates (4).…”

“…Trichomonas vaginalis is a urogenital protozoan parasite, and immunochemical characterization of the parasite surface has resulted in the identification of several prominent immunogens (1)(2)(3)(4)(6)(7)(8)(9)(10). Our initial attempts to raise monoclonal antibodies (MAbs) toward these immunogens resulted in almost all of the MAbs being directed toward one particular molecule, and all of approximately 40 hybridomas selected for future work produced MAbs which had identical epitope specificities (10).…”

Antimicrobial action of antibodies against Giardia muris trophozoites

“…Complement is not always required for the lysis of protozoans. For example, trophozoites of G. lamhiia were killed by a MoAb within 7 min of exposure to ihe MoAb [15], Killing has also been demonstrated against Trichomonas vaginalis trophozoites by parasite-specific MoAb in the absence of complement [24], The precise mechanism of killing by parasitespecific MoAbs in the absence of complement is unknown, although it is known that the MoAbs against Trypanosotnacruzi affect viability by inhibiting the incorporation of nucleic acid precursors into culture fomis of the parasite [25], The agglutination of the flagella by MoAbs may kill parasites by affecting their attachment to critical substrates. More research is needed lo define precisely the mechanism(s) of the eytotoxicity of MoAbs in the absence of complement.…”