Antibodies to Trichomonas vaginalis surface glycolipid

Abstract

Background: Human trichomoniasis is the most common non-viral sexually transmitted disease, yet immune responses are not well studied.

Methods: Since the Trichomonas vaginalis lipophosphoglycan (TvLPG) is an important virulence factor, a bank of eight monoclonal antibodies was generated to define the antigen in clinical isolates. The TvLPG-specific antibody response of women who were culture positive (n=33) or negative (n=33) for T vaginalis infection was determined by isotype-specific ELISA.

Results: The bank of monoclonal antibodies reacted with conserved surface TvLPG epitopes in 27 isolates from pregnant women at their first prenatal visit. Conserved TvLPG epitopes were shown to be surface exposed by immunofluorescence. Sera collected from the same patients at the same time were assayed for specific antibodies. Serum and vaginal secretions from 33 T vaginalis-positive women had statistically higher IgG anti-TvLPG levels than age-matched and race-matched negative controls in the same clinical study (p<0.01). Vaginal IgA anti-TvLPG levels of the women with trichomoniasis were almost significantly higher than controls (p=0.055). Infected women with normal pregnancies had significantly higher vaginal IgG anti-TvLPG values than infected women with adverse outcomes of pregnancy.

Conclusions: These antibody responses show that infected women can respond to the conserved TvLPG antigen. Since antibodies to trichomonad surface LPG protect in a bovine model of trichomoniasis, the role of these antibodies in the human disease should be investigated.

Keywords: ANTIBODIES; ANTIGEN; GENITAL TRACT INFECT; TRICHOMONAS.

Figure 1

Reactivity of monoclonal antibodies. (A) Western blot of reactivity of monoclonal antibodies with Trichomonas vaginalis. Note the two broad bands, characteristic of highly glycosylated antigens. The conjugate control with no primary antibody was negative. Molecular weight markers are on the left. (B) Reactivity of monoclonal antibodies with T vaginalis and Tritrichomonas foetus fixed parasites or with purified LPG. Reactivity with mAb 14B11 is shown. Other antibodies gave similar results. Note that there is strong reactivity with T vaginalis and TvLPG but little reactivity (below the 0.2 absorbance cut-off) with T foetus or TfLPG. (C and D) Reactivity of monoclonal antibodies with the TvLPG ceramide-phosphoinositol-glycan core (CPI-GC) in ELISA.

Figure 2

Immunofluorescence reactivity of monoclonal antibody 5G6 with Trichomonas vaginalis strain T1. Note surface reactivity. Incubation with an unrelated bacterial surface mAb (3G9) gave no reactivity. See the online version for colours. Key: Red=Alexa 564 antimouse immunoglobulin; Blue=DAPI nuclear stain.

Figure 3

Comparison of vaginal IgG and IgA anti-Trichomonas vaginalis lipophosphoglycan (TvLPG) antibody ELISA absorbances in patients with positive T vaginalis cultures at the first prenatal visit who had adverse outcomes of pregnancy (AOP) or normal outcomes of pregnancy (NOP). Note that there were no differences in vaginal IgA anti-TvLPG antibodies in these two subgroups but that patients with trichomoniasis with AOP had significantly lower IgG anti-LPG values than those with normal pregnancy outcomes (p=0.019).