Serotype 8- and serocluster-specific surface-expressed antigens of Ureaplasma urealyticum

Screening of an antigen target for immunocontraceptives from cross-reactive antigens between human sperm and Ureaplasma urealyticum

Epidemiologic studies indicated that some infertile men who were infected with Ureaplasma urealyticum displayed positive antisperm antibodies in their serum and/or semen. The purpose of this study was to investigate the possible mechanism of antisperm antibodies production after infection with U. urealyticum and to analyze the relationship between U. urealyticum and infertility. The existence of cross-reactive antigens (61, 50, and 25 kDa) between U. urealyticum and human sperm membrane proteins was confirmed. Among the cross-reactive antigens, the urease complex component UreG of U. urealyticum was determined. By searching the Swiss-Prot protein database, a pentapeptide identity (IERLT) between UreG and human nuclear autoantigenic sperm protein (NASP) was found. Furthermore, using Western blot analysis and enzyme-linked immunosorbent assay, the cross-reaction between the NASP and UreG was verified. Both anti-rUreG antibody and the antiserum against the synthetic peptide NASP393-408 containing the pentapeptide inhibited mouse sperm egg binding and fusion. After immunization by rUreG or the synthetic peptide, 81.2 and 75% female mice became sterile, respectively. The effect on fertility in mice immunized with the synthetic peptide was reversible. These findings proved for the first time that it was feasible to screen antigens for immunocontraceptives from cross-reactive antigens between sperm and microorganisms which induce infertility.

Development of a monoclonal antibody to a Ureaplasma urealyticum serotype 9 antigen

We produced a monoclonal antibody (MAb) to Ureaplasma urealyticum Vancouver, the serotype 9 standard strain. By immunoblotting, this MAb showed a single, 85-kDa band with the homologous serotype and a minor, 100-kDa band with serotype 2 but did not react with any other serotype standard strain. Clinical isolates of U. urealyticum were tested with this MAb and with two sets of polyclonal antisera against the 14 serotype standard strains. The use of MAb 9-2H9 correctly identified certain serotype 9 strains but did not react with wild-type strains lacking the serotype 9 determinant.

Immunoblot analysis of anti-Ureaplasma urealyticum antibody in pregnant women and newborn infants

The purpose of the present study was to determine the frequency in which antibody reactive to Ureaplasma urealyticum could be detected in a population of pregnant women and newborn infants. Serum samples from a prospective cohort of 80 healthy, U. urealyticum culture-positive and culture-negative pregnant women and a retrospective cohort of 522 infants born at between 25 and 42 weeks of gestation were studied by immunoblot analysis. Cultures of specimens from the lower genital tract were positive for U. urealyticum for 83% of the pregnant women, and serum immunoglobulin G (IgG) antibody which reacted to U. urealyticum was detectable in 93% of the pregnant women. Samples from five women (8%) had increases in the number of anti-U. urealyticum IgG bands over the course of the pregnancy. Samples from four of these five women had corresponding increases in the number of antibody bands present in IgA immunoblots. Six of the 522 samples from newborns or cord blood (1.1%) were positive for anti-U. urealyticum IgA; 5 of these 6 samples were also positive for IgM. The six anti-U. urealyticum IgA-positive infants were distributed as follows; 3 of 67 (4.5%) infants were delivered at 25 to 30 weeks of gestation, 3 of 176 (1.7%) infants were delivered at 31 to 34 weeks of gestation, and 0 of 279 infants were delivered at > or = 35 weeks of gestation. An antibody response to U. urealyticum can be detected in pregnant women and preterm infants and may serve as a marker of infection.

Identification of serotype 1-, 3-, and 6-specific antigens of Ureaplasma urealyticum by using monoclonal antibodies

Little is known about the antigens responsible for serotype specificity in Ureaplasma urealyticum. We produced monoclonal antibodies to U. urealyticum serotypes 1, 3, and 6, the serotypes most commonly found in pregnant women, and analyzed serotype-specific antigens for the three serotypes. Clinical isolates belonging to serotype 1, 3, or 6 were tested in immunoblots with these monoclonal antibodies. The immunoblot patterns of these isolates were, in most cases, different from each other as well as from those of the reference strains, indicating a high rate of antigenic variation among U. urealyticum strains.

Identification and characterization of serotype 4-specific antigens of Ureaplasma urealyticum by use of monoclonal antibodies

Monoclonal antibodies against Ureaplasma urealyticum serotype 4 were produced by immunizing BALB/c mice with whole-cell antigens of the U. urealyticum serotype 4 reference strain. Ten monoclonal antibodies differentiated into two groups were found: one group included five monoclonal antibodies recognizing a band in immunoblotting that had a molecular mass of 81 kDa, and a second group included another five monoclonal antibodies recognizing three bands in immunoblotting that had molecular masses of 81, 75, and 71 kDa. Fifteen clinical U. urealyticum isolates were selected for serotyping with serotype 4-specific monoclonal antibodies and polyclonal antisera 1 to 14. The results obtained with polyclonal and monoclonal antibodies suggest the existence of heterogeneity of the serotype antigens among clinical isolates of U. urealyticum serotype 4.

Characterization of the immunoglobulin A protease of Ureaplasma urealyticum

Ureaplasma urealyticum strains of all serotypes express a specific human immunoglobulin A1 protease that cleaves immunoglobulin A1 to produce intact Fab and Fc fragments. The use of a variety of inhibitors suggests that the enzyme is a serine protease. N-terminal sequencing of the Fc digestion product showed that the enzyme cleaves between the proline and threonine residues 235 and 236 in the hinge region of the heavy chain of immunoglobulin A1.

Palmitoylated proteins in Ureaplasma urealyticum

After incubation of Ureaplasma urealyticum serotype 8 in the presence of 3H-labeled palmitic acid, about 25 acylated proteins were detected by electrophoresis and fluorography. Of these, at least six were shown to be antigenic by immunoprecipitation of solubilized palmitate-labeled cells with a homologous polyclonal serum. These six included the serotype 8-specific surface-expressed 96-kDa antigen. After phase partition of palmitate-labeled cells with Triton X-114, all but six acylated proteins partitioned entirely into the detergent phase. The others, including the 96-kDa antigen, partitioned preferentially into the detergent phase and were apparently amphipathic. These results are consistent with the acylated proteins being mainly membrane associated.

Variable antigens of Ureaplasma urealyticum containing both serovar-specific and serovar-cross-reactive epitopes

Currently there are 14 recognized serovars of Ureaplasma urealyticum, and it has been postulated that only certain ones may be associated with disease and that lack of serovar-specific antibody may be an important risk factor. Unfortunately, ureaplasma antigens important in the human immune response and disease pathogenesis are poorly defined. By using sera from ureaplasma-infected patients and antiureaplasma monoclonal antibodies, the present study has demonstrated, for serovars 3, 8, and 10, antigens which (i) are species specific, (ii) contain both serovar-specific and cross-reactive epitope(s), (iii) are produced not only in vitro but also in vivo, (iv) undergo a high rate of structural variation in vitro, (v) are present and structurally variable on invasive ureaplasma isolates (i.e., those from placenta, lung, and cerebrospinal fluid), and (vi) are among the predominant antigens recognized during infections in humans. Furthermore, we have shown that monoclonal antibodies to these antigens can inhibit the growth of the organisms in vitro, indicating the potential for these antigens to be important for host defense.