Experimental Infection of Pig-Tailed Macaques (Macaca nemestrina) with Mycoplasma genitalium

Abstract

Mycoplasma genitalium is an underappreciated cause of human reproductive tract disease, characterized by persistent, often asymptomatic, infection. Building on our previous experiments using a single female pig-tailed macaque as a model for Cosgrove Sweeney, and P. A. Totten, Infect Immun 81:2938 -2951, https://doi.org/10.1128/IAI.01322-12), we cervically inoculated eight additional animals, two of which were simultaneously inoculated in salpingeal tissue autotransplanted into abdominal pockets. Viable M. genitalium persisted in the lower genital tract for 8 weeks in three animals, 4 weeks in two, and 1 week in one; two primates resisted infection. In both animals inoculated in salpingeal pockets, viable M. genitalium was recovered for 2 weeks. Recovery of viable M. genitalium from lower genital tract specimens was improved by diluting the specimen in broth and by Vero cell coculture. Ascension to upper reproductive tract tissues was not detected, even among three persistently infected animals. M. genitalium-specific serum antibodies targeting the immunodominant MgpB and MgpC proteins appeared within 1 week in three animals inoculated both cervically and in salpingeal pockets and in one of three persistently infected animals inoculated only in the cervix. M. genitaliumspecific IgG, but not IgA, was detected in cervical secretions of serum antibodypositive animals, predominantly against MgpB and MgpC, but was insufficient to clear M. genitalium lower tract infection. Our findings further support female pigtailed macaques as a model of M. genitalium infection, persistence, and immune evasion. KEYWORDS Mycoplasma genitalium, animal model, antibody response, persistent infection, primateM ycoplasma genitalium is a fastidious, cell wall-less bacterium notable for its small size (0.1 m), reduced genome (580 kbp), parasitic lifestyle, and apparent specificity for the human host. In men, M. genitalium is a frequent cause of acute and chronic nonchlamydial nongonococcal urethritis (1-4), and in women, M. genitalium is increasingly recognized for its role in cervicitis, pelvic inflammatory disease, preterm birth, and spontaneous abortion (reviewed in reference 5). Additional studies have implicated M. genitalium in tubal factor infertility (6, 7) and endometritis (8). Significantly, M. genitalium infection increases cervical shedding (9) and the risk of acquiring and transmitting HIV (10, 11), further highlighting the potential adverse outcomes resulting from this underappreciated bacterial pathogen.M. genitalium infection can persist for months to years in infected patients (12-19), despite the presence of antibodies to M. genitalium in genital exudates of infected women (20) and in the sera of infected men (21). These data suggest that M. genitalium

Mycoplasma genitalium Nonadherent Phase Variants Arise by Multiple Mechanisms and Escape Antibody-Dependent Growth Inhibition

“…Phase and antigenic variations are also classically presumed to be mechanisms of immune evasion, thereby promoting recurrent and persistent infection. In this regard, in a primate model of M. genitalium infection, the appearance of antibodies to specific sequences of MgpB correlates with the clearance of those sequences from the genital tract, consistent with a model of selection and antigenic variation (44,45). Although antigenic variants may avoid antibodies recognizing MgpBC variable regions, the C-terminal conserved domain of MgpB is the most immunogenic region (46)(47)(48).…”

“…SDS-PAGE analysis of total M. genitalium proteins was performed according to standard procedures: 8% polyacrylamide gels were loaded with whole-cell lysates (10 g of total protein per lane), electrophoresed, and then stained with Coomassie blue. Immunoblot assays were performed as described previously (45) using antibodies (diluted 1:1,000) specific to amino acids 1123 to 1136 of MgpB combined with antibodies (diluted 1:5,000) specific to amino acids 36 to 308 of MgpC (44), followed by peroxidase-conjugated goat anti-rabbit IgG (whole molecule; Sigma-Aldrich) and colorimetric detection.…”

“…Cultures were treated with antibody and complement as described above and then cultured in SP-4 broth. Every 1 to 2 days, adherent bacteria were scraped into the culture supernatant and an aliquot was removed for genome quantitation by qPCR targeting the strain-typing region of mgpB, as previously described (45).…”

Contribution of the swine model in the study of human sexually transmitted infections

“…NHP studies: M. genitalium infection established classically by the urogenital route induces clinical manifestations in pig-tailed macaques similar to the ones observed in humans with a large number of polymorphonuclear leukocytes infiltrating the genital tract (Wood et al, 2017). In addition a specific serum antibody response could be demonstrated further proving host susceptibility (Wood et al, 2017 Swine model: No swine model has been described for the study of M. genitalium and since this bacterium is very restricted to a small number of primates, the opportunity to develop a new model in the pig seem limited and would need further assessment.…”

“…To date, few studies have been conducted to establish an animal model to obtain better knowledge of the M. genitalium pathogenesis. The literature includes mainly studies using several NHP infection surrogate models including chimpanzees (Pan troglodytesnot allowed anymore) and pig-tailed macaques to investigate pathogenesis and host responses (Taylor-Robinson et al, 1987;Wood et al, 2017).…”