Antigenic variation of Mycoplasma genitalium during persistent genital tract infection of pig-tailed macaques

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PROJECT SUMMARY Mycoplasma genitalium (MG), a sexually transmitted bacterial pathogen, is increasingly recognized as a significant public health concern. The prevalence of MG ranges from 1-4% in population-based studies to more than 20% in patients at high risk of acquiring sexually transmitted infections. The disease spectrum of MG is similar to Neisseria gonorrhoeae and Chlamydia trachomatis, and includes urethritis in men and cervicitis in women. Of particular concern, MG infection is associated with serious upper reproductive tract sequelae in women including pelvic inflammatory disease, infertility, preterm birth, and spontaneous abortion. Alarmingly, antimicrobial resistance in MG is increasing: 40-100% of strains are completely resistant to azithromycin and some infections are totally untreatable with US approved therapies. The recent FDA approval of two MG diagnostic tests will certainly increase public awareness of MG and demands for improved treatment. An animal model is urgently needed to understand the naturally history of MG infection including mechanisms of persistence and immune evasion, studies that are difficult in patients given the imperative to treat symptomatic infection. We have optimized our pig-tailed macaque model of persistent genital tract infection and now propose to use this model to study the role of antigenic variation in immune avoidance. Extending our previous work defining mechanisms of antigenic and phase variation of the immunodominant MgpB and MgpC adhesin proteins, we will determine if variation is required for persistence in the genital tract. First, using whole genome sequencing we will correlate the appearance of variants during 18 weeks of infection with the appearance of antibodies specific to MgpB and MgpC in three MG-infected primates and archived specimens from prior primate experiments. Second, the ability of the identical vs variant strain to re-infect animals that clear genital tract infection will be assessed in order to understand strain specific immunity. Third, a non-variable, “locked” MG strain that is unable to undergo antigenic variation will be constructed and characterized in vitro. Three primates will be inoculated cervically with a mixed inoculum of wild type and “locked” MG to compare the persistence and upper tract ascension of the two strains simultaneously over the 18 weeks of our model. All infected primates will undergo necropsy to examine the cervix, uterus, and Fallopian tubes for gross pathology and histology, and to assess the presence of MG in the upper reproductive tract. These experiments will not only determine if gene variation is required for persistence but will also provide additional observations in individual primates of the natural history of lower tract persistence, upper tract ascension, and immune response (including cytokines, cellular infiltrates and antibodies specific for conserved and variable MG antigens). These proposed experiments are highly significant in that they fill research gaps prioritized by NIAID-sponsored panels, namely the development of an animal model, the exploration of the role of MG in serious upper reproductive tract disease in women, and the development of an MG serologic test.