Antibody signature of spontaneous clearance of Chlamydia trachomatis ocular infection and partial resistance against re-challenge in a nonhuman primate trachoma model.

BACKGROUND: Chlamydia trachomatis is the etiological agent of trachoma the world's leading cause of infectious blindness. Here, we investigate whether protracted clearance of a primary infection in nonhuman primates is attributable to antigenic variation or related to the maturation of the anti-chlamydial humoral immune response specific to chlamydial antigens. METHODOLOGY/PRINCIPAL FINDINGS: Genomic sequencing of organisms isolated throughout the protracted primary infection revealed that antigenic variation was not related to the inability of monkeys to efficiently resolve their infection. To explore the maturation of the humoral immune response as a possible reason for delayed clearance, sera were analyzed by radioimmunoprecipitation using intrinsically radio-labeled antigens prepared under non-denaturing conditions. Antibody recognition was restricted to the antigenically variable major outer membrane protein (MOMP) and a few antigenically conserved antigens. Recognition of MOMP occurred early post-infection and correlated with reduction in infectious ocular burdens but not with infection eradication. In contrast, antibody recognition of conserved antigens, identified as PmpD, Hsp60, CPAF and Pgp3, appeared late and correlated with infection eradication. Partial immunity to re-challenge was associated with a discernible antibody recall response against all antigens. Antibody recognition of PmpD and CPAF was destroyed by heat treatment while MOMP and Pgp3 were partially affected, indicating that antibody specific to conformational epitopes on these proteins may be important to protective immunity. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that delayed clearance of chlamydial infection in NHP is not the result of antigenic variation but rather a consequence of the gradual maturation of the C. trachomatis antigen-specific humoral immune response. However, we cannot conclude that antibodies specific for these proteins play the primary role in host protective immunity as they could be surrogate markers of T cell immunity. Collectively, our results argue that an efficacious subunit trachoma vaccine might require a combination of these antigens delivered in their native conformation.

Placental site trophoblastic tumor: analysis of presentation, treatment, and outcome.

OBJECTIVE: Placental-site trophoblastic tumor (PSTT) is the rarest form of gestational trophoblastic disease (GTD). A risk-adapted treatment approach has been advocated, but controversy exists as to the most important prognostic markers for this disease. Our goal was to determine the prognostic markers for patients with PSTT seen at our center. METHODS: We conducted a retrospective analysis of patients with PSTT seen at a single tertiary care center between 1996 and 2011. The association of FIGO stage, interval from antecedent pregnancy, antecedent pregnancy outcome, human chorionic gonadotropin (hCG) level, and age to overall survival was examined using univariate log-rank tests. Presentation, treatment, and outcome were summarized using descriptive statistics. RESULTS: Data from 17 patients were analyzed. Eight (47%) had Stage I/II disease and 9 (53%) had Stage III/IV disease. Median overall survival for the entire cohort was 86 months (range, 2-101 months). Median duration of follow-up for surviving patients was 56 months. Increasing FIGO stage (I-III versus IV) was associated with a worse overall survival (p=0.009). Interval from antecedent pregnancy (≥12months), antecedent pregnancy outcome (full-term), hCG (≥1000 IU/L), and age (≥40) were not associated with worse survival. CONCLUSION: FIGO stage, specifically Stage IV disease, was the most important predictor of overall survival in our cohort of PSTT patients.

A live-attenuated chlamydial vaccine protects against trachoma in nonhuman primates.

Blinding trachoma is an ancient neglected tropical disease caused by Chlamydia trachomatis for which a vaccine is needed. We describe a live-attenuated vaccine that is safe and efficacious in preventing trachoma in nonhuman primates, a model with excellent predictive value for humans. Cynomolgus macaques infected ocularly with a trachoma strain deficient for the 7.5-kb conserved plasmid presented with short-lived infections that resolved spontaneously without ocular pathology. Multiple infections with the attenuated plasmid-deficient strain produced no inflammatory ocular pathology but induced an anti-chlamydial immune response. Macaques vaccinated with the attenuated strain were either solidly or partially protected after challenge with virulent plasmid-bearing organisms. Partially protected macaques shed markedly less infectious organisms than controls. Immune correlates of protective immunity were not identified, but we did detect a correlation between MHC class II alleles and solid versus partial protection. Epidemiological models of trachoma control indicate that a vaccine with this degree of efficacy would significantly reduce the prevalence of infection and rates of reinfection, known risk factors which drive blinding disease.