For detection of anti-Chlamydia trachomatis antibodies by serological assays, use of classical whole-organism chlamydial antigens results in high cross-reactivity. These antigens bind mainly antibodies against the major outer membrane protein (OmpA) and bind antibodies against other immunodominant non-OmpA proteins to a lesser extent, resulting in poor assay sensitivity. The specificity of C. trachomatis serology is also compromised by the high prevalence of cross-reactive anti-C. pneumoniae antibodies in human populations. We previously identified 48 highly specific C. trachomatis B cell epitope peptide antigens of 21 immunodominant proteins. This study validated peptide antigen-based novel ELISAs that provide highly specific and sensitive detection of anti-C. trachomatis antibodies. Compared to four commercial ELISAs that achieved only poor sensitivities (51.5% to 64.8%), the combined signals of 5 to 11 peptides provided high sensitivity (86.5% to 91.8%) at the same 98% specificity. Thus, by using multiple peptide antigens of immunodominant proteins, we created simple ELISAs with specificity and sensitivity superior to standard C. trachomatis serodiagnosis.

Background. Chlamydia trachomatis can cause reproductive morbidities after ascending to the upper genital tract of women, and repeated infection can lead to worse disease. Data related to protective immune responses at the cervical mucosa that could limit chlamydial infection to the cervix and/or prevent reinfection inform vaccine approaches and biomarkers of risk. Methods. We measured 48 cytokines in cervical secretions from women having chlamydial cervical infection alone (n = 92) or both cervical and endometrial infection (n = 68). Univariable regression identified cytokines associated with differential odds of endometrial infection and reinfection risk, and multivariable stepwise regression identified cytokine ratios associated with differential risk. Results. Elevated interleukin (IL) 15/CXCL10 (odds ratio [OR], 0.55 [95% confidence interval {CI}, .37-.78]), IL-16/tumor necrosis factor-α (OR, 0.66 [95% CI, .45-.93]), and CXCL14/IL-17A (OR, 0.73 [95% CI, .54-.97]) cytokine ratios were significantly (P ≤ .05) associated with decreased odds of endometrial infection. A higher Flt-3L/IL-14 ratio was significantly (P = .001) associated with a decreased risk of reinfection (hazard ratio, 0.71 [95% CI, .58-.88]). Conclusions. Cytokines involved in humoral, type I interferon, and T-helper (Th) 17 responses were associated with susceptibility to C. trachomatis, whereas cytokines involved in Th1 polarization, recruitment, and activation were associated with protection against ascension and reinfection.

Chlamydia trachomatis (CT) is the most frequently reported bacterial sexually transmitted infection in the U.S., with 1 in 20 sexually active young women being infected. Infections are easily curable with antibiotics, but reinfections are frequent and infection can lead to reproductive tract sequelae. Adaptive immune responses generated during infection likely limit extent of infection, but frequently fail to prevent reinfection. We developed a 35 marker CyTOF panel to phenotype PBMCs. We examined PBMCs from women infected with CT alone (N=8), women with CT co-infected with gonorrhea or Mycoplasma genitalium (N=6), and from these same women 1 month post antibiotic treatment, and compared them to 11 healthy uninfected women. Compared to uninfected women, the frequency of B cells was increased in CT-infected women and remained elevated at 1 month, with no effects observed on various B cell subsets. Among T cells, Th1 and Tc1 percentages were reduced in CT-infected women and remained low at 1 month. Th2 and Th17 phenotype percentages were not different than uninfected women. Th1/Th2/Th17 cells expressing CD107a were reduced in CT-infected women, but rebounded towards normal at 1 month. Myeloid DCs were reduced in CT-infected women, but rebounded towards normal at 1 month. All of these differences were present regardless of coinfection. CD107a+ NK cells were reduced in CT-only infected women and failed to rebound at one month. The reductions in these various cell types is likely due to their trafficking to the infected tissue. CyTOF analysis of PBMCs from additional patients and of endometrial biopsy samples from these same subjects should provide important data related to the female host response to CT.

Background Chlamydia trachomatis (CT) is the leading bacterial sexually transmitted infection worldwide. CT can ascend to the upper reproductive tract in women, and cause tissue damage resulting in reproductive sequalae. Data from animal and human studies indicate a role for the Th1 cytokine, IFNγ, in protection from infection and disease. Methods We recruited 246 women at high risk for CT infection. Cervical swabs and endometrial biopsies were collected for detection of sexually transmitted pathogens, including CT, by nucleic acid amplification test (NAAT). Cervical secretions collected using cervical sponges were screened for 57 cytokines using multiplex bead arrays. Data were analyzed by logistic regression. Results 92 (37%) women were NAAT+ for CT in only their cervix and 69 (28%) women had CT infection detected at both their cervix and endometrium. Compared to women with endometrial infection, women with only cervical infection had higher levels of CX3CL1 (p<0.05), a potent chemoattractant of T cells and monocytes; CXCL14 (p<0.01), a chemoattractant and activator of dendritic cells, monocytes, and NK cells; and the Th1 inducing cytokine IL-12p70 (p=0.07). Conversely, type I IFN-inducible proteins CXCL9 (p<0.05) and CXCL10 (p<0.01) were significantly increased in women with endometrial infection, compared to women with cervical infection only. Conclusions Th1-associated cytokines in cervical secretions are associated with limitation of infection to the cervix, whereas type I IFN-associated chemokines are associated with endometrial CT infection. These proteins may be used as biomarkers to identify women at increased risk for upper reproductive tract pathology and those who could benefit from enhanced screening.