Advances in Chlamydia trachomatis Vaccination: Unveiling the Potential of Major Outer Membrane Protein Derivative Constructs.

Chlamydia (C.) trachomatis, a leading cause of sexually transmitted infections (STIs) worldwide, continues to be a significant public health concern. The majority of infections are asymptomatic and, when left untreated, severe sequelae such as infertility and chronic pelvic pain can occur. Despite decades of research, an effective vaccine remains elusive. This review focuses on the potential of Major Outer Membrane Protein (MOMP)-derived constructs as promising candidates for C. trachomatis vaccination. MOMP, the most abundant protein in the outer membrane of C. trachomatis, has been a focal point of vaccine research over the years due to its antigenic properties. To overcome issues associated with the use of full MOMP as a vaccine antigen, derivative constructs have been studied. As these constructs are often not sufficiently immunogenic, antigen delivery systems or accompanying adjuvants are required. Additionally, several immunization routes have been explored with these MOMP-derived vaccine antigens, and determining the optimal route remains an ongoing area of research. Future directions and challenges in the field of C. trachomatis vaccination are discussed.

Challenges in Chlamydial Serology: Insights from a Belgian and a Dutch Population Cohort.

Serology routinely serves as a diagnostic tool to confirm Chlamydia infections in humans. Particularly in delayed settings, such as post-outbreak scenarios where the acute phase of infection has subsided, serology is invaluable. Multiple studies, nonetheless, indicate deficiencies in specificity and sensitivity of current chlamydial antibody detection assays. Incorporation of multiple antigens per target is known to improve the accuracy of chlamydial serological assays. We, therefore, used the recomLine test (Mikrogen diagnostics) on serological samples of two cohorts, as it is the only commercially available test allowing detection of antibodies against three human pathogenic Chlamydia species (C. trachomatis, C. pneumoniae and C. psittaci) using multiple antigens per target. The first cohort (n = 156; samples collected between 2008 and 2022 during a C. trachomatis screening initiative) comprised women from the Netherlands (NL) with past exposure to C. trachomatis, while the second cohort (n = 44; samples collected in 2018 in a health examination survey) consisted of Belgian citizens (BE) with occupational or recreational exposure to chickens, representing a risk population for C. psittaci. The test indicated a statistically equivalent C. pneumoniae seroprevalence in both cohorts (39.10% in NL and 34.09% in BE; p = 0.337). As expected C. trachomatis seroprevalence was significantly higher (p < 0.001) in the Dutch cohort (48.72%), as compared to the Belgian cohort (4.55%). Lastly, C. psittaci seroprevalence did not significantly differ between the two groups (2.27% in BE and 1.92% in NL; p = 0.633), even though a higher prevalence was expected for the Belgian cohort. This prompts us to question whether the Belgian cohort truly constituted a C. psittaci risk population or whether the recomLine test is susceptible to cross-reaction of species-specific antibodies, thereby increasing C. psittaci prevalence in the Dutch cohort. We advocate for the development of affordable, highly sensitive antibody detection assays that can effectively distinguish between chlamydial species, addressing the increasing demand for enhanced serological testing methodologies.

The association between non-viral sexually transmitted infections and pregnancy outcome in Latin America and the Caribbean: A systematic review.

Introduction: Non-viral sexually transmitted infections are known to be associated with adverse pregnancy outcomes. For these pathogens, standard antenatal screening is not broadly performed in Latin America and the Caribbean. The aim of this study was to comprehensively review the association of non-viral sexually transmitted infections and neonatal outcomes among pregnant women in the region. Methods: Four databases (PubMed, Embase, SciELO and LILACS) were examined to identify eligible studies published up to September 2022. English or Spanish cross-sectional, case-control and cohort studies assessing the association of non-viral sexually transmitted infections and adverse pregnancy outcomes were evaluated. Articles were firstly screened by means of title and abstract. Potential articles were fully read and assessed for inclusion according to the eligibility criteria. Snowballing search was performed by screening of bibliographies of the chosen potentially relevant papers. Risk of bias within studies was assessed using the Joanna Briggs Institute reviewer's manual. Results: A selection of 10 out of 9772 search records from five Latin America and the Caribbean countries were included. Six studies associated Treponema pallidum infection with preterm birth (1/6), history of previous spontaneous abortion (2/6), fetal and infant death (1/6), low birth weight (1/6) and funisitis of the umbilical cord (1/6). Three studies associated Chlamydia trachomatis infection with preterm birth (2/3), ectopic pregnancy (1/3) and respiratory symptoms on the newborn (1/3). One study associated Mycoplasma genitalium infection with preterm birth. Conclusion: This review provides evidence on the association of non-viral sexually transmitted infections with adverse pregnancy outcomes. Further investigation is needed to establish more associations between non-viral sexually transmitted infections and pregnancy outcome, especially for Mycoplasma genitalium, Trichomonas vaginalis and Neisseria gonorrhoeae. Overall, this review calls for more research for public health interventions to promote screening of non-viral sexually transmitted infections during pregnancy, among high-risk population groups of pregnant women living in the region.

Belgian Cross-Sectional Epidemiological Study on Zoonotic Avian Chlamydia spp. in Chickens.

Chlamydia psittaci, Chlamydia gallinacea, and Chlamydia abortus are the most common Chlamydia spp. in chickens and have a confirmed or suggested zoonotic potential. No recent data are available on their prevalence and impact in the Belgian chicken industry or in the recreational chicken branch. Therefore, a cross-sectional epidemiological study was executed where samples were collected from both factory-farmed and backyard chickens. More specifically, pharyngeal chicken swabs were obtained from 20 chicken farms, 5 chicken abattoirs, and 38 different backyard locations and were analyzed using species-specific Polymerase Chain Reactions (PCRs) for the presence of the three avian Chlamydia spp. To investigate their zoonotic potential, samples were simultaneously collected from 54 backyard chicken caretakes and 37 professional chicken caretakers or abattoir employees and analyzed using species-specific PCRs as well. This study confirmed the presence of DNA of all three Chlamydia species in both the chicken industry and backyard settings. Chlamydia psittaci was the most prevalent in the industry chickens (11.0%), whereas Chlamydia gallinacea was the dominant species in the backyard chickens (14.5%). Chlamydia abortus infections were more common in the commercial chickens (9.0%) compared to the backyard chickens (2.6%). The DNA of all three species was also detected in humans (3.9% Chlamydia psittaci, 2.9% Chlamydia gallinacea, and 1.0% Chlamydia abortus).