Chlamydia trachomatis as a Current Health Problem: Challenges and Opportunities

Study Models for Chlamydia trachomatis Infection of the Female Reproductive Tract

Chlamydia trachomatis (Ct) is a leading cause of sexually transmitted infections globally, often resulting in inflammatory disorders, ectopic pregnancies, and infertility. Studying Ct's pathogenesis remains challenging due to its unique life cycle and host-specific interactions, which require diverse experimental models. Animal studies using mouse, guinea pig, pig, and non-human primate models provide valuable insights into immune responses, hormonal influences, and disease progression. However, they face limitations in terms of translational relevance due to physiological differences, as well as ethical concerns. Complementing these, in vitro systems, ranging from simple monolayer to advanced three-dimensional models, exhibit improved physiological relevance by replicating the human tissue architecture. This includes the detailed investigation of epithelial barrier disruptions, epithelium-stroma interactions, and immune responses at a cellular level. Nonetheless, in vitro models fall short in mimicking the intricate tissue structures found in vivo and, therefore, cannot faithfully replicate the host-pathogen interactions or infection dynamics observed in living organisms. This review presents a comprehensive overview of the in vivo and in vitro models employed over the past few decades to investigate Ct and its pathogenesis, addressing their strengths and limitations. Furthermore, we explore emerging technologies, including organ-on-chip and in silico models, as promising tools to overcome the existing challenges and refine our understanding of Ct infections.

Pgp3 monoclonal antibody inhibits the pathogenicity of Chlamydia muridarum to the genital tract of mice

BACKGROUND

Chlamydia trachomatis (Ct) is the leading cause of tubal inflammation in women, with a high tendency for persistent asymptomatic infections. Antibiotics are currently the primary treatment for Ct infections of the reproductive tract. However, mounting evidence indicates an increasing incidence of persistent infections and recurrence due to antibiotic treatment failure, highlighting the urgent need for novel therapeutic approaches.

METHODS

In this study, a monoclonal antibody against plasmid-encoded protein Pgp3 was prepared using hybridoma technology and its effects on the pathogenicity of Ct were investigated both in vitro and in vivo.

RESULTS

Infectivity of Chlamydia muridarum (Cm) elementary bodies (EBs) increased after incubation with His-Pgp3. When Pgp3mAb-pretreated Ct EBs or Cm-infected cell lysates were used to inoculate HeLa cells, a significantly reduced number of inclusions was observed compared with untreated controls. Cm-infected HeLa cells began to secrete Pgp3 after 6 h. Infection with Cm progeny was significantly inhibited by the addition of Pgp3mAb co-cultured during the first developmental cycle of Cm. Immunofluorescence assays revealed that Pgp3mAb could not enter the host cells. His-Pgp3 stimulated the secretion of IL-6 and IL-8 in human fallopian tube epithelial cells, while Pgp3mAb inhibited this pro-inflammatory effect of His-Pgp3. Cm-infected mice subcutaneously injected with Pgp3mAb demonstrated reduced shedding of live organisms in the lower genital tract, shorter infection cycles, reduced hydrosalpinx, and a reduced inflammatory response.

CONCLUSION

Pgp3 enhanced Cm infectivity in host cells. In vitro, Pgp3mAb inhibited Cm infection by binding to secreted Pgp3 and membrane-bound Pgp3, with a more pronounced effect on secreted Pgp3. Furthermore, Pgp3mAb inhibited the pro-inflammatory effects of Pgp3, thereby attenuating the inflammatory response. Subcutaneous administration of Pgp3mAb effectively reduced Cm-induced pathogenicity in the murine reproductive tract.

Chlamydia trachomatis: From Urogenital Infections to the Pathway of Infertility

Chlamydia trachomatis (CT) is a major cause of sexually transmitted infections (STIs) worldwide, with significant implications for reproductive health. The bacterium's genome contains highly polymorphic regions, influencing both the type and severity of infections. These genetic variations, particularly those occurring in the major outer membrane protein (MOMP) gene, are critical for classifying the bacterium into distinct serovars and enable CT to adapt to diverse host environments, contributing to its immune evasion, persistence, and pathogenicity. Persistent or untreated urogenital infections can lead to chronic inflammation, tissue damage, and pelvic inflammatory disease, ultimately increasing the risk of ectopic pregnancy, spontaneous abortion, and infertility. This review consolidates current knowledge on the genetic diversity of CT, its potential role in modulating infection outcomes, and its immune evasion mechanisms. By integrating scientific evidence linking chlamydial infections to infertility, we underscore the urgent need for targeted research to address this critical public health challenge.

The secreted host-cell protein clusterin interacts with PmpD and promotes Chlamydia trachomatis infection

Attachment and uptake into host cells are pivotal steps in the life cycle of the Chlamydiaceae, a family of obligate intracellular pathogens. Chlamydia trachomatis (Ctr) possesses a family of nine polymorphic membrane proteins (Pmps), which have been shown to be crucial for adhesion and internalization. However, the host-cell molecules involved have so far remained unknown. Here, we show that a fragment of Ctr PmpD, which forms high-molecular-weight oligomers in solution and adheres to epithelial cells, also binds to secreted clusterin (sCLU), a chaperone-like protein that is secreted into the extracellular space by the host cell, and forms part of the chaperone- and receptor-mediated extracellular protein degradation (CRED) pathway. Using in vitro assays, we demonstrate that sCLU interacts directly with soluble rPmpD. In infection experiments, depletion of sCLU from the culture medium leads to a significant decrease in Ctr infection. Thus, sCLU is the first host-cell interaction partner identified for a Ctr Pmp and the first case in which sCLU has been shown to be a vital component for the establishment of a bacterial infection.

Screening for STIs: Results of a Health-Promotion Programme in a Portuguese University

Sexually Transmitted Infections (STIs) are an important and growing public health concern. Implementation of screening programmes and awareness campaigns are crucial to mitigate this problem. A university in the central region of Portugal has devised a health-promotion programme, named Protection+, specifically directed towards the sexual health of the university community. The present study aimed to evaluate the results of the different actions undertaken as part of the health-promotion programme during the 2023-2024 academic year. Chlamydia, gonorrhoea, trichomoniasis and infection with Mycoplasma genitalium were assessed through real-time polymerase chain reaction protocols. Syphilis, infection with HIV, HBV and HCV were assessed through immunological assays. The adherence to the health-promotion programme after the awareness campaigns was also evaluated. STIs have been diagnosed in 13.7% of the 475 screened participants. Chlamydia was the STI most frequently diagnosed (8.4%), followed by infection with M. genitalium (2.3%), T. pallidum (2.0%) and N. gonorrhoeae (1.1%). HIV, HBV and HCV were diagnosed in a residual number of cases, and T. vaginalis was not detected in any of the screened participants. At the time of diagnosis, more than half of the infected patients were asymptomatic. After the implementation of awareness campaigns, an increase in the adherence to STI screening was observed, with the expected simultaneous increase in STI diagnoses. The high prevalence of STIs, particularly chlamydia, in the university population, along with the asymptomatic nature of these infections, demonstrated the importance of STI screenings and the implementation of campaigns that raise awareness on the prevention and consequences of untreated STIs.

Chlamydia trachomatis Inc Ct226 is vital for FLI1 and LRRF1 recruitment to the chlamydial inclusion

The obligate intracellular pathogen, Chlamydia trachomatis, establishes an intracellular niche within a host membrane-derived vacuole called the chlamydial inclusion. From within this inclusion, C. trachomatis orchestrates numerous host-pathogen interactions, in part, by utilizing a family of type III secreted effectors, termed inclusion membrane proteins (Incs). Incs are embedded within the inclusion membrane, and some function to recruit host proteins to the inclusion. Two such recruited host proteins are leucine rich repeat Flightless-1 interacting protein 1 (LRRF1/LRRFIP1) and its binding partner Flightless 1 (FLI1/FLII). Previously, LRRF1 has been shown to interact with Inc protein Ct226/CTL0478. This is the first study to examine interactions of FLI1 with candidate Incs or with LRRF1 during infection. We hypothesized that FLI1 recruitment to the inclusion would be dependent on LRRF1 localization. We demonstrated that FLI1 co-immunoprecipitated with Ct226 but only in the presence of LRRF1. Furthermore, FLI1 localized to the inclusion when LRRF1 was depleted via small interfering RNA, suggesting that FLI1 may have an alternative recruitment mechanism. We further developed a series of CRISPRi knockdown and complementation strains in C. trachomatis serovar L2 targeting ct226 and co-transcribed candidate Incs, ct225 and ct224. Simultaneous knockdown of ct226, ct225, and ct224 prevented localization of both FLI1 and LRRF1 to the inclusion, and only complementation of ct226 restored their localization. Thus, we demonstrated Ct226 is critical for FLI1 and LRRF1 localization to the inclusion. Our results also indicate an LRRF1-independent localization mechanism for FLI1, which likely influence their mechanism(s) of action during chlamydial infection.IMPORTANCEChlamydia trachomatis is a leading cause of both bacterial sexually transmitted infections and preventable infectious blindness worldwide. As an obligate intracellular pathogen, C. trachomatis has evolved multiple ways of manipulating the host to establish a successful infection. As such, it is important to understand host-chlamydial protein-protein interactions as these reveal strategies that C. trachomatis uses to shape its intracellular environment. This study looks in detail at interactions of two host proteins, FLI1 and LRRF1, during chlamydial infection. Importantly, the series of CRISPR inference knockdown and complement strains developed in this study suggest these proteins have both independent and overlapping mechanisms for localization, which ultimately will dictate how these proteins function during chlamydial infection.

Cell-Free Screening, Production and Animal Testing of a STI-Related Chlamydial Major Outer Membrane Protein Supported in Nanolipoproteins

BACKGROUND

Vaccine development against Chlamydia, a prevalent sexually transmitted infection (STI), is imperative due to its global public health impact. However, significant challenges arise in the production of effective subunit vaccines based on recombinant protein antigens, particularly with membrane proteins like the Major Outer Membrane Protein (MOMP).

METHODS

Cell-free protein synthesis (CFPS) technology is an attractive approach to address these challenges as a method of high-throughput membrane protein and protein complex production coupled with nanolipoprotein particles (NLPs). NLPs provide a supporting scaffold while allowing easy adjuvant addition during formulation. Over the last decade, we have been working toward the production and characterization of MOMP-NLP complexes for vaccine testing.

RESULTS

The work presented here highlights the expression and biophysical analyses, including transmission electron microscopy (TEM) and dynamic light scattering (DLS), which confirm the formation and functionality of MOMP-NLP complexes for use in animal studies. Moreover, immunization studies in preclinical models compare the past and present protective efficacy of MOMP-NLP formulations, particularly when co-adjuvanted with CpG and FSL1.

CONCLUSION

Ex vivo assessments further highlight the immunomodulatory effects of MOMP-NLP vaccinations, emphasizing their potential to elicit robust immune responses. However, further research is warranted to optimize vaccine formulations further, validate efficacy against Chlamydia trachomatis, and better understand the underlying mechanisms of immune response.

Addressing Challenges in Chlamydia trachomatis Detection: A Comparative Review of Diagnostic Methods

Chlamydial infections are one of the most common sexually transmitted bacterial infections worldwide, which is related to serious consequences for the mental, sexual, and reproductive health of women and men. The infection is commonly asymptomatic; consequently, screening programs for infection control have been introduced in some countries. The detection methods of Chlamydia trachomatis infections have evolved since the establishment of the first gold-standard detection method in the 1970s, the culture assay. Over the decades, many efforts were made to find methods with a higher sensitivity, until the 1990s, when, as a result of advances in molecular biology, nucleic acid amplification tests came into use with more sensitivity, and, currently, there are several available with which to detect infection. Therefore, herein, we will review the main methods used for CT detection and the differences between them, in terms of targets, infections that can be detected, sensitivity, and specificity. We will focus on some of the FDA-approved CT detection tests and highlight the major advantages and superiority of using molecular biology techniques. In addition, we will examine the larger challenges and limitations of the methods currently in use and discuss how they might be surpassed. Moreover, in this review, we will describe the next step to carry out after testing positive for CT infection.

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.

Sequence, structure prediction, and epitope analysis of the polymorphic membrane protein family in Chlamydia trachomatis

The polymorphic membrane proteins (Pmps) are a family of autotransporters that play an important role in infection, adhesion and immunity in Chlamydia trachomatis. Here we show that the characteristic GGA(I,L,V) and FxxN tetrapeptide repeats fit into a larger repeat sequence, which correspond to the coils of a large beta-helical domain in high quality structure predictions. Analysis of the protein using structure prediction algorithms provided novel insight to the chlamydial Pmp family of proteins. While the tetrapeptide motifs themselves are predicted to play a structural role in folding and close stacking of the beta-helical backbone of the passenger domain, we found many of the interesting features of Pmps are localized to the side loops jutting out from the beta helix including protease cleavage, host cell adhesion, and B-cell epitopes; while T-cell epitopes are predominantly found in the beta-helix itself. This analysis more accurately defines the Pmp family of Chlamydia and may better inform rational vaccine design and functional studies.

Deciphering the Puzzle: Literature Insights on Chlamydia trachomatis-Mediated Tumorigenesis, Paving the Way for Future Research

Some infectious agents have the potential to cause specific modifications in the cellular microenvironment that could be propitious to the carcinogenesis process. Currently, there are specific viruses and bacteria, such as human papillomavirus (HPV) and Helicobacter pylori, that are well established as risk factors for neoplasia. Chlamydia trachomatis (CT) infections are one of the most common bacterial sexually transmitted infections worldwide, and recent European data confirmed a continuous rise across Europe. The infection is often asymptomatic in both sexes, requiring a screening program for early detection. Notwithstanding, not all countries in Europe have it. Chlamydia trachomatis can cause chronic and persistent infections, resulting in inflammation, and there are plausible biological mechanisms that link the genital infection with tumorigenesis. Herein, we aimed to understand the epidemiological and biological plausibility of CT genital infections causing endometrial, ovarian, and cervical tumors. Also, we covered some of the best suitable in vitro techniques that could be used to study this potential association. In addition, we defend the point of view of a personalized medicine strategy to treat those patients through the discovery of some biomarkers that could allow it. This review supports the need for the development of further fundamental studies in this area, in order to investigate and establish the role of chlamydial genital infections in oncogenesis.

Characteristics of reproductive tract infections caused by common pathogens among the outpatients of reproductive medicine center in Putian: retrospective study

BACKGROUND

This study aims to explore the infection and age distribution of Ureaplasma urealyticum (UU), Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and Herpes simplex virus type II (HSV II) among the outpatients of Reproductive Medicine Center in Putian, Fujian Province to provide a clinical basis for the early diagnosis and treatment of various reproductive tract diseases and infertility in this region.

METHODS

A total of 1736 samples of secretions and exfoliated cervical cells were collected from the outpatients of the Reproductive Medicine Center of the Affiliated Hospital of Putian University from December 2021 to April 2023. The infections of UU, CT, NG and HSVII were detected by real-time fluorescence polymerase chain reaction (PCR), and the infection statuses of the patients with different genders, ages and diagnoses were analysed.

RESULTS

Among the 1736 patients, 611 were male and 1125 were female. The male patients had higher UU infection rate but lower HSV II infection rate than the female patients. No significant difference in CT and NG infection rates was observed between the genders. The CT infection rate gradually decreased with the increase in the age. The difference in UU, NG and HSV II infection rates among the different age groups was not statistically significant. For UU infection, the male infertile patients had the highest rate of 37.72% (172/456). Meanwhile, the differences in CT, NG and HSV II infection rates among the different diagnosis groups were not statistically significant. Among the male and female infertile patients, the CT infection rate was the highest in the 21-25 years of age group at 11.11% (2/18) and 9.47% (9/95), respectively. No statistically significant difference in UU, CT, NG and HSV II infection rates was observed among the different age groups of patients diagnosed in relation to the family planning guidance and between the male and female patients with other diagnoses results.

CONCLUSIONS

This study showed that UU was the most frequently identified pathogen in infertile men in Putian, Fujian Province. The CT infection rate was the highest in people under 20 years old, and the infection showed a tendency toward young individuals. Therefore, the publicity of sexual health knowledge must be strengthened, and the prevention and treatment of venereal diseases among young and middle-aged people must be improved. Moreover, the pathogen infection is related to infertility to a certain extent, which is conducive to clinical diagnosis and treatment.

Metabolic dormancy in Chlamydia trachomatis treated with different antibiotics

Diseases caused by Chlamydia spp. are often associated with persistent infections. Chlamydial persistence is commonly associated with a unique non-infectious intracellular developmental form, termed an aberrant form. Although infectious chlamydiae can be cultured consistently in cells stressed to aberrancy, their role in persistence is not clear. Recovery from antibiotic stress was explored as a model to determine how survival of non-aberrant chlamydiae, in the presence of fully inhibitory drug concentrations, may participate in persistence. Assays included incubation in quinolones, tetracyclines, or chloramphenicol for differing lengths of time, followed by an extended recovery period in antibiotic-free media. Culturable elementary bodies were not detected during treatment with each antibiotic, but viable and culturable Chlamydia trachomatis emerged after the drug was removed. Time-lapse imaging of live, antibiotic-treated infected cells identified metabolically dormant developmental forms within cells that emerged to form typical productive inclusions. The effects of the increasing concentration of most tested antibiotics led to predictable inhibitory activity, in which the survival rate decreased with increasing drug concentration. In contrast, in fluoroquinolone-treated cells, there was a paradoxical increase in productive development that was directly correlated with drug concentration and inversely associated with aberrant form production. This model system uncovers a unique chlamydial persistence pathway that does not involve the chlamydial aberrant form. The association between productive latency and metabolic dormancy is consistent with models for many bacterial species and may lead to a different interpretation of mechanisms of chlamydial persistence in patients.IMPORTANCEThe life history of most pathogens within the genus Chlamydia relies on lengthy persistence in the host. The most generally accepted model for Chlamydia spp. persistence involves an unusual developmental stage, termed the aberrant form, which arises during conditions that mimic a stressful host environment. In this work, we provide an alternate model for chlamydial persistence in the face of antibiotic stress. This model may be relevant to antibiotic treatment failures in patients infected with C. trachomatis.

Chlamydia trachomatis upregulates lncRNA CYTOR to mediate autophagy through miR-206/MAPK1 axis

Chlamydia trachomatis infection can be regulated by autophagy-related genes. LncRNA CYTOR has been proven to be involved in autophagy. In this research, we investigated the role of CYTOR in autophagy induced by C. trachomatis and the potential mechanisms. After C. trachomatis infection, CYTOR and MAPK1 were up-regulated and miR-206 was down-regulated, meanwhile, the autophagy-related protein Beclin1 and LC3-Ⅱ/LC3-Ⅰ ratio were increased. Interference with CYTOR or overexpression with miR-206 downregulated the autophagy-related protein Beclin1 and the number of autophagic spots LC3, decreased the protein ratio of LC3-II/LC3-I, and upregulated the expression of P62 protein. The luciferase reporter assay confirmed that CYTOR acted as a sponge for miR-206 to target MAPK1. In addition, CYTOR promoted autophagy induced by C. trachomatis infection through the MAPK1/ERK signaling pathway activation. Taken together, we have identified a novel molecular mechanism that the CYTOR/miR-206/MAPK1 axis was involved in the regulation of autophagy in C. trachomatis infection. This work provides an experimental basis for elucidating the pathogenesis of C. trachomatis for the treatment, prevention and control of related infectious diseases.

Insights into innate immune cell evasion by Chlamydia trachomatis

Chlamydia trachomatis, is a kind of obligate intracellular pathogen. The removal of C. trachomatis relies primarily on specific cellular immunity. It is currently considered that CD4+ Th1 cytokine responses are the major protective immunity against C. trachomatis infection and reinfection rather than CD8+ T cells. The non-specific immunity (innate immunity) also plays an important role in the infection process. To survive inside the cells, the first process that C. trachomatis faces is the innate immune response. As the "sentry" of the body, mast cells attempt to engulf and remove C. trachomatis. Dendritic cells present antigen of C. trachomatis to the "commanders" (T cells) through MHC-I and MHC-II. IFN-γ produced by activated T cells and natural killer cells (NK) further activates macrophages. They form the body's "combat troops" and produce immunity against C. trachomatis in the tissues and blood. In addition, the role of eosinophils, basophils, innate lymphoid cells (ILCs), natural killer T (NKT) cells, γδT cells and B-1 cells should not be underestimated in the infection of C. trachomatis. The protective role of innate immunity is insufficient, and sexually transmitted diseases (STDs) caused by C. trachomatis infections tend to be insidious and recalcitrant. As a consequence, C. trachomatis has developed a unique evasion mechanism that triggers inflammatory immunopathology and acts as a bridge to protective to pathological adaptive immunity. This review focuses on the recent advances in how C. trachomatis evades various innate immune cells, which contributes to vaccine development and our understanding of the pathophysiologic consequences of C. trachomatis infection.

[Pathogenesis and pathological anatomy of chlamydial infections]

The review presents modern view on the global problem of chlamydial infections. Current nomenclature of chlamydiae was adduced. Epidemiology, etiology, clinical features, pathogenesis, diagnosis and treatment of chlamydiosis received full coverage. The potential involvement of chlamydiae in the progression of various infectious and somatic diseases was revealed. Special attention was paid to pathomorphological alterations in human tissues, which develop during primary infection with chlamydia as well as during chronic infection. Key problems were demonstrated: underestimation of prevalence of chlamydiae among humans in worldwide clinical practice, the difficulty of detection of extragenital chlamydiosis, the lack of effective methods for diagnosis and treatment of persistent forms, the paucity of descriptions of pathomorphological picture of human chlamydiosis, the absence of specific prevention of infection.

Prevalence of human papilloma virus and Chlamydia trachomatis in endometrial and cervical carcinoma: a comparative study in North Indian women

Cervical cancer (Cacx) is the second and endometrial cancer (Ec) is the third most common gynecological cancer worldwide. The present study aims to understand the complex and unexplored conditions occurring in cervix and endometrium of the female genital tract caused due to the infection of the human papilloma viruses (HPVs) and Chlamydia trachomatis (CT). A total of 300 tissue biopsy samples of cervix and endometrium were included in the present study and tested for the presence of HPV and CT deoxyribonucleic acid (DNA) by using polymerase chain reaction (PCR) technique. The odds ratios and 95% confidence interval were considered for the calculation of the association of HPV and CT infection with the risk of cervical or Ec. Among endometrial patients, samples were 5% positive for HPV and 5% positive for CT infection. Among endometrial control group, no sample was found positive for either HPV or CT infection. Among cervical patients, 72% samples were positive for only HPV infection and 1% samples were positive for only CT infection. Among control group, 7% of samples were positive for only HPV infection and 3% were positive for only CT infection. The co-infection of CT with HPV in 9% of Cacx cases and in 2% of cervical control samples was also observed. This is the first study in Indian women to detect the prevalence of HPV and CT infections in endometrium cases and control. An updated estimate regarding the HPV and CT prevalence in cervix cases and control samples was also provided.

When Bacteria and Viruses Collide: A Tale of Chlamydia trachomatis and Sexually Transmitted Viruses

The global incidence of sexually transmitted infections (STIs) remains high, with the World Health Organization (WHO) estimating that over 1 million people acquire STIs daily. STIs can lead to infertility, pregnancy complications, and cancers. Co-infections with multiple pathogens are prevalent among individuals with an STI and can lead to heightened infectivity and more severe clinical manifestations. Chlamydia trachomatis (CT) is the most reported bacterial STI worldwide in both men and women, and several studies have demonstrated co-infection of CT with viral and other bacterial STIs. CT is a gram-negative bacterium with a unique biphasic developmental cycle including infectious extracellular elementary bodies (EBs) and metabolically active intracellular reticulate bodies (RBs). The intracellular form of this organism, RBs, has evolved mechanisms to persist for long periods within host epithelial cells in a viable but non-cultivable state. The co-infections of CT with the most frequently reported sexually transmitted viruses: human immunodeficiency virus (HIV), human papillomavirus (HPV), and herpes simplex virus (HSV) have been investigated through in vitro and in vivo studies. These research studies have made significant strides in unraveling the intricate interactions between CT, these viral STIs, and their eukaryotic host. In this review, we present an overview of the epidemiology of these co-infections, while specifically delineating the underlying mechanisms by which CT influences the transmission and infection dynamics of HIV and HSV. Furthermore, we explore the intricate relationship between CT and HPV infection, with a particular emphasis on the heightened risk of cervical cancer. By consolidating the current body of knowledge, we provide valuable insights into the complex dynamics and implications of co-infection involving CT and sexually transmitted viruses.

Chlamydial and Gonococcal Genital Infections: A Narrative Review

Sexually transmitted infections (STIs) constitute one of the leading causes of disease burden worldwide, leading to considerable morbidity, mortality, health expenditures, and stigma. Of note are the most common bacterial STIs, chlamydial and gonococcal infections, whose etiological agents are Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG), respectively. Despite being usually asymptomatic, in some cases these infections can be associated with long-term severe complications, such as pelvic inflammatory disease, chronic pelvic pain, infertility, ectopic pregnancy, and increased risk of other STIs acquisition. As the symptoms, when present, are usually similar in both infections, and in most of the cases these infections co-occur, the dual-test strategy, searching for both pathogens, should be preferred. In line with this, herein we focus on the main aspects of CT and NG infections, the clinical symptoms as well as the appropriate state-of-the-art diagnostic tests and treatment. Cost-effective strategies for controlling CT and NG infections worldwide are addressed. The treatment for both infections is based on antibiotics. However, the continuing global rise in the incidence of these infections, concomitantly with the increased risk of antibiotics resistance, leads to difficulties in their control, particularly in the case of NG infections. We also discuss the potential mechanism of tumorigenesis related to CT infections. The molecular bases of CT and NG infections are addressed, as they should provide clues for control or eradication, through the development of new drugs and/or effective vaccines against these pathogens.

The Association Between Female Genital Schistosomiasis and Other Infections of the Lower Genital Tract in Adolescent Girls and Young Women: A Cross-Sectional Study in South Africa

OBJECTIVES/PURPOSES OF THE STUDY

This study aimed to explore the relationship between female genital schistosomiasis (FGS), sexually transmitted infections, bacterial vaginosis, and yeast among young women living in Schistosoma haematobium-endemic areas.

METHODS

In a cross-sectional study of young women, sexually active, aged 16 to 22 years in rural KwaZulu-Natal, South Africa, in 32 randomly selected rural schools in schistosomiasis-endemic areas, the authors performed gynecological and laboratory investigations, diagnosed FGS and other infections, and did face-to-face interviews.

RESULTS

Female genital schistosomiasis was the second most prevalent current genital infection (23%), significantly more common in those who had urinary schistosomiasis (35%), compared with those without (19%, p < .001). In the FGS-positive group, 35% had human papillomavirus compared with 24% in the FGS-negative group (p = .010). In the FGS-positive group, 37% were seropositive for herpes simplex virus infection, compared with 30% in the FGS-negative group (p = .079). There were significantly fewer chlamydia infections among women with FGS (20%, p = .018) compared with those who did not have FGS (28%).

CONCLUSIONS

Female genital schistosomiasis was the second most common genital infection after herpes simplex virus. Human papillomavirus infection was significantly associated with FGS, but Chlamydia was negatively associated with FGS. Women with FGS may have had more frequent contact with the health system for genital discharge. The results show the importance of the inclusion of FGS in the national management protocols for genital infections in areas endemic for S. haematobium and highlight a more comprehensive approach to diagnosis and genital disease management.

Epigenetic changes induced by pathogenic Chlamydia spp

Chlamydia trachomatis, C. pneumoniae, and C. psittaci, the three Chlamydia species known to cause human disease, have been collectively linked to several pathologies, including conjunctivitis, trachoma, respiratory disease, acute and chronic urogenital infections and their complications, and psittacosis. In vitro, animal, and human studies also established additional correlations, such as between C. pneumoniae and atherosclerosis and between C. trachomatis and ovarian cancer. As part of their survival and pathogenesis strategies as obligate intracellular bacteria, Chlamydia spp. modulate all three major types of epigenetic changes, which include deoxyribonucleic acid (DNA) methylation, histone post-translational modifications, and microRNA-mediated gene silencing. Some of these epigenetic changes may be implicated in key aspects of pathogenesis, such as the ability of the Chlamydia spp. to induce epithelial-to-mesenchymal transition, interfere with DNA damage repair, suppress cholesterol efflux from infected macrophages, act as a co-factor in human papillomavirus (HPV)-mediated cervical cancer, prevent apoptosis, and preserve the integrity of mitochondrial networks in infected host cells. A better understanding of the individual and collective contribution of epigenetic changes to pathogenesis will enhance our knowledge about the biology of Chlamydia spp. and facilitate the development of novel therapies and biomarkers. Pathogenic Chlamydia spp. contribute to epigenetically-mediated gene expression changes in host cells by multiple mechanisms.

Therapeutic Options for Chlamydia trachomatis Infection: Present and Future

Sexually transmitted infections (STIs), such as Chlamydia trachomatis (Ct) infection, have serious consequences for sexual and reproductive health worldwide. Ct is one of the most common sexually transmitted bacterial infections in the world, with approximately 129 million new cases per year. C. trachomatis is an obligate intracellular Gram-negative bacterium. The infection is usually asymptomatic, notwithstanding, it could also be associated with severe sequels and complications, such as chronic pain, infertility, and gynecologic cancers, and thus there is an urgent need to adequately treat these cases in a timely manner. Consequently, beyond its individual effects, the infection also impacts the economy of the countries where it is prevalent, generating a need to consider the hypothesis of implementing Chlamydia Screening Programs, a decision that, although it is expensive to execute, is a necessary investment that unequivocally will bring financial and social long-term advantages worldwide. To detect Ct infection, there are different methodologies available. Nucleic acid amplification tests, with their high sensitivity and specificity, are currently the first-line tests for the detection of Ct. When replaced by other detection methods, there are more false negative tests, leading to underreported cases and a subsequent underestimation of Ct infection's prevalence. Ct treatment is based on antibiotic prescription, which is highly associated with drug resistance. Therefore, currently, there have been efforts in line with the development of alternative strategies to effectively treat this infection, using a drug repurposing method, as well as a natural treatment approach. In addition, researchers have also made some progress in the Ct vaccine development over the years, despite the fact that it also necessitates more studies in order to finally establish a vaccination plan. In this review, we have focused on the therapeutic options for treating Ct infection, expert recommendations, and major difficulties, while also exploring the possible avenues through which to face this issue, with novel approaches beyond those proposed by the guidelines of Health Organizations.