Human leukocyte antigen (HLA)-B, DRB1, and DQB1 allotypes associated with disease and protection of trachoma endemic villagers

HLA-DR and HLA-DQ Polymorphism Correlation with Sexually Transmitted Infection Caused by Chlamydia trachomatis

Background and Objectives: Chlamydia trachomatis (C. trachomatis) represents one of the most prevalent bacterial sexually transmitted diseases. This study aims to explore the relationship between HLA alleles/genotypes/haplotypes and C. trachomatis infection to better understand high-risk individuals and potential complications. Materials and Methods: This prospective study recruited participants from Transylvania, Romania. Patients with positive NAAT tests for C. trachomatis from cervical/urethral secretion or urine were compared with controls regarding HLA-DR and -DQ alleles. DNA extraction for HLA typing was performed using venous blood samples. Results: Our analysis revealed that the presence of the DRB1*13 allele significantly heightened the likelihood of C. trachomatis infection (p = 0.017). Additionally, we observed that individuals carrying the DRB1*01/DRB1*13 and DQB1*03/DQB1*06 genotype had increased odds of C. trachomatis infection. Upon adjustment, the association between the DRB1*01/DRB1*13 genotype and C. trachomatis remained statistically significant. Conclusions: Our findings underscore the importance of specific HLA alleles and genotypes in influencing susceptibility to C. trachomatis infection. These results highlight the intricate relationship between host genetics and disease susceptibility, offering valuable insights for targeted prevention efforts and personalized healthcare strategies.

Chlamydia trachomatis and the HLA involvement in the development of infection and disease: a narrative review

Introduction

CT (Chlamydia trachomatis) is among the most common pathogens leading to sexually transmitted diseases. Considering the uncertain mechanism by which HLA polymorphisms influence the CT infection, reinfection, comorbidities or evolution and because there is no consensus regarding the alleles involved in the pathogenesis of the infection, we considered necessary to perform a review to summarize the current knowledge of HLA related to CT.

Methods

Pubmed was researched using key terms. Out of the 198 results found, we analyzed articles of all types which describe how the MHC, through HLA alleles, participates in the different stages of CT penetration in the body, including studies about cells or other molecules involved in the process.

Results

Almost 40% of the variation in the clinical course of CT infection depends on host genetic factors. There are haplotypes that influence the infection susceptibility/resistance, haplotypes that are involved in the recurrence of the infection, haplotypes that are related to tubal infertility, pelvic inflammatory disease development or trachoma. Antibody to Chsp60 (influenced by MHC genes) has been observed to correlate with late tissue-damaging sequelae. Toll-like receptors were found to increase the susceptibility to CT. The association of HLA-B27 creates susceptibility of reactive arthritis in the organisms infected by CT, but does not influence the carriage of CT.

Conclusion

We identified HLA haplotypes belonging both to MHC class l and ll, which influence different stages of CT infection. Genetic risk factors still need research, especially on Caucasians. Studies are moving towards designing a safe and effective vaccine.

Toll like receptor 4: an important molecule in recognition and induction of appropriate immune responses against Chlamydia infection

Chlamydia species are obligate intracellular pathogens causing different infectious diseases particularly asymptomatic genital infections and are also responsible for a wide range of complications. Previous studies showed that there are different immune responses to Chlamydia species and their infections are limited to some cases. Moreover, Chlamydia species are able to alter immune responses through modulating the expression of some immune system related molecules including cytokines. Toll like receptors (TLRs) belonge to pathogen recognition receptors (PRRs) and play vital roles in recognition of microbes and stimulation of appropriate immune responses. Therefore, it appears that TLRs may be considered as important sensors for recognition of Chlamydia and promotion of immune responses against these bacterial infections. Accordingly, TLR4 detects several microbial PAMPs such as bacterial lipopolysacharide (LPS) and subsequently activates transcription from pro-inflammatory cytokines in both MYD88 and TRIF pathways dependent manner. The purpose of this review is to provide the recent data about the status and major roles played by TLR4 in Chlamydia species recognition and promotion of immune responses against these infections and also the relationship between TLR4 activities and pathogenesis of Chlamydia infections.

Genetic Polymorphisms of TLR4 and MICA are Associated with Severity of Trachoma Disease in Tanzania

Aim

To examine the association of TLR4 Asp299Gly and MICA exon 5 microsatellites polymorphisms with severity of trachoma in a sub-Saharan East Africa population of Tanzanian villagers.

Methods

The samples were genotyped for MICA exon 5 microsatellites and the TLR4 299 A/G polymorphism by Restriction Fragment Length Polymorphism (RFLP), and GeneScan^®, respectively. The association of TLR4 Asp299Gly and MICA exon 5 microsatellites with inflammatory trachoma (TI) and trichiasis (TI) were examined.

Results

The results showed an association between TLR4 and MICA polymorphisms and trachoma disease severity, as well as with protection. TLR4 an allele was significantly associated with inflammatory trachoma (p=0.0410), while the G allele (p=0.0410) was associated with protection.

Conclusion

TLR4 and MICA may modulate the risk of severity to trachoma disease by modulating the immune response to Ct. In addition; the increased frequency of MICA-A9 heterozygote in controls may suggest a positive selection of these alleles in adaptation to environments where Ct is endemic.

Immunopathogenesis of Chlamydial Infections

Chlamydial infections lead to a number of clinically relevant diseases and induce significant morbidity in human populations. It is generally understood that certain components of the host immune response to infection also mediate such disease pathologies. A clear understanding of pathogenic mechanisms will enable us to devise better preventive and/or intervention strategies to mitigate the morbidity caused by these infections. Over the years, numerous studies have been conducted to explore the immunopathogenic mechanisms of Chlamydia-induced diseases of the eye, reproductive tract, respiratory tract, and cardiovascular systems. In this article, we provide an overview of the diseases caused by Chlamydia, animal models used to study disease pathology, and a historical context to the efforts to understand chlamydial pathogenesis. Furthermore, we discuss recent findings regarding pathogenesis, with an emphasis on the role of the adaptive immune response in the development of chlamydial disease sequelae. Finally, we summarize the key insights obtained from studies of chlamydial pathogenesis and avenues that remain to be explored in order to inform the next steps of vaccine development against chlamydial infections.

Conjunctival fibrosis and the innate barriers to Chlamydia trachomatis intracellular infection: a genome wide association study

Chlamydia trachomatis causes both trachoma and sexually transmitted infections. These diseases have similar pathology and potentially similar genetic predisposing factors. We aimed to identify polymorphisms and pathways associated with pathological sequelae of ocular Chlamydia trachomatis infections in The Gambia. We report a discovery phase genome-wide association study (GWAS) of scarring trachoma (1090 cases, 1531 controls) that identified 27 SNPs with strong, but not genome-wide significant, association with disease (5 × 10⁻⁶ > P > 5 × 10⁻⁸). The most strongly associated SNP (rs111513399, P = 5.38 × 10⁻⁷) fell within a gene (PREX2) with homology to factors known to facilitate chlamydial entry to the host cell. Pathway analysis of GWAS data was significantly enriched for mitotic cell cycle processes (P = 0.001), the immune response (P = 0.00001) and for multiple cell surface receptor signalling pathways. New analyses of published transcriptome data sets from Gambia, Tanzania and Ethiopia also revealed that the same cell cycle and immune response pathways were enriched at the transcriptional level in various disease states. Although unconfirmed, the data suggest that genetic associations with chlamydial scarring disease may be focussed on processes relating to the immune response, the host cell cycle and cell surface receptor signalling.

Trachoma and Ocular Chlamydial Infection in the Era of Genomics

Trachoma is a blinding disease usually caused by infection with Chlamydia trachomatis (Ct) serovars A, B, and C in the upper tarsal conjunctiva. Individuals in endemic regions are repeatedly infected with Ct throughout childhood. A proportion of individuals experience prolonged or severe inflammatory episodes that are known to be significant risk factors for ocular scarring in later life. Continued scarring often leads to trichiasis and in-turning of the eyelashes, which causes pain and can eventually cause blindness. The mechanisms driving the chronic immunopathology in the conjunctiva, which largely progresses in the absence of detectable Ct infection in adults, are likely to be multifactorial. Socioeconomic status, education, and behavior have been identified as contributing to the risk of scarring and inflammation. We focus on the contribution of host and pathogen genetic variation, bacterial ecology of the conjunctiva, and host epigenetic imprinting including small RNA regulation by both host and pathogen in the development of ocular pathology. Each of these factors or processes contributes to pathogenic outcomes in other inflammatory diseases and we outline their potential role in trachoma.

Significant roles played by IL-10 in Chlamydia infections

Chlamydia species are obligate intracellular parasites which cause usually asymptomatic genital tract infections and also are associated with several complications. Previous studies demonstrated that immune responses to Chlamydia species are different and the diseases will be limited to some cases. Additionally, Chlamydia species are able to modulate immune responses via regulating expression of some immune system molecules including cytokines. IL-10, as the main anti-inflammatory cytokine, plays important roles in the induction of immune-tolerance against self-antigen and also immune-homeostasis after microbe elimination. Furthermore, it has been documented that ectopic expression of IL-10 is associated with several chronic infectious diseases. Therefore, it can be hypothesized that changes in the regulation of this cytokine can be associated with infection with several species of Chlamydia and their associated complications. This review collected the recent information regarding the association and relationship of IL-10 with Chlamydia infections. Another aim of this review article is to address recent data regarding the association of genetic variations (polymorphisms) of IL-10 and Chlamydia infections.

Genetic variation in Chlamydia trachomatis and their hosts: impact on disease severity and tissue tropism

Chlamydia trachomatis infections are a global health problem. This obligate intracellular bacterial pathogen comprises lymphogranuloma venereum (L1-L3), ocular (A-C) and genital (D-K) serovars. Although genetically similar, each serovar group differs in disease severity and tissue tropism through mechanisms that are not well understood. It is clear that host genetic differences also play a role in chlamydial disease outcome and key host polymorphisms are beginning to emerge from both human and experimental animal studies. In this review, we will highlight pathogen and host genes that link genetic diversity, disease severity and tissue tropism. We will also use this information to provide new insights that may be helpful in developing improved management strategies for these important pathogens.

Ocular Clinical Pictures Disclosed by PCR Molecular Diagnosis and Chlamydia Trachomatis Infection Performed following the Appropriate Sampling Modality in Ocular Ecosystem

Four clinical cases regarding the correct diagnosis of early ocular Chlamydia trachomatis (Ct) inflammation, performed by two different modalities on the ocular ecosystem, are discussed. The present study was carried out in parallel using a cotton flock ocular swab and the scraping of upper lid conjunctiva. The ocular samplings were carried out by a first ocular swab from inner canthus and fornix, while the second by a conjunctival scraping from upper the conjunctiva of four patients. In the first case, by ocular swab, all samples resulted negative to Ct-DNA research by PCR, while the cultural analyses showed a growth of saprophytic and opportunist germs in all patients. No growth micetes resulted. On the contrary, in the second case, by conjunctival scraping, three of four samples were positive to Ct-DNA research. No fungal growth was observed, while only the 3rd patient, negative to Ct-DNA research, showed microbial growth. Our study, carried out with two different modalities of sampling on different areas of the same ecosystem, showed different results, demonstrating the importance of sampling accuracy for chlamydial research by molecular analysis in PCR, during the slight phase of inflammation. These initial data indicate that laboratory diagnosis by PCR for precocious Ct infection, not revealed clinically, could represent the first step for a correct diagnostic procedure, eliminating one of the critical points, allowing an accurate, effective and precocious antibiotic therapy. We hypothesize that only by following these correct procedures of sampling during the early phase of chlamydial inflammation, in the future, will it be possible to reduce a pejorative evolution of this worsening disease in people genetically susceptible, building a more efficacious Public Health program of prevention against chronic conjunctivitis and to favour a major prevention of trachoma in endemic areas.

Jugulodigastric Lymph Node Inflammation Derived from Chronic Atypical Oropharyngeal Phlogosis Recurring Annually after Flu Virus Vaccination: A Holistic Vision and a Clinical Case Solved after Chlamydicidal Antibiotic Therapy

In this report, we evaluated the case history of a patient with longstanding chronic pharyngitis who had periodic clinical manifestation for three years after a flu vaccine administration, and after various treatments tried to resolve the chronic pharyngitis with unsuccessful antibiotic and anti-inflammatory therapies. The patient occasionally presented a slight ocular inflammation, while dysuria occurred after sexual activity. The search for common pathogens by use of pharyngeal swabs resulted only in Corynebacterium ulcerans growth. After this first result, we focused our investigations on ocular and uro-genital infections of Chlamydiaceae (Ct and Cp) and Mycoplasmataceae (Mh and Uu) families. We examined the patient's pharynx using molecular and culture techniques from three different sites. Although several infectious agents, including viruses and bacteria, causing chronic pharyngitis are reported in the literature, these ocular and uro-genital pathogens are seldomly routinely investigated in the same patient in ORL. Furthermore, while episodes of chronic pharyngitis is one of the most common clinical manifestation in ENT patients, these atypical pharyngitis represent ever-increasing infections which must always be considered and researched by suitable instruments such as PCR. Only from the collection of detailed medical history and careful observations of clinical manifestation, indicative of an oral chronic pathologic phenomenon of low intensity initiated several years previously, starting with sudden outbreak and relapse like a bout of flu', we suggest to study these atypical infecting agents frequently localized in the urogenital human area, awhich would allow to highlight and to recognize these clinical cases that manifest themselves as chronic inflammation of jugulodigastric lymph nodes, remaining still unrecognized and rarely associated to chlamydial infection, confused with the response to flu vaccination. After several specific cycles of antibiotic therapy, the patient's health improved considerably and showed almost complete regression of jugulodigastric lymph node inflammation.

Molecular Approach by PCR is the Best Method to Detect the Presence of Chlamydia Trachomatis and to Define the True Agent of Ocular Bacterial Inflammation

Chlamydia trachomatis (Ct) is an atypical agent for acute, subclinical and chronic conjunctivitis in developed countries, as stated by the International League against Trachoma. In order to evaluate the presence of Ct, from a total of 3,520 patients visiting the consulting room of the Eye Clinic of G. d'Annunzio University of Chieti, Italy from 2006–2008, we enrolled 171 patients affected by occasional mild, moderate or severe conjunctivitis in a three-arm prospective open study, using traditional analysis such as Immune Fluorescent Assay and Enzyme–Linked Fluorescent Assay (IFA and ELFA) and molecular analysis with Polymerase Chain Reaction (PCR) procedure for Ct DNA research (Ct DNA). At the same time, microbiological culture was carried out for common germs and mycetes. These patients were analyzed at different subsequent times. In the first arm (Group A) of 82 patients with IFA and ELFA only 10 people (12.2%) resulted positive to Ct infection with both methods. The presence of Ct was never alone, but always overlapped with contaminants, like corynebacteria, staphylococci, streptococci and colonbacteria, randomly distributed, while no growth of mycetes was observed. Of these positive patients, only one 47-year-old female, suffering from a moderate form of ocular chlamydial infection, showed serological conversion against this infection; furthermore, this female had also been suffering from reactive arthritis for sometime. In the second arm (Group B) of 89 patients, we carried out PCR for Ct detection: 82 (94.25%) were found positive to Ct – DNA research, with common germ growth randomly associated, without sex or age prevalence, as in group A; no mycetes were found. The third arm (Group C) included 37 negative patients from Group A with severe or moderate chronic conjunctivitis, randomly recruited between relapsing cases, with the addition of the single previously positive seroconversion case, for a total of 38 patients, who were re-evaluated by PCR Ct-DNA analysis. All these patients, negative to IFA and ELFA, were positive to Ct-DNA analysis. These data indicate a higher rate of Ct infection in patients with severe or moderate chronic conjunctivitis, resistant to usual therapies even after eradication of common germs, thus showing the advantage of introducing this molecular technique of analysis in mild to severe chronic or recurrent conjunctivitis.