Haematopoietic innate interleukin 17A production drives immunopathology in female mouse genital Chlamydia muridarum infection.

Chlamydia trachomatis infection is the leading cause of bacterial urogenital infection and has been demonstrated to drive inflammation and scarring of the reproductive tract. Recent studies have identified key triggers of proinflammatory adaptive immune responses driven by innate leukocytes and epithelia driving immunopathology. Utilizing chimeric mouse models, we investigated the definitive source and role of IL17 and IL17 signalling receptors during early Chlamydia muridarum infection of the female urogenital tract. Bone marrow transplants from wild-type (WT) and IL17A-/- mice to recipients demonstrated equivocal infection kinetics in the reproductive tract, but interestingly, adoptive transfer of IL17A-/- immune cells to WT recipients resulted in no infertility, suggesting a haematopoietic (as opposed to tissue) source of IL17 driving immunopathology. To further delineate the role of IL17 in immunopathology, we infected WT and IL17 receptor A (IL17RA)-/- female mice and observed a significant reduction in immunopathology in IL17RA-/- mice. WT bone marrow transplants to IL17RA-/- recipient mice prevented hydrosalpinx, suggesting signalling through IL17RA drives immunopathology. Furthermore, early chemical inhibition of IL17 signalling significantly reduced hydrosalpinx, suggesting IL17 acts as an innate driver of disease. Early during the infection, IL17 was produced by γδ T cells in the cervico-vagina, but more importantly, by neutrophils at the site of infertility in the oviducts. Taken together, these data suggest innate production of IL17 by haematopoietic leukocytes drives immunopathology in the epithelia during early C. muridarum infection of the female reproductive tract.

A TriAdj-Adjuvanted Chlamydia trachomatis CPAF Protein Vaccine Is Highly Immunogenic in Pigs.

Chlamydia trachomatis (Ct) infections are the most common sexually transmitted infection (STI). Despite effective antibiotics for Ct, undetected infections or delayed treatment can lead to infertility, ectopic pregnancies, and chronic pelvic pain. Besides humans, chlamydia poses similar health challenges in animals such as C. suis (Cs) in pigs. Based on the similarities between humans and pigs, as well as their chlamydia species, we use pigs as a large biomedical animal model for chlamydia research. In this study, we used the pig model to develop a vaccine candidate against Ct. The vaccine candidate consists of TriAdj-adjuvanted chlamydial-protease-like activity factor (CPAF) protein. We tested two weekly administration options-twice intranasal (IN) followed by twice intramuscular (IM) and twice IM followed by twice IN. We assessed the humoral immune response in both serum using CPAF-specific IgG (including antibody avidity determination) and also in cervical and rectal swabs using CPAF-specific IgG and IgA ELISAs. The systemic T-cell response was analyzed following in vitro CPAF restimulation via IFN-γ and IL-17 ELISpots, as well as intracellular cytokine staining flow cytometry. Our data demonstrate that while the IN/IM vaccination mainly led to non-significant systemic immune responses, the vaccine candidate is highly immunogenic if administered IM/IN. This vaccination strategy induced high serum anti-CPAF IgG levels with strong avidity, as well as high IgA and IgG levels in vaginal and rectal swabs and in uterine horn flushes. In addition, this vaccination strategy prompted a pronounced cellular immune response. Besides inducing IL-17 production, the vaccine candidate induced a strong IFN-γ response with CD4 T cells. In IM/IN-vaccinated pigs, these cells also significantly downregulated their CCR7 expression, a sign of differentiation into peripheral-tissue-homing effector/memory cells. Conclusively, this study demonstrates the strong immunogenicity of the IM/IN-administered TriAdj-adjuvanted Ct CPAF vaccine candidate. Future studies will test the vaccine efficacy of this promising Ct vaccine candidate. In addition, this project demonstrates the suitability of the Cs pre-exposed outbred pig model for Ct vaccine development. Thereby, we aim to open the bottleneck of large animal models to facilitate the progression of Ct vaccine candidates into clinical trials.

IgG exacerbates genital chlamydial pathology in females by enhancing pathogenic CD8+ T cell responses.

Chlamydia trachomatis infections are an important sexually transmitted infection that can lead to inflammation, scarring and hydrosalpinx/infertility. However, infections are commonly clinically asymptomatic and do not receive treatment. The underlying cause of asymptomatic immunopathology remains unknown. Here, we demonstrate that IgG produced during male infection enhanced the incidence of immunopathology and infertility in females. Human endocervical cells expressing the neonatal Fc Receptor (FcRn) increased translocation of human IgG-opsonized C. trachomatis. Using total IgG purified from infected male mice, we opsonized C. muridarum and then infected female mice, mimicking sexual transmission. Following infection, IgG-opsonized Chlamydia was found to transcytose the epithelial barrier in the uterus, where it was phagocytosed by antigen-presenting cells (APCs) and trafficked to the draining lymph nodes. APCs then expanded both CD4+ and CD8+ T cell populations and caused significantly more infertility in female mice infected with non-opsonized Chlamydia. Enhanced phagocytosis of IgG-opsonized Chlamydia significantly increased pro-inflammatory signalling and T cell proliferation. As IgG is transcytosed by FcRn, we utilized FcRn-/- mice and observed that shedding kinetics of Chlamydia were only affected in FcRn-/- mice infected with IgG-opsonized Chlamydia. Depletion of CD8+ T cells in FcRn-/- mice lead to a significant reduction in the incidence of infertility. Taken together, these data demonstrate that IgG seroconversion during male infection can amplify female immunopathology, dependent on FcRn transcytosis, APC differentiation and enhanced CD8 T cell responses.

Immunohistochemical characterization of the immune cell response during chlamydial infection in the male and female koala (Phascolarctos cinereus) reproductive tract.

Chlamydiosis is one of the main causes of the progressive decline of koala populations in eastern Australia. While histologic, immunologic, and molecular studies have provided insights into the basic function of the koala immune system, the in situ immune cell signatures during chlamydial infection of the reproductive tract in koalas have not been investigated. Thirty-two female koalas and 47 males presented to wildlife hospitals with clinical signs suggestive of Chlamydia infection were euthanized with the entire reproductive tract collected for histology; immunohistochemistry (IHC) for T-cell (CD3ε, CD4, and CD8α), B-cell (CD79b), and human leukocyte antigen (HLA)-DR markers; and quantitative real-time polymerase chain reaction (rtPCR) for Chlamydia pecorum. T-cells, B-cells, and HLA-DR-positive cells were observed in both the lower and upper reproductive tracts of male and female koalas with a statistically significant associations between the degree of the inflammatory reaction; the number of CD3, CD4, CD79b, and HLA-DR positive cells; and the PCR load. CD4-positive cells were negatively associated with the severity of the gross lesions. The distribution of immune cells was also variable according to the location within the genital tract in both male and female koalas. These preliminary results represent a step forward towards further exploring mechanisms behind chlamydial infection immunopathogenesis, thus providing valuable information about the immune response and infectious diseases in free-ranging koalas.

Enhanced clearance of C. muridarum infection using azithromycin-loaded liposomes.

Chlamydia trachomatis is an intracellular bacterium which infects around 129 million people annually. Despite similar infection rates between sexes, most research investigating the effects of chlamydial infection on fertility has focused on females. There is now emerging evidence of a potential link between Chlamydia and impaired male fertility. The only treatments for chlamydial infection are antibiotics, with azithromycin (AZI) being one of the commonly used drugs. However, recent studies have suggested that optimizing the treatment regime is necessary, as higher concentrations of AZI may be required to effectively clear the infection in certain cell types, particularly testicular macrophages. To address this challenge, we have prepared liposomes consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) loaded with AZI for clearing Chlamydia. These liposomes exhibited stability over time and were readily taken up by both macrophages and epithelial cells. Moreover, they demonstrated significant enhancement of chlamydial clearance in both cell types. In a mouse model, the drug-loaded liposomes cleared Chlamydia within the penile urethra more efficiently than the same dose of unencapsulated drug. Furthermore, the liposome-drug treatment showed significant protective effects on sperm motility and morphology, suggesting potential benefits in reducing sperm damage caused by the infection.

Characterisation of the koala (Phascolarctos cinereus) pouch microbiota in a captive population reveals a dysbiotic compositional profile associated with neonatal mortality.

BACKGROUND: Captive koala breeding programmes are essential for long-term species management. However, breeding efficacy is frequently impacted by high neonatal mortality rates in otherwise healthy females. Loss of pouch young typically occurs during early lactation without prior complications during parturition and is often attributed to bacterial infection. While these infections are thought to originate from the maternal pouch, little is known about the microbial composition of koala pouches. As such, we characterised the koala pouch microbiome across the reproductive cycle and identified bacteria associated with mortality in a cohort of 39 captive animals housed at two facilities. RESULTS: Using 16S rRNA gene amplicon sequencing, we observed significant changes in pouch bacterial composition and diversity between reproductive time points, with the lowest diversity observed following parturition (Shannon entropy - 2.46). Of the 39 koalas initially sampled, 17 were successfully bred, after which seven animals lost pouch young (overall mortality rate - 41.18%). Compared to successful breeder pouches, which were largely dominated by Muribaculaceae (phylum - Bacteroidetes), unsuccessful breeder pouches exhibited persistent Enterobacteriaceae (phylum - Proteobacteria) dominance from early lactation until mortality occurred. We identified two species, Pluralibacter gergoviae and Klebsiella pneumoniae, which were associated with poor reproductive outcomes. In vitro antibiotic susceptibility testing identified resistance in both isolates to several antibiotics commonly used in koalas, with the former being multidrug resistant. CONCLUSIONS: This study represents the first cultivation-independent characterisation of the koala pouch microbiota, and the first such investigation in marsupials associated with reproductive outcomes. Overall, our findings provide evidence that overgrowth of pathogenic organisms in the pouch during early development is associated with neonatal mortality in captive koalas. Our identification of previously unreported, multidrug resistant P. gergoviae strains linked to mortality also underscores the need for improved screening and monitoring procedures aimed at minimising neonatal mortality in future. Video Abstract.

Pathogenic NKT cells attenuate urogenital chlamydial clearance and enhance infertility.

Urogenital chlamydial infections continue to increase with over 127 million people affected annually, causing significant economic and public health pressures. While the role of traditional MHCI and II peptide presentation is well defined in chlamydial infections, the role of lipid antigens in immunity remains unclear. Natural killer (NK) T cells are important effector cells that recognize and respond to lipid antigens during infections. Chlamydial infection of antigen-presenting cells facilitates presentation of lipid on the MHCI-like protein, CD1d, which stimulates NKT cells to respond. During urogenital chlamydial infection, wild-type (WT) female mice had significantly greater chlamydial burden than CD1d-/- (NKT-deficient) mice, and had significantly greater incidence and severity of immunopathology in both primary and secondary infections. WT mice had similar vaginal lymphocytic infiltrate, but 59% more oviduct occlusion compared to CD1d-/- mice. Transcriptional array analysis of oviducts day 6 post-infection revealed WT mice had elevated levels of Ifnγ (6-fold), Tnfα (38-fold), Il6 (2.5-fold), Il1ß (3-fold) and Il17a (6-fold) mRNA compared to CD1d-/- mice. In infected females, oviduct tissues had an elevated infiltration of CD4+ -invariant NKT (iNKT) cells, however, iNKT-deficient Jα18-/- mice had no significant differences in hydrosalpinx severity or incidence compared to WT controls. Lipid mass spectrometry of surface-cleaved CD1d in infected macrophages revealed an enhancement of presented lipids and cellular sequestration of sphingomyelin. Taken together, these data suggest an immunopathogenic role for non-invariant NKT cells in urogenital chlamydial infections, facilitated by lipid presentation via CD1d via infected antigen-presenting cells.

Prophylactic and therapeutic vaccination protects sperm health from Chlamydia muridarum-induced abnormalities.

Chlamydia is the most common bacterial sexually transmitted infection worldwide and it is widely acknowledged that controlling the rampant community transmission of this infection requires vaccine development. In this study, for the first time, we elucidate the long-term response to male mouse chlamydial vaccination with chlamydial major outer membrane protein (MOMP) and ISCOMATRIX (IMX) both prophylactically and in a novel therapeutic setting. Vaccination significantly reduced and, in some cases, cleared chlamydial burden from the prostates, epididymides, and testes, which correlates with high IgG and IgA tires in tissues and serum. Important markers of sperm health and fertility were protected including sperm motility and proteins associated with fertility in men. Within splenocytes, expression of IFNγ, TNFα, IL17, IL13, IL10, and TGFß were changed by both infection and vaccination within CD4 and CD8 T cells and regulatory T cells. Within the testicular tissue, phenotypic and concentration changes were observed in macrophages and T cells (resident and transitory). This revealed some pathogenic phenotypes associated with infection and critically that vaccination allows maintenance of testicular homeostasis, likely by preventing significant influx of CD4 T cells and promoting IL10 production. Finally, we demonstrated the testes contained immature (B220+) B cells and mature (CD138+) Chlamydia-specific plasma cells. Thus, through vaccination, we can maintain the healthy function of the testes, which is vital to protection of male fertility.

Primary oral vaccination followed by a vaginal pull protects mice against genital HSV-2 infection.

PROBLEM: HSV-2 infected more than 491 million people aged 15-49 world-wide in 2016. The morbidity associated with recurrent infections and the increased risk of HIV infection make this a major health problem. To date there is no effective vaccine. Because HSV-2 ascends to the dorsal route ganglion within 12-18 h of infection, an effective vaccine will need to elicit a strong local resident CD8+ T cell response to prevent the infection from becoming life-long. METHOD OF STUDY: Using a mouse model we investigated the potential of oral immunization with a novel lipid adjuvant (LiporaleTM ) followed by local vaginal application of an inflammatory agents to protect against primary HSV-2 infections. RESULTS: Oral vaccination of mice with live-attenuated HSV-2 in Liporale followed by vaginal application of DNFB or CXCL9/10 led to recruitment of tissue-resident CD8+ memory cells into the genital epithelia. This prime and pull vaccination strategy provided complete protection against wild-type HSV-2 challenge and prevented viral dissemination to the spinal cords. CONCLUSIONS: Activation of mucosal immunity by oral immunization, combined with induction of transient local genital inflammation can recruit long-lived tissue resident CD8+ T cells into the genital epithelium, providing significant protection against primary HSV-2 infection.

Controlled release vaccine implants for delivery of booster immunisations.

Most current animal vaccine regimes involve a primary vaccination followed sometime later by a booster vaccination. This presents challenges when vaccinating difficult to access animals such as livestock. Mustering livestock to deliver a vaccine boost is costly and stressful for animals. Thus, we have produced a platform system that can be administered at the same time as the priming immunisation and delivers payload after an appropriate delay time to boost the immune response, without need for further handling of animals. A 30 × 2 mm osmotically triggered polymer implant device with burst-release characteristics delivered the booster dose of a tetanus vaccine. Blood samples were collected from an experimental group that received the priming vaccine and implant on day 0 and control group that received the initial vaccine (tetanus toxoid) and then a bolus dose 28 days later via subcutaneous injection. The two groups showed identical weight gain curves. T cell proliferation following in vitro stimulation with antigen was identical between the two groups at all time points. However, serum IgG antibody responses to the tetanus toxoid antigen were significantly higher in the control group at weeks 8 and 12. The implant capsules stayed at the site of implantation and at week 12 there was evidence of tissue integration. No local reactions at the implant site were observed, other than mild thickening of the skin in half of the experimental group animals and no other adverse health events were recorded in either group.

Chlamydiosis and cystic dilatation of the ovarian bursa in the female koala (Phascolarctos cinereus): Novel insights into the pathogenesis and mechanisms of formation.

Infection with Chlamydia pecorum is one of the main causes of progressive decline of koala (Phascolarctos cinereus) populations in Eastern Australia. Pathological changes associated with the chlamydial infection in the genital tract of female and male koalas have been widely described with reports of acute and chronic lymphoplasmacytic inflammation and the description of the cystic dilatation of the ovarian bursa. Although these disease manifestations can result in severe chronic inflammation, structural changes and even sterility, only limited data is currently available on the organism's distribution and associated histopathological and ultrastructural changes within the upper genital tract of affected females. This study examined the pathogenesis of the most common pathological lesion associated with chlamydiosis in female koalas, the cystic dilation of the ovarian bursa starting from the evidence that Chlamydia spp. induces disruption of the intercellular junctions in the epithelium of the reproductive organs in humans. Histology, immunohistochemistry (IHC) and transmission electron microscopy (TEM) were performed to evaluate the structural features and the expression of epithelial cell and cellular junctions' markers in affected bursae from 39 Chlamydia-infected female koalas. Epithelial cells from the ovarian bursae of one affected animal examined by transmission electron microscopy showed severe widening of the intercellular space, as morphologic evidence of disrupted permeability of the epithelial barrier. The epithelial cell-cell junctions markers E-cadherin, ß-catenin and ZO-1 expressions were significantly reduced in samples from cystic bursae when compared to normal tissue samples (P < 0.0001). On the other end, a significantly higher expression of the proliferation marker Ki67 was observed in cystic bursae compared to control samples (P < 0.0001). As these proteins are required to maintain epithelial functional integrity and cell-cell adhesive interactions, their loss may permanently impair and affect female koala fertility and suggest the molecular basis of the pathogenesis of the cystic accumulation of bursal fluid within this tissue.

Chlamydia pneumoniae can infect the central nervous system via the olfactory and trigeminal nerves and contributes to Alzheimer's disease risk.

Chlamydia pneumoniae is a respiratory tract pathogen but can also infect the central nervous system (CNS). Recently, the link between C. pneumoniae CNS infection and late-onset dementia has become increasingly evident. In mice, CNS infection has been shown to occur weeks to months after intranasal inoculation. By isolating live C. pneumoniae from tissues and using immunohistochemistry, we show that C. pneumoniae can infect the olfactory and trigeminal nerves, olfactory bulb and brain within 72 h in mice. C. pneumoniae infection also resulted in dysregulation of key pathways involved in Alzheimer's disease pathogenesis at 7 and 28 days after inoculation. Interestingly, amyloid beta accumulations were also detected adjacent to the C. pneumoniae inclusions in the olfactory system. Furthermore, injury to the nasal epithelium resulted in increased peripheral nerve and olfactory bulb infection, but did not alter general CNS infection. In vitro, C. pneumoniae was able to infect peripheral nerve and CNS glia. In summary, the nerves extending between the nasal cavity and the brain constitute invasion paths by which C. pneumoniae can rapidly invade the CNS likely by surviving in glia and leading to Aß deposition.

In vitro transmission of Chlamydia using naturally infected koala (Phascolarctos cinereus) semen.

Transmission of Chlamydia pecorum infection has generally been assumed to be via the urogenital route and in an attempt to confirm this we investigated an in vitro method of Chlamydia infection using naturally infected koala semen to inoculate a cell line and attempt to estimate C. pecorum infectious load. A total of 57% of 122 koala semen samples had low C. pecorum copy number or no burden, while 18% of semen samples contained >10000 inclusion-forming units/mL, as determined by quantitative polymerase chain reaction. In vitro inoculation of a McCoy cell line resulted in successful infection from 4% of semen samples where C. pecorum burden was >105 inclusion-forming units/mL. Our preliminary study suggests that transmission of C. pecorum infectious dose may be restricted to peak bacterial shedding in semen associated with recent infection. Here, we report venereal transmission of C. pecorum in koala semen is possible; however, we speculate that antimicrobial factors and innate immune function receptors associated with semen may inhibit chlamydial growth. These mechanisms have yet to be reported in marsupial semen.

Investigation of pathology associated with Chlamydia pecorum infection in the male reproductive tract, and the effect on spermatogenesis and semen quality in the koala (Phascolarctos cinereus).

There is growing evidence that Chlamydia pecorum infection of the male koala reproductive tract causes inflammation and pathology of the urogenital tract. Previous studies have revealed that male koalas exhibiting severe clinical signs of urogenital chlamydial disease had an increased incidence of sperm DNA fragmentation and abnormal sperm morphology, suggestive of chronic exposure to C. pecorum infection and/or inflammation in the testis and epididymis, with residual pathology and lesions disrupting spermatogenesis and maturation of spermatozoa. This study specifically aimed to determine whether pathology associated with chlamydial infection in different regions of the male koala reproductive tract had an adverse effect on classical seminal parameters, sperm DNA quality and endocrine function (testosterone secretion) of naturally infected males. Semen from 58 sexually mature male koalas deemed not suitable for rehabilitation or treatment was assessed, in addition to undertaking a GnRH challenge to determine the androgenic capacity of the testis. Following euthanasia, tissue samples from testes, epididymis and prostate were evaluated for histopathology and real time polymerase chain reaction (qPCR). A significant difference in sperm concentration was observed between males with unilateral and bilateral testicular atrophy and C. pecorum infection (P = 0.011); and between males with unilateral atrophy and C. pecorum infection in one testis and bilateral normal testes with no C. pecorum infection (P = 0.008). No significant association was found for any other semen parameters when categorised by histopathology and C. pecorum tissue presence within the testes, epididymis and prostate. Plasma testosterone concentrations did not significantly differ between testicular histopathology diagnosis and/or C. pecorum infection status. This study suggests Chlamydia infection and inflammation may not be the predominant reason of disruption to spermatogenesis in the wild koala but rather testicular degeneration and atrophy, irrespective of Chlamydia infection, appears to be the primary reason of decreased sperm concentration.

Short-term heat acclimation preserves knee extensor torque but does not improve 20 km self-paced cycling performance in the heat.

PURPOSE: This study investigated the effect of 5 days of heat acclimation training on neuromuscular function, intestinal damage, and 20 km cycling (20TT) performance in the heat. METHODS: Eight recreationally trained males completed two 5-day training blocks (cycling 60 min day-1 at 50% peak power output) in a counter-balanced, cross-over design, with a 20TT completed before and after each block. Training was conducted in hot (HA: 34.9 ± 0.7 °C, 53 ± 4% relative humidity) or temperate (CON: 22.2 ± 2.6 °C, 65 ± 8% relative humidity) environment. All 20TTs were completed in the heat (35.1 ± 0.5 °C, 51 ± 4% relative humidity). Neuromuscular assessment of knee extensors (5 × 5 s maximum voluntary contraction; MVC) was completed before and after each 20TT and on the first and last days of each training block. RESULTS: MVC torque was statistically higher after 5 days of HA training compared to CON (mean difference = 14 N m [95% confidence interval; 6, 23]; p < 0.001; d = 0.77). However, 20TT performance after 5 days of HA training was not statistically different to CON, with a between-conditions mean difference in the completion time of 68 s [95% confidence interval; - 9, 145] (p = 0.076; d = 0.35). CONCLUSION: Short-term heat acclimation training may increase knee extensor strength without changes in central fatigue or intestinal damage. Nevertheless, it is insufficient to improve 20 km self-paced cycling performance in the heat compared to workload-matched training in a temperate environment. These data suggest that recreationally trained athletes gain no worthwhile performance advantage from short-term heat-training before competing in the heat.

DNA damage contributes to transcriptional and immunological dysregulation of testicular cells during Chlamydia infection.

Chlamydia is the most commonly reported sexually transmitted bacterial infection, with 127 million notifications worldwide each year. Both males and females are susceptible to the pathological impacts on fertility that Chlamydia infections can induce. However, male chlamydial infections, particularly within the upper reproductive tract, including the testis, are not well characterized. In this study, using mouse testicular cell lines, we examined the impact of infection on testicular cell lineage transcriptomes and potential mechanisms for this impact. The somatic cell lineages exhibited significantly fragmented genomes during infection. Likely resulting from this, each of the Leydig, Sertoli and germ cell lineages experienced extensive transcriptional dysregulation, leading to significant changes in cellular biological pathways, including interferon and germ-Sertoli cell signalling. The cell lineages, as well as isolated spermatozoa from infected mice, also contained globally hypomethylated DNA. Cumulatively, the DNA damage and epigenetic-mediated transcriptional dysregulation observed within testicular cells during chlamydial infection could result in the production of spermatozoa with abnormal epigenomes, resulting in previously observed subfertility in infected animals and congenital defects in their offspring.

The occurrence and pathology of chlamydiosis in the male reproductive tract of non-human mammals: A review.

Organisms belonging to the Family Chlamydiaceae are responsible for a broad range of diseases in humans, livestock, companion animals and non-domestic species. Infection of the reproductive organs can cause a range of syndromes of which sub- and infertility are the most frequently observed clinical manifestations. While the gross and histological lesions associated with the isolation of Chlamydiaceae from the non-human female reproductive tract are well documented, little attention has been given to the pathological effects of this infection in the male genital system. As such, the occurrence and importance of Chlamydia-associated disease in male non-human mammalian species is less well documented. In order to improve our understanding of the significance of chlamydiosis in domestic, laboratory and wild animals, this review provides an up-to-date summary of Chlamydia-associated male reproductive pathology, whether that infection occurs naturally or experimentally. Although most lesions in males are described as incidental and of minor significance, results of recent studies suggest that infection with Chlamydiaceae can adversely impact male fertility and/or be instrumental in disease transmission. Although in humans, bulls and mice Chlamydia infection has been associated with morphological and functional abnormalities of the spermatozoa, this review will focus on the gross and histological findings linked to the colonisation of the genital system by this pathogen. Advances in our understanding of male reproductive chlamydiosis are necessary for diagnostic and therapeutic strategies, as well as epidemiological and conservation studies.

Testicular inflammation and infertility: Could chlamydial infections be contributing?

Despite the global incidence of both male infertility and sexually transmitted infections rising each year, the relationship between the two is relatively unstudied. Chlamydia is the most common bacterial sexually transmitted pathogen; however, the majority of research remains focussed on women, while the role of infection and resulting immunopathology in male factor infertility is largely unknown. Chlamydia was found in testicular biopsies from asymptomatic men with idiopathic infertility, which highlights this potential role. In animal models, testicular Chlamydia, and potentially other bacterial and viral infections, cause histopathology that is likely to adversely affect spermatogenesis and fertility. This likely occurs through infiltration of inflammatory cells, functional dysregulation of immunosuppressive testicular macrophages and Sertoli cells and destruction of key testicular cell types including sperm progenitors. Here, testicular damage due to infection and/or inflammation is reviewed, as it represents a probable underestimated and unrecognized factor leading to male infertility.

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development†.

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality.

Burkholderia pseudomallei invades the olfactory nerve and bulb after epithelial injury in mice and causes the formation of multinucleated giant glial cells in vitro.

The infectious disease melioidosis is caused by the bacterium Burkholderia pseudomallei. Melioidosis is characterised by high mortality and morbidity and can involve the central nervous system (CNS). We have previously discovered that B. pseudomallei can infect the CNS via the olfactory and trigeminal nerves in mice. We have shown that the nerve path is dependent on mouse strain, with outbred mice showing resistance to olfactory nerve infection. Damage to the nasal epithelium by environmental factors is common, and we hypothesised that injury to the olfactory epithelium may increase the vulnerability of the olfactory nerve to microbial insult. We therefore investigated this, using outbred mice that were intranasally inoculated with B. pseudomallei, with or without methimazole-induced injury to the olfactory neuroepithelium. Methimazole-mediated injury resulted in increased B. pseudomallei invasion of the olfactory epithelium, and only in pre-injured animals were bacteria found in the olfactory nerve and bulb. In vitro assays demonstrated that B. pseudomallei readily infected glial cells isolated from the olfactory and trigeminal nerves (olfactory ensheathing cells and trigeminal Schwann cells, respectively). Bacteria were degraded by some cells but persisted in other cells, which led to the formation of multinucleated giant cells (MNGCs), with olfactory ensheathing cells less likely to form MNGCs than Schwann cells. Double Cap mutant bacteria, lacking the protein BimA, did not form MNGCs. These data suggest that injuries to the olfactory epithelium expose the primary olfactory nervous system to bacterial invasion, which can then result in CNS infection with potential pathogenic consequences for the glial cells.