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.

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.

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), Il1β (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.

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.

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 (Liporale^TM ) 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.

Vaccination protects from chlamydial infertility

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 TGFβ 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.

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.

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.

Hematogenous dissemination of Chlamydia muridarum from the urethra in macrophages causes testicular infection and sperm DNA damage†

The incidence of Chlamydia infection, in both females and males, is increasing worldwide. Male infections have been associated clinically with urethritis, epididymitis, and orchitis, believed to be caused by ascending infection, although the impact of infection on male fertility remains controversial. Using a mouse model of male chlamydial infection, we show that all the major testicular cell populations, germ cells, Sertoli cells, Leydig cells, and testicular macrophages can be productively infected. Furthermore, sperm isolated from vas deferens of infected mice also had increased levels of DNA damage as early as 4 weeks post-infection. Bilateral vasectomy, prior to infection, did not affect the chlamydial load recovered from testes at 2, 4, and 8 weeks post-infection, and Chlamydia-infected macrophages were detectable in blood and the testes as soon as 3 days post-infection. Partial depletion of macrophages with clodronate liposomes significantly reduced the testicular chlamydial burden, consistent with a hematogenous route of infection, with Chlamydia transported to the testes in infected macrophages. These data suggest that macrophages serve as Trojan horses, transporting Chlamydia from the penile urethra to the testes within 3 days of infection, bypassing the entire male reproductive tract. In the testes, infected macrophages likely transfer infection to Leydig, Sertoli, and germ cells, causing sperm DNA damage and impaired spermatogenesis.

Detection of chlamydia infection within human testicular biopsies

STUDY QUESTION

Can Chlamydia be found in the testes of infertile men?

SUMMARY ANSWER

Chlamydia can be found in 16.7% of fresh testicular biopsies and 45.3% of fixed testicular biopsies taken from a selection of infertile men.

WHAT IS KNOWN ALREADY

Male chlamydial infection has been understudied despite male and female infections occurring at similar rates. This is particularly true of asymptomatic infections, which occur in 50% of cases. Chlamydial infection has also been associated with increased sperm DNA damage and reduced male fertility.

STUDY DESIGN, SIZE, DURATION

We collected diagnostic (fixed, n = 100) and therapeutic (fresh, n = 18) human testicular biopsies during sperm recovery procedures from moderately to severely infertile men in a cross-sectional approach to sampling.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The diagnostic and therapeutic biopsies were tested for Chlamydia-specific DNA and protein, using real-time PCR and immunohistochemical approaches, respectively. Serum samples matched to the fresh biopsies were also assayed for the presence of Chlamydia-specific antibodies using immunoblotting techniques.

MAIN RESULTS AND THE ROLE OF CHANCE

Chlamydial major outer membrane protein was detected in fixed biopsies at a rate of 45.3%. This was confirmed by detection of chlamydial DNA and TC0500 protein (replication marker). C. trachomatis DNA was detected in fresh biopsies at a rate of 16.7%, and the sera from each of these three positive patients contained C. trachomatis-specific antibodies. Overall, C. trachomatis-specific antibodies were detected in 72.2% of the serum samples from the patients providing fresh biopsies, although none of the patients were symptomatic nor had they reported a previous sexually transmitted infection diagnosis including Chlamydia.

LIMITATIONS, REASONS FOR CAUTION

No reproductively healthy male testicular biopsies were tested for the presence of Chlamydia DNA or proteins or Chlamydia-specific antibodies due to the unavailability of these samples.

WIDER IMPLICATIONS FOR THE FINDINGS

Application of Chlamydia-specific PCR and immunohistochemistry in this human male infertility context of testicular biopsies reveals evidence of a high prevalence of previously unrecognised infection, which may potentially have a pathogenic role in spermatogenic failure.

STUDY FUNDING/COMPETING INTEREST(S)

Funding for this project was provided by the Australian NHMRC under project grant number APP1062198. We also acknowledge assistance from the Monash IVF Group and Queensland Fertility Group in the collection of fresh biopsies, and the Monash Health and co-author McLachlan (declared equity interest) in retrieval and sectioning of fixed biopsies. E.M. declares an equity interest in the study due to financing of fixed biopsy sectioning. All other authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Rhinovirus infections in Tecumseh, Michigan: frequency of illness and number of serotypes

We studied rhinovirus-associated illnesses from 1976 to 1981 among residents of the community of Tecumseh, Michigan, in a continuation of similar studies done in 1966-1971. Rhinoviruses were the most frequently isolated respiratory pathogen in all age groups, including young children. The pattern of age-specific isolation rates was similar to that for total respiratory illness. Rhinovirus-associated illnesses were generally mild but of relatively long duration; restriction of daily activity was frequent, especially in certain age groups. Typing of all isolates has been completed; with high-quality antisera nearly all isolates could be typed. Thus, new serotypes are probably not evolving, and most have already been identified. Differences in frequency of occurrences of different serotypes were evident, but ranking in order of importance was difficult based on existing data.

The Tecumseh Study of Illness. XIV. Occurrence of respiratory viruses, 1976-1981

During 1976-1981, surveillance of respiratory infection in Tecumseh, Michigan included isolation of respiratory viruses using methods similar to those employed in 1965-1971. As in the earlier period, influenza viruses continued to be isolated annually, but not without some changes in regularity of appearance. Parainfluenzaviruses also exhibited some marked changes in patterns of occurrence, but years of activity of parainfluenza types 1 and 2 were similar to those reported in other studies. Respiratory syncytial viruses continued to be limited in appearance to relatively brief periods. Rates of isolation of parainfluenzaviruses and respiratory syncytial viruses demonstrated their importance in reinfections of older children and adults. This was confirmed by examination of characteristics of associated illnesses.

Relative efficacy of embryonated eggs and cell culture for isolation of contemporary influenza viruses

The efficiency of embryonated eggs and primary monkey kidney cell culture for isolation of contemporary influenza viruses was compared over three seasons by parallel inoculation of clinical materials. For the type A (H1N1) strains of 1977-1978 and for type B strains eggs were very inefficient, and nearly all viruses were isolated in cell culture alone. For the type A (H1N1) strains of 1978-1979 and for type A (H3N2) strains, isolations were more frequently made in eggs, but even here eggs were not as efficient for primary isolation as were cell cultures. It is concluded that primary monkey kidney cell cultures can be used as the single system for primary isolation of current type A and B influenza viruses.

Susceptibility to rhinovirus infection in chronic bronchitis

The role of rhinoviruses in chronic bronchitis was examined serologically in the community of Tecumseh, Michigan. Five different rhinovirus types had been identified by isolation to be present in the community during the time of the study. They were tested against serums obtained from persons with chronic bronchitis and matched control subjects. Both males and females with chronic bronchitis had more frequent infections than did the control subjects; for males, the differences were significant. The higher infection rate among the bronchitic subjects was not related to their being deficient in antibody at the start of the study. It was concluded that persons with chronic bronchitis appear to be more susceptible to rhinovirus infection, as they are to other viral pathogens.

The Tecumseh study of respiratory illness. VII. Further observations on the occurrence of respiratory syncytial virus and Mycoplasma pneumoniae infections

The occurrence of infection with respiratory syncytial (RS) virus and Mycoplasma pneumoniae was determined over a 6-year period among residents of Tecumseh, Michigan by isolation and serology. RS virus infection was detected for a variable time each year during the months extending from November to May. There was little viral activity in intervals between these periods of prevalence, which occurred on an alternating short-long cycle. Higher infection rates were detected in periods preceding the long interval than were detected in periods preceding the short interval. Viruses isolated from serial annual outbreaks did not show any sequential changes in antigens, although some variation in antigenic structure was apparent. Infections were common in school-age children, indicating the role of this population in transmission. Young girls were infected as often as young boys, suggesting that observed differences in occurrence of illness must be related to differences in expression of infection. In contrast to RS virus, M. pneumoniae did not appear and disappear annually, but like it, the school-age group was most heavily involved in infection.