- Title
- The roles of mast cells and mast cell proteases during Chlamydia reproductive tract infection
- Creator
- Chevalier, Anne
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Chlamydia trachomatis is the most common bacterial sexually transmitted infection (STI), with approximately 130 million cases of infection occurring annually worldwide. Although Chlamydia infections are relatively simple to diagnose and treat, the majority of infected women do not develop any symptoms, hence they often go undiagnosed and untreated. Over time, untreated infections may ascend from the vagina into the upper female reproductive tract (FRT) and cause severe complications including pelvic inflammatory disease, ectopic pregnancy and tubal factor infertility. The host immune responses to Chlamydia infections are very complex and a greater understanding of the host responses, including immune cells and factors, that contribute to clearance of infection versus those that underpin infection-associated pathology is required. Mast cells (MCs) are large, tissue-resident, immune cells of haematopoietic origin that are present in the FRT. They are characterised by their numerous intracellular secretory granules that hold a wide variety of preformed inflammatory mediators, including histamine, serglycin proteoglycans and MC proteases. Upon MC activation, these preformed mediators are released into the extracellular matrix through a mechanism called degranulation. Although MCs are well recognised for their detrimental role in allergy, they are also key mediators of immune responses to an extensive number of pathogens. However, the role that MCs play during STIs remains largely unknown. To address this, my PhD studies aimed to investigate the role(s) of MCs and MC proteases during Chlamydia FRT infections, using a suite of genetically modified mice that are deficient in MCs or in specific MC proteases and a murine model of Chlamydia FRT infection. My results suggest that the number of uterine MCs and their expression of the MC proteases, mouse MC protease (mMCP)4, mMCP5, mMCP6 and carboxypeptidase (Cpa)3 are regulated by female sex hormones and/or stage of oestrous cycle in the absence of Chlamydia FRT infection. Whilst the number, phenotype and degranulation status of MCs appear unchanged 3 days post infection (dpi) with Chlamydia, the number of MCs and their expression of mMC4, mMCP5, mMCP6 and CPA3 are slightly reduced at 14dpi. In contrast, I show that the expression of protease serine member S31 (Prss31), a unique MC protease that possesses a membrane anchor that binds it to the plasma membrane of MCs upon degranulation, appear to be independent of female sex hormones and Chlamydia FRT infection. Together, these data suggest that female sex hormones and Chlamydia FRT infection may affect the number and phenotype of MCs in the FRT. Moreover, my studies reveal a novel role for MCs in mediating Chlamydia FRT infection. I show that MC-deficient mice are protected against Chlamydia-induced pathology and have slightly reduced eosinophils, neutrophils, monocytes and macrophages in their uterus, suggesting a role for MCs in contributing to the recruitment of innate immune cells, associated with development of Chlamydia-induced pathology, in the upper FRT. By using intravaginal treatments with the MC stabiliser cromolyn, I show evidence that MC degranulation is detrimental, especially during the early stages of Chlamydia FRT infection. Mice that received cromolyn throughout the early stages of Chlamydia infection have reduced infection at 3dpi. However, this protective effect is not maintained at later stages of infection. Importantly, mice that receive cromolyn treatment during the early stages of infection are protected against infection-induced pathology during the later stages. These observations show that the inhibition of MC degranulation does not recapitulate the effects observed in MC-deficient mice, suggesting that some of the factors released through degranulation might have differential effects to other factors released by MCs through other pathways. I next sought to identify the role(s) of some of the key factors, specifically factors that are stored in the secretory granules of MCs that are released during MC degranulation, in the pathogenesis of Chlamydia FRT infection. In my first series of experiments, N-Deacetylase/N-Sulfotransferase 2 (Ndst2)-deficient mice were subjected to Chlamydia FRT infection. These mice lack the important enzyme for N-deacetylation and N-sulfation of heparan sulfate in MCs, which causes abnormal storage of the MC mediators that are normally bound to heparin in the secretory granules of MCs, including histamine and the MC proteases, mMCP4, mMCP5, mMCP6 and Cpa3. Interestingly, I show that Ndst2-deficient mice are more susceptible to infection, while being protected against Chlamydia–induced pathology. This increase in susceptibility to infection and protection against pathology is associated with a decrease in the number of innate and adaptive cells present in the uterus, suggesting that the factors that are affected by Ndst2 deficiency, play important role in the induction of the recruitment of immune cell associated with clearance of infection (E.g. CD4+ T cells) and with development of Chlamydia–associated pathology (E.g. neutrophils). I next sought to assess the individual roles played by specific MC proteases in the pathogenesis of Chlamydia FRT infection. To do this, mMCP5-, mMCP6-, Prss31-deficient and mMCP6-deficient/mMCP7-sufficient mice were infected with Chlamydia FRT. I show that whilst mMCP6-deficient mice have similar course of infection as wild type (WT) control mice, mMCP5-deficient mice are protected against infection at 3dpi. Interestingly, the presence of mMCP7 (which is naturally deficient in the WT control mice used) in mMCP6-deficient mice slightly protected against the early stages of infection as well as infection-induced pathology during the later stages of infection compared to WT controls. I also show that Prss31-deficient mice are more susceptible to infection early, but have no change in infection-induced pathology at later stages of Chlamydia infection. My studies also show that absence of Prss31 results in a decrease in immune cell recruitment to the uterus during infection. Importantly, daily intravaginal treatments with recombinant Pss31 protects against infection and infection-induced pathology. Together, my studies show important role(s) for MCs and MC degranulation in the pathogenesis of Chlamydia FRT infection. My studies also show that different MC proteases may play different roles in infection and infection-induced disease. Importantly, whilst the mechanisms involved remain to be elucidated, my studies highlight that MC-mediated responses may be therapeutically manipulated in order to treat/prevent Chlamydia FRT infection and/or infection-induced FRT pathology.
- Subject
- Chlamydia infection; mast cells; mast cell proteases; tryptases; chymases
- Identifier
- http://hdl.handle.net/1959.13/1411375
- Identifier
- uon:36328
- Rights
- Copyright 2020 Anne Chevalier
- Language
- eng
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