Induction of partial immunity in both males and females is sufficient to protect females against sexual transmission of Chlamydia.

Sexually transmitted Chlamydia trachomatis causes infertility, and because almost 90% of infections are asymptomatic, a vaccine is required for its eradication. Mathematical modeling studies have indicated that a vaccine eliciting partial protection (non-sterilizing) may prevent Chlamydia infection transmission, if administered to both sexes before an infection. However, reducing chlamydial inoculum transmitted by males and increasing infection resistance in females through vaccination to elicit sterilizing immunity has yet to be investigated experimentally. Here we show that a partially protective vaccine (chlamydial major outer membrane protein (MOMP) and ISCOMATRIX (IMX) provided sterilizing immunity against sexual transmission between immunized mice. Immunizing male or female mice before an infection reduced chlamydial burden and disease development, but did not prevent infection. However, infection and inflammatory disease responsible for infertility were absent in 100% of immunized female mice challenged intravaginally with ejaculate collected from infected immunized males. In contrast to the sterilizing immunity generated following recovery from a previous chlamydial infection, protective immunity conferred by MOMP/IMX occurred independent of resident memory T cells. Our results demonstrate that vaccination of males or females can further protect the opposing sex, whereas vaccination of both sexes can synergize to elicit sterilizing immunity against Chlamydia sexual transmission.

Chlamydia pneumoniae and Chlamydia Trachomatis Infection Differentially Modulates Human Dendritic Cell Line (MUTZ) Differentiation and Activation.

Chlamydia trachomatis and Chlamydia pneumoniae are important human pathogens that infect the urogenital/anorectal and respiratory tracts, respectively. Whilst the ability of these bacteria to infect epithelia is well defined, there is also considerable evidence of infection of leucocytes, including dendritic cells (DCs). Using a human dendritic cell line (MUTZ), we demonstrate that the infection and replication of chlamydiae inside DCs is species and serovar specific and that live infection with C. pneumoniae is required to upregulate costimulatory markers CD80, CD83 and human leucocyte antigen (HLA)-DR on MUTZ cells, as well as induce secretion of interleukin (IL)-2, IL-6, IL-8, IL-12 (p70), interferon-gamma and tumour necrosis factor-alpha Conversely, C. trachomatis serovar D failed to upregulate DC costimulatory markers, but did induce secretion of high concentrations of IL-8. Interestingly, we also observed that infection of MUTZ cells with C. pneumoniae or C. trachomatis serovar L2, whilst not replicative, remained infectious and upregulated lymph node migratory marker CCR7 mRNA. Taken together, these data confirm the findings of other groups using primary DCs and demonstrate the utility of MUTZ cells for further studies of chlamydial infection.

The mouse model of Chlamydia genital tract infection: a review of infection, disease, immunity and vaccine development.

Chlamydia trachomatis is the most common sexually transmitted bacterial infection worldwide. The impact of this pathogen on human reproduction has intensified research efforts to better understand chlamydial infection and pathogenesis. Whilst there are animal models available that mimic many aspects of human chlamydial infection, the mouse is regarded as the most practical and widely used of the models. Studies in mice have greatly contributed to our understanding of the host-pathogen interaction and provided an excellent medium for evaluating vaccines. Here we explore the advantages and disadvantages of all animal models of chlamydial genital tract infection, with a focus on the murine model and what we have learnt from it so far.

Ovarian steroid hormones: effects on immune responses and Chlamydia trachomatis infections of the female genital tract.

Female sex hormones are known to regulate the adaptive and innate immune functions of the female reproductive tract. This review aims to update our current knowledge of the effects of the sex hormones estradiol and progesterone in the female reproductive tract on innate immunity, antigen presentation, specific immune responses, antibody secretion, genital tract infections caused by Chlamydia trachomatis, and vaccine-induced immunity.

Constitutive production of IL-13 promotes early-life Chlamydia respiratory infection and allergic airway disease.

Deleterious responses to pathogens during infancy may contribute to infection and associated asthma. Chlamydia respiratory infections in early life are common causes of pneumonia and lead to reduced lung function and asthma. We investigated the role of interleukin-13 (IL-13) in promoting early-life Chlamydia respiratory infection, infection-induced airway hyperresponsiveness (AHR), and severe allergic airway disease (AAD). Infected infant Il13(-/-) mice had reduced infection, inflammation, and mucus-secreting cell hyperplasia. Surprisingly, infection of wild-type (WT) mice did not increase IL-13 production but reduced IL-13Rα2 decoy receptor levels compared with sham-inoculated controls. Infection of WT but not Il13(-/-) mice induced persistent AHR. Infection and associated pathology were restored in infected Il13(-/-) mice by reconstitution with IL-13. Stat6(-/-) mice were also largely protected. Neutralization of IL-13 during infection prevented subsequent infection-induced severe AAD. Thus, early-life Chlamydia respiratory infection reduces IL-13Rα2 production, which may enhance the effects of constitutive IL-13 and promote more severe infection, persistent AHR, and AAD.

Dual purpose contraceptives: targeting fertility and sexually transmitted disease.

There have been no radically new forms of contraception since the pill was introduced 1960 and even this form of fertility regulation can be traced back to endocrine advances that were made in the 1920s. Whatever new forms of fertility control we introduce for the future, they should exploit the significant advances that have been made in our understanding of the reproductive system in recent years and be tailored to the needs of the 21st century. In this context, there is an urgent need to develop novel, safe, effective, dual-purpose contraceptive agents that combine the prevention of pregnancy with protection against sexually transmitted diseases (STDs). To achieve this aim we have researched a class of a topical contraceptive agent that selectively and instantaneously immobilizes millions of spermatozoa, while suppressing the infectivity of pathogenic microbes, such as Chlamydia, in the ejaculate. This approach is based upon the ability of small molecular mass organic compounds to selectively and covalently adduct key proteins in spermatozoa and pathogenic organisms and disrupt their biological function. We have also successfully developed strategies for the preparation of latent formulations that would only become activated on contact with seminal plasma. The further development and refinement of these molecules should permit a radical rethink in the way that safe, effective topical protection is provided to control both fertility and the world-wide spread of STDs.

Streptococcus pneumoniae infection suppresses allergic airways disease by inducing regulatory T-cells.

An inverse association exists between some bacterial infections and the prevalence of asthma. We investigated whether Streptococcus pneumoniae infection protects against asthma using mouse models of ovalbumin (OVA)-induced allergic airway disease (AAD). Mice were intratracheally infected or treated with killed S. pneumoniae before, during or after OVA sensitisation and subsequent challenge. The effects of S. pneumoniae on AAD were assessed. Infection or treatment with killed S. pneumoniae suppressed hallmark features of AAD, including antigen-specific T-helper cell (Th) type 2 cytokine and antibody responses, peripheral and pulmonary eosinophil accumulation, goblet cell hyperplasia, and airway hyperresponsiveness. The effect of infection on the development of specific features of AAD depended on the timing of infection relative to allergic sensitisation and challenge. Infection induced significant increases in regulatory T-cell (Treg) numbers in lymph nodes, which correlated with the degree of suppression of AAD. Tregs reduced T-cell proliferation and Th2 cytokine release. The suppressive effects of infection were reversed by anti-CD25 treatment. Respiratory infection or treatment with S. pneumoniae attenuates allergic immune responses and suppresses AAD. These effects may be mediated by S. pneumoniae-induced Tregs. This identifies the potential for the development of therapeutic agents for asthma from S. pneumoniae.

Granulocyte-macrophage colony-stimulating factor enhances wound healing in diabetes via upregulation of proinflammatory cytokines.

BACKGROUND: Chronic ulceration, especially in diabetes, remains a substantial clinical problem. Exogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) is efficacious in the treatment of chronic wound healing in both animal models and patients, but its role in diabetic wounds remains to be explored. Objectives Using a diabetic mouse model, to investigate the role of GM-CSF in wound healing. METHODS: Clinical observation, histopathology, immunohistochemistry and cytokine assays. RESULTS: There was a significant reduction (50%) in GM-CSF production in the wounds of the diabetics compared with nondiabetics. Exogenous GM-CSF substantially enhanced the wound healing in diabetic mice, accompanied by increased interleukin-6 and monocyte chemoattractant protein-1 production. The elevated cytokines correlated with increased neovascularization, and infiltration of macrophages and neutrophils. GM-CSF showed no beneficial effects in nondiabetic wound healing. CONCLUSIONS: Our results provide useful guidelines for the clinical management of chronic ulceration in diabetes.

The role of granulocyte macrophage-colony stimulating factor in gastrointestinal immunity to salmonellosis.

Human Salmonella infection, in particular, typhoid fever is a highly infectious disease that remains a major public health problem causing significant morbidity and mortality. The outcome of these infections depends on the host's immune response, particularly the actions of granulocytes and macrophages. Using a mouse model of human typhoid fever, with Salmonella typhimurium infection of wild type and granulocyte macrophage-colony stimulating factor (GM-CSF) knock out mice we show a delay in the onset of immune-mediated tissue damage in the spleens and livers of GM-CSF(-/-) mice. Furthermore, GM-CSF(-/-) mice have a prolonged sequestration of S. typhimurium in affected tissues despite an increased production of F4/80+ effector cells. Moreover in the absence of GM-CSF, a decrease in pro-inflammatory cytokine expression of tumor necrosis factor-alpha, interleukin-12 (IL-12) and IL-18 was found, which may alter the host's immune response to infection. GM-CSF appears to play an important role in the pathogenesis of Salmonellosis, and may contribute significantly to the development of protective gastrointestinal mucosal immune responses against oral pathogens.

Genetic background affects susceptibility in nonfatal pneumococcal bronchopneumonia.

A nonfatal pneumococcal lung infection model was required to investigate immune responses during recovery, and the interaction of other diseases subsequent to infection. A murine model of nonfatal pneumococcal lung infection was developed and the effect of genetic background on susceptibility was determined in BALB/c and C57BL/6 mice. Bacteria colonised the lungs and mice developed mild clinical illness with pathophysiology similar to human bronchopneumonia. Recovery was associated with immune cell influx, which cleared bacteria but induced tissue damage characteristic of pneumococcal bronchopneumonia. After clearance, immune cell populations returned to normal and tissues appeared less inflamed. Although bacterial exposure and clearance were similar, the extent of immune cell influx and tissue damage differed significantly. Larger numbers of neutrophils and lymphocytes entered lung tissue and the affected area was greater in BALB/c compared with C57BL/6 mice. An inflammatory basis for differences was determined with greater levels of phagocytosis and oxidative burst observed in BALB/c mice. C57BL/6 mice cleared the low inoculum with a reduced immune response; however, C57BL/6 mice are more susceptible to larger inocula, which overwhelms the immune system. These different susceptibilities result from a greater inflammatory response in BALB/c compared with C57BL/6 mice.

Effects of exogenous interleukin-6 during Pseudomonas aeruginosa corneal infection.

Lack of interleukin-6 (IL-6) during Pseudomonas aeruginosa corneal infection leads to more severe disease with changes in neutrophil recruitment. Exogenous IL-6 leads to increased efficiency of neutrophil recruitment and reduced bacterial loads in corneal infection in both IL-6 gene knockout and wild-type mice. This may be mediated by IL-6 increasing the production of corneal macrophage inflammatory protein 2 and intercellular cell adhesion molecule 1. We conclude that effective recruitment of neutrophils into the cornea is dependent on the production of IL-6 and that early augmentation of IL-6 may be protective in corneal infection.

Chlamydia trachomatis infection: incidence, health costs and prospects for vaccine development.

Chlamydia trachomatis infection is now the most common sexually transmitted disease worldwide. World Health Organisation figures estimated that 89 million new cases of genital Chlamydia infections occurred in 1995, highlighting the worldwide prevalence of infections and the economic burden on healthcare delivery. A number of methods have been developed for detection of chlamydial infection, which vary in sensitivity and specificity. No single method has yet gained general acceptance and in many countries Chlamydia infections are not reported, suggesting that the above figures may be an underestimate of the problem. As yet there is no consensus as to what constitutes a protective immune response against genital Chlamydia infection. Studies in animal models have shown that cell-mediated immunity, both Th1-driven macrophage activation and cytotoxic T cell responses, as well as antibody can mediate protection at different stages of the chlamydial life cycle. A successful vaccine would probably need to elicit both a systemic cell-mediated immune response to limit/resolve established infections and a mucosal IgA response to reduce bacterial shedding and the resulting spread of infection to partners of infected individuals. The immune response to Chlamydia, either through natural infection or following immunisation, also has the potential to enhance inflammation and to act as a driving force for constant mutation in the variable regions of the major outer membrane protein. As a result a constant prevalence of infection is maintained even in an immune population through the emergence of new allelic variants. Immune responses against antigens such as the 60 kDa heat shock protein can exacerbate inflammation through molecular mimicry and must not be elicited as a result of vaccination. Thus there are many challenges for the development of a successful vaccine which must elicit immunity against multiple serovars while at the same time minimising damaging pro-inflammatory immune responses.

Interferon-gamma plays a critical role in intestinal immunity against Salmonella typhimurium infection.

Salmonella bacteria are a major cause of food-borne infectious diarrhoea and there is great interest in understanding the pathogenesis of Salmonella infection and in vaccine development. Potential vaccines include the aromatic mutants of S. typhimurium. Such non-lethal Aro mutants have also been useful for studying Salmonella infections in mouse models. Studies of systemic infection, using these Aro mutants, in both normal and cytokine gene knockout mice, indicate that interferon-gamma (IFN-gamma) plays a key role in the resolution of Salmonella infection. The present studies have investigated the outcome of oral infection in mice with attenuated Salmonella because this infection route mimics natural infection in humans. In IFN-gamma gene knockout (IFN-gamma-/-) mice, intestinal immunity was impaired and oral challenge resulted in disseminated septicaemia 2 weeks later. No dissemination of infection was seen in wild-type mice. In wild-type mice, both CD4 and CD8 cell numbers increased in the gut following Salmonella challenge, together with increased expression of major histocompatibility complex (MHC) II and vascular cell adhesion molecule-1 (VCAM-1). No such changes were seen in IFNgamma-/- mice. Following oral challenge, antilipopolysaccharide (LPS) and antiphosphoryl choline antibodies increased by more than 100-fold in both serum and faecal pellet extracts of IFNgamma-/- mice compared with wild-type mice. Our data show that IFN-gamma production is essential for resolution of enteric Salmonella infection and that antibody has little effect on this process.

Transcutaneous immunization induces mucosal and systemic immunity: a potent method for targeting immunity to the female reproductive tract.

Female BALB/c mice were immunized with tetanus toxoid (TT) admixed with cholera toxin by direct application to shaved skin (Transcutaneous immunization, TCI). Tetanus toxoid-specific IgG and IgA in serum, saliva, vaginal lavage and fecal pellets were assayed by ELISA. Tetanus toxoid specific antibody-secreting cell (ASC) numbers were also determined by immunohistochemistry in sections of vagina, uterus, salivary gland and small intestine of immunized mice. TCI elicited significant levels of TT-specific IgG in serum, saliva and vaginal lavage, with the greatest increases over background seen in saliva (80-400 fold) and vaginal lavage (2-87 fold). TCI induced only modest levels of IgA in any of the samples tested (range 2-7 fold increase). In the absence of cholera toxin, application of TT alone did not result in detectable TT-specific antibodies in mucosal secretions. ASCs were found in all tissues following TCI. Cells were most frequent in uterus and vaginal tissues with ASC numbers less frequent in small intestine and salivary gland. This suggests that local production, rather than transudation from serum, is a major contributor of antibody in reproductive tract secretions. Further studies focussed on the role of sex hormones and immune induction following TCI. Animals immunized at the stage of oestrus cycle at which estrogen is abundant (Estrus), showed significantly lower levels of TT-specific IgG in vaginal lavage samples. Collectively, these data confirm the findings of Glenn and colleagues (1998), who showed TCI using cholera toxin can elicit high levels of serum IgG to both the toxin and co-administered antigen and further demonstrates that this route of immunization is particularly effective at eliciting humoral immunity in saliva and in the female reproductive tract.

Analysis of the mucosal microenvironment: factors determining successful responses to mucosal vaccines.

The predominance of IgA antibodies in mucosal sites reflects a combination of high rate IgA isotype switching among precursor cells in induction sites, their selective localisation in mucosal effector tissues and vigorous proliferation of these cells after extravasation. Each of these steps leading to IgA expression at the mucosa is under cytokine control. This paper will address the role of cytokines in induction and expression of IgA responses, the contribution of various precursor cell subsets and their differential responses to cytokine signals and strategies for manipulating cytokine expression. With respect to IgA antibody production in the gut whereas IL-4 and TGF-beta have been implicated in isotype switching of precursor cells to IgA commitment, their subsequent localisation, proliferation and effector activity expression is dependent on IL-5 and IL-6 expression locally. Most IgA plasma cells in the intestine derive from cells of the B2 lineage in the Peyer's patch, but a subpopulation of cells derived from the peritoneal cavity (B1 cells) also contribute to the IgA plasma cell population in the intestinal lamina propria. Whereas IgA+ cells of the B2 lineage are IL-6 dependent but IL-5 independent, B1-derived IgA+ cells are IL-5 dependent and IL-6 independent. On the other hand, cell mediated immune responses in the gut are highly dependent on IFN-gamma production by both Th1 CD4 cells and CD8 cells and in enteric Salmonella infection IFN-gamma production is essential but antibody has little effect on this process.Therapeutic interventions based on the information emerging from these studies will lead to improved vaccination responses and correction of immunodeficiencies especially in young animals.

Protection against Helicobacter pylori infection by intestinal immunisation with a 50/52-kDa subunit protein.

A mouse model of Helicobacter pylori infection was used to evaluate the vaccine antigen potential of the citrate synthase homologue protein purified from the H. pylori NCTC 11637 strain. Mice were immunised with the protein by intra-Peyer's patch immunisation. This route gives maximal intestinal immunisation and was used to screen oral vaccine candidate antigens without the added complication of simultaneously testing oral delivery systems. Two weeks post-immunisation mice were infected with Sydney strain H. pylori and 4 weeks after infection the mice were killed and the level of H. pylori infection in the stomach determined. Pre-immunisation with the 50/52-kDa protein led to a 84-91% reduction in H. pylori infection compared to unimmunised controls.

B1 B cell numbers and antibodies against phosphorylcholine and LPS are increased in IL-6 gene knockout mice.

Peritoneal cavity cells were isolated from IL6-gene knockout (IL6(-/-)) and wild-type mice and stained for expression of IgM, CD5, and CD23. B1 cell (IgM(+)/CD23(-), CD5(+)/IgM(+)) numbers were increased twofold in IL6(-/-) mice compared to normals while IgM(+)/CD23(+) (B2) cell numbers were reduced threefold. Intestinal antibody levels were also determined for both total immunoglobulin and phosphorylcholine (PC)-specific and LPS-specific antibody following oral challenge with attenuated Salmonella typhimurium. Total immunoglobulin levels (IgM, IgG, and IgA) were reduced 60-80% in intestinal secretions of IL6(-/-) mice compared to wild-type controls; however, PC-specific antibody was significantly higher in IL6(-/-) mice. Anti-LPS antibodies were also three- to sevenfold higher in IL6(-/-) mice compared to controls following Salmonella challenge. These data suggest that in IL6(-/-) mice the development of mucosal B2 cells is impaired but that intestinal B1 cells responding to microbial antigens such as PC and LPS develop normally and are fully functional.

Increased severity of Candida vaginitis in BALB/c nu/nu mice versus the parent strain is not abrogated by adoptive transfer of T cell enriched lymphocytes.

The role of the host immune system in combating candidal infections in the vagina is poorly understood. A murine model of Candida vaginitis was used to elucidate the role of T cells in a candidal infection. Athymic BALB/c nu/nu mice or normal BALB/c mice were induced into estrus and then infected with 1 x 10(6) Candida albicans intravaginally. The infection was monitored over 1 week. Samples from blood, small intestine, tongue, kidney, spleen, liver, uterus and vagina were tested for recoverable C. albicans. Histology of the vagina was assessed for both inflammation and extent of infection. Results indicated that the BALB/c nu/nu mice had similar levels of vaginal yeast load to the normal BALB/c mice. In 25-30% of nude mice Candida was also recovered from extra vaginal sites (kidney, liver, small intestine), however, extra vaginal dissemination was not observed in any normal BALB/c animals. Histologically, both the nu/nu and control BALB/c had similar levels of vaginal inflammation; however, the nu/nu mice had more florid fungal growth in the vaginal epithelium. Adoptive transfer of either immune or non-immune BALB/c T cells into nude mice had no affect on either infection or vaginal inflammation. Immunohistochemical staining of vaginal tissues from normal BALB/c mice or nude mice adoptively transferred with either immune or non-immune T cells with anti-CD3 monoclonal antibody revealed no significant difference between groups in the numbers of CD3+ vaginal T cells. However, in mice receiving either immune or non-immune T cells no yeast was recovered from any tissues except the vagina. These data show that T cells have a limited role in protecting the vagina from C. albicans infection.

Intestinal IgA plasma cells of the B1 lineage are IL-5 dependent.

Two lineages of B cells, designated B1 and B2 cells, have been identified based upon their origins, anatomical distribution, cell surface markers, antibody repertoire and self-replenishing potential. B1 cells are maintained by self-renewal of cells resident in the peritoneal cavity (PerC) and they utilize a limited repertoire of germline V-region genes, mostly directed against ubiquitous bacterial antigens such as phosphoryl choline (PC). B2 cells are replenished from bone marrow precursors and use a larger repertoire of immunoglobulin V-region genes. Whereas most immunoglobulin A (IgA) plasma cells in the intestine derive from B2 lineage precursors in the Peyer's patch, a subpopulation of Per C-derived B1 cells populate the intestinal lamina propria where they mature into IgA plasma cells. In previous in vivo studies we have shown that whereas IgA+ B2 cells are interleukin (IL)-6 dependent, B1 cells are IL-6 independent. In view of the in vitro evidence that IL-5 is also involved in IgA expression, in the studies reported here we have used IL-5-deficient mice to evaluate the role of IL-5 in vivo in IgA expression in the gut. The results demonstrate that although total IgA cell numbers are only marginally depressed in IL-5-deficient mice, there is a marked selective depletion of IgA+ cells of the B1 lineage in the gut and a corresponding depression in the capacity of these mice to mount an intestinal response to a B1 antigen (PC) but not to a B2 antigen (oralbumin; OVA), reflecting intact B2-derived IgA cell function but a defect in the B1 cell contribution to IgA responses in IL-5 deficient mice. Collectively these data demonstrate differential cytokine regulation of subsets of IgA+ cells in the gut in that IgA+ cells of the B2 lineage are IL-6 dependent but IL-5 independent, but B1-derived IgA+ cells are IL-5 dependent and IL-6 independent.