Local Th1-like responses are induced by intravaginal infection of mice with the mouse pneumonitis biovar of Chlamydia trachomatis

Initial route of antigen administration alters the T-cell cytokine profile produced in response to the mouse pneumonitis biovar of Chlamydia trachomatis following genital infection

A Th1-type response develops following vaginal infection with the mouse pneumonitis biovar of Chlamydia trachomatis (MoPn). Since the type of response, i.e., Th1 versus Th2, can be influenced by factors present during T-cell activation, we examined the effects of different routes of MoPn administration on the cytokine profile and resistance against infection following a MoPn vaginal challenge. A dominant Th1-type cytokine profile developed in mice given live MoPn via the intranasal, oral, and vaginal routes with ratios of gamma interferon-secreting cells to interleukin 4-secreting cells greater than 10. In contrast, mice injected subcutaneously produced a Th2-type profile with a gamma interferon/interleukin 4 ratio of only 0.7. These mice also had significantly higher anti-MoPn immunoglobulin G1 serum titers, confirming a Th2-type cytokine profile. Exposure of mice to live MoPn, by any route prior to vaginal challenge, resulted in a shortened course of infection. However, the subcutaneous group resolved the vaginal infection more slowly, with 60% (6 of 10 mice) of the mice still isolation positive 12 days after challenge compared with only 20% of mice given live MoPn by other routes. Administration of UV-inactivated MoPn did not provide protection against a vaginal challenge. The decreased ability to clear infection was not associated with a shift in the cytokine profile, since intranasal and oral administration of UV-inactivated MoPn resulted in a predominant Th1-type response. Taken together, these data indicate that the initial route of MoPn administration can direct the type of response produced after a local MoPn infection and thus influence the ability of the immune response to protect against subsequent infection.

Potential of preventing Pseudomonas aeruginosa lung infections in cystic fibrosis patients: experimental studies in animals

In patients with cystic fibrosis (CF), respiratory tract infections caused by Staphylococcus aureus and Haemophilus influenzae are followed by Pseudomonas aeruginosa with increasing age. Chronic endobronchial lung infection with P. aeruginosa is the leading cause of morbidity and mortality. In Danish CF patients we noted that both onset of initial colonization and chronic lung infection with P. aeruginosa peaked during the winter months which is the season for respiratory virus infections. Virus may therefore pave the way for P. aeruginosa. We established a chronic P. aeruginosa lung infection in rats by embedding mucoid bacteria in seaweed alginate and installing the beads intratracheally into the lower part of the left lung. Although the rats did not suffer from CF, the antibody responses and the pathologic changes of the lungs mimicked the findings in CF patients. By using this model in normal and athymic rats we showed that the T-cell response during the "natural" course of the infection played no major role. In a model of acute P. aeruginosa pneumonia we found that the macroscopic inflammatory response of the lungs was immense and that the natural capacity to clear P. aeruginosa was very efficient and could not be improved by immunization, although high serum levels of IgM, IgG and IgA antibodies to P. aeruginosa alginate, LPS, exotoxin A and sonicate were induced. We developed a method for collecting and measuring IgA in saliva and noted that mucosal IgA antibodies were induced by vaccination; they did not significantly prevent inflammation, however. In the chronic rat model we succeeded to improve the survival significantly and to change the inflammatory response subsequent to vaccination from an acute type inflammation dominated by polymorphonuclear leukocytes (PMNs) as in CF patients to a chronic type inflammation dominated by mononuclear leukocytes. Furthermore, we found that rats immunized with an alginate containing vaccine had a significantly earlier cellular shift to a chronic type inflammation as well as a significant reduction in the severity of the macroscopic inflammation compared to two other vaccine groups and to nonimmunized controls. Similar results were obtained in rats treated with the TH1 cytokine, interferon-gamma (IFN-gamma). Several authors have shown that the lung tissue damage during chronic infection in CF patients is caused by a type III hypersensitivity reaction leading to release of elastase by PMNs surrounding the bacterial microcolonies. The cellular shift we have induced by vaccination and by IFN-gamma treatment therefore offers a possible new strategy for improving the clinical course in chronically infected CF patients.

T lymphocytes in the murine vaginal mucosa are phenotypically distinct from those in the periphery

The results from both clinical studies of women with recurrent vulvovaginal candidiasis and a murine model of experimental vaginitis indicate that systemic cell-mediated immunity may not represent a dominant host defense mechanism against vaginal infections by Candida albicans. Recent experimental evidence indicates the presence of local vaginal immune reactivity against C. albicans. The present study was designed to examine T-lymphocyte subpopulations in the vaginal mucosae of naive CBA/J mice. Vaginal lymphocytes (VL) were isolated by collagenase digestion of whole vaginal tissues. Cell populations were identified by flow cytometry, and the results were compared with those for both lymph node cells (LNC) and peripheral blood lymphocytes (PBL). The results of flow cytometry showed that 45% +/- 10% of lymphocytes in the vaginal mucosa are CD3+ compared with 75% +/- 5% in LNC and 50% +/- 5% in PBL. The majority (85%) of CD3+ VL are CD4+ and express the alpha/beta T-cell receptor (TCR), similar to the results for LNC and PBL. In contrast to LNC and PBL, VL contain a significantly higher percentage (15 to 20%) of gamma/delta TCR+ cells, 80% or more of which appear to express CD4. In addition, while CD4-CD8 cell ratios in LNC and PBL were 3:1 and 6:1, respectively, only 1% of VL expressed CD8, resulting in a CD4-CD8 cell ratio of > 100:1. Finally, while LNC and PBL recognized two epitope-distinct (GK 1.5 and 2B6) anti-CD4 antibodies, VL recognized only 2B6 anti-CD4 antibodies. Further analysis of VL showed that Thy-1 cells, but not CD4 cells, were reduced after intravaginal injection of complement-fixing anti-Thy-1.2 and GK 1.5 anti-CD4 antibodies, respectively. Taken together, these data suggest that T lymphocytes in the vaginal mucosae of mice are phenotypically distinct from those in the periphery and that CD4+ VL have an uncharacteristic or atypical expression of the CD4 receptor.

Role of gamma-delta T cells in murine Chlamydia trachomatis infection

The role of gamma-delta T cells in host resistance to Chlamydia trachomatis was characterized by using a murine model of pneumonia caused by the mouse pneumonitis agent (MoPn), murine C. trachomatis. At days 3 and 7 after infection, gamma-delta T-cell-deficient knockout mice had significantly higher levels of MoPn in the lungs than did immunologically intact controls. At day 20, paradoxically, gamma-delta T-cell-deficient mice were more resistant to MoPn than were controls. This increased resistance was not due to an increased production of toxic cytokines or interleukin-10 in controls on that day. Gamma-delta T cells play a role in protection early in MoPn infection, but they may be deleterious later in infection, as has been observed in models of salmonella and trypanosome infection.

Immunopathogenesis of recurrent vulvovaginal candidiasis

Recurrent vulvovaginal candidiasis (RVVC) is a prevalent opportunistic mucosal infection, caused predominantly by Candida albicans, which affects a significant number of otherwise healthy women of childbearing age. Since there are no known exogenous predisposing factors to explain the incidence of symptomatic vaginitis in most women with idiopathic RVVC, it has been postulated that these particular women suffer from an immunological abnormality that prediposes them to RVVC. Because of the increased incidence of mucosal candidiasis in individuals with depressed cell-mediated immunity (CMI), defects in CMI are viewed as a possible explanation for RVVC. In this review, we attempt to place into perspective the accumulated information regarding the immunopathogenesis of RVVC, as well as to provide new immunological perspectives and hypotheses regarding potential immunological deficiencies that may predispose to RVVC and potentially other mucosal infections by the same organism. The results of both clinical studies and studies in an animal model of experimental vaginitis suggest that systemic CMI may not be the predominant host defense mechanism against C. albicans vaginal infections. Rather, locally acquired mucosal immunity, distinct from that in the peripheral circulation, is now under consideration as an important host defense at the vaginal mucosa, as well as the notion that changes in local CMI mechanism(s) may predispose to RVVC.

Immune Protection Against Chlamydia trachomatis in Females

Despite significant advances in our understanding of the biology and antigenic structure of Chlamydia trachomatis, and the epidemiology and clinical spectrum of chlamydial disease, the magnitude of morbidity from human chlamydial infections remains an important public health concern. Control of chlamydial disease will likely depend on a multidisciplinary approach, including the development of immunoprophylactic or immunotherapeutic strategies. Reasonable progress has been made in understanding specific immune mechanisms that contribute to host immunity in experimental models of chlamydial infection. However, studies of human immunity have not been so successful. This is particularly evident in that studies to address the development and role of mucosal immune responses to urogenital chlamydial infections have not been forthcoming. The following review is a brief summary of our current knowledge of protective immunity to chlamydial urogenital infections of females. It is not meant to be exhaustive, but instead to touch upon aspects of protective immunity that have been described in both human and experimental animal models of chlamydial infection.