Analysis of the immune response in mice following intrauterine infection with the Chlamydia trachomatis mouse pneumonitis biovar

Forty years of development of salpingitis animal modeling

This review summarizes and examines research in the area of salpingitis animal modeling in the last 40 years, focusing primarily on Chlamydia trachomatis animal models, which are the most numerous in the literature. Early animal models are examined, followed by a discussion of study parameters and their impact on modeling success, subsequent considerations of fertility measures in modeling, explorations of treatment options, and finally exploring recent directions with a brief discussion of models using other bacterial pathogens.

Characterization of the Horizontal and Vertical Sexual Transmission of Chlamydia Genital Infections in a New Mouse Model

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen worldwide, and there is a need to control this epidemic. So far there is no established animal model in which both the horizontal and the vertical transmission of Chlamydia can be studied. To implement a horizontal sexual transmission model, male mice were inoculated in the meatus urethra with Chlamydia muridarum and they were caged with naive female mice. Urine and vaginal swab specimens were collected for culture. To study vertical transmission, newborns were euthanized and specimens were cultured. As controls, females were mated with sham-infected male mice. All C. muridarum-inoculated male mice had positive urine cultures. As determined by serology, all females caged with C. muridarum-inoculated males became infected, and 93% of them had positive vaginal swab specimen cultures. More females mated with C. muridarum-infected male mice (35%) than females mated with sham-infected male mice (0%) were infertile (P < 0.05). Also, C. muridarum-infected females delivered significantly fewer pups (3.8 ± 3.2/mouse) than control females (6.3 ± 1.6/mouse) (P < 0.05). Of the newborn mice, 32% were C. muridarum positive either in the lungs or in the intestines. Female mice housed with sham-infected males had no positive vaginal swab specimen cultures or C. muridarum-positive pups. This new mouse model of horizontal and vertical sexual transmission of Chlamydia closely parallels C. trachomatis sexual transmission in humans and may be a good model system to better understand the pathogenesis of these infections.

Effects of "Danzhi Decoction" on Chronic Pelvic Pain, Hemodynamics, and Proinflammatory Factors in the Murine Model of Sequelae of Pelvic Inflammatory Disease

Objective. To evaluate the effect of Danzhi decoction (DZD) on chronic pelvic pain (CPP), hemodynamics, and proinflammatory factors of sequelae of pelvic inflammatory diseases (SPID) in murine model. Methods. SPID mice were randomly treated with high-dose DZD, mid-dose DZD, low-dose DZD, aspirin, and vehicle for 3 estrous circles. The Mouse Grimace Scale (MGS) was performed to evaluate CPP; blood flows of the upper genital tract, pelvic wall, and mesentery were used to assess hemodynamics in SPID mice; expressions of vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2), and osteopontin (OPN) were measured by Western blot and immunochemistry. Results. Treatment with dose-dependent DZD significantly decreased the MGS scores, accelerated blood flows of the pelvis, and reduced expressions of VEGF, Ang-2, and OPN in the upper genital tract. Conclusions and Discussions. DZD was effective in relieving CPP and improving hemodynamics of the pelvic blood-stasis microenvironment in SPID mice. There was a relationship between CPP and the pelvic blood-stasis microenvironment. Furthermore, DZD might play a positive role in the anti-inflammatory process.

Decreased cervical epithelial sensitivity to nonoxynol-9 (N-9) after four daily applications in a murine model of topical vaginal microbicide safety

BACKGROUND

The disappointing clinical failures of five topical vaginal microbicides have provided new insights into factors that impact microbicide safety and efficacy. Specifically, the greater risk for human immunodeficiency virus type 1 (HIV-1) acquisition associated with multiple uses of a nonoxynol-9 (N-9)-containing product has highlighted the importance of application frequency as a variable during pre-clinical microbicide development, particularly in animal model studies.

METHODS

To evaluate an association between application frequency and N-9 toxicity, experiments were performed using a mouse model of cervicovaginal microbicide safety. In this model system, changes in cervical and vaginal epithelial integrity, cytokine release, and immune cell infiltration were assessed after single and multiple exposures to N-9.

RESULTS

After the initial application of N-9 (aqueous, 1%), considerable damage to the cervical epithelium (but not the vaginal epithelium) was observed as early as 10 min post-exposure and up to 8 h post-exposure. Subsequent daily exposures (up to 4 days) were characterized by diminished cervical toxicity relative to single exposures of like duration. Levels of pro-inflammatory cytokines released into the cervicovaginal lumen and the degree of CD14-positive immune cell infiltration proximal to the cervical epithelium were also dependent on the number of N-9 exposures.

CONCLUSIONS

Rather than causing cumulative cervical epithelial damage, repeated applications of N-9 were characterized by decreased sensitivity to N-9-associated toxicity and lower levels of immune cell recruitment. These results provide new insights into the failure of N-9-based microbicides and illustrate the importance of considering multiple exposure protocols in pre-clinical microbicide development strategies.

Chlamydial infection increases gonococcal colonization in a novel murine coinfection model

Genital tract infections caused by Neisseria gonorrhoeae and Chlamydia trachomatis serovars D to K occur at high incidence in many areas of the world. Despite high rates of coinfection with these pathogens, investigations of host-parasite interactions have focused on each pathogen individually. We describe here a coinfection model in which female BALB/c mice were first infected with the mouse Chlamydia species C. muridarum and then inoculated with N. gonorrhoeae following treatment with water-soluble 17β-estradiol to promote long-term gonococcal infection. Viable gonococci and chlamydiae were recovered for an average of 8 to 10 days, and diplococci and chlamydial inclusions were observed in lower genital tract tissue by immunohistochemical staining. Estradiol treatment reduced proinflammatory cytokine and chemokine levels in chlamydia-infected mice; however, coinfected mice had a higher percentage of vaginal neutrophils compared to mice infected with either pathogen alone. We detected no difference in pathogen-specific antibody levels due to coinfection. Interestingly, significantly more gonococci were recovered from coinfected mice compared to mice infected with N. gonorrhoeae alone. We found no evidence that C. muridarum increases gonococcal adherence to, or invasion of, immortalized murine epithelial cells. However, increased vaginal concentrations of inflammatory mediators macrophage inflammatory protein 2 and tumor necrosis factor alpha were detected in C. muridarum-infected mice prior to inoculation with N. gonorrhoeae concurrently with the downregulation of cathelicidin-related antimicrobial peptide and secretory leukocyte peptidase inhibitor genes. We conclude that female mice can be successfully infected with both C. muridarum and N. gonorrhoeae and that chlamydia-induced alterations in host innate responses may enhance gonococcal infection.

Evaluation of a recombinant enzyme-linked immunosorbent assay for detecting Chlamydophila psittaci antibodies in turkey sera

Chlamydophila psittaci (formerly Chlamydia psittaci) is one of the major pathogens associated with turkey respiratory disease. Devastating outbreaks with high mortality rates, similar to those of 1950 to 1970 in the USA occasionally occur, but respiratory signs without or with low mortality mostly characterize outbreaks now a day. Accurate diagnostic methods should be made available. The present study examined the sensitivity and specificity of a recombinant ELISA (rMOMP ELISA) for detecting Cp. psittaci major outer membrane specific antibodies in turkey sera. Test results were compared to those of immunoblotting and of a competitive ELISA (Chlamydia-psittaci-AK-EIA, Röhm Pharma, Germany) and an indirect ELISA (LPS/LGP) detecting antibodies to the lipopolysaccharide/lipoglycoprotein complex. The rMOMP ELISA was most sensitive as determined on serial dilutions of positive control sera originating from experimentally infected SPF turkeys. The competitive ELISA gave false positives since three negative controls reacted positive. For conventional sera, the sensitivities of the competitive ELISA, immunoblotting and the indirect ELISA were found to be 99.4, 93.1 and 82.2%, respectively, as compared to the rMOMP ELISA (100%). The specificities of the rMOMP ELISA, immunoblotting and the indirect ELISA were found to be 100% while the specificity of the competitive ELISA was only 2.7%. The rMOMP ELISA was chosen to compare the prevalence of chlamydiosis in 2002 with the one from 1992. In 2002, 188 on 200 (94%) turkey sera reacted positive compared to 175 on 200 (87.5%) in 1992 and like 10 years ago all examined farms were seropositive at slaughter. Interestingly, Belgian as well as French farms were seropositive.

Immunoblotting, ELISA and culture evidence for Chlamydiaceae in sows on 258 Belgian farms

The prevalence of Chlamydiaceae infections on 258 closed pig breeding farms in Belgium was examined. For this purpose, 258 farms were randomly selected in the provinces West-Vlaanderen (44%), Oost-Vlaanderen (20%), Antwerpen (10%) and Vlaams-Brabant (6%). Of all farms examined, 96.5% were positive for Chlamydia-specific antibodies in ELISA and most were moderately to strongly positive. ELISA results revealed only 9 (3.5%) sero-negative farms. None of the ELISA negative sera reacted in immunoblotting. Only 212 of 249 ELISA positive sera reacted positive in immunoblotting. Additionally, 23 autopsy samples were examined by isolation in Vero cells. The major outer membrane sequence of the one isolate obtained showed 98.6% amino acid homology to the one of Chlamydophila psittaci strain CP3, formerly isolated from a pigeon. Present observations indicate that chlamydial infections are nearly endemic in the Belgian pig population and that Belgian pigs can become infected with C. psittaci. Nevertheless, the role and significance of Chlamydiaceae as pathogens in pigs remain unsolved and require further investigation.

Current problems of perinatal Chlamydia trachomatis infections

Chlamydia trachomatis has been recognized as a pathogen of trachoma, nongonococcal urethritis, salpingitis, endocervicitis, pelvic inflammatory disease, inclusion conjunctivitis of neonates, follicular conjunctivitis of adults, infantile pneumonia and associated conditions. Chlamydial infections during pregnancy may also cause a variety of perinatal complications. Different antigenic strains of C. trachomatis from endocervical, nasopharyngeal and conjunctival origins have been associated with different clinical conditions. Control programs emphasizing early diagnosis, targeted screening, and effective treatment will lead to an eventual decline in the incidence of perinatal chlamydial infection. This review focuses on current problems of perinatal C. trachomatis infections in the aspects of microbiological and immunological pathogenesis.

Adjuvant modulation of the immune responses and the outcome of infection with Chlamydia pneumoniae

Immunization with different adjuvants resulted in antithetic outcomes of infection with Chlamydia pneumoniae. Immunization with the outer major protein-2 from C. pneumoniae (OMP-2) emulsified in Freund's complete adjuvant (FCA) thus increased the susceptibility of mice to infection with the bacteria. The detrimental effect was not observed upon inoculation of irrelevant antigens or major outer membrane protein (MOMP) in FCA, but was also observed after immunization with FCA-chlamydial heat shock protein-60 (HSP-60). The harmful effect of FCA-OMP-2 depended on the presence of both CD4+ and CD8+ cells and was mediated by IL-10, as shown using gene-ablated mice. The increased susceptibility to infection caused by FCA-OMP-2 immunization was long-lasting and observed in mice infected 4 months after the last dose of immunogen. In contrast, partial protection against C. pneumoniae was observed when FCA was replaced with oligodeoxynucleotides containing immunostimulatory CpG motifs mixed with Freund's incomplete adjuvant (FIA-IS-CpG). These polar outcomes of infection related to the cytokine pattern: antigen-stimulated spleen cells from FCA-OMP-2-immunized mice showed higher IL-10/IFN-gamma ratios than FIA-IS-CpG-OMP-2-immunized animals. In agreement, sera from FCA-OMP-2 showed higher anti-OMP-2 IgG1/IgG2a ratios than FIA-IS-CpG-OMP-2-immunized animals. Finally, OMP-2 also generated a protective response when delivered by a eukaryotic expression vector in tandem with CTLA4, a procedure that targeted OMP-2 to antigen-presenting cells.

Recognition of the 60 kilodalton cysteine-rich outer membrane protein OMP2 by CD4(+) T cells from humans infected with Chlamydia trachomatis

T cell-mediated immunity is important in the control of chlamydia infection but chlamydia-specific T cells are also implicated in the inflammation and tissue damage which characterize chlamydia associated diseases. To investigate target antigens of the T cell-mediated immune response to chlamydia infection, Chlamydia trachomatis-specific CD4+ T cell clones were isolated from a patient with chlamydia-induced reactive arthritis. T cell immunoblotting indicated that an antigen of approximately 60 kilodaltons molecular mass was recognized, and recombinant 60 kilodalton cysteine-rich outer membrane 2 (OMP2) proved to be stimulatory. By using deletion constructs and synthetic peptides an epitope presented by HLA-DRB1*0401 was defined and proved to contain the nonamer peptide within the OMP2 sequence predicted to have the greatest binding affinity for DRB1*0401 The sequence of the epitope is conserved in all C. trachomatis strains but not in C. pneumoniae. Investigation of patients with acute urethritis and additional patients with sexually acquired reactive arthritis showed that OMP2-reactive T cells were readily detectable in peripheral blood and synovial fluid. Thus OMP2 is a target antigen of the T cell-mediated immune response to CT infection.

Chlamydia trachomatis persistence in the female mouse genital tract: inducible nitric oxide synthase and infection outcome

It was previously reported that female mice resolve a primary Chlamydia trachomatis urogenital infection independent of inducible nitric oxide synthase (iNOS). We now report that although iNOS-deficient (NOS2(-/-)) mice resolve culture-apparent infection in a fashion similar to that of normal control (NOS2(+/+)) mice, they sustain significantly increased rates of disease, as assessed by hydrosalpinx formation. PCR amplification of ompA followed by Southern blot detection of amplicands revealed the presence of chlamydial DNA in the lower genital tracts of both NOS2(-/-) and NOS2(+/+) mice at > or =120 days postinfection and in upper genital tract tissues at >120 days postinfection. However, only NOS2(-/-) mice shed low numbers of viable chlamydiae from the lower genital tract after immunosuppressive treatment at 120 days postinfection. When cultured primary murine lung fibroblasts were activated in the presence of gamma interferon (IFN-gamma), inhibition of chlamydial growth occurred in both NOS2(+/+) and NOS2(-/-) cells, but the inhibition was reversible after removal of the cytokine in the NOS2(-/-) primary cell culture only. The iNOS-independent inhibition was microbistatic but was independent of 2,3-indoleamine dioxygenase activity. We conclude that chlamydial DNA and antigens persist in mice subsequent to culture-apparent resolution. In addition, IFN-gamma induces in vivo inhibition of chlamydial growth through microbistatic mechanisms in the absence of iNOS activity, but in the presence of iNOS activity, IFN-gamma is microbicidal and effects eradication.

Expression of mucosal homing receptor alpha4beta7 is associated with enhanced migration to the Chlamydia-infected murine genital mucosa in vivo

The CD4 T helper cell type 1 (Th1) response is essential for the resolution of chlamydial genital infection in mice. However, not all Th1 clones are equally protective in eradicating the infection. Since oral immunization regimens produce protective immunity, we evaluated the role of the mucosa-associated homing receptor, alpha4beta7, in trafficking to the genital mucosa. Using a panel of CD4, Th1 cell lines and clones, we compared the lymphocyte homing patterns of a Chlamydia-specific, protective clone (P-MoPn), a nonprotective clone (N-MoPn), and a keyhole limpet hemocyanin (KLH)-specific cell line (KLH-1). T cells were labeled with the fluorescent dye PKH-26, adoptively transferred into Chlamydia-infected mice, and monitored at different time points throughout the course of a genital infection. We found that clones P-MoPn and N-MoPn migrated to similar extents to the genital tract and in significantly greater numbers than the KLH-specific T-cell line. Both clones and the KLH-1 line expressed similar levels of the adhesion molecules alpha4, beta1, CD44, and CD11a. However, clones P-MoPn and N-MoPn expressed higher levels of the mucosal homing receptor, alpha4beta7. Also, clones P-MoPn and N-MoPn but not the KLH-1 line migrated to the mesenteric lymph node, suggesting a mucosal recirculation pattern. Moreover, blocking alpha4beta7 adhesion interaction in vivo significantly reduced the recruitment of P-MoPn but not KLH-1 to the genital tract. These findings show that the mucosal homing receptor alpha4beta7 is utilized by a subset of CD4 cells during migration to the Chlamydia-infected genital tract.

Immunogenic and protective ability of the two developmental forms of Chlamydiae in a mouse model of infertility

To compare the ability of elementary bodies (EB) and reticulate bodies (RB) of the Chlamydia trachomatis mouse pneumonitis (MoPn) biovar to induce a protective immune response, two groups of BALB/c mice were inoculated and boosted twice, with UV-inactivated EB or RB in Freund's adjuvant. Two weeks after the last immunization mice were challenged with C. trachomatis in the ovarian bursa. Vaginal cultures collected for 6 weeks after the intrabursal challenge showed that mice inoculated with EB were significantly protected, while mice inoculated with RB were not. Six weeks after the genital challenge mice were mated. Mice immunized with EB showed significant protection as demonstrated by the number of animals which were fertile and the number of embryos present in the uterine horns. In contrast, no significant protection against infertility was observed in the mice immunized with RB.

Immunization with an acellular vaccine consisting of the outer membrane complex of Chlamydia trachomatis induces protection against a genital challenge

The ability to induce protection against a genital challenge was studied in BALB/c female mice with three Chlamydia trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP) preparations as well as an acellular vaccine consisting of the chlamydial outer membrane complex (COMC). The MOMP preparations were extracted with three different types of detergents, sodium dodecyl sulfate (SDS), n-octyl-beta-D-glucopyranoside (OGP), and Zwittergent 3-14 (Z3-14). A positive immunization control consisted of mice inoculated intranasally with 10(4) C. trachomatis MoPn inclusion-forming units (IFU). Mice inoculated with ovalbumin served as a negative control. Furthermore, a sham-immunized, nonchallenged group was included as a fertility control. Two weeks after the last immunization, the mice were challenged in the left ovarian bursa with 10(5) C. trachomatis MoPn IFU. Vaginal swabs were collected for culture, vaginal and serum samples were assayed for chlamydial-specific antibodies, and splenocytes were collected to determine the lymphoproliferative response. At 42 days after the challenge, the mice were mated with proven male breeder mice. Animals that were considered to be pregnant (as determined by weight) were killed, and the embryos were counted. A significant humoral and cell-mediated immune response was observed in all the groups of mice inoculated with chlamydial antigens. Antibodies to variable domain (VD)1 of the MOMP were detected in serum samples from all the immunized groups. However, antibodies to VD3 and VD4 were detected only in the groups immunized with the Z3-14-MOMP and the COMC. Mice immunized with COMC developed significant immunoglobulin A chlamydia-specific antibodies in the vagina, while mice immunized with the detergent-extracted MOMPs had low antibody titers. Following the intrabursal challenge, a significant decrease in the intensity and duration of vaginal shedding was noted in the mice immunized with COMC and a moderate decrease was noted in the group immunized with OGP-MOMP. No protection against the infection was noted in the groups of animals immunized with SDS- and Z3-14-MOMP. Furthermore, of the mice immunized with the COMC preparation, only 25% (4 of 20) shed C. trachomatis, as determined by vaginal culture, while 83% (40 of 48) of the control mice inoculated with ovalbumin were culture positive (P < 0.05). In addition, after mating, the mice inoculated with COMC were found to have fertility rates comparable to those of the control sham-immunized, nonchallenged animals (70% [14 of 20] versus 81% [17 of 21], respectively [P > 0.05]), and there were no significant differences between the average number of embryos per mouse in the two groups (5.1 versus 5.9, respectively [P > 0.05]). In contrast, mice immunized with the purified MOMP preparations were not protected against infertility. In summary, a preparation of the COMC protected mice against infection and infertility, supporting the feasibility of the development of an acellular vaccine against C. trachomatis infections.

Reactivation of chlamydial genital tract infection in mice

A model was developed to study chlamydial quiescence in C3H/HeN (C3H) and C57BL/6N (C57) mice following genital tract infection by Chlamydia trachomatis MoPn. Reactivation of chlamydial shedding following immunosuppression indicated that viable MoPn remained in the genital tract for up to 4 or 5 weeks after the apparent clearance of a primary infection. Either cyclophosphamide or cortisone acetate treatment could cause reactivation, but cyclophosphamide was more effective. However, the frequency of reactivation by either drug diminished with time in both mouse strains. Progesterone treatment prior to infection of C57 mice greatly reduced the frequency of reactivation by cyclophosphamide and also correlated with the development of marked fluid accumulation and distension of the uterine horns in the vast majority of those animals. This pathology was apparent by 5 to 7 weeks postinfection and was consistently seen through 110 days postinfection. Neither of these phenomena was observed in C57 mice that had not been treated with progesterone or in C3H mice under any conditions tested. The infecting dose of MoPn did not clearly influence the frequency of reactivation in either inbred strain as defined by this model.

Monoclonal immunoglobulin A antibody to the major outer membrane protein of the Chlamydia trachomatis mouse pneumonitis biovar protects mice against a chlamydial genital challenge

In order to analyze the protective role that IgA may play in a chlamydial infection two IgA monoclonal antibodies (mAb), MoPn 4-2 and MoPn 13-2, were raised against the major outer membrane protein (MOMP) of the Chlamydia trachomatis mouse pneumonitis (MoPn) biovar. mAb MoPn 4-2 was found to be serovar specific while mAb MoPn 13-2 was species specific. mAb MoPn 4-2 recognized a surface exposed conformational epitope as shown by its ability to bind to native EBs and nonreduced MOMP while failing to bind to heat and trypsin treated EBs, to reduced MOMP and to synthetic MOMP peptides. In contrast, mAb MoPn 13-2 recognized a nonconformational epitope since it was able to bind treated EBs, to reduced MOMP and to the synthetic peptide MTTWNPTISGSGI located in variable domain 4 of the MOMP. Both mAbs agglutinated intact EBs and had in vitro neutralizing activity. However, mAb MoPn 4-2 had a 20-fold higher in vitro neutralizing ability when compared to mAb MoPn 13-2 (50% neutralization at 5 micrograms ml-1 vs 100 micrograms ml-1). In an in vitro in vivo infectivity assay, mAb MoPn 4-2 protected mice against infertility when C. trachomatis MoPn elementary bodies were preincubated with the mAb before inoculation. In addition, passive transfer of mAb MoPn 4-2 resulted in significant protection as measured by a decrease in the number of mice infected, and in the intensity and duration of vaginal shedding. These results support previous findings suggesting that IgA antibodies can play a role in protection against a chlamydial infection, and further encourage work to develop vaccination strategies that elicit mucosal immunity.

Intranasal immunization induces long-term protection in mice against a Chlamydia trachomatis genital challenge

In an attempt to confer long-term protective immunity, BALB/c female mice were immunized intranasally with 10(4) inclusion-forming units (IFU) of the Chlamydia trachomatis mouse pneumonitis biovar (MoPn). Animals were subsequently challenged in the ovarian bursa with 10(5) C. trachomatis MoPn IFU at 60, 120, or 180 days post-intranasal immunization. Two control groups were included in the study. One control was sham immunized and mock challenged, and another group was sham immunized and challenged with 10(5) C. trachomatis MoPn IFU. Vaginal cultures were collected at regular intervals following the intrabursal challenge. In comparison with the sham-immunized mice, the animals that were intranasally immunized with C. trachomatis had significant protection, as shown by a reduction in the number of animals that had positive vaginal cultures and by a decrease in the intensity and length of the shedding. Furthermore, histopathological characterization of the genital tract following challenge, in the three groups of mice, showed a minimal inflammatory infiltrate in the C. trachomatis-immunized animals, when compared with the sham-immunized control group. Subsequently, the three groups of female mice that were challenged at 60, 120 and 180 days postimmunization were mated at 6 weeks following the challenge. Overall, in the mice intranasally immunized with C. trachomatis the fertility rates and the number of embryos were similar to those in the sham-immunized and mock-challenged group. In contrast, there was a significant increase in infertility in the groups of mice that were sham immunized and C. trachomatis challenged. In conclusion, intranasal immunization with C. trachomatis induces long-term protection against a genital challenge as shown by a decrease in the infection and infertility rates when compared with sham-immunized animals. Thus, this model may help to characterize the parameters of the immune response that are important in maintaining long-term protection and may aid in identifying the antigenic determinants involved in eliciting protection.

Role of neutrophils in controlling early stages of a Chlamydia trachomatis infection

Inoculation of mice with the granulocyte-depleting monoclonal antibody RB6-8C5 showed that neutrophils are critical protective effector cells during a Chlamydia trachomatis infection. In addition, administration of monoclonal antibody 2E6 demonstrated that extravasation of neutrophils into the peritoneal cavity in response to inoculation with the C. trachomatis MoPn biovar is dependent on the surface beta-2 integrin molecule CD18.

A 28 kDa major immunogen of Chlamydia psittaci shares identity with Mip proteins of Legionella spp. and Chlamydia trachomatis-cloning and characterization of the C. psittaci mip-like gene

Chlamydia psittaci strain guinea-pig inclusion conjunctivitis (GPIC) produces a self-limiting ocular infection of guinea-pigs, and this condition is a representative animal model of ocular chlamydial disease. Convalescent guinea-pigs, which are resistant to reinfection, produce antibodies to several elementary-body proteins, including an uncharacterized antigen of 28 kDa. Convalescent guinea-pig sera were used to identify, from a lambda expression library, two overlapping GPIC genomic clones that produced the 28 kDa antigenic protein. Nucleotide sequence analysis revealed that the gene coding for the 28 kDa protein was similar to the mip (macrophage infectivity potentiator) genes from Legionella pneumophila and Chlamydia trachomatis. The GPIC gene and its product were accordingly designated mip and Mip, respectively. Analysis of the regions flanking mip identified three tightly linked open reading frames coding for predicted products with sequence similarity to asparagine tRNA ligase (AspS), rRNA methylase (SpoU), and thioredoxin (TrxA). The arrangement of these genes in GPIC was aspS-mip-spoU-trxA. Sequence analysis of PCR products produced using genomic DNA from an ovine abortion strain of C. psittaci and from C. trachomatis strain LGV-434 demonstrated that the arrangement of mip, spoU and trxA is common among these chlamydiae.

Purification and measurement of secretory IgA in mouse milk

An important factor limiting better understanding of the protective role of sIgA at mucosal surfaces is the limited availability of the purified immunoglobulin. Among other things, purified sIgA is needed for use as a standard in measurements of the concentration of this immunoglobulin in mucosal secretions, particularly in mice, where several models of mucosal infections are available. We describe here a simple method by which one can obtain a mean of 3.5 ml of milk per mouse without a breast pump. Immunoblotting studies after native PAGE demonstrated that the milk contained mainly 420 kDa dimeric sIgA and higher polymeric forms of sIgA; only a trace of monomeric IgA was present. Similar immunoblotting studies after SDS-PAGE revealed that a portion of the sIgA was dissociated by this treatment. The 420 kDa sIgA was purified by salt fractionation, gel filtration, and affinity chromatography, and the purity of the final product was demonstrated by immunoblot analysis of biotinylated polypeptides after reduction of biotinylated protein. The concentration of 420 kDa sIgA in whey was measured by densitometry of immunoblot bands, using the purified 420 kDa sIgA as a standard, and found to be 1.0 +/- 0.3 mg/ml.

Protection against infertility in a BALB/c mouse salpingitis model by intranasal immunization with the mouse pneumonitis biovar of Chlamydia trachomatis

Female BALB/c mice were immunized intranasally with the mouse pneumonitis biovar of Chlamydia trachomatis and subsequently challenged in the ovarian bursa (C. trachomatis immunized, C. trachomatis challenged). Two groups of mice served as controls. One group was sham immunized intranasally with mock-infected HeLa 229 cell extracts and was challenged in the ovarian bursa with C. trachomatis MoPn (sham immunized, C. trachomatis challenged). The second control group was sham immunized and not challenged (sham immunized, nonchallenged). Before challenge, the C. trachomatis-immunized, C. trachomatis-challenged animals mounted a significant humoral response as shown by high immunoglobulin G (IgG), IgM, and IgA levels and high levels of neutralizing antibodies in serum and moderate IgG and IgA titers in vaginal secretions. Reactivity by Western blot (immunoblot) to the lipopolysaccharide, 30-, 40- (major outer membrane protein), and 60-kDa cysteine-rich proteins and 75- and 100-kDa chlamydial components could be demonstrated. However, reactivity to the 60-kDa heat shock protein was only observed 22 days after challenge. In addition, this group of animals mounted a significant immune response to chlamydial antigens, as shown by a lymphocyte proliferation assay, compared with the sham-immunized nonchallenged mice. After intrabursal challenge, there was no C. trachomatis shedding from the vagina in the C. trachomatis-immunized, C. trachomatis-challenged animals, while 63% of the sham-immunized, C. trachomatis-challenged mice had a positive C. trachomatis culture. In addition, histological sections from the genital tract showed, at 2 weeks postchallenge, a marked acute inflammatory reaction in the sham-immunized, C. trachomatis-challenged animals while in the C. trachomatis-immunized, C. trachomatis-challenged mice there was minimal inflammatory reaction. When the animals were mated, only 12% of the mice from the sham-immunized, C. trachomatis-challenged mice were fertile. In contrast, 94 and 80% of the sham-immunized, nonchallenged and C. trachomatis-immunized, C. trachomatis-challenged mice, respectively, were fertile.

Intravaginal inoculation of mice with the Chlamydia trachomatis mouse pneumonitis biovar results in infertility

In an attempt to establish a model of chlamydial ascending salpingitis and infertility, three inbred strains of mice, C3H/HeN (H-2k), C57BL/6N (H-2b), and BALB/cAnN (H-2d), were inoculated intravaginally with 3 x 10(7) inclusion-forming units of the Chlamydia trachomatis mouse pneumonitis biovar. Mice mated 6 weeks following inoculation were found to have a significant decrease in fertility rate compared with the control groups, as shown by a reduction in the number of pregnant mice and a decrease in the number of embryos.

Protein antigens of Chlamydia psittaci present in infected cells but not detected in the infectious elementary body

Ocular infection of guinea pigs with the guinea pig inclusion conjunctivitis (GPIC) strain of Chlamydia psittaci produces a clinical condition representative of acute chlamydial conjunctivitis in humans. Guinea pigs which had recovered from two challenges with GPIC were used as a source of sera for the identification of antigens present in GPIC-infected tissue culture cells but absent in the infectious elementary body (EB). Immunoblots of lysates of infected HeLa cells probed with the convalescent-phase sera identified protein antigens of 22, 34, and 52 kDa (p22, p34, and p52, respectively) that were not detected in lysates of purified EB or in uninfected HeLa cells. Protein p22 was also not detected in lysates of purified reticulate bodies. Immunoblotting of lysates of HeLa cells infected with other chlamydiae demonstrated that the antigenicity of p22 and p34 was subspecies specific. Immunoblotting was also used to detect p22 and p34 in lysates of the conjunctivae of infected guinea pigs. Adsorption of convalescent-phase sera with GPIC EB produced a reagent with dominant reactivity toward p22, p34, and a 28-kDa EB protein. Immunofluorescent staining of GPIC-infected HeLa cells demonstrated that these adsorbed sera labeled the inclusion and inclusion membrane, with no apparent reactivity toward EB or reticulate bodies. Collectively, these data identify non-EB chlamydial components which may be released into the inclusion during intracellular growth.