Chlamydial heat shock proteins and disease pathology: New paradigms for old problems?

Toll-like receptors in pregnancy disorders and placental dysfunction

The Toll receptor was originally identified as a regulator of embryogenesis in Drosophila. Toll-like receptors (TLRs) in mammals recognize infectious agents and other danger signals. Activation of TLRs on trophoblast influences immune cell recruitment, cytokine secretion, and decidual responses to invading pathogens during pregnancy. Importantly, biological effects of TLR signal transduction at multiple maternal-fetal interfaces may contribute to several pregnancy pathologies associated with placental dysfunction, including pre-eclampsia, intrauterine growth restriction, and preterm labor. We herein discuss mechanisms by which TLRs regulate the maternal immune response during normal and abnormal gestation, and we highlight recent data that assign a role to TLRs in the pathophysiology of selected pregnancy-associated complications.

Serological profiling with Chlamycheck, a commercial multiplex recombinant antigen Western blot assay of chlamydial infections

A new chlamydial test system, the Chlamycheck assay, which uses 4 purified recombinant antigens of Chlamydia trachomatis and Chlamydophila pneumoniae and one antigen of Chlamydophila psittaci , has been developed and commercialized. We investigated the reactivities of the recombinant antigens with sera from a group of 30 patients with acute Chlamydia trachomatis infection, 88 patients consulting for sexually transmitted infections, and 46 patients with serological evidence of Chlamydophila pneumoniae infection. The results obtained from human and infected mouse sera suggest that Chlamycheck serology against multiple proteins may provide additional useful information that is not available by conventional whole elementary body microimmunofluorescence or single-antigen enzyme-linked immunosorbent assay serology. Specific serological profiles were associated with acute versus past Chlamydia trachomatis infection or with Chlamydia trachomatis primo-infection versus infection in a Chlamydophila pneumoniae history context.

Live-attenuated influenza viruses as delivery vectors for Chlamydia vaccines

Effective delivery systems are needed to design efficacious vaccines against the obligate intracellular bacterial pathogen, Chlamydia trachomatis. Potentially effective delivery vehicles should promote the induction of adequate levels of mucosal T-cell and antibody responses that mediate long-term protective immunity. Antigen targeting to the nasal-associated lymphoid tissue (NALT) is effective for inducing high levels of specific immune effectors in the genital mucosa, and therefore suitable for vaccine delivery against genital chlamydial infection. We tested the hypothesis that live attenuated influenza A viruses are effective viral vectors for intranasal delivery of subunit vaccines against genital chlamydial infection. Recombinant influenza A/PR8/34 (H1N1) viruses were generated by insertion of immunodominant T-cell epitopes from chlamydial major outer membrane protein into the stalk region of the neuraminidase gene. Intranasal immunization of mice with viral recombinants resulted in a strong T helper 1 (Th1) response against intact chlamydial elementary bodies. Also, immunized mice enjoyed a significant state of protective immunity (P > 0.002) by shedding less chlamydiae and rapidly clearing the infection. Furthermore, a high frequency of Chlamydia-specific Th1 was measured in the genital mucosal and systemic draining lymphoid tissues within 24 hr after challenge of vaccinated mice. Moreover, multiple epitope delivery provided a vaccine advantage over single recombinants. Besides, long-term protective immunity correlated with the preservation of a robustly high frequency of specific Th1 cells and elevated immunoglobulin G2a in genital secretions. Because live attenuated influenza virus vaccines are safe and acceptable for human use, they may provide a new and reliable approach to deliver efficacious vaccines against sexually transmitted diseases.

Laparoscopic Management of Hydrosalpinx

Hydrosalpinx is a common cause of female infertility. Lower implantation and pregnancy rates have been reported in women with hydrosalpinges. How hydrosalpinx exerts its negative effect on the implantation process is not clearly understood. Mechanical factors, toxicity of the hydrosalpingeal fluid, and receptivity dysfunction may explain the impaired IVF outcome in the presence of hydrosalpinx. Laparoscopic surgery has a place in the diagnosis and management of hydrosalpinx. Analysis of the results of laparoscopic management of hydrosalpinx underscores the positive role of laparoscopy in fertility outcomes in women with this pathological tubal disease. Laparoscopic salpingectomy should be offered in those women who have bilateral disease or in cases where hydrosalpinges are large enough to be visible on ultrasound. Further randomized trials are required to assess other surgical treatment options for hydrosalpinx, such as laparoscopic salpingostomy, laparoscopic or hysteroscopic tubal occlusion, and drainage of hydrosalpinx before or during oocyte retrieval.

ChlamydiaHeat Shock Protein 60 Induces Trophoblast Apoptosis through TLR4

Intrauterine infection affects placental development and function, and subsequently may lead to complications such as preterm delivery, intrauterine growth retardation, and preeclampsia; however, the molecular mechanisms are not clearly known. TLRs mediate innate immune responses in placenta, and recently, TLR2-induced trophoblast apoptosis has been suggested to play a role in infection-induced preterm delivery. Chlamydia trachomatis is the etiological agent of the most prevalent sexually transmitted bacterial infection in the United States. In this study, we show that in vitro chlamydial heat shock protein 60 induces apoptosis in primary human trophoblasts, placental fibroblasts, and the JEG3 trophoblast cell line, and that TLR4 mediates this event. We observed a host cell type-dependent apoptotic response. In primary placental fibroblasts, chlamydial heat shock protein 60-induced apoptosis was caspase dependent, whereas in JEG3 trophoblast cell lines it was caspase independent. These data suggest that TLR4 stimulation induces apoptosis in placenta, and this could provide a novel mechanism of pathogenesis for poor fertility and pregnancy outcome in women with persistent chlamydia infection.

Low prevalence of antibodies against heat shock protein 10 of Chlamydophila pneumoniae in patients with coronary heart disease

In this study the prevalence of antibodies against the heat shock protein 10 (HSP10) of Chamydophila pneumoniae (CP) (as assessed by ELISA) in patients with coronary heart disease (CHD) and seropositive or seronegative to CP, as assessed by microimmunofluorescence (MIF), was investigated. The controls were age- and sex-matched healthy subjects. The HSP10 preparation used throughout this study was a 6-his-tagged recombinant protein preliminarily shown to be immunogenic in mice. Low level IgG reactivity against CP-HSP10 was detected in 19 out of 200 and 5 out of 100 CHD patients and controls, respectively. No IgM or IgA isotypes were found. Furthermore, there was no difference in the frequency or level of anti-HSP10 IgG between CP-positive and CP-negative sera either in patients (11/140=7.9% vs. 8/60=13%) or in healthy subjects (3/40=7.5% vs. 2/60=3.3%). Overall, our data indicate that CP-HSP10, at variance with CP-HSP60, to which it is genetically and physiologically linked, should not be regarded as a major expressed immunogen or a marker of infection by CP in CHD patients.

Delivery of Chlamydia vaccines

The plethora of ocular, genital and respiratory diseases of Chlamydia, including nongonococcal urethritis, cervicitis pelvic inflammatory disease, ectopic pregnancy, tubal factor infertility, conjunctivitis, blinding trachoma and interstitial pneumonia, and chronic diseases that may include atherosclerosis, multiple sclerosis, adult onset asthma and Alzheimer's disease, still pose a considerable public health challenge to many nations. Although antibiotics are effective against Chlamydia when effectively diagnosed, asymptomatic infections are rampart, making clinical presentation of complications often the first evidence of an infection. Consequently, the current medical opinion is that an effective prophylactic vaccine would constitute the best approach to protect the human population from the most severe consequences of these infections. Clinical and experimental studies have demonstration that Chlamydia immunity in animals and humans is mediated by T cells and a complementary antibody response, and the completion of the genome sequencing of several isolates of Chlamydia is broadening our knowledge of the immunogenic antigens with potential vaccine value. Thus, major advances have been made in defining the essential elements of a potentially effective subunit vaccine design and parameters for evaluation. However, the challenge to develop effective delivery systems and human compatible adjuvants that would boost the immune response to achieve long-lasting protective immunity remains an elusive objective in chlamydial vaccine research. In response to evolving molecular and cellular technologies and novel vaccinology approaches, considerable progress is being made in the construction of novel delivery systems, such as DNA and plasmid expression systems, viral vectors, living and nonliving bacterial delivery systems, the use of chemical adjuvants, lipoprotein constructs and the codelivery of vaccines and specific immuno-modulatory biological agonists targeting receptors for chemokines, Toll-like receptors, and costimulatory molecules. The application of these novel delivery strategies to Chlamydia vaccine design could culminate in timely achievement of an efficacious vaccine.

Immunoreactivity and differential developmental expression of known and putative Chlamydia trachomatis membrane proteins for biologically variant serovars representing distinct disease groups

Chlamydia trachomatis is an intracellular bacterium that causes ocular and urogenital diseases worldwide. Membrane proteins have only been partially characterized, and the discovery of a nine-member polymorphic membrane protein gene family has enhanced interest in defining their function. We previously reported two putative insertion sequence-like elements in pmpC for biovariant Ba and one each for G and L2, suggesting horizontal gene transfer. Because of this and the tissue tropism differences for these biovariants, we analyzed by quantitative real-time RT-PCR pmpC expression relative to immunogenic protein genes ompA, groEL and gseA throughout development. Sera from infected adolescents were reacted by immunoblot against recombinant (r)PmpC and rMOMP. ompA and groEL revealed different developmental transcriptome profiles among the biovariants. pmpC expression occurred at 2 h, peaked at 18 for L2 (at 24 for Ba and G), with the highest mRNA levels throughout development for L2. pmpC expression as a function of time paralleled ompA expression with higher mRNA levels compared with groEL later in development. Only sera from D-, E- and G-infected patients reacted to rPmpC; all infected patients reacted to rMOMP. pmpC expression during logarithmic growth suggests a role in membrane building and/or integrity, which is supported by the presence of a signal peptidase and C-terminal phenylalanine in PmpC. Because phylogenetic analyses of pmpC segregate serovars according to tissue tropism, we speculate that biovariant transcriptome differences may contribute to this tropism. The heterogeneous biovariant pmpC expression throughout development and differential PmpC immunoreactivity also suggest a role for pmpC in antigenic variation.

Role of Chlamydia pneumoniae-infected macrophages in atherosclerosis developments of the carotid artery

Chlamydia pneumoniae (C. pneumoniae) infection has been recently accepted as an important cause of atherosclerosis. However, the precise mechanisms remain unclear. The present study was aimed to clarify the distribution link among C. pneumoniae, chlamydial HSP 60, and activated macrophages. Atheromatous carotid plaques were obtained from 40 consecutive carotid endarterectomies (CEA). The specimens were prepared for HE and elastica-van Gieson staining. Parallel sections were stained immunocytochemically with monoclonal antibodies for a C. pneumoniae-specific antigen, chlamydial HSP 60, activated macrophages, and smooth muscle cells. Immunoreactivity for the C. pneumoniae-specific antigen was observed within the endothelial cells, activated macrophages, and smooth muscle cells in 36 of 40 specimens (90%). Chlamydial HSP 60 was found in all specimens positive for the C. pneumoniae-specific antigen, and mainly co-localized with the C. pneumoniae-specific antigen within the activated macrophages. The present results suggest that C. pneumoniae is a key microbial organ that causes atheroma developments in the carotid artery. Chlamydia pneumoniae-infected macrophages may come into the arterial intima and mediate inflammatory and autoimmune processes through the production of chlamydial HSP 60, leading to atherosclerosis.

Antibodies to Chlamydia trachomatis heat-shock protein 60 kDa and detection of Mycoplasma genitalium and ureaplasma urealyticum are associated independently with chronic nongonococcal urethritis

BACKGROUND

Chronic nongonococcal urethritis (NGU) is a well-recognized clinical problem in genitourinary medicine clinics, but its etiology and optimal management are poorly understood.

GOAL

The authors showed previously that antibody to chlamydial hsp60 is associated with urethritis 30 to 92 days after treatment of acute NGU (chronic NGU) and that the detection of ureaplasmas or is associated with chronic NGU in which symptoms or signs are present. The aim was to determine whether these associations are independent of each other.

STUDY DESIGN

This was a longitudinal prospective follow-up study over a 3-month period of 86 men with acute NGU. Men were tested for, ureaplasmas, and antibody to chlamydia hsp60 at presentation and during follow-up.

RESULTS

The detection of either ureaplasmas or (OR, 29.45; 95% CI, 1.78-487) and the occurrence of hsp60 antibody at 30 to 92 days' follow-up (OR, 26.45; 95% CI, 1.34-523) were associated independently with the development of chronic NGU 30 to 92 days after treatment of acute NGU. The presence of chlamydial hsp60 antibody at 30 to 92 days was not associated with the development of chronic NGU in which symptoms or signs were present (P= 0.363). Chlamydial hsp60 antibody associated, however, with chronic NGU in which there were no symptoms or signs (P = 0.01).

CONCLUSION

The results suggest that the immune response to chlamydial hsp60 may have a role in the etiology of chronic NGU in asymptomatic men who have no discharge on examination. The clinical relevance of this is unknown.

The cellular paradigm of chlamydial pathogenesis

Diseases caused by Chlamydia are based on intense and chronic inflammation elicited and maintained by reinfection or persistent infection. The traditional view in the field is that disease is mediated by antigen-dependent delayed-type hypersensitivity or autoimmunity. This immunological paradigm has served as the basis for years of chlamydial research but the mechanism or the antigen that causes pathology has yet to be unequivocally revealed. Recent research on responses elicited in Chlamydia-infected cells defines a new direction for our understanding of this microorganism-host interaction and provides the basis for a reassessment of disease mechanisms. Chlamydia-infected non-immune mammalian cells produce proinflammatory chemokines, cytokines, growth factors and other cellular modulators. This cellular response to infection supports an alternative hypothesis for chlamydial pathogenesis: the inflammatory processes of chlamydial pathogenesis are elicited by infected host cells and are necessary and sufficient to account for chronic and intense inflammation and the promotion of cellular proliferation, tissue remodeling and scarring, the ultimate cause of disease sequelae.

The role of IFN-gamma in the outcome of chlamydial infection

Chlamydia are intracellular bacteria which infect many vertebrates, including humans. They cause a myriad of severe diseases, ranging from asymptomatic infection to pneumonia, blindness or infertility. IFN-gamma plays an important role in defense against acute infection and in the establishment of persistence. Chlamydia have evolved mechanisms to escape IFN-gamma functions. IFN-gamma-mediated effector mechanisms may involve effects on the metabolism of tryptophan or iron, on the inducible NO synthase (iNOS), on the secretion of chemokines and adhesion molecules or on the regulation of T-cell activities. IFN-gamma is secreted by the innate and the adaptive arms of the immune system. Within the former, Chlamydia-infected macrophages express IFN-gamma that in turn mediates resistance to infection. IFN-alpha/beta are pivotal for both IFN-gamma- and iNOS-mediated resistance to chlamydial infection in macrophages.

Chlamydial heat shock protein 60 activates macrophages and endothelial cells through Toll-like receptor 4 and MD2 in a MyD88-dependent pathway

Active inflammation and NF-kappaB activation contribute fundamentally to atherogenesis and plaque disruption. Accumulating evidence has implicated specific infectious agents including Chlamydia pneumoniae in the progression of atherogenesis. Chlamydial heat shock protein 60 (cHSP60) has been implicated in the induction of deleterious immune responses in human chlamydial infections and has been found to colocalize with infiltrating macrophages in atheroma lesions. cHSP60 might stimulate, enhance, and maintain innate immune and inflammatory responses and contribute to atherogenesis. In this study, we investigated the signaling mechanism of cHSP60. Recombinant cHSP60 rapidly activated NF-kappaB in human microvascular endothelial cells (EC) and in mouse macrophages, and induced human IL-8 promoter activity in EC. The inflammatory effect of cHSP60 was heat labile, thus excluding a role of contaminating LPS, and was blocked by specific anti-chlamydial HSP60 mAb. In human vascular EC which express Toll-like receptor 4 (TLR4) mRNA and protein, nonsignaling TLR4 constructs that act as dominant negative blocked cHSP60-mediated NF-kappaB activation. Furthermore, an anti-TLR4 Ab abolished cHSP60-induced cellular activation, whereas a control Ab had no effect. In 293 cells, cHSP60-mediated NF-kappaB activation required both TLR4 and MD2. A dominant-negative MyD88 construct also inhibited cHSP60-induced NF-kappaB activation. Collectively, our results indicate that cHSP60 is a potent inducer of vascular EC and macrophage inflammatory responses, which are very relevant to atherogenesis. The inflammatory effects are mediated through the innate immune receptor complex TLR4-MD2 and proceeds via the MyD88-dependent signaling pathway. These findings may help elucidate the mechanisms by which chronic asymptomatic chlamydial infection contribute to atherogenesis.

Heat shock protein 60 specific T-cell response in chlamydial infections

Heat shock proteins (HSPs) of most pathogens, including Chlamydia, are major immune targets of both humoral- and cell-mediated immune mechanisms. During the last decade, many investigators have focused their research to elucidate the complex relationship of chlamydial HSPs, especially chlamydial HSP60, and the host immune response. A central issue is whether the pathologic mechanisms in chronic chlamydial diseases are associated with an enhanced immune response to chlamydial HSP60 which can mediate tissue destruction through cytotoxic reactions, or whether they are related to the Th2 type of response that eventually leads to partial or temporary suppression of an effective antichlamydial response. Our review highlights the available knowledge between immune responses to chlamydial HSP60 and chronic chlamydial infections in human.

Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions

Data from a spectrum of epidemiologic, pathologic, and animal model studies show that Chlamydia pneumoniae infection is associated with coronary artery disease, but it is not clear how the organism may initiate or promote atherosclerosis. It is postulated that C. pneumoniae triggers key atherogenic events through specific virulence determinants. C. pneumoniae induces mononuclear phagocyte foam cell formation by chlamydial lipopolysaccharide (cLPS) and low-density lipoprotein oxidation by chlamydial hsp60 (chsp60). Thus, different chlamydial components may promote distinct events implicated in the development of atherosclerosis. Data implicating cLPS and chsp60 in the pathogenesis of atherosclerosis are discussed and novel approaches are presented for attempting to elucidate how these putative virulence determinants signal mononuclear phagocytes to modulate lipoprotein influx and modification.