Antibody response to the 60-kDa chlamydial heat-shock protein is associated with scarring trachoma

Impact of Low Humidity on Damage-associated Molecular Patterns at the Ocular Surface during Dry Eye Disease

SIGNIFICANCE

Dry eye is one of the leading causes for individuals to seek eye care, whereas the pathogenesis is poorly understood. One mechanism in which dry eye inflammation may ensue is by the release of damage-associated molecular patterns (DAMPs) by damaged cells to stimulate the production of cytokines and matrix metalloproteinases. Examining DAMP levels on the ocular surface during dry eye disease (DED) will increase our understanding of their potential involvement in the pathogenesis of DED.

PURPOSE

This study aimed to quantitate DAMPs, high-mobility group box 1 (HMGB1), and heat shock proteins on the ocular surface of normal and dry eye subjects and to examine the impact of low-humidity environment (LHE) on DAMPs and inflammation in dry eye subjects.

METHODS

Basal tears (10 to 20 μL) and conjunctival impression cytology samples were analyzed for HMGB1, HSP-27, HSP-60, HSP-70, and HSP-90α by ELISA or Luminex assays in normal (n = 15) and DED (n = 15) subjects. In addition, a subset of DED subjects were exposed to LHE for 2 hours. The level of DAMPs in the tear film was evaluated by ELISA or Luminex assay. Interleukin 6, interleukin 8, or metalloproteinase (MMP) 9 mRNA were quantitated by real-time polymerase chain reaction from conjunctival impression cytology samples.

RESULTS

Compared with age-matched normal subjects, HMGB1 was significantly elevated in the tear film of DED subjects (P = .03), whereas there was no significant difference in heat shock proteins. Conjunctival impression cytology samples revealed no significant difference in intracellular DAMP levels between both groups. After exposure to an LHE, there was an increase in corneal staining (P = .005), HSP-60 levels in the tear film (P = .01), and MMP-9 mRNA in the conjunctiva (P = .001).

CONCLUSIONS

Dry eye subjects had higher levels of HMGB1 in their tear film. Exposure to an LHE worsened corneal staining, increased conjunctival MMP-9 mRNA expression, and increased tear film HSP-60 levels. Larger studies are needed to understand the involvement of DAMPs in stimulating dry eye inflammation.

Elevated serum antibody against Schistosoma japonicum HSP60 as a promising biomarker for liver pathology in schistosomiasis

The pathology associated with Schistosoma japonicum (S. japonicum) infection in humans is attributed to parasite egg-induced granulomatous inflammation and fibrosis in the host liver. Currently, a marker that is reliable, cheap, less device-dependent, and can be easily and repeatedly used on a large scale to monitor the progression of liver pathology in schistosomiasis japonica endemic areas is lacking. The levels of serum S. japonicum heat shock protein 60 (SjHSP60)-specific IgG and its subtype antibodies in animals (mice and rabbits) or patients with schistosomiasis were measured by ELISA. Liver pathologies in mice and rabbits were evaluated by gross pathology and histopathology, and hepatic fibrosis in patients was examined with ultrasound imaging. The results revealed that the titers of the total IgG and subtype IgG1 anti-SjHSP60 antibodies were positively correlated with the severity of liver pathology after S. japonicum infection. Our findings indicate that the SjHSP60 IgG and IgG1 antibody levels can be used as potential candidate biomarkers for evaluation of liver pathology in schistosomiasis; however, validation remains to be explored in further work.

Profiling and validation of individual and patterns of Chlamydia trachomatis-specific antibody responses in trachomatous trichiasis

BACKGROUND

Ocular Chlamydia trachomatis (Ct) infection causes trachoma, the leading infectious cause of blindness. A Ct D/UW3 proteome microarray and sera from Gambian adults with trachomatous trichiasis (TT) or healthy matched controls previously identified several novel antigens, which suggested differential recognition in adults with TT.

METHODS

We re-analysed this serological microarray data using more robust microarray analysis techniques accounting for typical problems associated with highly dimensional data. We examined the Ct-specific antibody profile concerning the overall diversity of responses, antigen expression stage and cellular localisation of antigens. We tested differentially recognised antigens by further serological testing of the screened sera and used larger independent sample sets for validation.

RESULTS

Antibody responses identified High-Performance on antigens expressed early and late in the Ct developmental cycle and those secreted or localised to the outer membrane. Eight antigens were preferentially recognised by scarred individuals and one antigen by healthy individuals. Three of these antigens, two associated with scarring (CT667 and CT706) and one healthy-associated (CT442), were not associated with the presence or absence of scarring following specific serological testing of the arrayed sera and sera from larger, independent case-control cohorts.

CONCLUSIONS

This study identified focussed Ct-specific antibody profiles targeting proteins expressed during entry and exit from cells and localised to interact with the host. A small panel of antibody responses could discriminate between adults with and without TT in a trachoma-endemic community. Heterogenous responses in the independent validation of these antibody targets highlighted the need for large sample sizes, clearly defined clinical phenotypes and follow-up work.

Lysine acetylation of major Chlamydia trachomatis antigens

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Chlamydia trachomatis causes trachoma and sexually transmitted diseases.

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Molecular mechanisms of chlamydial pathogenesis and immunity remain unclear.

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Acetylation of lysine is a post-translational modification that occurs in prokaryotes.

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Lysine acetylation sites were discovered in major chlamydial antigens.

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60 kDa chaperonin, EF-G and PmpB showed the highest degree of acetylation.

Chlamydia trachomatis (Ct) is a human pathogen causing trachoma and infertility. We investigated acetylation at lysine residues of chlamydial antigenic proteins: major outer membrane protein (MOMP), 60 kDa chaperonin (chlamydial Hsp60), elongation factor G (EF-G), enolase and the polymorphic membrane proteins PmpB, PmpE and PmpF. 60 kDa chaperonin, EF-G and PmpB showed the highest degree of acetylation.

Our data show that important Ct antigens could be post-translationally modified by acetylation of lysine residues at multiple sites. Further studies are needed to investigate total acetylome of Ct and the impact PTMs might have on Ct biology and pathogenicity.

A vaccine formulated with the major outer membrane protein can protect C3H/HeN, a highly susceptible strain of mice, from a Chlamydia muridarum genital challenge

C3H/HeN female mice were vaccinated with native Chlamydia muridarum major outer membrane protein (MOMP), using Montanide+CpG or Alum+CpG as adjuvants. Negative control groups were immunized with ovalbumin (OVA) and the same adjuvants. As positive control, mice were inoculated intranasally with live Chlamydia. Mice were challenged in the ovarian bursa with 10(5) C. muridarum inclusion forming units. Six weeks after the genital challenge the animals were caged with male mice and monitored for pregnancy. Mice vaccinated with MOMP+Montanide+CpG developed high levels of C. muridarum-specific antibodies, with a high IgG2a/IgG1 ratio and neutralizing titres. Animals immunized using Alum+CpG had low antibody levels. Cellular immune responses were significantly higher in mice vaccinated with MOMP and Montanide+CpG, but not with Alum+CpG, when compared with negative controls. Following the genital challenge, only 20% (4/20) of mice vaccinated with MOMP+CpG+Montanide had positive vaginal cultures whereas 100% (9/9) of mice immunized with MOMP+CpG+Alum had positive cultures. Of the positive control animals inoculated with live Chlamydia only 15% (3/20) had positive vaginal cultures. In contrast, 100% (20/20) of mice immunized with OVA+CpG+Montanide, or minimal essential medium, had positive cultures. Following mating, 80% (16/20) of mice vaccinated with MOMP+CpG+Montanide, and 85% (17/20) of animals inoculated intranasally with live C. muridarum carried embryos in both uterine horns. No protection against infertility was observed in mice immunized with MOMP and CpG+Alum or OVA. In conclusion, this is the first time that a subunit vaccine has been shown to elicit a protective immune response in the highly susceptible C3H/HeN strain of mice against an upper genital challenge.

Trachoma and Ocular Chlamydial Infection in the Era of Genomics

Trachoma is a blinding disease usually caused by infection with Chlamydia trachomatis (Ct) serovars A, B, and C in the upper tarsal conjunctiva. Individuals in endemic regions are repeatedly infected with Ct throughout childhood. A proportion of individuals experience prolonged or severe inflammatory episodes that are known to be significant risk factors for ocular scarring in later life. Continued scarring often leads to trichiasis and in-turning of the eyelashes, which causes pain and can eventually cause blindness. The mechanisms driving the chronic immunopathology in the conjunctiva, which largely progresses in the absence of detectable Ct infection in adults, are likely to be multifactorial. Socioeconomic status, education, and behavior have been identified as contributing to the risk of scarring and inflammation. We focus on the contribution of host and pathogen genetic variation, bacterial ecology of the conjunctiva, and host epigenetic imprinting including small RNA regulation by both host and pathogen in the development of ocular pathology. Each of these factors or processes contributes to pathogenic outcomes in other inflammatory diseases and we outline their potential role in trachoma.

Transcriptional regulation of the Chlamydia heat shock stress response in an intracellular infection

Bacteria encode heat shock proteins that aid in survival during stressful growth conditions. In addition, the major heat shock proteins of the intracellular bacterium Chlamydia trachomatis have been associated with immune pathology and disease. We developed a ChIP-qPCR method to study the regulation of chlamydial heat shock gene regulation during an intracellular infection. This approach allowed us to show that chlamydial heat shock genes are regulated by the transcription factor HrcA within an infected cell, providing validation for previous in vitro findings. Induction of chlamydial heat shock gene expression by elevated temperature was due to loss of HrcA binding to heat shock promoters, supporting a mechanism of derepression. This heat shock response was rapid, whereas recovery of HrcA binding and return to non-stress transcript levels occurred more slowly. We also found that control of heat shock gene expression was differentially regulated over the course of the intracellular Chlamydia infection. There was evidence of HrcA-mediated regulation of heat shock genes throughout the chlamydial developmental cycle, but the level of repression was lower at early times. This is the first study of Chlamydia-infected cells showing the effect of an environmental signal on transcription factor-DNA binding and target gene expression in the bacterium.

Trachoma

Trachoma is the most common infectious cause of blindness. Repeated episodes of infection with Chlamydia trachomatis in childhood lead to severe conjunctival inflammation, scarring, and potentially blinding inturned eyelashes (trichiasis or entropion) in later life. Trachoma occurs in resource-poor areas with inadequate hygiene, where children with unclean faces share infected ocular secretions. Much has been learnt about the epidemiology and pathophysiology of trachoma. Integrated control programmes are implementing the SAFE Strategy: surgery for trichiasis, mass distribution of antibiotics, promotion of facial cleanliness, and environmental improvement. This strategy has successfully eliminated trachoma in several countries and global efforts are underway to eliminate blinding trachoma worldwide by 2020.

Towards a safe and effective chlamydial vaccine: lessons from the eye

As well as being the most common bacterial sexually transmitted infection, Chlamydia trachomatis (Ct) is the leading infectious cause of blindness. The pathogenesis of ocular chlamydial infection (trachoma) is similar to that of genital infection. In the 1960s the efficacy of Ct vaccines against ocular infection was evaluated in major field trials in Saudi Arabia, Taiwan, The Gambia, India and Ethiopia. These trials showed that it was possible to induce short term immunity to ocular infection, and to reduce the incidence of inflammatory trachoma, by parenteral immunisation with killed or live whole organism vaccines. In one study, it was also shown that the incidence of scarring sequelae was reduced in vaccinated children. Detailed studies in non-human primates conducted at this time suggested that vaccination could lead to more severe inflammatory disease on subsequent challenge. Since that time there have been many studies on the immunological correlates of protective immunity and immunopathology in ocular Ct infection in humans and non-human primates, and on host genetic polymorphisms associated with protection from adverse sequelae. These have provided important information to guide the development and evaluation of a human Ct vaccine.

Trachoma: protective and pathogenic ocular immune responses to Chlamydia trachomatis

Trachoma, caused by Chlamydia trachomatis (Ct), is the leading infectious blinding disease worldwide. Chronic conjunctival inflammation develops in childhood and leads to eyelid scarring and blindness in adulthood. The immune response to Ct provides only partial protection against re-infection, which can be frequent. Moreover, the immune response is central to the development of scarring pathology, leading to loss of vision. Here we review the current literature on both protective and pathological immune responses in trachoma. The resolution of Ct infection in animal models is IFNγ-dependent, involving Th1 cells, but whether this is the case in human ocular infection still needs to be confirmed. An increasing number of studies indicate that innate immune responses arising from the epithelium and other innate immune cells, along with changes in matrix metalloproteinase activity, are important in the development of tissue damage and scarring. Current trachoma control measures, which are centred on repeated mass antibiotic treatment of populations, are logistically challenging and have the potential to drive antimicrobial resistance. A trachoma vaccine would offer significant advantages. However, limited understanding of the mechanisms of both protective immunity and immunopathology to Ct remain barriers to vaccine development.

Genome-wide identification of Chlamydia trachomatis antigens associated with trachomatous trichiasis

PURPOSE

Chlamydia trachomatis is the leading infectious cause of blindness. The goal of the current study was to search for biomarkers associated with C. trachomatis-induced ocular pathologies.

METHODS

We used a whole genome scale proteome array to systematically profile antigen specificities of antibody responses to C. trachomatis infection in individuals from trachoma-endemic communities with or without end-stage trachoma (trichiasis) in The Gambia.

RESULTS

When 61 trichiasis patients were compared with their control counterparts for overall antibody reactivity with organisms of different chlamydial species, no statistically significant difference was found. Both groups developed significantly higher titers of antibodies against C. trachomatis ocular serovars A and B than ocular serovar C, genital serovar D, or Chlamydia psittaci, whereas the titers of anti-Chlamydia pneumoniae antibodies were the highest. When antisera from 33 trichiasis and 26 control patients (with relatively high titers of antibodies to C. trachomatis ocular serovars) were reacted with 908 C. trachomatis proteins, 447 antigens were recognized by at least 1 of the 59 antisera, and 10 antigens by 50% or more antisera, the latter being designated as immunodominant antigens. More importantly, four antigens were preferentially recognized by the trichiasis group, with antigens CT414, CT667, and CT706 collectively reacting with 30% of trichiasis antisera but none from the normal group, and antigen CT695 reacting with 61% of trichiasis but only 31% of normal antisera. On the other hand, eight antigens were preferentially recognized by the control group, with antigens CT019, CT117, CT301, CT553, CT556, CT571, and CT709 together reacting with 46% of normal antisera and none from the trichiasis group, whereas antigen CT442 reacted with 35% of normal and 19% of trichiasis antisera respectively.

CONCLUSIONS

The current study, by mapping immunodominant C. trachomatis antigens and identifying antigens associated with both ocular pathology and protection, has provided important information for further understanding chlamydial pathogenesis and the development of subunit vaccines.

A Chlamydia-specific C-terminal region of the stress response regulator HrcA modulates its repressor activity

Chlamydial heat shock proteins have important roles in Chlamydia infection and immunopathogenesis. Transcription of chlamydial heat shock genes is controlled by the stress response regulator HrcA, which binds to its cognate operator CIRCE, causing repression by steric hindrance of RNA polymerase. All Chlamydia spp. encode an HrcA protein that is larger than other bacterial orthologs because of an additional, well-conserved C-terminal region. We found that this unique C-terminal tail decreased HrcA binding to CIRCE in vitro as well as HrcA-mediated transcriptional repression in vitro and in vivo. When we isolated HrcA from chlamydiae, we only detected the full-length protein, but we found that endogenous HrcA had a higher binding affinity for CIRCE than recombinant HrcA. To examine this difference further, we tested the effect of the heat shock protein GroEL on the function of HrcA since endogenous chlamydial HrcA has been previously shown to associate with GroEL as a complex. GroEL enhanced the ability of HrcA to bind CIRCE and to repress transcription in vitro, but this stimulatory effect was greater on full-length HrcA than HrcA lacking the C-terminal tail. These findings demonstrate that the novel C-terminal tail of chlamydial HrcA is an inhibitory region and provide evidence that its negative effect on repressor function can be counteracted by GroEL. These results support a model in which GroEL functions as a corepressor that interacts with HrcA to regulate chlamydial heat shock genes.

Chlamydiales and the innate immune response: friend or foe?

Pathogenicity of Chlamydia and Chlamydia-related bacteria could be partially mediated by an enhanced activation of the innate immune response. The study of this host pathogen interaction has proved challenging due to the restricted in vitro growth of these strict intracellular bacteria and the lack of genetic tools to manipulate their genomes. Despite these difficulties, the interactions of Chlamydiales with the innate immune cells and their effectors have been studied thoroughly. This review aims to point out the role of pattern recognition receptors and signal molecules (cytokines, reactive oxygen species) of the innate immune response in the pathogenesis of chlamydial infection. Besides inducing clearance of the bacteria, some of these effectors may be used by the Chlamydia to establish chronic infections or to spread. Thus, the induced innate immune response seems to be variable depending on the species and/or the serovar, making the pattern more complex. It remains crucial to determine the common players of the innate immune response in order to help define new treatment strategies and to develop effective vaccines. The excellent growth in phagocytic cells of some Chlamydia-related organisms such as Waddlia chondrophila supports their use as model organisms to study conserved features important for interactions between the innate immunity and Chlamydia.

Immunopathogenic consequences of Chlamydia trachomatis 60 kDa heat shock protein expression in the female reproductive tract

Chlamydia trachomatis is an obligate intracellular bacterium that infects chiefly urogenital and ocular epithelial cells. In some infected women the microorganism migrates to the upper reproductive tract resulting in a chronic, but asymptomatic, infection. The immune response to this infection, production of interferon-gamma and pro-inflammatory cytokines, results in interruption of chlamydial intracellular replication. However, the Chlamydia remains viable and enters into a persistent state. In this form, most chlamydial genes are inactive. An exception is the gene coding for the 60 kDa heat shock protein (hsp60), which is synthesized in increased amounts and is released into the extracellular milieu. The chronic release of chlamydial hsp60 induces a local pro-inflammatory immune response in fallopian tube epithelia and results in scar formation and tubal occlusion. In addition, long-term exposure of the maternal immune system to the chlamydial hsp60 eventually results in the release of tolerance and generation of an immune response that recognizes regions of the chlamydial hsp60 that are also present in the human hsp60. Production of cross-reacting antibodies and cell-mediated immunity to the human hsp60 is detrimental to subsequent pregnancy outcome and may also possibly increase susceptibility to atherosclerosis, autoimmune disorders, or malignancies.

Chlamydia pneumoniae infection and risk for lung cancer

BACKGROUND

We evaluated the relationship of Chlamydia pneumoniae infection with prospective lung cancer risk using traditional serologic markers [microimmunoflourescence (MIF) IgG and IgA antibodies] and Chlamydia heat shock protein-60 (CHSP-60) antibodies, a marker for chronic chlamydial infection.

METHODS

We conducted a nested case-control study (593 lung cancers and 671 controls) within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 77,464). Controls were matched to cases by age, sex, randomization year, follow-up time, and smoking (pack-years of smoking, time since quitting). We assessed C. pneumoniae seropositivity and endpoint antibody titers (IgG and IgA against C. pneumoniae elementary bodies and IgG against CHSP-60).

RESULTS

C. pneumoniae seropositivity by microimmunoflourescence IgG or IgA antibodies was not associated with lung cancer [odds ratio of 0.88 and 95% confidence interval (95% CI) of 0.69-1.13 for IgG; odds ratio of 0.98 and 95% CI of 0.75-1.27 for IgA]. In contrast, individuals seropositive for CHSP-60 IgG antibodies had significantly increased lung cancer risk (odds ratio, 1.30; 95% CI, 1.02-1.67), and risk increased with increasing antibody titers (P trend = 0.006). CHSP-60-related risk did not differ significantly by lung cancer histology, follow-up time, or smoking. CHSP-60 seropositivity was associated with increased risk 2 to 5 years before lung cancer diagnosis (odds ratio, 1.77; 95% CI, 1.16-2.71; P trend = 0.006), thus arguing against reverse causality.

CONCLUSIONS

CHSP-60 seropositivity and elevated antibody titers were associated with significantly increased risk for subsequent lung cancer, supporting an etiologic role for C. pneumoniae infection in lung carcinogenesis.

IMPACT

Our results highlight the potential for lung cancer risk reduction through treatments targeted toward C. pneumoniae infections and chronic pulmonary inflammation.

Characterization of humoral immune responses to chlamydial HSP60, CPAF, and CT795 in inflammatory and severe trachoma

PURPOSE

Chlamydia trachomatis (Ct) remains the leading global cause of preventable blindness. There are limited data on humoral immune responses in trachoma. Evaluating these responses is important for understanding host-pathogen interactions and informing vaccine design. Antibodies to chlamydial heat shock protein 60 (cHSP60) have been associated with infertility and trachomatous scarring. Other proteins, including chlamydial protease-associated factor (CPAF) and a hypothetical protein unique to the family Chlamydiaceae, CT795, elicit strong immune responses in urogenital infections, but their role in trachomatous disease is unknown.

METHODS

This study was conducted to expand on previous cHSP60 findings and evaluate the association of CPAF and CT795 antibodies with ocular Ct infection and disease. Clinical trachoma grading was performed, and conjunctival samples were obtained from individuals with trachomatous trichiasis (TT; one or more inturned eyelashes) or inflammatory trachoma without trichiasis and control subjects without disease, all of whom resided in trachoma-endemic regions of Nepal. Ct infection was determined using commercial PCR. IgG and IgA tear antibodies against cHSP60, CT795, and CPAF fusion proteins were measured by quantitative ELISA.

RESULTS

Significantly higher IgG antibody levels were found against cHSP60, CPAF, and CT795 in the inflammatory cases compared with levels in the controls (P < 0.005 for all three). Ct infection was independently associated with IgG antibodies against all three immunogens in the inflammatory cases but not in the controls (P = 0.025, P = 0.03 and P = 0.017, respectively). Only IgG antibodies against CPAF were significantly elevated among the TT cases (P = 0.013).

CONCLUSIONS

Among individuals with trachoma, IgG antibody responses to CPAF are likely to be both a marker and risk factor for inflammatory trachoma and severe trachomatous disease.

Chlamydophila pneumoniae infection and COPD: more evidence for lack of evidence?

Chlamydophila pneumoniae has been recognized as a common cause of respiratory tract infections affecting all age groups. The organism has been implicated as an infectious trigger for acute exacerbations of COPD. Moreover, the intracellular existence of this pathogen and the ability to cause chronic respiratory infections have led to a number of studies that investigated its possible association with disease development. The present paper examines and discusses the possible association of acute C. pneumoniae infection in episodes of acute exacerbation of COPD. It also reviews the existing evidence of chronic C. pneumoniae infection with disease pathogenesis and severity. The significant interstudy variation of the choice of diagnostic methods and criteria applied is most likely responsible for the great diversity of results observed. The use of well-standardized, commercially available diagnostic tools, as well as the adoption of a more unified diagnostic approach is probably the key element missing in order to clarify the exact role of C. pneumoniae in COPD.

Host immune responses to chlamydial inclusion membrane proteins B and C in Chlamydia trachomatis infected women with or without fertility disorders

BACKGROUND

With an increase in the number of putative inclusion membrane proteins (incs) in chlamydial genomes, there is a need for understanding their contribution in host-pathogen interactions. Thus in this study we determined the host mucosal and peripheral immune responses to incs (IncB and IncC) of Chlamydia trachomatis (CT).

METHODS

Female patients (n = 296) attending the gynaecology out patient department of Safdarjung hospital, New Delhi were enrolled for the study and were clinically characterized into two groups; CT-positive fertile women (n = 38) and CT-positive women with fertility disorders (n = 29). Uninfected healthy fertile women were enrolled as controls (n = 31). Gene specific PCRs were used for detection of incB and incC genes in endocervical samples of CT-positive patients. ELISA and Western blot assay were used for detection of IgA and IgG antibodies to IncB and IncC in cervical washes and sera. Effect of IncB and IncC stimulation of cervical cells and PBMCs on cellular proliferation and cytotoxity was determined using MTT assay and Lactate dehydrogenase (LDH)-cytotoxicity assay respectively. Modulation of cytokines (Interleukin (IL)-1 Beta, IL-4, IL-5, IL-6, IL-10, Interferon-gamma, IL-12, Tumor Necrosis Factor-alpha and Granulocyte macrophage colony-stimulating factor (GM-CSF)) in cervical cells and PBMCs upon stimulation with IncB and IncC was determined by real-time reverse-transcriptase (RT)-PCR and ELISA. Further, CD4 positive T cells were purified from cervical cells and peripheral blood mononuclear cells (PBMCs) and secreted cytokines (Interferon-gamma and IL-4) were evaluated by ELISPOT and real-time RT-PCR.

RESULTS

Using MTT assay, significantly high proliferative responses (P < 0.05) were observed in inc-stimulated cervical cells and PBMCs from CT-positive fertile women compared to CT-positive women with fertility disorders and controls. Interferon-gamma, IL-12 and GM-CSF were found to be elevated in inc-stimulated cervical cells and PBMCs of CT-positive fertile women compared to CT-positive women with fertility disorders and controls (P < 0.05). In contrast, IL-1 Beta, IL-4, IL-5, IL-6 and IL-10 levels were found to be higher in CT-positive women with fertility disorders compared to CT-positive fertile women and controls (P < 0.05). Interferon-gamma secreting cells and mRNA expression in inc-stimulated cervical and peripheral CD4 positive T cells were significantly higher (P < 0.05) in CT positive fertile women compared to CT-positive women with fertility disorders.

CONCLUSION

Our data overall suggests that CT incs, IncB and IncC modulate host immune responses and may have a role in protection/pathogenesis of genital chlamydial infection in women.

Chlamydial heat shock protein 60 induces acute pulmonary inflammation in mice via the Toll-like receptor 4- and MyD88-dependent pathway

Heat shock protein 60 derived from Chlamydia pneumoniae (cHSP60) activates Toll-like receptor 4 (TLR4) signaling through the MyD88 pathway in vitro, but it is not known how cHSP60 contributes to C. pneumoniae-induced lung inflammation. We treated wild-type (WT), TLR2(-/-), TLR4(-/-), or MyD88(-/-) mice intratracheally (i.t.) with recombinant cHSP60 (50 microg), UV-killed C. pneumoniae (UVCP; 5 x 10(6) inclusion-forming units/mouse), lipopolysaccharide (2 microg), or phosphate-buffered saline (PBS) and sacrificed mice 24 h later. Bronchoalveolar lavage (BAL) was obtained to measure cell counts and cytokine levels, lungs were analyzed for histopathology, and lung homogenate chemokine concentrations were determined. Bone marrow-derived dendritic cells (BMDDCs) were generated and stimulated with live C. pneumoniae (multiplicity of infection [MOI], 5), UVCP (MOI, 5), or cHSP60 for 24 h, and the expression of costimulatory molecules (CD80 and CD86) was measured by fluorescence-activated cell sorting. cHSP60 induced acute lung inflammation with the same intensity as that of UVCP-induced inflammation in WT mice but not in TLR4(-/-) or MyD88(-/-) mice. cHSP60- and UVCP-induced lung inflammation was associated with increased numbers of cells in BAL, increased neutrophil recruitment, and elevated BAL interleukin-6 (IL-6) levels. Both cHSP60 and UVCP induced IL-6 release and CD80 and CD86 expression in WT cells but not in MyD88(-/-) BMDDCs. cHSP60 stimulated DC activation in a TLR4- and MyD88-dependent manner with an intensity similar to that induced by UVCP. These data suggest that cHSP60 promotes lung inflammation and DC activation via TLR4 and MyD88 and therefore may play a significant role in the pathogenesis of C. pneumoniae-induced chronic inflammatory lung diseases.

Multiple chaperonins in bacteria--why so many?

A significant proportion of bacteria express two or more chaperonin genes. Chaperonins are a group of molecular chaperones, defined by sequence similarity, required for the folding of some cellular proteins. Chaperonin monomers have a mass of c. 60 kDa, and are typically found as large protein complexes containing 14 subunits arranged in two rings. The mechanism of action of the Escherichia coli GroEL protein has been studied in great detail. It acts by binding to unfolded proteins and enabling them to fold in a protected environment where they do not interact with any other proteins. GroEL can assist the folding of many proteins of different sizes, sequences, and structures, and homologues from many different bacteria can functionally replace GroEL in E. coli. What then are the functions of multiple chaperonins? Do they provide a mechanism for cells to increase their general chaperoning ability, or have they become specialized to take on specific novel cellular roles? Here I will review the genetic, biochemical, and phylogenetic evidence that has a bearing on this question, and show that there is good evidence for at least some specificity of function in multiple chaperonin genes.

Age, sex, and cohort effects in a longitudinal study of trachomatous scarring

PURPOSE

To determine the 5-year incidence rate of scarring, and associated factors, in the population of Maindi, Tanzania.

METHODS

A census of every resident was obtained at baseline, and ocular examinations for the presence and severity of trachoma were performed. Images of the upper eyelid were taken and graded for the presence and severity of scarring, according to a four-step severity scale based on photographs. Five years after baseline, a second series of images was taken and graded for scarring. Incident scarring was defined as new scars in those without scarring at baseline; progression was defined as those with scars that worsened by one step or more at 5 years.

RESULTS

The rate of scarring at baseline increased with age, from 1% in the <6-year to 38% in the 41+-year age group. Females at any age had more scarring than did males. The 5-year incidence rate of scarring was 0.20 (95% confidence interval [CI], 0.16-0.25), but varied with age up to 0.43 in the 41+-year group. There was a striking cohort effect, with those aged less than 16 years at baseline having more prevalent scarring and incidence rates comparable to those aged 16 to 40. Progression rates averaged 0.47 (95% CI, 0.36-0.58).

CONCLUSIONS

In this trachoma-endemic community, incident scarring was high, especially in the younger cohorts. A dramatic increase in risk of trachomatous scarring occurred approximately 15 years ago and appears to be unabated. Trachoma control programs to reduce risk of scarring are urgently needed to avoid blinding complications in this community.

Airflow limitation, asthma, and Chlamydia pneumoniae-specific heat shock protein 60

BACKGROUND

Chlamydia pneumoniae has been associated with asthma. It has also been suggested that C pneumoniae infection may lead to lung remodeling in a subset of asthmatic patients. Seroreactivity against Chlamydia trachomatis heat shock protein 60 (hsp60), a highly conserved, immunoreactive chaperone protein, is associated with immunopathologic abnormalities, leading to blinding trachoma and tubal infertility. This suggests that the host response to infection may affect chronic inflammatory damage to the eye and the fallopian tubes. The pathogenesis of C trachomatis disease associations is thought to include molecular mimicry (autoimmunity), direct activation of the innate immune response via the CD14/toll-like receptor 4 complex, or both.

OBJECTIVE

To study whether airflow limitation in asthma in C pneumoniae-exposed individuals is associated with a specific antibody response to the C pneumoniae hsp60 molecule and not with a genus-specific response to the hsp60 molecule.

METHODS

In a case-control study, we evaluated 138 C pneumoniae-exposed primary care patients (86 adult asthmatic cases and 52 nonasthmatic controls) for seroreactivity against a C pneumoniae-specific hsp60 fragment and against the C trachomatis hsp60 molecule. We analyzed associations with asthma and irreversible lung remodeling as measured by means of postbronchodilator forced expiratory volume in 1 second.

RESULTS

Twenty-seven percent of asthmatic patients were C pneumoniae hsp60 seropositive vs 8% of controls (P < .01). Controlling for age, sex, and smoking, C pneumoniae hsp60 seropositivity was associated with lower postbronchodilator forced expiratory volume in 1 second in asthmatic patients (P < .05). No comparable associations were present for C trachomatis hsp60.

CONCLUSIONS

In individuals with evidence of previous exposure to C pneumoniae infection, a host antibody response against a C pneumoniae hsp60 fragment but not against C trachomatis hsp60 was associated with airflow limitation in adults with asthma.

Constant ocular infection with Chlamydia trachomatis predicts risk of scarring in children in Tanzania

OBJECTIVE

Clinically, constant severe trachoma predicts an increased risk of scarring in children. There are no data on the risk of scarring associated with constant infection with Chlamydia trachomatis, regardless of clinical manifestation. We propose to determine the 5-year incidence of scarring in children with a history of constant severe trachoma, constant infection, or both compared with children who had a history of neither.

DESIGN

A 5-year, longitudinal observational study.

PARTICIPANTS

Children aged less than 10 years with data on trachoma and infection for 3 of the 5 visits in the first 18 months, and follow-up 5-year data on scarring.

METHODS

Data were collected on clinical trachoma, and ocular swabs were taken to determine the presence of C. trachomatis in children in a hyperendemic village in Tanzania. Images were graded for scarring. Data were collected at baseline; 2, 6, 12, and 18 months; and 5 years from baseline. Severe trachoma was defined as the presence of 10 or more follicles, or trachoma intense. A child had constant infection (severe trachoma) if infection (severe trachoma) was present on at least 3 visits before the 5-year survey.

MAIN OUTCOME MEASURES

Five-year risk of scarring.

RESULTS

Of the 189 children, 22 (11.6%) had constant severe trachoma, but not constant infection. Nine children (4.8%) had constant infection but not constant severe trachoma. Both constant severe trachoma and constant infection were present in 16 children (8.5%). The 5-year incidence of scarring was similar in all 3 groups; children with constant severe trachoma only, with constant infection only, and with both were most likely to develop scars (35.0%, 44.4%, 31.2%, respectively) compared with those with sporadic trachoma or infection (15.2%) or neither (6.8%) (P = 0.0002).

CONCLUSIONS

Children with constant infection are also likely to have constant severe trachoma, and their 5-year risk of scarring is high compared with children with sporadic severe trachoma or infection. These data further support the presence of a subgroup of children who cannot clear infection with C. trachomatis, who may manifest a severe immunologic response to infection, and who are at increased risk of scarring sequelae.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Trachoma

Trachoma is a keratoconjunctivitis caused by ocular infection with Chlamydia trachomatis. Repeated or persistent episodes lead to increasingly severe inflammation that can progress to scarring of the upper tarsal conjunctiva. Trichiasis develops when scarring distorts the upper eyelid sufficiently to cause one or more lashes to abrade the cornea, scarring it in turn and causing blindness. Active trachoma affects an estimated 84 million people; another 7.6 million have end-stage disease, of which about 1.3 million are blind. Trachoma should stand on the brink of extinction thanks to a 1998 initiative launched by WHO--the Global Elimination of Trachoma by 2020. This programme advocates control of trachoma at the community level with four inter-related population-health initiatives that form the SAFE strategy: surgery for trichiasis, antibiotics for active trachoma, facial cleanliness, and environmental improvement. Evidence supports the effectiveness of this approach, and if current world efforts continue, blinding trachoma will indeed be eliminated by 2020.

Multiple Chlamydiaceae species in trachoma: implications for disease pathogenesis and control

BACKGROUND

Chlamydia trachomatis is a unique obligate intracellular bacterium that remains the leading cause of sexually transmitted bacterial diseases and preventable blindness worldwide. Chronic ocular infections are referred to as trachoma, and predominate in developing countries. Since 2001, the World Health Organization has promoted control strategies including antibiotics, improved hygiene, and environmental measures with limited success. Consequently, a vaccine is urgently needed. Integral to vaccine design is an understanding of the interactions of the pathogen and host immune response. Various animal models of trachoma show that urogenital C. trachomatis strains and other species of the family Chlamydiaceae produce severe conjunctival inflammation and scarring similar to that of the ocular C. trachomatis strains. However, we do not know the extent of organisms that may be involved in human trachoma. Furthermore, C. trachomatis heat shock protein 60 (Hsp60) has been implicated in inflammation and conjunctival scarring but the role of other Chlamydiaceae Hsp60 in disease pathogenesis has not been examined. In this study, we set out to identify whether other Chlamydiaceae species are present in trachoma, and determine their association with severity of clinical disease and with mucosal and systemic immune responses to Chlamydiaceae species-specific Hsp60 to further investigate the immunopathogenesis of this blinding disease.

METHODS AND FINDINGS

We randomly selected nine of 49 households in a trachoma-endemic region of Nepal. Trachoma was graded, and real-time, quantitative (k)PCR was used to detect genomic DNA and cDNA (from RNA) for Chlamydiaceae ompA and 16S rRNA genes, respectively, from conjunctival swabs. IgG antibody responses to recombinant (r) Chlamydiaceae species-specific Hsp60 were determined for tears and sera. Surprisingly, all three species-C. trachomatis, Chlamydophila psittaci, and Chlamydophila pneumoniae-were detected in eight (89%) study households; one household had no members infected with C. pneumoniae. Of 80 (63%; n = 127) infected individuals, 28 (35%) had infection with C. psittaci, or C. pneumoniae, or both; single and dual infections with C. psittaci and C. pneumoniae were significantly associated with severe conjunctival inflammation (OR 4.25 [95% confidence interval (CI), 2.9-11.3], p = 0.009] as were single infections with C. trachomatis (OR 5.7 [95% CI, 3.8-10.1], p = 0.002). Of the 80 infected individuals, 75 (93.8%) were also positive for 16S rRNA by kPCR for the same organism identified by ompA. Individuals with tear IgG immunoreactivity to Chlamydiaceae rHsp60 were eight times more likely than individuals without tear immunoreactivity to be infected (95% CI 6.4-15.1; p = 0.003), 6.2 times more likely to have severe inflammation (95% CI 4.4-12.6; p = 0.001), and 5.7 times more likely to have scarring (95% CI 3.9-11.1; p = 0.019) while individuals with serum IgG immunoreactivity were 4.1 times more likely to be infected (95% CI 3.1-10.1; p = 0.014).

CONCLUSIONS

We provide substantial evidence for the involvement of C. psittaci and C. pneumoniae, in addition to C. trachomatis, in trachoma. The distribution of Chlamydiaceae species by household and age suggests that these infections are widespread and not just sporadic occurrences. Infection with multiple species may explain the failure to detect chlamydiae among active trachoma cases, when only C. trachomatis is assayed for, and the failure of clinically active cases to resolve their disease following what would be considered effective C. trachomatis treatment. The evidence for viable (RNA-positive) organisms of all three species in single and coinfections, the significant association of these infections with severe inflammation, and the significant association of tear and serum IgG responses to Chlamydiaceae Hsp60 with inflammation and scarring, support the role of all three species in disease pathogenesis. Thus, while our findings should be confirmed in other trachoma-endemic countries, our data suggest that a reevaluation of treatment regimens and vaccine design may be required. Understanding the full impact of Chlamydiaceae species on the epidemiology, immunopathology, and disease outcome of trachoma presents a new challenge for Chlamydiaceae research.

In pursuit of a human chlamydial vaccine

The best way to control chlamydial diseases is with an effective vaccine. Although previous studies suggest that a vaccine is an achievable goal, progress has been limited even though many vaccination strategies have been tested. A clearer understanding of the immunobiological basis of chlamydial protection and pathology will be critical for future research in chlamydial vaccination.

In silico identification of functional divergence between the multiple groEL gene paralogs in Chlamydiae

Background

Heat-shock proteins are specialized molecules performing different and essential roles in the cell including protein degradation, folding and trafficking. GroEL is a 60 Kda heat-shock protein ubiquitous in bacteria and has been regarded as an important molecule implicated in chronic inflammatory processes caused by Chlamydiae infections. GroEL in Chlamydiae became duplicated at the origin of the Chlamydiae lineage presenting three distinct molecular chaperones, namely the original protein GroEL1 (Ct110), and its paralogous proteins GroEL2 (Ct604) and GroEL3 (Ct755). These chaperones present differential and independent expressions during the different stages of Chlamydiae infections and have been suggested to present differential physiological and regulatory roles.

Results

In this comprehensive in silico study we show that GroEL protein paralogs have diverged functionally after the different gene duplication events and that this divergence has occurred mainly between GroEL3 and GroEL1. GroEL2 presents an intermediate functional divergence pattern from GroEL1. Our results point to the different protein-protein interaction patterns between GroEL paralogs and known GroEL protein clients supporting their functional divergence after groEL gene duplication. Analysis of selective constraints identifies periods of adaptive evolution after gene duplication that led to the fixation of amino acid replacements in GroEL protein domains involved in the interaction with GroEL protein clients.

Conclusion

We demonstrate that GroEL protein copies in Chlamydiae species have diverged functionally after the gene duplication events. We also show that functional divergence has occurred in important functional regions of these GroEL proteins and that very probably have affected the ancestral GroEL regulatory role and protein-protein interaction patterns with GroEL client proteins. Most of the amino acid replacements that have affected interaction with protein clients and that were responsible for the functional divergence between GroEL paralogs were fixed by adaptive evolution after the groEL gene duplication events.

Prevalence of chlamydia in patients attending gynecological clinics in south eastern Nigeria

BACKGROUND

Chlamydia infections have been reported to cause silent infections in communities which becomes endemic and could remain unnoticed for a very long time. In most parts of Nigeria these organisms are not screened for, and hence relative information about frequencies of the organisms are sparse.

METHOD

Five hundred and sixty five blood samples and ten umbilical cord fluids were collected from various patients attending clinics in South Eastern Nigeria and were screened for Chlamydia Complement Fixing Antibody (CCFA). Endocervical swabs and urethral discharges or swabs were collected from patients whose serum was positive and were cultured into embryonic eggs which was later observed, harvested and stained using the Romanowsky-Giemsa staining techniques. The positive sera were further confirmed by distinguishing the species of Chlamydia using the monoclonal antibody spot test kit.

RESULT

Of the five hundred and sixty five (565) samples collected only three hundred and forty were positive to CCFA, of which 141 were males and 204 females. From the cultured samples 230 were positive for Chlamydia trachomatis and 99 positive to Chlamydia pneumoniae. Statistical analysis using the student's t test at 95% confidence interval shows that there was no significant difference between the number of females and males that presented themselves for screening.

CONCLUSION

Proper screening of patients to include Chlamydia should be encouraged at all levels of medical diagnosis in the country so as to proffer treatment. Otherwise the infection will remain a "silent epidemic", as is the case currently.

Why do we need quality-assured diagnostic tests for sexually transmitted infections?

The bacterial sexually transmitted infections (STIs) syphilis, gonorrhoea and chlamydia can all be cured with a single dose of antibiotic. Unfortunately, however, these infections often remain undiagnosed as many infected individuals have few if any symptoms. Diagnostic tests with high sensitivity and specificity are available for all three infections but, owing to their expense and the lack of laboratory capacity, most people in developing countries do not have access to these tests. There is a great need for simple, cheap diagnostic tests for STIs that can be performed at the point of care, enabling treatment to be given immediately. It is hoped that recent advances in our understanding of the pathogenesis of these infections, and the availability of the complete genome sequences for each causative organism, will lead to the development of improved point-of-care tests that will reduce the burden of these diseases in developing countries.

Why do we need quality-assured diagnostic tests for sexually transmitted infections?

The bacterial sexually transmitted infections (STIs) syphilis, gonorrhoea and chlamydia can all be cured with a single dose of antibiotic. Unfortunately, however, these infections often remain undiagnosed as many infected individuals have few if any symptoms. Diagnostic tests with high sensitivity and specificity are available for all three infections but, owing to their expense and the lack of laboratory capacity, most people in developing countries do not have access to these tests. There is a great need for simple, cheap diagnostic tests for STIs that can be performed at the point of care, enabling treatment to be given immediately. It is hoped that recent advances in our understanding of the pathogenesis of these infections, and the availability of the complete genome sequences for each causative organism, will lead to the development of improved point-of-care tests that will reduce the burden of these diseases in developing countries.

Chlamydial GroEL autoregulates its own expression through direct interactions with the HrcA repressor protein

In the pathogenic bacterium Chlamydia trachomatis, a transcriptional repressor, HrcA, regulates the major heat shock operons, dnaK and groE. Cellular stress causes a transient increase in transcription of these heat shock operons through relief of HrcA-mediated repression, but the pathway leading to derepression is unclear. Elevated temperature alone is not sufficient, and it is hypothesized that additional chlamydial factors play a role. We used DNA affinity chromatography to purify proteins that interact with HrcA in vivo and identified a higher-order complex consisting of HrcA, GroEL, and GroES. This endogenous HrcA complex migrated differently than recombinant HrcA, but the complex could be disrupted, releasing native HrcA that resembled recombinant HrcA. In in vitro assays, GroEL increased the ability of HrcA to bind to the CIRCE operator and to repress transcription. Other chlamydial heat shock proteins, including the two additional GroEL paralogs present in all chlamydial species, did not modulate HrcA activity.

Risk of trachomatous scarring and trichiasis in Gambians varies with SNP haplotypes at the interferon-gamma and interleukin-10 loci

Experimental evidence implicates interferon gamma (IFNgamma) in protection from and resolution of chlamydial infection. Conversely, interleukin 10 (IL10) is associated with susceptibility and persistence of infection and pathology. We studied genetic variation within the IL10 and IFNgamma loci in relation to the risk of developing severe complications of human ocular Chlamydia trachomatis infection. A total of 651 Gambian subjects with scarring trachoma, of whom 307 also had potentially blinding trichiasis and pair-matched controls with normal eyelids, were screened for associations between single-nucleotide polymorphisms (SNPs), SNP haplotypes and the risk of disease. MassEXTEND (Sequenom) and MALDI-TOF mass spectrometry were used for detection and analysis of SNPs and the programs PHASE and SNPHAP used to infer haplotypes from population genetic data. Multivariate conditional logistic regression analysis identified IL10 and IFNgamma SNP haplotypes associated with increased risk of both trachomatous scarring and trichiasis. SNPs in putative IFNgamma and IL10 regulatory regions lay within the disease-associated haplotypes. The IFNgamma +874A allele, previously linked to lower IFNgamma production, lies in the IFNgamma risk haplotype and was more common among cases than controls, but not significantly so. The promoter IL10-1082G allele, previously associated with high IL10 expression, is in both susceptibility and resistance haplotypes.

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.

Trachoma: new assault on an ancient disease

Trachoma is the leading infectious cause of blindness worldwide. The World Health Organization (WHO) estimated that approximately 5.9 million persons are blind or have severe vision-loss as a result of trachoma, and another 10 million are at high risk. Trachoma preferentially affects the most deprived communities, and within these communities, women and children bear the brunt of the burden. In recent years, there has been a renewed focus on research and heightened enthusiasm for strengthening trachoma control programs in afflicted countries. WHO has convened an alliance of member countries, non-governmental organizations, and other partners for the Global Elimination of Blinding Trachoma by the year 2020, and endorsed the multi-faceted SAFE strategy for trachoma control. SAFE-Surgery, Antibiotics, Face-washing, and Environmental improvement-has incorporated sound research on elements likely to reduce trachoma, and trachomatis blindness, in endemic communities. This review summarizes current knowledge about trachoma and its causative agent, Chlamydia trachomatis, the epidemiology and risk factors for trachoma as a prelude to reviewing the SAFE strategy. While ongoing research to support the knowledge base for SAFE must continue to be a priority, the full implementation of SAFE is the best hope for countries to reduce the global burden of blindness from this preventable cause.

Stress response gene regulation in Chlamydia is dependent on HrcA-CIRCE interactions

HrcA is a transcriptional repressor that regulates stress response genes in many bacteria by binding to the CIRCE operator. We have previously shown that HrcA regulates the promoter for the dnaK heat shock operon in Chlamydia. Here we demonstrate that HrcA represses a second heat shock promoter that controls the expression of groES and groEL, two other major chlamydial heat shock genes. The CIRCE element of C. trachomatis groEL is the most divergent of known bacterial CIRCE elements, and HrcA had a decreased ability to bind to this nonconsensus operator and repress transcription. We demonstrate that the CIRCE element is necessary and sufficient for transcriptional regulation by chlamydial HrcA and that the inverted repeats of CIRCE are the binding sites for HrcA. Addition of a CIRCE element upstream of a non-heat-shock promoter allowed this promoter to be repressed by HrcA, showing in principle that a chlamydial promoter can be genetically modified to be inducible. These results demonstrate that HrcA is the regulator of the major chlamydial heat shock operons, and we infer that the mechanism of the heat shock response in Chlamydia is derepression. However, derepression is likely to involve more than a direct effect of increased temperature as we found that HrcA binding to CIRCE and HrcA-mediated repression were not altered at temperatures that induce the heat shock response.

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.

Trachoma

Trachoma is the most common infectious cause of blindness. It is caused by ocular serovars of Chlamydia trachomatis. Transmission is favoured in poor communities, where crowding is common and access to water and sanitation inadequate. Repeated reinfection over many years causes dense scarring of the upper eyelid. The resultant inversion of the lashes abrades the eyeball, and the abrasion leads to corneal opacification and visual impairment. The host immune response is probably at least partly the cause of this process. The "SAFE" strategy is used for the control of trachoma: surgery for in-turned lashes, antibiotics for active disease, facial cleanliness, and environmental improvement. The demonstration that a single oral dose of the antibiotic azithromycin is as effective as 6 weeks of topical tetracycline was an important advance in trachoma control. By means of the SAFE strategy, WHO and its partners aim to eliminate trachoma as a public-health problem by the year 2020.

Infection with Chlamydia pneumoniae and risk of multiple sclerosis

BACKGROUND

Chlamydia pneumoniae (Cpn) has been proposed as a possible etiologic agent for multiple sclerosis (MS), but results of previous studies are conflicting.

METHODS

Using a nested case-control design, we examined the association between Cpn infection and MS in the Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II) cohorts. Among 32,826 women in the NHS and 29,722 women in the NHS II with blood samples, 141 incident cases of definite or probable MS were documented. Each case was matched to two healthy controls on year of birth and NHS cohort. Serum samples were tested for the presence of Cpn-specific immunoglobin G antibodies using microimmunofluorescence.

RESULTS

Cpn immunoglobin G seropositivity was positively associated with risk of MS (odds ratio [OR] = 1.7; 95% confidence interval [CI] = 1.1-2.7). This association did not change after adjusting for age at blood collection, ancestry, latitude of residence at birth, and smoking (OR = 1.9; CI = 1.1-3.1). Seropositivity for Cpn was only moderately associated with risk of relapsing-remitting MS (OR = 1.7; CI = 0.9-3.2), but it was strongly associated with risk of progressive MS (OR = 7.3; CI = 1.4-37.2). Geometric mean titers of Cpn-specific immunoglobin G antibody were similar in women with relapsing-remitting MS as compared with matched controls (44 vs 39), but they were elevated in women with progressive MS (99 vs 40).

CONCLUSIONS

These results support a positive association between Cpn infection and progressive MS.

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.

Serum Immunoglobulin G Antibodies to Chlamydial Heat Shock Protein 60 but Not to Human and Bacterial Homologs Are Associated With Coronary Artery Disease

Background— Evidence for an association between Chlamydia pneumoniae infection and coronary artery disease (CAD) has been reported by numerous studies, cross-reactive heat shock protein (Hsp) antibody responses have been causally linked to CAD, and the severity of chlamydial disease pathogenesis correlates with Hsp serology. Our aim was to determine if chlamydial Hsp (cHsp) antibody responses are predictive of CAD.

Methods and Results— Patients were recruited in a case-control study: 250 cases had angiographically significant CAD (stenosis ≥70%), and 250 controls had normal coronary arteries (stenosis <10%). Serum immunoglobulin G reactivity to Hsp10 and Hsp60 antigens (chlamydial, Escherichia coli , and human), and C pneumoniae whole organisms were measured by ELISA. Univariate analysis confirmed that classical CAD risk factors were predictors of CAD. Univariate analysis showed that cHsp60 ( P = 0.001, OR 3.9), cHsp10 ( P =0.045, OR 3.8), E coli Hsp60 ( P =0.04, OR 1.5) and C pneumoniae ( P =0.03, OR 1.8) ELISA optical density (OD) values were significantly different between cases and controls. Multivariate analysis found that only upper-quintile cHsp60 seroreactivity remained a significant predictor of CAD after controlling for classical CAD risk factors and seroreactivity to the other antigens (cHsp60 OD, P =0.005, OR 3.9 per OD unit; cHsp60 quintile, 5 versus 1 to 4; P =0.01, OR 2.1).

Conclusions— The presence of elevated anti-cHsp60 immunoglobulin G antibodies, but not anti-human or anti– E coli homologs, was independently associated with CAD. This finding argues against previous suggestions that cross-reactive or autoimmune Hsp60 responses may contribute to disease progression. High anti-cHsp60 antibody response appears to identify the subset of patients with chlamydial infection and significant CAD.

Chlamydia pneumoniae and severity of asthma

A substantial increase in the prevalence of asthma in the Western world during the last few decades has led to a continuous search for novel factors that might be involved in the development of the disease. We carried out a study to clarify whether there is a relationship between severity of asthma and Chlamydia pneumoniae-specific titres at the group level and whether antibodies to the 60 kDa chlamydial heat shock protein (chsp60) are associated with asthma. A total of 116 (31 men, 85 women) consecutive asthma patients from a chest clinic were recruited and divided into 3 groups according to the severity of the disease: there were 13 asthmatics with severe, 54 with moderate and 49 with mild asthma. In addition, 50 (31 men, 19 women) consecutive blood donors were enrolled to serve as a control group. Sera for the measurements of specific IgG, IgA and IgM antibodies using a microimmunofluorescence test and of chsp60 using an enzyme immunoassay were obtained upon enrolment and also 3-4 months later from the asthma patients. Severe and moderate asthma were found to be strongly associated with elevated IgA antibody levels to C. pneumoniae [odds ratio (OR) 5.58, 95% confidence interval (CI) 1.31-23.72 for severe and OR 5.65, 95% CI 2.05-15.53 for moderate asthma] in a logistic regression model. Furthermore, in women, the occurrence of elevated IgA antibody levels and the age-adjusted geometric mean titres of IgA antibodies were significantly higher among the asthmatics than the controls (p = 0.003 and 0.04, respectively). Antibodies to chsp60 occurred more frequently and in higher concentrations among the asthmatics than the controls, although the differences did not reach significance. In conclusion, severe and moderate asthma were significantly associated with elevated IgA antibody levels to C. pneumoniae suggestive of chronic infection. Antibodies to chsp60 did not prove to be a useful marker of such an infection among the asthmatics studied here.

Stress proteins: nomenclature, division and functions

The heat shock response, characterized by increased expression of heat shock proteins (Hsps) is induced by exposure of cells and tissues to extreme conditions that cause acute or chronic stress. Hsps function as molecular chaperones in regulating cellular homeostasis and promoting survival. If the stress is too severe, a signal that leads to programmed cell death, apoptosis, is activated, thereby providing a finely tuned balance between survival and death. In addition to extracellular stimuli, several nonstressfull conditions induce Hsps during normal cellular growth and development. The enhanced heat shock gene expression in response to various stimuli is regulated by heat shock transcription factors.

Immune response to chlamydial 60-kilodalton heat shock protein in tears from Nepali trachoma patients

Although the host immune response to the 60-kDa chlamydial heat shock protein (hsp60) has been implicated in trachoma pathogenesis, no studies have examined mucosal immune responses to hsp60 in populations for which chlamydia is endemic. Tears and sera from Nepali villagers were reacted against hsp60 fusion proteins, whole hsp60, and the major outer membrane protein (MOMP). Tears from villagers without disease were anti-hsp60 immunoglobulin G (IgG) reactive in 6 (38%) of 16 villagers compared with 36 (90%) of 40 with follicular trachoma (TF) (P < 0.001); 47 (89%) of 53 with inflammatory trachoma (TI) (P < 0.001); and 31 (84%) of 37 with conjunctival scarring (TS) (P = 0.002). By multivariate analysis, odds ratios for tear hsp60 IgG immunoreactivity in villagers with TF, TI, and TS were 49.2 (confidence interval [CI], 2.7 to 898), 22.6 (CI, 3 to 170), and 13.6 (CI, 1.4 to 133), respectively. There were no significant differences for tear IgA or secretory IgA (sIgA) reactivity to hsp60 or for tear sIgA and IgG reactivity to MOMP. Serum anti-hsp60 IgG immunoreactivity was associated with TI only. These data suggest that anti-hsp60 IgG immunoreactivity represents largely locally derived antibodies, which may promote disease pathology. In contrast, nonspecific high rates of anti-hsp60 sIgA antibodies suggest chronic or repeat stimulation from an endemic source of organisms.

Progression of active trachoma to scarring in a cohort of Tanzanian children

Risk factors for the incidence of scarring are needed to inform trachoma control programs in countries hyperendemic for this blinding disease. A cohort of pre-school children with constant, severe trachoma, and an age, sex, and neighborhood matched cohort of children without constant severe trachoma were followed for seven years to determine the incidence of scarring. The incidence of scarring in the children with constant severe trachoma was 29.2% versus 9.6% in the comparison group. In a model adjusting for multiple factors, significant predictors of scarring were increasing age, female, and constant severe trachoma (OR = 4.85, 95% CL = 2.05, 11.40). Infection with C. trachomatis at follow up was also associated with scarring in both groups of children. It is likely that these children have a different host response to infection, and represent a subgroup at high risk for the blinding complications of trachoma. Reducing exposure to infection in the community through antibiotics and changes in hygiene practices is still the most promising control strategy.

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.

Host immune response to Chlamydia pneumoniae heat shock protein 60 is associated with asthma

Chlamydia pneumoniae infection has been associated with asthma. It has also been suggested that heat shock protein 60 (Hsp60) belonging to a class of highly conserved proteins may play a role in the pathogenesis of chlamydial infections. The purpose was to study whether the host immune response to C. pneumoniae Hsp60 is associated with asthma and decreased pulmonary function. An enzyme immunoassay was used to measure immunoglobulin-(Ig)A and IgG antibodies against recombinant C. pneumoniae Hsp60 and human Hsp60 in a study group consisting of 24 cases of recently symptomatic asthma and 62 nonasthmatic controls. A strong (r=0.50) and significant (p<0.001) correlation was observed between C. pneumoniae and human Hsp60 IgA antibodies, but only C. pneumoniae Hsp60 IgA antibodies were significantly associated with asthma (p = 0.02). Pulmonary function, as measured by forced expiratory volume in one second, also inversely correlated (r = -0.23, p = 0.04) with the quantity of C. pneumoniae Hsp60 IgA antibodies, suggesting an association with the severity of pulmonary obstruction. By showing an association of Chlamydia pneumoniae heat shock protein 60 immunoglobulin A antibodies with asthma, the results support the hypothesis of an association between Chlamydia pneumoniae infection and asthma and support the need for further investigations on the role of heat shock protein 60 in the pathogenesis of asthma.

Genetic differences in the Chlamydia trachomatis tryptophan synthase alpha-subunit can explain variations in serovar pathogenesis

The human pathogen Chlamydia trachomatis is an obligate intracellular bacterium, characterized by a developmental cycle that alternates between the infectious, extracellular elementary bodies and intracellular, metabolically active reticulate bodies. The cellular immune effector interferon gamma (IFN-gamma) inhibits chlamydial multiplication in human epithelial cells by induction of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase. IFN-gamma causes persistent C. trachomatis serovar A infections with atypical reticulate bodies that are unable to redifferentiate into elementary bodies and show diminished expression of important immunogens, but not of GroEL. However, the sensitivity to IFN-gamma varies among serovars of C. trachomatis. In our previous study significant IFN-gamma-specific, but tryptophan reversible, induction of proteins in C. trachomatis A and L2 with molecular masses of approximately 30 and 40 kDa was observed on 2D-gels. The 30-kDa protein from C. trachomatis L2 migrated with a significantly lower molecular weight in C. trachomatis A. In this paper we include C. trachomatis B, C and D in our investigations and identify the proteins as alpha- and beta-subunits of the chlamydial tryptophan synthase using matrix-assisted laser desorption/ionization mass spectrometry. DNA sequencing of the trpA genes from C. trachomatis A and C shows that the TrpA in these serovars is a 7.7-kDa truncated version of C. trachomatis D and L2 TrpA. The truncation probably impairs the TrpA activity, thus elucidating a possible molecular mechanism behind variations in the pathogenesis of C. trachomatis serovars.

Protective DNA immunization against Chlamydia pneumoniae

We have investigated the efficacy of the DNA vaccination using the heat shock protein 60 (HSP-60) gene of C. pneumoniae, for protection of mice against infection with the bacteria. C57Bl/6 mice had a 5-20-fold reduction of C. pneumoniae numbers in lungs when immunized intranasally (i.n.) with plasmids (p) encoding pHSP-60. The reduction of the bacterial load coincided with a decreased severity of disease. No specific antibodies were detected after protective i. n. immunization. In contrast, mice immunized intradermally (i.d.) were not protected against challenge with C. pneumoniae, although specific humoral Immunoglobulin (Ig)G responses were generated. Co-inoculation i.n. of pHSP-60 with pIL-12 but not with pGM-CSF further increased protection of mice against infection with C. pneumoniae. Lungs from pHSP-60 i.n. immunized and infected mice showed higher levels of interferon (IFN)-gamma mRNA, and spleen cells from these mice co-cultured with r-HSP-60 released higher levels of IFN-gamma and displayed higher proliferative responses than nonimmunized and infected controls. pHSP-60 immunized IFN-gamma receptor (R)-/- mice were not protected against infection with C. pneumoniae. Likewise, i.n. administration of pIFN-gamma alone induced significant protection. DNA vaccine-induced protection was CD4+ and CD8+ T-cell dependent, as shown by DNA-vaccination of MHC class II-/-, CD4-/-, CD8-/- and CD4-/-CD8-/-mice. Interestingly, DNA vaccine induced CD4+ T cells, in the absence of CD8+ T cells, were involved in worsening the outcome of infection. This worsening was linked with a shift towards a Th2 cytokine pattern.

Serologic markers for Chlamydia pneumoniae in asthma

BACKGROUND

Chlamydia pneumoniae infection has been reported as a possible etiologic agent in asthma, which in primary care settings often appears to be initiated by acute respiratory infections.

OBJECTIVE

To determine if serologic markers for C. pneumoniae are associated with adult asthma that first became symptomatic after an acute respiratory illness (asthma associated with infection: AAWI).

METHODS

Serum samples from 164 primary care outpatients, mean age 44 years, (68 with AAWI; 36 with atopic, occupational or exercise-induced asthma (non-AAWI); 16 nonasthmatic patients with acute bronchitis; and 44 asymptomatic nonasthmatic controls) were tested for the presence of C. pneumoniae-specific IgG and IgA antibodies. Levels of chlamydial heat shock protein 60 (CHSP60) antibody were also measured. Those positive for CHSP60 were tested for C. pneumoniae-specific IgE antibodies by immunoblotting.

RESULTS

Statistically significant differences in IgG and IgA seroreactivity were noted between groups: acute bronchitis and AAWI had the highest levels (93% to 94% IgG seroreactivity, 69% to 75% IgA seroreactivity) whereas non-AAWI and asymptomatic controls had the lowest levels (61% to 84% IgG seroreactivity, 31% to 43% IgA seroreactivity, P < .02 after adjustment for age, sex and smoking). CHSP60 antibodies were significantly more prevalent in AAWI than in non-AAWI (19% versus 3%, P = .02). IgE antibodies against C. pneumoniae 60, 62, and/or 70 kD antigens were detected in 5 of 13 CHSP60 positive AAWI patients. Persistent IgG, IgA, and CHSP60 seroreactivities were noted in all seropositive asthma patients with serial serum samples.

CONCLUSIONS

Serologic markers of C. pneumoniae infection were associated with acute bronchitis and with asthma that first became symptomatic following respiratory illness. Serologic responses to C. pneumoniae may be useful in the classification and diagnosis of asthma.