Isolation and sequence analysis of the Chlamydia pneumoniae GroE operon

The serodiagnositic value of Chlamydia trachomatis antigens in antibody detection using luciferase immunosorbent assay

Introduction

Among the different antigens used in the detection of anti-Chlamydia trachomatis antibodies, significant differences in sensitivity and specificity have been observed. Further evaluation of C. trachomatis antigens in antibody detection is urgently needed for the development and application of C. trachomatis serologic assays.

Methods

Chlamydia trachomatis antigens Pgp3, TmeA, InaC, and HSP60 were selected and used in luciferase immunosorbent assay (LISA). The detection results obtained from well-defined C. trachomatis positive and negative samples were compared with the commercial C. trachomatis ELISA (Mikrogen) for performance evaluation.

Results

Pgp3, TmeA, InaC, and HSP60-based LISA showed sensitivity of 92.8, 88.8, 90.4, and 94.4%, and specificity of 99.2, 99.2, 99.2, and 92%, respectively. ROC analysis indicated that Pgp3-based LISA showed similar performance to Mikrogen ELISA (AUC 0.986 vs. 0.993, p = 0.207). Furthermore, four C. trachomatis antigens achieved strong diagnostic efficiency, i.e., positive likelihood ratios [+LR] ≥ 10 in C. trachomatis-infected women and negative likelihood ratios [-LR] ≤ 0.1 in C. trachomatis negative low exposure risk children, but only Pgp3 and TmeA showed strong diagnostic value in general adults. In addition, Pgp3, TmeA, and InaC, but not HSP60, achieved high performance, i.e., both positive predictive value (PPV) and negative predictive value (NPV) ≥ 90.9%, and showed no significant cross-reactivity with anti-Chlamydiapneumoniae.

Conclusion

Three C. trachomatis species-specific antigens Pgp3, TmeA, and InaC show superior performance in the detection of anti-C. trachomatis antibody, indicating the potential to be used in developing C. trachomatis serologic tests.

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.

Immune responses and vaccination against periodontal infections

BACKGROUND

The infectious aetiology of periodontitis is complex and no curative treatment modality exists. Palliative therapy is available.

AIMS

To review the evidence that active or passive immunization against periodontitis provides immune protection.

MATERIAL AND METHODS

PubMed (Medline), the National Institutes of Health, the Food and Drug Administration, and the Center for Disease Control electronic databases were searched to extrapolate information on immune responses to immunization against periodontitis.

RESULTS

Studies in non-human primate models using ligature-induced experimental periodontitis suggest that antibody responses by active immunization against Porphyromonas gingivalis can safely be induced, enhanced, and obtained over time. Immune responses to whole bacterial cell and purified protein preparations considered as vaccine candidates have been evaluated in different animal models demonstrating that there are several valid vaccine candidates. Data suggest that immunization reduces the rate and severity of bone loss. It is also, temporarily, possible to alter the composition of the subgingival microflora. Natural active immunization by therapeutic interventions results in antibody titre enhancement and potentially improves treatment outcomes. Passive immunization of humans using P. gingivalis monoclonal antibodies temporarily prevents colonization of P. gingivalis. Probiotic therapy may be an alternative approach. Regulatory and safety issues for human periodontal vaccine trials must be considered. Shared infectious aetiology between periodontitis and systemic diseases may enhance vaccine effort developments.

CONCLUSIONS

Proof of principle that active and passive immunization can induce protective antibody responses is given. The impact of natural immunization and passive immunization in humans should be explored and may, presently, be more feasible than active immunization studies.

Production of Chlamydia pneumoniae proteins in Bacillus subtilis and their use in characterizing immune responses in the experimental infection model

Due to intracellular growth requirements, large-scale cultures of chlamydiae and purification of its proteins are difficult and laborious. To overcome these problems we produced chlamydial proteins in a heterologous host, Bacillus subtilis, a gram-positive nonpathogenic bacterium. The genes of Chlamydia pneumoniae major outer membrane protein (MOMP), the cysteine-rich outer membrane protein (Omp2), and the heat shock protein (Hsp60) were amplified by PCR, and the PCR products were cloned into expression vectors containing a promoter, a ribosome binding site, and a truncated signal sequence of the alpha-amylase gene from Bacillus amyloliquefaciens. C. pneumoniae genes were readily expressed in B. subtilis under the control of the alpha-amylase promoter. The recombinant proteins MOMP and Hsp60 were purified from the bacterial lysate with the aid of the carboxy-terminal histidine hexamer tag by affinity chromatography. The Omp2 was separated as an insoluble fraction after 8 M urea treatment. The purified proteins were successfully used as immunogens and as antigens in serological assays and in a lymphoproliferation test. The Omp2 and Hsp60 antigens were readily recognized by the antibodies appearing after pulmonary infection following intranasal inoculation of C. pneumoniae in mice. Also, splenocytes collected from mice immunized with MOMP or Hsp60 proteins proliferated in response to in vitro stimulation with the corresponding proteins.

Multiple Chlamydia pneumoniae antigens prime CD8+ Tc1 responses that inhibit intracellular growth of this vacuolar pathogen

CD8(+) T cells play an essential role in immunity to Chlamydia pneumoniae (Cpn). However, the target Ags recognized by Cpn-specific CD8(+) T cells have not been identified, and the mechanisms by which this T cell subset contributes to protection remain unknown. In this work we demonstrate that Cpn infection primes a pathogen-specific CD8(+) T cell response in mice. Eighteen H-2(b) binding peptides representing sequences from 12 Cpn Ags sensitized target cells for MHC class I-restricted lysis by CD8(+) CTL generated from the spleens and lungs of infected mice. Peptide-specific IFN-gamma-secreting CD8(+) T cells were present in local and systemic compartments after primary infection, and these cells expanded after pathogen re-exposure. CD8(+) T cell lines to the 18 Cpn epitope-bearing peptides were cytotoxic, displayed a memory phenotype, and secreted IFN-gamma and TNF-alpha, but not IL-4. These CTL lines lysed Cpn-infected macrophages, and the lytic activity was inhibited by brefeldin A, indicating endogenous processing of CTL Ags. Finally, Cpn peptide-specific CD8(+) CTL suppressed chlamydial growth in vitro by direct lysis of infected cells and by secretion of IFN-gamma and other soluble factors. These studies provide information on the mechanisms by which CD8(+) CTL protect against Cpn, furnish the tools to investigate their possible role in immunopathology, and lay the foundation for future work to develop vaccines against acute and chronic Cpn infections.

Chlamydia trachomatis serology: diagnostic value of outer membrane protein 2 compared with that of other antigens

Different immunoassays using recombinant antigens or synthetic peptides were evaluated for the serodiagnosis of Chlamydia trachomatis infections. Antigens used included cysteine-rich outer membrane protein 2 (OMP2), heat shock protein 60, the polypeptide encoded by open reading frame 3 of the plasmid (pgp3), synthetic peptides derived from species-specific epitopes in variable domain IV of the major OMP (MOMP) (Labsystems, Helsinki, Finland), and a fragment of the total lipopolysaccharide (Medac, Hamburg, Germany). Because cross-reactions between chlamydial species have been reported, Chlamydia pneumoniae-specific antibodies were also determined by immunoassays (Labsystems). Responses obtained with serum samples from patients with well-defined diseases (i.e., urethral or endocervical samples from which C. trachomatis DNA was amplified) were compared to those obtained with samples from healthy blood donors. The best sensitivity (79%) associated with the best specificity (82%) was obtained when immunoglobulin G (IgG) responses to both MOMP and pgp3 were considered. The highest sensitivity (89%) was obtained with anti-OMP2 IgG, but the lowest specificity (57%) was obtained with this antibody, due to probable cross-reactivity with C. pneumoniae OMP2.

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.

Chlamydial serology: comparative diagnostic value of immunoblotting, microimmunofluorescence test, and immunoassays using different recombinant proteins as antigens

To improve the reliability of the serodiagnosis of Chlamydia trachomatis infections, an immunoblot analysis, a microimmunofluorescence titration, and different immunoassays using synthetic peptides derived from species-specific epitopes in variable domain IV of the major outer membrane protein or recombinant antigens (heat shock protein 70 [hsp70], hsp60, hsp10, polypeptide encoded by open reading frame 3 of the plasmid [pgp3], macrophage infectivity potentiator, and a fragment of the total lipopolysaccharide) were evaluated. Because cross-reactions between chlamydial species have been reported, the microimmunofluorescence tests were also performed with Chlamydia pneumoniae and Chlamydia psittaci used as antigens, and C. pneumoniae-specific antibodies were also determined by immunoassays. Since the presence of antimicrobial antibodies must be interpreted in light of their prevalence in the general population, responses obtained with serum samples from patients with well-defined infection (i.e., with positive urethral or endocervical C. trachomatis DNA amplification) were compared to those obtained with samples from healthy blood donors. The best sensitivity (86%) with a specificity of 81% was obtained for immunoblotting results, when the number of individuals with > or =10 immunoglobulin G (IgG) and/or > or =2 IgM responses to the different C. trachomatis antigens was considered. A 13-kDa antigen was recognized by most of the samples (86% for IgG) from patients with acute urogenital infection but rarely (3%) by those from healthy blood donors (P < 0.0001). The sensitivity and specificity results obtained for serum antibodies to peptides or recombinant antigens were slightly lower than those results obtained for the number of responses to whole C. trachomatis antigens, which were 76 and 77%, respectively, when IgG responses to both recombinant hsp60 and pgp3 were considered.

Chlamydia pneumoniae proteins induce secretion of the 92-kDa gelatinase by human monocyte- derived macrophages

Chlamydia pneumoniae, an intracellular Gram-negative respiratory bacterium, and macrophages are present in inflammatory tissue sites such as atherosclerotic lesions, where abnormal degradation of the extracellular matrix takes place. To evaluate the potential of C pneumoniae for participation in matrix destruction, we studied the effect of this bacterium on the production of 3 matrix-degrading metalloproteinases, 92-kDa gelatinase, interstitial collagenase-1, and stromelysin-1, and their natural inhibitor TIMP-1 (tissue inhibitor of metalloproteinases-1) by human monocyte-derived macrophages differentiated in vitro. Spontaneous production of collagenase and stromelysin by these cells was minimal and was not influenced by C pneumoniae. In contrast, the cells secreted substantial basal quantities of 92-kDa gelatinase, the secretion of which was stimulated (on average, 2.5-fold) by C pneumoniae. C pneumoniae regulated the expression of 92-kDa gelatinase by macrophages at the pretranslational level. Macrophages secreted only small quantities of TIMP-1. The chlamydial proteins Omp2, MOMP, and HSP60 were also found to participate in the induction of 92-kDa gelatinase by C pneumoniae. Denaturation of chlamydial proteins by boiling reduced 92-kDa gelatinase secretion only partially (by 35%), suggesting that the heat-stabile lipopolysaccharide molecules also stimulate secretion of the enzyme. The results show that production of 92-kDa gelatinase by human macrophages is selectively upregulated by C pneumoniae, which suggests that these bacteria, when present in a macrophage-containing inflammatory environment, actively participate in the destruction of the extracellular matrix.

Comparative analysis of the putative amino acid sequences of chlamydial heat shock protein 60 and Escherichia coli GroEL

The nucleotide sequences of the gene encoding chlamydial heat shock protein 60 (cHSP60) of 7 Chlamydia psittaci strains were determined. Comparison of sequences of the cHSP60 gene among chlamydiae showed high identities of the nucleotide sequences by 81.0% or greater and of the deduced amino acid sequences by 92.2% or greater. Comparison of the amino acid sequences between chlamydia and the other bacterial HSP60s resulted in the finding of three highly conserved regions, suggesting that these regions play a role in some function. In addition, 26- or 27-functional residues in the Escherichia coli GroEL out of the 28-residues are conserved in the amino acid sequences of the cHSP60. The data suggest that the function of the cHSP60 may be the same as that of the E. coli GroEL.

Characterization of the koala biovar of Chlamydia pneumoniae at four gene loci--ompAVD4, ompB, 16S rRNA, groESL spacer region

Koalas are infected with two species of Chlamydia, C. pecorum and C. pneumoniae. While it is known that significant genetic diversity occurs in the C. pecorum strains infecting koalas, very little is known about the C. pneumoniae strains that infect this host. In the current study, 10 isolates of koala C. pneumoniae were analysed at four gene loci and found to be different to both the human and horse C. pneumoniae strains at all loci (biovar differences ranging from 0.3% at groESL up to 9.0% at ompAVD4). All koala biovar isolates studied were found to be 100% identical at ompAVD4 (all 10 isolates) and at ompB (all three isolates) gene. This lack of allelic polymorphisms at ompAVD4 has now been observed for koala C. pneumoniae, human C. pneumoniae, guinea pig inclusion conjuctivitis C. psittaci and feline conjuctivitis C. psittaci and may be correlated to a lack of antibody response to the chlamydial major outer membrane protein (MOMP) in these same strain/host combinations. This study also provides the first documented case of natural C. pneumoniae infection causing a severe and extended respiratory episode in a captive koala population. This captive episode is in contrast to most free-range observations in which koala C. pneumoniae is rarely documented as causing respiratory, ocular or urogenital tract disease.

Is vasculitis a significant component of atherosclerosis?

Although atherosclerosis was linked to infections many decades ago, only recently there has been a renewed interest to study this association further. These research endeavors have provided a substantial amount of knowledge concerning the mechanisms that may link inflammation, immunity, and infections to the molecular and cellular events in the arterial wall leading to atherosclerotic lesions.

Use of monoclonal antibodies to facilitate identification, cloning, and purification of Chlamydia trachomatis hsp10

As a requisite for a physiological and immunological investigation, reagents were developed that facilitated the identification and purification of Chlamydia trachomatis hsp10 (chsp10). Monoclonal antibodies that specifically recognize chsp10 were generated with multiple-antigen peptides (MAPs) to promote recognition of Chlamydia-specific epitopes. MAP2, containing amino acids 54 to 69 of the hsp10 sequence, elicited strong antibody responses after immunization of BALB/c mice. Monoclonal antibodies from several cloned hybridomas reacted on immunoblots with an approximately 15-kDa chlamydial protein and recombinant chsp10. Because of its strict specificity for chsp10, monoclonal antibody M1.2 was selected for routine use. M1.2 reacted by immunoblot with the hsp10s of several C. trachomatis strains but not with Chlamydia psittaci hsp10 or Escherichia coli homolog GroES, suggesting that M1.2 recognizes a species-specific epitope. Recombinant chsp10 was purified by immunoaffinity chromatography with M1.2. For large-scale purification, chsp10 was appended with a C-terminal six-histidine tag for purification by nickel chelate affinity chromatography. The hypA gene encoding the chsp10 of C. trachomatis serovar E/Bour was cloned into the pQE-60 vector (QIAGEN, Inc.) following PCR amplification from genomic DNA. E. coli DH5 transformants were screened for chsp10 expression by colony immunoblotting with M1.2, were tested for nickel matrix binding, and were sequenced. The sequence of serovar E/Bour chsp10 was found to be closely homologous to those of hsp10s of other chlamydiae. Purified chsp10 and specific anti-chsp10 monoclonal antibodies will be useful for investigating the biological and immunological roles of hsp10 in chlamydial infections.

Transcriptional organization and regulation of the dnaK and groE operons of Chlamydia trachomatis

The transcriptional organization and regulation of the dnaK and groE heat shock operons of Chlamydia trachomatis were studied and found to resemble those of the cognate operons of Bacillus subtilis and Clostridium acetobutylicum. The gene order is conserved (hrcA-grpE-dnaK), but no dnaJ homolog could be identified in this region. The dnaK operon was transcribed as a low-abundance polycistronic mRNA whose levels did not increase upon exposure to heat shock. In contrast, a more abundant 2.3-kb mRNA encoding only the dnaK sequence was detectable, and its steady-state level increased upon heat shock. The transcription initiation sites of the dnaK and groE operons were found to be preceded by sequences that resemble an Escherichia coli sigma70 consensus promoter. Upstream of each putative promoter is an inverted repeat sequence which resembles a similar element (CIRCE [controlling inverted repeat of chaperone expression]) found upstream of the dnaK and groE operons in at least 27 eubacterial species. In vitro transcription studies utilizing partially purified C. trachomatis RNA polymerase demonstrated that the regions containing the putative promoter elements of the dnaK and groE operons are functional, although heat shock-regulated expression could not be demonstrated.

Serological response to Chlamydia pneumoniae in patients with sarcoidosis

The antigen-specific serological response to Chlamydia pneumoniae was studied in 24 patients with sarcoidosis and compared to that seen in acute C. pneumoniae respiratory infection. By the micro-immunofluorescence test, five sarcoidosis patients had acute antibody, 15 had chronic antibody and four had no antibody against C. pneumoniae. By enzyme immunoassay, 20 sarcoidosis patients had antibody against ReLPS but that cross-reacts with chlamydial LPS. Immunoblot analysis of sera using purified C. pneumoniae elementary bodies showed that recognition of the 40 kDa C. pneumoniae major outer membrane protein was rare (20%). Reactivities with proteins with Mw of 42 K (70%), 60 K (65%), 98 K (55%) and 52 K (50%) were often noted. To study reactivity of chlamydial HSP 60 in sarcoidosis sera, sarkosyl-soluble (contains the 60 kDa HSP) and sarkosyl-insoluble (contains the 60 kDa structural protein) fractions of C. pneumoniae elementary bodies were prepared. The 60 kDa structural protein was recognized with equal frequency by sera from patients with sarcoidosis and acute respiratory infection, while the HSP 60 was more frequently recognized by sera with acute respiratory infection than sarcoidosis. Recombinant fusion proteins expressed from pGEX-2T containing overlapping DNA fragments of the C. pneumoniae 60 kDa HSP gene were purified. Different recognition patterns were identified for sera from sarcoidosis patients and from patients with acute C. pneumoniae respiratory infection.

Characterization of the murine antibody response to peptides representing the variable domains of the major outer membrane protein of Chlamydia pneumoniae

In an attempt to gain more knowledge about the immunogenicity of the variable domains (VDs) of the major outer membrane protein (MOMP) of Chlamydia pneumoniae, peptides representing these areas were used to immunize BALB/c and C57BL/6 mice. Antisera to the peptides and to peptides conjugated to keyhole limpet hemocyanin (KLH) were characterized by their ability to recognize the immunizing peptide and elementary bodies (EBs) of C. pneumoniae by enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot). In addition, antiserum was analyzed for its molecular specificity by a pepscan as well as its in vitro neutralizing ability. In general, results obtained with antisera to the peptides paralleled the results obtained with the antisera to the KLH-conjugated peptides except that the titers or strength of reaction in the assays was less. Antisera to the VDs in both strains of mice gave ELISA titers to the homologous VD peptide ranging from 1,000 to >64,000. The strength of reactivity with the reduced MOMP as judged by Western blot, in most cases, paralleled the ELISA titer to the peptide. However, only antisera raised in both strains of mice to the VD1 and VD4 peptides reacted strongly with the EBs, suggesting surface exposure of these VDs. In addition, antisera to VD3 from C57BL/6 mice gave strong reactivity to EBs. By pepscan analysis antisera from both strains of mice reacted with several VD1 and VD3 octameric peptides, with weaker reactivity being seen with the octameric peptides in the other two VDs. This was in contrast to antisera raised to EBs of C. pneumoniae TW-183, which identified two immunogenic regions, one in VD1 and the other mapped to VD4. While antisera raised to EBs strongly neutralized the infectivity of C. pneumoniae, none of the peptide antisera was able to neutralize. In addition, peptides to the VDs were not able to block the neutralizing ability of the antisera to EBs of C. pneumoniae. Therefore, these results suggest that the VDs of the MOMP of C. pneumoniae are surface exposed but do not elicit neutralizing antibodies when linear peptides representing them are used as the immunogen.

Immune response to Chlamydia trachomatis heat-shock protein in infertile female patients and influence of Chlamydia pneumoniae antibodies

A total of 446 sera from 245 patients with primary or secondary infertility, all of whom were examined laparoscopically, 117 patients with Chlamydia trachomatis-positive cervical swabs, and 84 control persons (50 obstetric patients and 34 female blood donors) were tested for antibodies to Chlamydia trachomatis and to Chlamydia pneumoniae with the microimmunofluorescence (MIF) test. MIF test antibody rates were highest in patients with complete tubal occlusion (73%) and in patients with proven Chlamydia trachomatis infection (74%), whereas only 9 to 10% of the control group showed Chlamydia trachomatis antibodies. Reaction to the 60 kDa antigen of Chlamydia trachomatis, a heat-shock protein (hsp) analogue, has been suggested as a possible marker for the development of chronic sequelae after Chlamydia trachomatis infection. Immunoblot analysis of 222 sera (169 infertility patients, 20 antigen-positive patients, and 33 mothers) showed a significantly higher anti-hsp antibody rate in patients with complete tubal occlusion than in infertility patients with normal fallopian tubes (76% vs. 19%, p < 0.001). The presence of antibodies not only to Chlamydia trachomatis but also to Chlamydia pneumoniae in the MIF test was associated with a significantly higher rate of anti-hsp antibodies and with complete tubal occlusion. This association did not appear to be due to cross-reactivity between Chlamydia pneumoniae and Chlamydia trachomatis antibodies in the MIF test.

Chlamydia pneumoniae (TWAR)

Chlamydia pneumoniae (TWAR) is a recently recognized third species of the genus Chlamydia that causes acute respiratory disease. It is distinct from the other two chlamydial species that infect humans, C. trachomatis and C. psittaci, in elementary body morphology and shares less than 10% of the DNA homology with those species. The organism has a global distribution, with infection most common among children between the ages of 5 and 14 years. In children, TWAR infection is usually mild or asymptomatic, but it may be more severe in adults. Pneumonia and bronchitis are the most common clinical manifestations of infection, and TWAR is responsible for approximately 10% of cases of pneumonia and 5% of cases of bronchitis in the United States. The microimmunofluorescence serologic assay is specific for TWAR and can distinguish between recent and past infections. The organism can be isolated in cell culture; however, PCR techniques have recently facilitated its detection in tissues and clinical specimens.

The sequence of the groES and groEL genes from the mouse pneumonitis agent of Chlamydia trachomatis

The co-transcribed structural genes, groES and groEL, of the groE stress response operon from Chlamydia trachomatis mouse pneumonitis (MoPn), were cloned and sequenced. The calculated molecular masses of the encoded heat-shock proteins (Hsp), a small Hsp (GroES) and Hsp60 (GroEL), are 11,089 and 58,367 Da, respectively. By comparison with other known chlamydial groES and groEL sequences, there is 89 and 94% nucleotide (nt) identity with C. trachomatis human strains (serovars A and L2), 77 and 82% with C. psittaci strain GPIC, and 75 and 80% with C. pneumoniae isolate AR-39. At the amino-acid level, the MoPn Hsp60 shows a 99% identity with those from C. trachomatis human strains. In a mouse model, MoPn Hsp60 could prove useful in deciphering the pathogenesis of human chlamydial diseases.

Isolation and characterization of a gene encoding a Chlamydia pneumoniae 76-kilodalton protein containing a species-specific epitope

Chlamydia pneumoniae is a human respiratory pathogen. Unlike the other two Chlamydia species, no species-specific antigen has been defined for C. pneumoniae. An immunoreactive clone containing a 0.8-kb fragment was isolated from a C. pneumoniae (AR-39) genomic library by using anti-C. pneumoniae rabbit immune serum. By Southern hybridization analysis of chromosomal digests of the different Chlamydia spp., the 0.8-kb fragment was shown to react specifically with C. pneumoniae. Subcloning of this fragment into the pGEX-1 lambda T expression vector resulted in the expression of a 62-kDa fusion protein. This fusion protein as well as the cleaved C. pneumoniae peptide were recognized by anti-C. pneumoniae rabbit immune serum, while the glutathione S-transferase moiety was not recognized. The fusion protein was used to produce monospecific rabbit antiserum. This antiserum was shown to react with a 76-kDa protein in all C. pneumoniae isolates tested, specifically recognize C. pneumoniae inclusions in tissue culture, and neutralize infectivity of C. pneumoniae in cell culture. No reactivity was observed with Chlamydia trachomatis or Chlamydia psittaci. To isolate the entire coding sequence of the 76-kDa protein, two partially overlapping fragments of C. pneumoniae DNA, a 3.2-kb HindIII fragment and a 1.2-kb PvuII fragment, were isolated, cloned, and sequenced. No significant sequence similarity was found with any previously reported nucleotide or amino acid sequence of the other Chlamydia species. This C. pneumoniae protein containing a species-specific epitope could play a role in pathogenesis and may be useful as a diagnostic tool.

Identification of Chlamydia pneumoniae-specific protein antigens in immunoblots

The immunoblot patterns of 248 sera, all examined previously by the microimmunofluorescence test (MIF) for species-specific Chlamydia antibodies, were analyzed. Predominant specific antibody activity was directed to the 54 kDa protein of Chlamydia pneumoniae, which was recognized by 93% of sera positive for Chlamydia pneumoniae by MIF but by only 2% of sera positive for Chlamydia trachomatis and negative for Chlamydia pneumoniae and by 3% of sera negative for both Chlamydia pneumoniae and Chlamydia trachomatis. This antigen appears to be specific for Chlamydia pneumoniae. Other Chlamydia pneumoniae-specific protein antigens were recognized far less frequently. Absorption analysis indicated that the 54 kDa protein is located on the surface of the Chlamydia pneumoniae elementary bodies.

A novel approach to the laboratory diagnosis of Chlamydia trachomatis infections using monoclonal anti-idiotypic antibodies

We have developed a novel enzyme immunoassay (EIA) for the specific detection of Chlamydia trachomatis utilizing a monoclonal anti-idiotypic antibody to an antibody directed against a chlamydia specific epitope on 60 kDa heat-shock protein (HSP60). The basis of the assay is the inhibition of the binding of idiotype to anti-idiotype by antigen present in test samples. Two configurations of the assay were developed: a blocking EIA and a competition EIA. Greater sensitivity was observed using the competition EIA, with the assay detecting purified recombinant HSP60 and purified chlamydia in a concentration-dependent manner from 0.01 to 10 micrograms protein and from 0.5 to 12 micrograms total protein, respectively. The assay is highly specific and offers several potential advantages over currently available EIAs for the detection of this pathogen.

Complementary DNA sequence of bovine cpn10 (Hsp10), a chaperone protein from mitochondria

A cDNA sequence encoding a chaperone protein from bovine heart mitochondria is described. It is deduced from overlapping partial cDNAs amplified in polymerase chain reactions from bovine heart cDNA, using in the first instance mixtures of synthetic oligonucleotide primers based on the incomplete sequence of the cpn10 (Hsp10) chaperone protein from rat liver mitochondria. The encoded bovine protein sequence is 101 amino acids in length. By analogy with the rat homologue it is likely that the initiator methionine is removed after translation and that the mature N-terminal is modified. The mitochondrial proteins are members of the chaperonin 10 family which also includes the bacterial GroES chaperones. These proteins act in conjunction with members of the chaperonin-60 protein family, such as bacterial GroEL, to facilitate the folding of newly synthesised or translocated proteins.

Heat-shock proteins: immunity and autoimmunity

Antigens from a wide variety of pathogens have been identified as members of conserved heat-shock protein families, sharing upwards of 50% amino acid identity with corresponding host-cell proteins. Analysis of the responses to these conserved antigens may provide insights into regulation of the immune system during infection and autoimmunity.