Analysis of the human serological response to proteins of Chlamydia trachomatis

Antigenic variation among strains of Chlamydia pneumoniae

The antigenic profiles of six strains of Chlamydia pneumoniae were analyzed by the microimmunofluorescence test (MIF) and immunoblotting with human serum and murine monoclonal antibody. MIF-derived antibody titers in serum samples from culture-positive patients were four- to eightfold higher against autologous isolate antigen than they were against the prototype antigen strain TW-183. Sera of patients with respiratory illness that were culture negative and complement fixation positive for Chlamydia spp. produced higher titers by MIF against a strain of C. pneumoniae isolated in the area than they did against TW-183. For two of five cases, the criteria for establishing the diagnosis of acute infection were met only with use of the antigen from the local strain; TW-183 was inadequate for this purpose. Immunoblot profiles revealed antigenic differences between strains that varied with the human serologic response; i.e., unique antigens were recognized by the sera of some individuals and not by the sera of others. Using the reactivity of a genus-specific monoclonal antibody against a major outer membrane protein, we found that strain CWL-011, isolated in Atlanta, Ga., may possess a major outer membrane protein with a molecular mass between those of C. trachomatis L2 and other C. pneumoniae strains. These data provide evidence of several new and unique serotypes of C. pneumoniae and suggest that the serologic diagnosis of C. pneumoniae infection may require the use of antigens from more than one strain of this species.

Genetic diversity and identification of human infection by amplification of the chlamydial 60-kilodalton cysteine-rich outer membrane protein gene

The 60-kDa cysteine-rich outer membrane protein genes of Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis have very different 5' ends, but two areas flanking this variable region show absolute sequence conservation. This observation permitted differentiation of the three species of Chlamydia by the polymerase chain reaction (PCR), forming the basis of a diagnostic test for chlamydial infections. The PCR product containing the variable region of the respective 60-kDa CrP genes was also subjected to restriction endonuclease digestion, enabling differentiation of individual type strains of C. psittaci. Differentiation was possible between lymphogranuloma venereum and trachoma isolates of C. trachomatis. The PCR-based diagnostic test was successful with all strains of chlamydiae studied. The PCR primers showed high specificity and did not produce any product with common bacterial pathogens that may share the same sites of infection.

Characterization of a murine IgG3 monoclonal antibody against Chlamydia-specific lipopolysaccharide and its purification by affinity chromatography on IgG Fc-receptors from Streptococcus dysgalactiae

Purification of a murine IgG3 monoclonal antibody (Mab 22) directed against an epitope of Chlamydia-specific lipopolysaccharide by affinity chromatography on recently described solid phase IgG Fc-receptors from Streptococcus dysgalactiae is reported. SDS-PAGE studies revealed the purity of the eluted antibody. The purified Mab 22 was characterized by determination of class, subclass and light chain-type, and by dot tests and immunoblot analysis.

Cloning and sequence of the gene for heat shock protein 60 from Chlamydia trachomatis and immunological reactivity of the protein

We isolated and sequenced the gene for the chlamydial heat shock protein 60 (HSP-60) from a Chlamydia trachomatis genomic library by molecular genetic methods. The DNA sequence derived revealed an operon-like gene structure with two open reading frames encoding an 11,122- and a 57,956-Da protein. The translated amino acid sequence of the larger open reading frame showed a high degree of homology with known sequences for HSP-60 from several bacterial species as well as with plant and human sequences. By using the determined nucleotide sequence, fragments of the gene were cloned into the plasmid vector pGEX for expression as fusion proteins consisting of glutathione S-transferase and peptide portions of the chlamydial HSP-60. HSP-60 antigenic identity was confirmed by an immunoblot with anti-HSP-60 rabbit serum. Sera from patients that exhibited both high antichlamydial titers and reactivity to chlamydial HSP-60 showed reactivity on immunoblots to two fusion proteins that represented portions of the carboxyl-terminal half of the molecule, whereas fusion proteins defining the amino-terminal half were nonreactive. No reactivity with the fusion proteins was seen with sera from patients that had been previously screened as nonreactive to native chlamydial HSP-60 but which had high antichlamydial titers. Sera from noninfected control subjects also exhibited no reactivity. Definition of recognized HSP-60 epitopes may provide a predictive screen for those patients with C. trachomatis infections who may develop damaging sequelae, as well as providing tools for the study of immunopathogenic mechanisms of Chlamydia-induced disease.

Serological response to Chlamydia pneumoniae infection

The human serological response was analyzed by using sera from patients who were serologically positive but isolation negative for Chlamydia pneumoniae and from patients with proven C. pneumoniae infection based on serology and isolation. To assess whether seroreactivity to C. pneumoniae proteins had potential diagnostic value, the cross-reactivities of these sera to other Chlamydia species and of sera from patients infected with C. trachomatis and C. psittaci to C. pneumoniae proteins were determined. In all serum samples from patients with proven C. pneumoniae infections, reactivities were seen with 98-, 68-, 60-, 39.5-, and 30-kilodalton proteins. Similar patterns were seen in sera from patients who were serologically positive and isolation negative. The onset of seropositivity for C. pneumoniae was accompanied by reactivities against presumably shared chlamydial antigens and a C. pneumoniae-specific 98-kilodalton protein.

Cloning, characterization and sequence of a novel 59-kDa protein of Chlamydia trachomatis

Chlamydia trachomatis (Ct) serovar L2 DNA was partially digested with BamHI, ligated with plasmid vector pBR325 and used to transform Escherichia coli JMB83. Recombinant colonies were screened for their ability to synthesize chlamydial (chl) proteins by dot immunoblot and by in vitro transcription translation assays. A clone, B1, expressing a 59-kDa protein was further characterized, and the encoding gene was subcloned in the expression vector, pKK223-3, containing the tac promoter. Elevated levels of the 59-kDa protein were produced in E. coli in the presence of the lac inducer, IPTG. Sequencing identified one long open reading frame encoding a polypeptide of 59,075 Da (59 kDa). The partially purified 59-kDa protein was recognized by sera from patients with chl infections as shown in immunoblotting. In addition, the 59-kDa protein was located in the sarcosyl-soluble fraction of chl lysates. When used as a DNA probe in dot hybridization assays, the clone encoding the 59-kDa protein showed high homology to all serovars of Ct and four strains of Chlamydia psittaci. The cloned 59-kDa protein is neither related to the 60-kDa heat-shock protein found in many strains of bacteria, nor to the Cys-rich sarcosylinsoluble protein described in other studies of chlamydia.

A soluble 60 kiloDalton antigen of Chlamydia spp. is a homologue of Escherichia coli GroEL

Two major 60 kD protein species can be separated by differential detergent extraction in Chlamydia spp. A Sarkosyl-soluble 60 kD protein is (i) structurally and antigenically distinct from the previously characterized 60 kD Omp2 outer membrane protein; and (ii) antigenically related to a bacterial common antigen of similar molecular weight which includes a 65 kD mycobacterial antigen and the GroEL heat-shock protein of Escherichia coli. Among GroEL homologues, the chlamydial protein (chl-GroEL) uniquely displays affinity towards immobilized thiol groups. The significance of this property is discussed with respect to the synthesis and assembly of the chlamydial disulphide-rich cell wall late in the growth cycle. Chl-GroEL is identical to the Triton X-100-soluble, ocular delayed-type hypersensitivity agent (Morrison et al., 1989), an essential component in the development of blinding trachoma. An autoimmune mechanism for chronic chlamydial diseases based on chl-GroEL homology to host proteins is hypothesized.

Structural and antigenic analysis of Chlamydia pneumoniae

Several isolates of Chlamydia pneumoniae were compared with each other and to Chlamydia trachomatis and Chlamydia psittaci by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblots. Protein profiles of the C. pneumoniae isolates appeared to be the same and were distinct from the other Chlamydia species. A 39.5-kilodalton (kDa) protein, similar in molecular weight to the major outer membrane proteins (MOMP) of C. trachomatis and C. psittaci, was found in the Sarkosyl-insoluble fraction, demonstrating its association with the outer membrane complex. In the outer membrane complex, the MOMP was shown to exist in disulfide-linked protein complexes. Electron microscopy of the Sarkosyl-extracted elementary bodies showed that the structural rigidity and pear-shaped morphology remained intact. Rabbit immune sera prepared against C. pneumoniae demonstrated immunoreactive proteins of 98-, 77-, 75-, 66-, 60-, 39.5-, 28-, and 17.5-kDa proteins. Cross-reactivity experiments revealed that most of the antigenic reactivities shared between C. psittaci and C. trachomatis extend to C. pneumoniae and that the 98-kDa protein recognition appeared to be C. pneumoniae specific. In contrast to the other Chlamydia spp., the recognition of the C. pneumoniae MOMP by homologous immune sera was weak and was cross-reactive with the MOMPs of the other Chlamydia species. These results suggest that the C. pneumoniae MOMP is less immunogenic and antigenically complex than are the MOMPs of C. trachomatis and C. psittaci.

Cartilage matrix glycoprotein is present in serum in experimental canine osteoarthritis

We have described previously a disulfide-bonded 550,000-D cartilage matrix glycoprotein (CMGP), which is found in normal hyaline cartilage, fibrocartilage, and the vitreous of the eye, and consists of subunits with apparent molecular weights of 130,000 in 4% gels (116,000 in 9% gels). In osteoarthritic cartilage from dogs subjected to transection of the anterior cruciate ligament (ACL), CMGP is cleaved to major immunoreactive fragments with apparent molecular weights of 65,000 and 75,000 after reduction with 2-mercaptoethanol. In the present study, using immunolocation analysis, a monoclonal antibody to CMGP did not react with serum from 8 of 12 dogs before ACL transection but did react with serum from seven of these animals 4 wk after surgery and with serum from 10 dogs at sacrifice, 8-14 wk after ACL transection. Serum from four dogs reacted with the monoclonal antibody before ACL transection. Serum from two dogs was negative at all time points. Immunolocation studies using a polyclonal antiserum to CMGP were performed in seven of these dogs and produced results identical with the monoclonal antibody in four dogs. In contrast, analysis of serial serum samples from three dogs with cartilage atrophy revealed no evidence of CMGP at any time point. These data suggest that CMGP may be a serum marker for osteoarthritis in this canine model.

Antichlamydial specificity of conjunctival lymphocytes during experimental ocular infection

Antigen-specific responses to chlamydiae have been demonstrated with lymphocytes isolated from the conjunctiva after primary ocular infection and after topical challenge of chlamydia-immune cynomolgus monkeys with noninfectious, Triton X-100-extracted antigen. Proliferative to viable elementary bodies homologous to the original infecting serovar were demonstrated. In addition, in vitro production of antichlamydial antibody by conjunctival B cells was demonstrated by enzyme-linked immunosorbent assay of culture supernatants collected after 7 to 21 days of culture. These findings demonstrate that antigen-specific lymphocytes appear in the conjunctiva as a result of ocular chlamydial infection and that a noninfectious chlamydial antigen stimulates their reappearance or expansion at the site of original infection.

Identification of genus-specific epitopes on the outer membrane complexes of Chlamydia trachomatis and Chlamydia psittaci immunotypes 1 and 2

Polyclonal and monoclonal antibodies were used to study the immunogenic and antigenic characteristics of chlamydiae. We focused on the most predominant proteins in the outer membrane complex, the major outer membrane protein (MOMP) and the doublet consisting of proteins of 57 and 62 kilodaltons (57-62 kDa doublet). Immunoblot analyses were performed with chlamydial elementary bodies by using (i) immune sera from sheep which had undergone a recent episode of abortion due to the ovine abortion (OA) strain of C. psittaci, (ii) rabbit hyperimmune anti-C. psittaci (OA) and -C. trachomatis sera, and (iii) monoclonal antibodies to the MOMP of C. trachomatis. The typical pattern of response with polyclonal antisera against heterologous elementary bodies was reactivity with the 57-62 kDa doublet and lipopolysaccharide with weak and sometimes no anti-MOMP activity. Three distinct genus-specific anti-C. trachomatis MOMP monoclonal antibodies showed different patterns of reactivity with the MOMPs of the two immunotypes of C. psittaci and C. trachomatis serovars. Our data confirm the predominance of a genus-specific 57-62 kDa doublet response despite the presence of genus-specific epitopes on the MOMP.

Characterization of native and recombinant 75-kilodalton immunogens from Chlamydia trachomatis serovar L2

A 75-kilodalton (kDa) immunogen from Chlamydia trachomatis serovar L2 was characterized. The 75-kDa protein was localized in the cytoplasm of chlamydiae and was shown to be a protein synthesized early in the developmental cycle of chlamydiae. A gene library was made by the recombinant DNA technique, using the expression vectors pEX1, pEX2, and pEX3. From this library one clone was found which reacted with a monoclonal antibody against the 75-kDa immunogen of C. trachomatis. The 75-kDa protein produced by the recombinant Escherichia coli was expressed independently of the promoter for the hybrid protein cro-betagalactosidase. Thus it is not produced as a fusion protein. Epitope mapping of the 75-kDa protein from C. trachomatis L2 and from the recombinant E. coli performed by Staphylococcus aureus V8 protease digestion showed that the two proteins are identical. Furthermore, patient sera reacted with both proteins.

Humoral immune response to chlamydial genital infection of mice with the agent of mouse pneumonitis

The objective of this study was to characterize the humoral immune response to chlamydial genital infection of mice with the mouse pneumonitis agent (MoPn). With an enzyme-linked immunoabsorbent assay, immunoglobulin G antibodies to MoPn were first detected in plasma by day 14. Peak plasma antibody concentrations were reached by day 49, and this response did not decline significantly throughout the 300-day monitoring period. Immunoglobulin A against MoPn could first be detected in pooled vaginal washes by day 21 after infection and had reached peak concentrations by day 28, but anti-MoPn immunoglobulin G was not consistently present in secretions. The antibody response in secretions had declined slightly by day 300. Immunoblot analysis revealed that the early phase of the plasma antibody response to MoPn as a result of genital infection was against lipopolysaccharide, the major outer membrane protein, and a 62-kilodalton (kDa) protein. In secretions, early-phase immunoglobulin A antibodies were directed to the major outer membrane protein and lipopolysaccharide. Late reactions to 15-, 22-, and 83-kDa proteins in plasma were noted. Late reactions to the 62-kDa protein in secretions were also noted. The cause of these late responses remains unexplained. When mice were challenged intravaginally with MoPn at 50-day intervals after the primary infection, it was found that mice inoculated on day 100 or after were susceptible to reinfection. Susceptibility could not be related to a decline in the antibody concentration in plasma or secretions or in the antibody response to specific components of MoPn as measured by immunoblot analysis.

Accumulation of chlamydial lipopolysaccharide antigen in the plasma membranes of infected cells

The presence of a chlamydia-specified antigen associated with the plasma membrane of infected cell lines was demonstrated by indirect immunofluorescence staining with a monoclonal antibody, designated 47A2, specific for the chlamydial genus-specific lipopolysaccharide (LPS) antigen. Staining of HeLa, L-929, and McCoy cells infected with the L2 or F serovar of Chlamydia trachomatis was observed either without fixation or following aldehyde fixation and brief drying. The 47A2-reactive antigen appeared to be present on the plasma membrane, on bleb-like structures on the host cell surface, and on proximal processes of neighboring uninfected cells. Antibodies to chlamydial protein antigens such as the major outer membrane protein produced no surface staining under similar conditions. Membrane vesicles elaborated from infected cells were enriched for the 47A2-reactive antigen. Superinfection of chlamydia-infected cells with vesicular stomatitis virus, an enveloped virus which buds from the plasma membrane, allowed purification of progeny virions that were enriched with chlamydial LPS. These results are consistent with the presence of chlamydial LPS in the plasma membranes of infected host cells.

Laboratory diagnosis of human chlamydial infections

Chlamydia trachomatis is a human pathogen that causes ocular disease (trachoma and inclusion conjunctivitis), genital disease (cervicitis, urethritis, salpingitis, and lymphogranuloma venereum), and respiratory disease (infant pneumonitis). Respiratory chlamydioses also occur with infection by avian strains of C. psittaci or infection by the newly described TWAR agent. Diagnosis of most acute C. trachomatis infections relies on detection of the infecting agent by cell culture, fluorescent antibody, immunoassay, cytopathologic, or nucleic acid hybridization methods. Individual non-culture tests for C. trachomatis are less sensitive and specific than the best chlamydial cell culture system but offer the advantages of reduced technology and simple transport of clinical specimens. Currently available nonculture tests for C. trachomatis perform adequately as screening tests in populations in which the prevalence of infection is greater than 10%. A negative culture or nonculture test for C. trachomatis does not, however, exclude infection. The predictive value of a positive nonculture test may be unsatisfactory when populations of low infection prevalence are tested. Tests that detect antibody responses to chlamydial infection have limited utility in diagnosis of acute chlamydial infection because of the high prevalence of persistent antibody in healthy adults and the cross-reactivity due to infection by the highly prevalent C. trachomatis and TWAR agents. Assays for changes in antibody titer to the chlamydial genus antigen are used for the diagnosis of respiratory chlamydioses. A single serum sample that is negative for chlamydial antibody excludes the diagnosis of lymphogranuloma venereum.

Chlamydial disease pathogenesis. Ocular hypersensitivity elicited by a genus-specific 57-kD protein

Recurrent or persistent infections with Chlamydia trachomatis are thought to provide the antigenic stimulus for the chronic inflammation associated with blinding trachoma. We used the guinea pig model of inclusion conjunctivitis to identify chlamydial antigens that may be involved in this deleterious immune response. We purified from chlamydial elementary bodies a genus-specific 57-kD protein that elicited an ocular hypersensitivity response when placed topically onto the conjunctiva of ocular immune guinea pigs. This response was characterized by a predominantly mononuclear macrophage and lymphocyte cellular infiltrate of the submucosal epithelium. The clinical and histological findings were consistent with those of a delayed hypersensitivity response. These data demonstrated that the 57-kD chlamydial protein was a potent stimulator of ocular delayed hypersensitivity. Our findings may be critical to understanding the pathogenesis of the debilitating chlamydial diseases associated with chronic inflammation, such as trachoma and many urogenital syndromes.

Identification by sequence analysis of two-site posttranslational processing of the cysteine-rich outer membrane protein 2 of Chlamydia trachomatis serovar L2

The 60,000-molecular-weight cysteine-rich outer membrane protein (OMP2) from Chlamydia trachomatis participates in the disulfide-mediated outer-membrane organization unique to this organism. In addition, this protein is a primary focus of the host immune response. We cloned and sequenced the gene for OMP2 from C. trachomatis serovar L2. A lambda gt11 recombinant that expressed an antigenic portion of this protein was selected by antibody screening and provided a probe for the selection in lambda 1059 of a clone containing the entire gene. DNA sequencing of this clone identified one open reading frame of 1,641 base pairs, starting with a methionine codon and coding for a polypeptide with a molecular weight of 58,792. Amino-terminal protein sequencing and analysis of the translated DNA sequence demonstrated that processing at alternate signal peptide cleavage sites accounts for the molecular-weight polymorphism of this protein. The mature proteins had a net positive charge and contained 24 cysteine residues.

Ultrastructural study of endocytosis of Chlamydia trachomatis by McCoy cells

The entry of Chlamydia trachomatis into McCoy cells (fibroblasts) was studied by transmission electron microscopy. On adsorption of elementary bodies (EBs) to host cells at 37 degrees C, the EBs were bound primarily to preexisting cell-surface microvilli. They were also observed in coated pits located at the bases of the microvilli and along smooth surfaces of the host cells and were internalized within coated vesicles at this temperature. Postembedding immunogold labeling on Lowicryl thin sections with anti-clathrin antibody as the primary reagent revealed the gold marker localized in pits and vesicles containing chlamydiae. Some EBs were present in smooth-surfaced invaginations at or near the bases of microvilli and in vesicles devoid of distinguishable coat material. A similar entry process was observed with centrifugation-assisted inoculation of EBs onto the McCoy cells. Individual EBs were initially internalized into tightly bound endocytic vesicles. However, within 1 to 3 h postinfection, multiple C. trachomatis EBs were observed in large, loosely bound vesicles. Evidence suggests that vesicles containing C. trachomatis may have fused with one another early in the infectious process. These results indicate that chlamydiae can exploit the specific process of adsorptive endocytosis for entry into host cells and for translocation to a given intracellular destination, which may be different for each species.

Chlamydia specific IgG and IgA antibodies in women with obstructive infertility as determined by immunoblotting and immunoperoxidase assays

The prevalence rate of IgG and IgA antibodies to Chlamydia was analyzed in 50 women with laparoscopy-verified tubal infertility and in 50 age-matched control women by single serovar (L2) inclusion immunoperoxidase assay (IPA) and by immunoblotting technique (IB). Women with tubal infertility had significantly (p less than 0.001) elevated IPA Chlamydia IgG antibody titer greater than or equal to 128 and greater than or equal to 256 than controls (64% vs 16%. Odds ratios = 9.3 and 50% vs 10%, Odds ratio = 9 respectively). The prevalence rate of IPA IgA antibody titer (greater than or equal to 16) to Chlamydia was also significantly higher (p less than 0.001) in women with tubal infertility than controls (48% vs 8%, Odds ratio = 10.6). Antibodies to at least 19 chlamydial structural polypeptides ranging in molecular weight from 30 kD to 204 kD, were detected by the IB technique in the IPA seropositive sera. Antibodies to 57-60 kD were detectable in almost all the IPA IgG and IgA seropositive sera. The prevalence rate of IgG antibody to 57 kD-60 kD was significantly higher in women with obstructive infertility than healthy woman (84% vs. 56% p less than 0.01; Odds ratio = 3.8). More significantly, higher differences to 57-60 kD polypeptide were found in the case of IgA between the infertile women and controls (52% vs. 10%, p less than 0.001; Odds ratio = 9.7). The significance of IPA and IB technique for screening of infertile women is discussed.

Identification of cartilage matrix glycoprotein in synovial fluid in human osteoarthritis

Cartilage matrix glycoprotein (CMGP) is a high molecular weight protein found in hyaline cartilage and fibrocartilage. It consists of disulfide-bonded subunits, each with an apparent molecular weight of 116,000. Fragmentation of CMGP is noted in extracts of osteoarthritic canine cartilage. CMGP has been identified in the serum and synovial fluid of dogs with experimentally induced osteoarthritis. It has now been identified in synovial fluid from osteoarthritic human joints but not in synovial fluid from joints of patients with other arthritides or joint abnormalities. The possible significance of CMGP in synovial fluid in human osteoarthritis is discussed.

Diagnosis of Chlamydia trachomatis infection--culture versus serology

The diagnostic value of different laboratory methods in detecting Chlamydia trachomatis infections in high risk groups was analysed. The efficiency of a direct specimen test was compared with serology (IgG and IgM ELISA) and culture in L929 cells, stained either with fluorescein conjugated monoclonal antibodies or with iodine. Patients (no. = 1041) with localized genital infections attending a STD clinic, sexual contacts and patients with ascending infections from urological and gynecological clinics were examined. Chlamydia trachomatis was detected in 225 patients: 210 (93.3%) were reactive in the direct test (smears stained with monoclonal antibodies), whereas culture missed only 5 (sensitivity 97.8%) when stained by the same method. Cultures stained with iodine produced the lowest recovery rate (73.8%), but this rate increased to 80.9% when a second passage was performed. In addition the prevalence of Neisseria gonorrhoeae, Mycoplasma hominis, Ureaplasma urealyticum, Candida albicans and Trichomonas vaginalis was investigated. In patients with non-gonococcal urethritis (no. = 331) and cervicitis (no. = 353), Chlamydia trachomatis was isolated in 32.3% and 12.8% respectively. However, this pathogen could be isolated in only 3 (15.8%) out of 19 patients with epididymitis and 15 (14%) out of 107 patients with adnexitis, although 66.7% and 93.3% respectively had specific IgG antibodies. Specific IgM could by detected with a sandwich ELISA in patients with adnexitis (46.7%), epididymitis (33.3%), cervicitis (22.2%), non-gonococcal urethritis (14%) and in the sexual partners of patients with genital infections (35.7%). The direct specimen test with monoclonal antibodies is the method of choice for the diagnosis of a C. trachomatis infection in patients with urethritis and cervicitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonoxidative antimicrobial effects of human polymorphonuclear leukocyte granule proteins on Chlamydia spp. in vitro

Proteins from isolated granules of human polymorphonuclear leukocytes were assessed for their nonoxidative microbicidal effect on chlamydiae by two different methods: a radioisotope assay for elementary body integrity and a biological assay for inclusion development. Crude granule extract, which consisted of a mixture of all granule proteins, caused a 20 to 30% decrease in infectivity and a 52% decrease in infectivity when incubated with Chlamydia psittaci CAL-10 and Chlamydia trachomatis serovar E, respectively. To define more specifically the components that were damaging to chlamydiae, crude granule extract was subjected to Sephadex G-75 column chromatography and isolated granule fractions were obtained. Only fractions containing lysozyme as the major component consistently caused reductions in infectivity of C. trachomatis elementary bodies. In contrast, fractions collected after the lysozyme fraction, containing proteins with molecular masses of 13,000 daltons or less, had detrimental effects on C. psittaci infectivity. Additional experiments using highly purified human polymorphonuclear leukocyte lysozyme confirmed its infectivity-reducing action upon C. trachomatis but not upon C. psittaci.

Diversity of Chlamydia trachomatis major outer membrane protein genes

Genomic DNA libraries were constructed for Chlamydia trachomatis serovars B and C by using BamHI fragments, and recombinants that contained the major outer membrane protein (omp1) gene for each serovar were identified and sequenced. Comparisons between these gene sequences and the gene from serovar L2 demonstrated fewer base pair differences between serovars L2 and B than between L2 and C; this finding is consistent with the serologic and antigenic relationships among these serovars. The translated amino acid sequence for the major outer membrane proteins (MOMPs) contained the same number of amino acids for serovars L2 and B, whereas the serovar C MOMP contained three additional amino acids. The antigenic diversity of the chlamydial MOMP was reflected in four sequence-variable domains, and two of these domains were candidates for the putative type-specific antigenic determinant. The molecular basis of omp1 gene diversity among C. trachomatis serovars was observed to be clustered nucleotide substitutions for closely related serovars and insertions or deletions for distantly related serovars.

Immunochemical analysis of immune response to Chlamydia trachomatis in Reiter's syndrome and nonspecific urethritis

Chlamydia trachomatis (Ct) has been proposed as a causative agent in Reiter's syndrome (RS) when an infection occurs in a susceptible host. To assess whether this susceptibility is reflected in a characteristic humoral immune response we compared patients with complicated (RS) and uncomplicated courses of nonspecific urethritis (NSU). Geometric mean titres of antibodies to C. trachomatis by immunofluorescence were 89.6 for RS, 80.0 for NSU and 16.0 for normals. 125I-Protein A probing of immunoblotted antigens of C. trachomatis revealed no band unique to RS. 125I-anti-IgA probing of immunoblots demonstrated reactivity with the 59,000 dalton antigen in 11/11 RS and 2/6 NSU. The major outer membrane protein of C. trachomatis (40,000 daltons) bound immunoglobulin nonspecifically. There was no clearly differentiating feature between HLA-B27-positive and B27-negative RS. One sequentially studied patient revealed an augmentation in synovial fluid IgA reactivity during the course of disease. No pattern of humoral immune response to C. trachomatis could be regarded as specific for RS nor for HLA B27-positivity. The study did not identify a Reiter's-specific antigen in C. trachomatis but demonstrates the usefulness of applying blotting techniques to population studies of HLA modulation of immune response to infectious agents.

Specific interaction of bovine IgG1 and IgG2 subclasses with different chlamydial antigens

Antigens of the immunotype 1 strain B-577 of Chlamydia psittaci, which were separated by SDS-PAGE and electrophoretically transferred to nitrocellulose membranes were used to probe sequential serum samples of cattle with experimentally induced or naturally occurring chlamydial infections. Applying IgG1- and IgG2-specific markers in an enzyme immunoassay procedure, a predominance of IgG2 reactions with different proteins was determined. The interaction of IgG1 with antigens such as the genus-specific lipopolysaccharide and the major outer membrane protein was usually limited to periods immediately following overt clinical disease. Some other antigens like the 60,000 and 62,000 D proteins, for example, were recognized by both subclasses over the entire period of investigation. This indicates that it may be possible to determine the phase of infection through analysis of the IgG1 and IgG2 responses with the Western blot technique. The different IgG1 and IgG2 responses of cattle infected with different strains of Chlamydia psittaci as well as the diverse reactions of cattle from different herds with naturally occurring chlamydial infections further indicate that it may be feasible to distinguish the strains causing these chlamydial infections using different antigens in the Western blot technique. The results obtained by this method may have implications for the production of a subunit vaccine as well as for serodiagnostic purposes.

Comparative sensitivity of 125I-protein A and enzyme-conjugated antibodies for detection of immunoblotted proteins

Immunoblotting is a powerful technique for the detection of small amounts of immunologically interesting proteins in unpurified preparations. Iodinated protein A (PA) has been widely used as a second antibody for detection of proteins; however, it does not bind equally well to immunoglobulins from different species nor does it bind to all subclasses of immunoglobulin G (IgG). We compared the sensitivity of [125I]PA with those of both horseradish peroxidase-conjugated second antibodies (HRP) and glucose oxidase-anti-glucose oxidase (GAG) soluble complexes for visualizing bovine serum albumin, human IgG, or human C3 which was either dot blotted or electroblotted to nitrocellulose. [125I]PA was uniformly 10- to 100-fold less sensitive than either HRP or GAG. GAG was more sensitive than HRP except for C3 (electroblotting) and bovine serum albumin and IgG (dot blotting), in which they were equivalent. In general, dot blotting was 10- to 1,000-fold more sensitive than electroblotting. Although relative sensitivities varied depending on the proteins analyzed and the antisera used, GAG appeared to be superior to [125I]PA and HRP for detection of immunoblotted proteins.

Flow cytometric analysis of Chlamydia trachomatis interaction with L cells

Immunofluorescent staining and flow cytometric analysis have been investigated as means of studying the early stages of in vitro infection of Chlamydia trachomatis. The lymphogranuloma venereum strain of C. trachomatis was grown in vitro in L cells, fixed in p-formaldehyde, stained with fluorescein isothiocyanate (FITC)-conjugated monoclonal antibody to the chlamydial major outer membrane protein, and analyzed flow cytometrically. Infected cells stained 50-100 times more intensely than uninfected cells, and they could easily be discriminated by flow analysis. The number of infected cells and the fluorescence intensity of individual cells were proportional to the multiplicity of infection. The attachment of purified elementary bodies to L cells could be analyzed by immunofluorescence and flow cytometry. Cells exposed to 0.26 inclusion-forming units/cell could be discriminated from an unexposed population. Flow analysis of purified elementary bodies was possible after fluorescent staining with the aid of a laser-based cytometer and gating on low volume.

Tear and serum antibody response to Chlamydia trachomatis antigens during acute chlamydial conjunctivitis in monkeys as determined by immunoblotting

In this study, we examined the temporal antibody response by immunoblotting analysis in tears and sera of three cynomolgus monkeys (Macaca fasicularis) with primary acute Chlamydia trachomatis serovar B conjunctivitis. The objective was to identify chlamydial antigens stimulating antibody during the host responses in the course of this self-limiting infection with the rationale that they may be protective antigens. The major outer membrane protein (MOMP), lipopolysaccharide (LPS), and polypeptides of 60 and 68 kilodaltons (kDa) were the predominant antigens recognized by immunoglobulin A (IgA) in monkey tears. Tear IgA antibody specific for the MOMP was first detected 14 days postinfection, whereas tear IgA reactive with LPS or the 68- and 60-kDa polypeptides was first detectable on day 21. Tear IgA antibodies specific for each of these antigens persisted in tears through day 56, 4 weeks after both peak clinical disease and recovery of the organism from the conjunctivae. In contrast, tear IgG antibodies peaked at approximately 28 days postinfection, the time of maximal inflammatory response. The IgG response in monkey sera was similar to that observed for tear antibodies, in that the MOMP, 60-, and 68-kDa polypeptides were the primary immunogens. The exception was that IgG antibody against these antigens was detected 1 week later than that observed for tear IgA antibodies. Of three monkeys that responded with tear IgA antibody against LPS, one did not have detectable serum IgG LPS antibody. The specificity of the tear IgA antibody response of monkeys was determined by immunoblotting nine other C. trachomatis serovars in addition to the homologous B serovar. The tear IgA response to the MOMP was predominantly B complex subspecies-specific (serovars B, Ba, D, and E), whereas the response to chlamydial LPS was found to be species-specific. The significance of these observations in relation to previous vaccine studies in nonhuman primates is discussed.

Biosynthesis and disulfide cross-linking of outer membrane components during the growth cycle of Chlamydia trachomatis

The synthesis and accumulation of Chlamydia trachomatis outer membrane proteins within infected HeLa 229 host cells were monitored by assessing the uptake of [35S]cysteine into chlamydial proteins during the 48-h growth cycle of a lymphogranuloma venereum strain, L2/434/Bu. Synthesis of the major outer membrane protein, a protein that accounts for about 60% of the outer membrane protein mass of elementary bodies (EB), was first detected between 12 and 18 h after infection. The uptake of [35S]cysteine into the 60,000-molecular-weight doublet (60K doublet) and 12.5K cysteine-rich proteins was not observed until 30 h after infection, when the intracellularly dividing reticulate bodies were beginning to transform into infectious EBs. By using a more sensitive immunoblotting method in conjunction with monoclonal antibodies specific for the 60K doublet proteins, synthesis of these proteins was detected even earlier, by 18 h after infection. These data suggest that the time and extent of synthesis of these outer membrane proteins are regulated by processes that coincide in time with the transformation of reticulate bodies into EBs. Additional studies were performed to determine the extent of disulfide cross-linking of outer membrane proteins during the growth cycle. Both the major outer membrane protein and the 12.5K protein became progressively cross-linked to about 60% during the last 24 h of the growth cycle, whereas the 60K doublet proteins were extensively cross-linked during most of the cycle. These data may indicate an intracellular cross-linking mechanism, possibly enzymatic, that exists in addition to an auto-oxidation mechanism that occurs upon host cell lysis and exposure to the extracellular environment.

Class specific immunoglobulin response to individual polypeptides of Chlamydia trachomatis, elementary bodies, and reticulate bodies in patients with chlamydial infection

Sera from 10 women with Chlamydia trachomatis culture positive cervicitis and sera from six men with C trachomatis positive non-gonococcal urethritis were studied for the presence of IgG, IgM, and IgA antibodies to polypeptides of C trachomatis elementary bodies and reticulate bodies using immunoblotting techniques. All the sera with IgG, IgM, or IgA immunoglobulins specific to C trachomatis recognised the major outer membrane protein (MOMP) of elementary bodies. IgG antibodies also detected several other proteins, whereas IgM immunoglobulins recognised only MOMP and proteins of 60 kD, 62 kD, and 66 kD. The IgA reacted with MOMP and the 60 kD and 62 kD proteins in elementary bodies. Class specific antibody response against the proteins of reticulate bodies was similar to that observed for elementary body antigens--with one substantial difference: no reaction was observed in the 60 kD and 62 kD positions. This suggests that 60 kD and 62 kD proteins are deficient in reticulate bodies.

Sequence analysis of the major outer membrane protein gene from Chlamydia trachomatis serovar L2

The structural gene for the major outer membrane protein (MOMP) from Chlamydia trachomatis was cloned and sequenced. A lambda gt11 recombinant (lambda gt11/L2/33) that contains a portion of the MOMP coding sequence was used to probe a lambda 1059 library constructed from DNA obtained from C. trachomatis serovar L2. Selected lambda 1059 recombinants were mapped with endonuclease restriction enzymes. The MOMP gene was mapped to the 5' end of a BamHI fragment of approximately 9 kilobases. Contiguous endonuclease restriction fragments identified within this region permitted the selection of specific fragments for subcloning and DNA sequencing. The MOMP gene consisted of a 1,182-base-pair open reading frame that encoded 394 amino acids and ended with three stop codons. The known amino-terminal amino acid was preceded by 22 amino acids whose sequence was compatible with a leader or signal sequence. The primary structure of MOMP determined from the translated DNA sequence demonstrated nine cysteine residues and a remarkably homogeneous distribution of charged and hydrophobic residues.

Alterations in a cartilage matrix glycoprotein in canine osteoarthritis

A number of biochemical abnormalities have been described in osteoarthritic (OA) cartilage, but little study has been devoted to changes in the noncollagenous, nonproteoglycan proteins of cartilage in this condition. Using a canine model of OA produced by transection of the anterior cruciate ligament of the knee, we have demonstrated that distinct alterations occur in a 550,000-dalton cartilage matrix glycoprotein in OA canine cartilage. This protein is a major protein constituent of normal articular cartilage. Fragments which are immunologically cross-reactive with the 550,000-dalton protein were more abundant in OA cartilage than in normal articular cartilage. Immunofluorescence studies revealed that staining with specific antiserum to the protein was absent in OA cartilage. This was the only noncollagenous, nonproteoglycan protein noted to undergo significant changes in this model of OA.

Metabolism of a cartilage matrix glycoprotein in normal and osteoarthritic canine articular cartilage

We have recently described a 550,000-dalton noncollagenous cartilage matrix glycoprotein (CMGP), with subunits of 130,000, which is present in hyaline cartilage and fibrocartilage. Biosynthetic studies indicated that CMGP was synthesized by short-term organ cultures of normal canine articular cartilage, representing approximately 9% of the total 3H-leucine incorporated into protein in 24-hour cultures. There was no incorporation of 35S-sulfate or 3H-mannose into CMGP under these conditions, but the protein did incorporate 32P-phosphate. The majority of the 3H-leucine-labeled CMGP was removed after 24 hours of chase with unlabeled leucine, and only a small amount remained at 72 hours, which suggests that there was rapid metabolism of the protein. CMGP was not detected in cartilage after addition of cycloheximide to the culture medium; this confirms its short half-life. Cultures of osteoarthritic cartilage obtained from dogs 8-10 weeks after anterior cruciate ligament transection revealed no difference in the metabolism of CMGP in this tissue compared with that found in cultures of normal articular cartilage.

Vitreous contains a cartilage-related protein

The vitreous is a clear, gel-like mass in the posterior cavity of the eye. Its major components are type II collagen, hyaluronic acid, and water. A small amount of proteoglycan is also present. All of these molecules are found in cartilage as well. We have now identified a non-collagenous protein in bovine and human vitreous samples which has hitherto been found only in hyaline cartilage and fibrocartilage. This protein has a molecular weight of 550,000 and subunits of 130,000 MW and appears to be a shared cartilage and eye antigen. Its role, if any, in ocular disease associated with rheumatic disorders remains to be determined.

Antigenic analysis of the major outer membrane protein of Chlamydia trachomatis with murine monoclonal antibodies

We prepared monoclonal antibodies against prototype strains of the 15 serovars of Chlamydia trachomatis and identified a subset of reagents that reacted with the major outer membrane protein(s) (MOMPs) of one or more serovars. We then determined the specificities of these anti-MOMP monoclonal antibodies by radioimmunoassay and immunoblot assays against the 15 serovars of C. trachomatis and a C. psittaci strain. We identified 14 different anti-MOMP antibody specificities, including serovar-, several orders of subspecies-, and species-specific determinants. In addition, one antibody reacted with all C. trachomatis serovars and a C. psittaci strain, indicating the presence of a genus-specific epitope on MOMP. Many of the cross-reactions of the subspecies-specific antibodies were similar to those previously reported by use of the microimmunofluorescence technique. We also observed a number of cross-reactions that were unexpected but consistent with data derived by the microimmunofluorescence test. All antibodies, except the genus-specific antibodies, reacted with whole elementary bodies in a radioimmunoassay, suggesting surface exposure of the epitopes. These data confirm and extend previous observations that MOMPs among C. trachomatis serovars are antigenically complex and diverse. In addition, these data indicate that the cross-reaction patterns of some monoclonal antibodies directed against MOMP are similar to those detected by the microimmunofluorescence test and are consistent with the hypothesis that such determinants are contained within MOMPs.

Interaction between Chlamydia spp. and human polymorphonuclear leukocytes in vitro

Chlamydia psittaci and Chlamydia trachomatis elementary bodies (EB) incubated in the presence of complement or specific antibody or both caused chemotaxis of human polymorphonuclear leukocytes (PMN) in vitro. Reticulate bodies and culture supernatants had no effect on these cells. The ability of chlamydiae to enter and survive in PMN under nonopsonizing conditions was investigated by measuring the association of 3H-labeled EB and of inclusion-forming units with these phagocytes. Both assays indicated that C. psittaci as well as C. trachomatis EB are efficiently internalized. The mechanism by which this is accomplished is distinct from classical phagocytosis in that it is not dependent upon the presence of complement or antibody. Furthermore, uptake of at least C. psittaci appeared to be rapid, with no additional increase occurring after 15 min. The majority of cell-associated chlamydiae were rendered acid soluble or noninfectious within 1 h. Subsequently, there was a small but steady loss of infectivity for up to 10 h, which may have been due to the conversion of EB to the noninfectious reticulate-body form of the organism. However, even at 10 h after entry a small percentage of bacteria was still capable of infecting a second target cell. This is noteworthy in that PMN are relatively short-lived cells, and after lysis, intracellular organisms may be free to infect adjacent tissue. Electron microscopic observations were consistent with the data on uptake and persistence. The ability of a small percentage of infecting chlamydiae to maintain infectivity in PMN for at least several hours may enable these organisms subsequently to establish productive infection in permissive host cells.

Antigenic specificity of serological response in Chlamydia trachomatis urethritis detected by immunoblotting

Sera from 19 patients with Chlamydia trachomatis culture positive non-gonococcal urethritis were studied for the presence of antibodies to chlamydial proteins by immunoblotting. Ten C trachomatis negative patients with non-gonococcal urethritis and 10 healthy controls were also studied. Acute phase sera from C trachomatis positive patients with non-gonococcal urethritis reacted only with the major outer membrane protein whereas all the convalescent phase serum samples reacted with the major outer membrane protein and with a 60,000 and a 62,000 molecular weight protein. Some sera also reacted with a 45,000 molecular weight protein. Five of 10 convalescent phase samples from patients with C trachomatis negative non-gonococcal urethritis showed a reaction pattern comparable with that observed in convalescent sera from C trachomatis from C trachomatis positive patients with non-gonococcal urethritis. Sera from healthy seronegative subjects were negative by blotting.

Serovar determination of Chlamydia trachomatis isolates by using type-specific monoclonal antibodies

A panel of 15 monoclonal antibodies was prepared that could distinguish among the 15 serovars of Chlamydia trachomatis. Twelve of these antibodies were specific for a single serovar (A, B, C, D, E, F, G, H, I, K, L1, and L2) and three were specific for two serovars (B/Ba, C/J, and C/L3). Ten of the serovar-specific and two of the bispecific antibodies were shown by immunoblotting to recognize epitopes on the major outer membrane protein. These data provide evidence that such epitopes are closely correlated with and may be partly responsible for the antigenic variations detected by microimmunofluorescence that distinguish the currently recognized serovars. When used in a radioimmunoassay, these antibodies correctly identified the serovar of 17 strains that had been serotyped by the microimmunofluorescence test. In addition, we found that the chlamydial antigen derived from 1.0 cm2 of an infected HeLa cell monolayer was sufficient to allow serotyping with these antibodies. Thus, these monoclonal antibodies may provide a rapid and reliable alternative to mouse immunization and microimmunofluorescence for serotyping of clinical isolates.

Evidence for an interaction between canine synovial cell proteoglycans and link proteins

Link proteins are glycoproteins which stabilize aggregates of proteoglycans and hyaluronic acid in cartilage. We recently identified link proteins in canine synovial cell cultures. We now find that link proteins and proteoglycans extracted from these cells under dissociative conditions sediment in the high-buoyant-density fractions of an associative cesium chloride density gradient, suggesting that link proteins interact with high-buoyant-density proteoglycans. In gradients containing [35S]sulfate-labeled synovial cell extracts, 76% of the labeled sulfate and 54% of the uronic acid is found in the high-buoyant-density fractions. Under associative conditions, Sepharose 2B elution profiles of the crude synovial cell extract, synovial cell high-buoyant-density fractions, and culture medium indicate that synovial cell proteoglycans are present in monomeric form, rather than in aggregates. Synovial cell link proteins co-elute with the [35S]sulfate-labeled material under the same conditions. These proteoglycans do not interact in vitro with exogenous hyaluronic acid. Dermatan sulfate, chondroitin sulfate and heparan sulfate are the major cell-associated sulfated glycosaminoglycans synthesized by cultured canine synovial cells, while hyaluronic acid is found in the culture medium. Although the proteoglycans synthesized by cultured synovial cells interact with link proteins, these data indicate that they do not interact with hyaluronic acid to form aggregates.

Recent advances in Chlamydia trachomatis

Chlamydia trachomatis is an obligate intracellular energy parasitic bacterium with a genome of 660 X 10(6) daltons, possessing a plasmid and unique life cycle which includes the differentiation of the infective elementary body to a replicative reticulate body. C. trachomatis is the etiological agent of trachoma, which affects approximately 500 million people in developing countries. Recently it became evident that in industrialised Western nations certain strains of C. trachomatis are the most common cause of sexually transmitted infections such as non-gonococcal urethritis, cervicitis, endometritis, salpingitis and subsequent ectopic pregnancies or infertility, perihepatitis, neonatal conjunctivitis and pneumonia, adult conjunctivitis and epididymitis. Since C. trachomatis infections are often asymptomatic, widespread screening of sexually active young people is needed in order to initiate early antibiotic treatment which may prevent serious complications such as ectopic pregnancies and infertility. Development of sensitive and simple techniques for mass screening for detection of Chlamydia in excretions as well as techniques for detection of specific markers of chronic internal infections (such as Chlamydia specific IgA antibodies) is of great importance.