Characterization of Chlamydia DNA by restriction endonuclease cleavage

Genomic relatedness of Chlamydia isolates determined by amplified fragment length polymorphism analysis

The genomic relatedness of 19 Chlamydia pneumoniae isolates (17 from respiratory origin and 2 from atherosclerotic origin), 21 Chlamydia trachomatis isolates (all serovars from the human biovar, an isolate from the mouse biovar, and a porcine isolate), 6 Chlamydia psittaci isolates (5 avian isolates and 1 feline isolate), and 1 Chlamydia pecorum isolate was studied by analyzing genomic amplified fragment length polymorphism (AFLP) fingerprints. The AFLP procedure was adapted from a previously developed method for characterization of clinical C. trachomatis isolates. The fingerprints of all C. pneumoniae isolates were nearly identical, clustering together at a Dice similarity of 92.6% (+/- 1.6% standard deviation). The fingerprints of the C. trachomatis isolates of human, mouse, and swine origin were clearly distinct from each other. The fingerprints of the isolates from the human biovar could be divided into at least 12 different types when the presence or absence of specific bands was taken into account. The C. psittaci fingerprints could be divided into a parakeet, a pigeon, and a feline type. The fingerprint of C. pecorum was clearly distinct from all others. Cluster analysis of selected isolates from all species revealed groups other than those based on sequence data from single genes (in particular, omp1 and rRNA genes) but was in agreement with available DNA-DNA hybridization data. In conclusion, cluster analysis of AFLP fingerprints of representatives of all species provided suggestions for a grouping of chlamydiae based on the analysis of the whole genome. Furthermore, genomic AFLP analysis showed that the genome of C. pneumoniae is highly conserved and that no differences exist between isolates of respiratory and atherosclerotic origins.

Sequence diversity of the 60-kilodalton protein and of a putative 15-kilodalton protein between the trachoma and lymphogranuloma venereum biovars of Chlamydia trachomatis

DNA from Chlamydia trachomatis serovars L3, C, and E corresponding to the open reading frames of the 60-kDa protein and of a putative 15-kDa protein was sequenced. The open reading frames coding for the 60-kDa protein had 1,641 bp in the three serovars. Compared with the L3 serovar, there were 9 and 11 amino acid changes in the C and E serovars, respectively. The open reading frames corresponding to the putative 15-kDa protein had 450, 456, and 453 bp for the L3, C, and E serovars, respectively. When compared with the L3 serovar, the C and E serovars had 14 and 16 amino acid differences, respectively.

Comparison of avian Chlamydia psittaci isolates by restriction endonuclease analysis and serovar-specific monoclonal antibodies

Avian Chlamydia psittaci isolates were examined by restriction endonuclease analysis and serovar-specific monoclonal antibodies and compared with ovine abortion and polyarthritis isolates. The avian isolates were divided into four serovars (turkey, psittacine, pigeon, and duck) based on their reactivity to the monoclonal antibodies. The DNA digest patterns were similar across the four avian serovars; most bands were identical when the isolates were tested with PstI, BamHI, and EcoRI restriction endonuclease enzymes. The turkey group restriction endonuclease analysis patterns were distinguished from those of the other avian strains by three to four band differences with all enzymes. The duck and pigeon isolates showed only minor DNA pattern differences when compared with the psittacine isolates. Four psittacine isolates from various locations in Texas had an extra band with the EcoRI restriction enzyme, suggesting that they were from a common source; however, they were indistinguishable from the other psittacine isolates when examined with the monoclonal antibodies. The avian isolates were distinctly different from either abortion or polyarthritis isolates by both restriction endonuclease analysis and monoclonal antibody analysis. The data demonstrate that the avian isolates form a distinct group or separate biovar with at least four serovars.

Differences in susceptibilities of the lymphogranuloma venereum and trachoma biovars of Chlamydia trachomatis to neutralization by immune sera

Sera from seven patients from whom a C. trachomatis serovar L2 strain was isolated were tested in vitro for their ability to neutralize the infectivity of this organism. In one patient an inguinal lymph node was culture positive, whereas the remaining six patients had positive rectal biopsies. Sera from four of the patients, including the patient with the lymph node isolate, failed to neutralize serovar L2(434). In addition, the homologous strain recovered from the inguinal lymph node was available and was resistant to neutralization by the homologous sera. However, the same sera effectively neutralized a trachoma serovar, E(Bour). All four sera had inclusion immunofluorescent-antibody titers to C. trachomatis serovar L2 of 2,048 to 16,384 and microimmunofluorescent-antibody titers to the lymphogranuloma venereum biovar were equal or higher in all cases than to the 12 serovars of the trachoma biovar. The three remaining sera, while neutralizing the infectivity of the L2 strains tested, neutralized serovar E to a greater extent. These sera had the same inclusion immunofluorescent antibody titers as the sera that failed to neutralize serovar L2. To see whether this difference in the sensitivity of the biovars toward neutralization could be characterized, sera were obtained from mice immunized with different doses of both serovars L2 and E. Sera obtained from mice immunized with serovar E were able to effectively neutralize the homologous strain. In contrast, neutralization of the immunizing strain, L2(UCI-20), was not seen with sera obtained on days 7, 14, and 21 after immunization from animals receiving 8 x 10(5) and 8 x 10(4) inclusion-forming units of L2(UCI-20); however, these same sera neutralized serovar E. However, with a higher immunizing dose of L2 (10(7) IFUs), both E and L2 were neutralized with sera obtained 7 and 14 days after immunization. Therefore, the relative resistance to neutralization by serovar L2 compared with that of serovar E in the mouse model was inoculum dependent.

The 7.5-kb plasmid present in Chlamydia trachomatis is not essential for the growth of this microorganism

An L2 serovar of Chlamydia trachomatis, isolated from a patient with proctocolitis, has been identified that does not contain the common C. trachomatis 7.5-kb plasmid. This isolate was propagated in vitro showing that this plasmid is not required for the growth of C. trachomatis.

Cloning and characterization of a Chlamydia trachomatis L3 DNA fragment that codes for an antigenic region of the major outer membrane protein and specifically hybridizes to the C- and C-related-complex serovars

Chlamydia trachomatis L3 DNA was cloned and expressed in lambda gt11. A recombinant plaque that expressed an antigen that reacted with rabbit polyclonal antichlamydial L3 serum and with two monoclonal antibodies specific for serovars L3 and I was selected from this Chlamydia genomic library. The beta-galactosidase Chlamydia fusion protein was purified by immunoaffinity chromatography and injected into mice to produce monoclonal antibodies. These monoclonal antibodies reacted by Western (immuno-) blot with both the fusion protein and the major outer membrane protein from purified L3 elementary bodies. The chlamydial DNA fragment was shown by DNA sequence analysis to be 168 base pairs in length and to correspond to the constant regions 1 and 2 and the variable segment 1 of the major outer membrane protein gene. The recombinant chlamydial DNA fragment hybridized under stringent conditions by Southern and dot blot analysis exclusively with the DNA from the C- and C-related-complex C. trachomatis serovars.

Two distinct forms of Chlamydia psittaci associated with disease and infertility in Phascolarctos cinereus (koala)

While several diseases associated with Chlamydia psittaci infection have been reported in Phascolarctos cinereus (koala), it is still unclear whether one or more chlamydial strains are responsible. In this study, we provide evidence, obtained by restriction enzyme and gene probe analysis, that two quite distinct strains of C. psittaci infect koalas; one strain was isolated from the conjunctivae, and the other was isolated from the urogenital tract and the rectum. A gene probe, pFEN207, containing the coding sequence for an enzyme involved in the biosynthesis of the chlamydial genus-specific lipopolysaccharide antigen, and a separate probe, pCPML-4N, prepared from a DNA fragment of a koala-infecting strain of C. psittaci, were used to determine the patterns of hybridization in the koala-infecting strains; these patterns were found to be quite distinct from those observed with C. psittaci isolates from other animals. We also demonstrated by hybridization analysis with an avian strain plasmid that all three koala urogenital isolates contain a plasmid and that there is no evidence for the presence of a homologous plasmid in any of the ocular isolates.

Analysis of the entire nucleotide sequence of the cryptic plasmid of Chlamydia trachomatis serovar L1. Evidence for involvement in DNA replication

Chlamydia trachomatis serovar L1/440/LN possesses a 7498bp plasmid which was designated pLGV440. The plasmid was cloned at the BamH1 site of pAT153 into Escherichia coli and the recombinant plasmid was designated pCTL1. A detailed restriction endonuclease map of pCTL1 was constructed. A fragment of the chlamydial plasmid was shown to function as a promoter in E. coli when placed upstream of the lacZ gene. The entire plasmid was sequenced by the chain termination method. Open reading frames were identified from the resulting consensus sequence together with a candidate for the plasmid origin of replication consisting of four perfect tandem repeats of a 22bp sequence, an A:T rich sequence and an open reading frame which could generate a 34.8kdal product. The predicted polypeptide products of the open reading frames were compared by computer with all reported protein sequences. Homology of the predicted polypeptide product of an open reading frame to the E. coli dnaB protein and the analogous product of gene 12 of bacteriophage P22 is described.

Isolation and restriction endonuclease cleavage of Anaplasma marginale DNA in situ in agarose

Bacterial restriction endonucleases were used to produce DNA cleavage patterns that could be useful as tools to study the relatedness among Anaplasma marginale isolates. Bovine erythrocytes infected with A. marginale were lysed, washed, and embedded in agarose. The embedded erythrocytes and bacterial pathogens were partially digested by sequential infiltration of the agarose with acetone, lysozyme, sodium dodecyl sulfate, and proteinase K. The unfragmented genomic DNA was left supported and protected in a porous matrix. The DNA was digested in situ in agarose under the following conditions: (i) brief treatment with phenol, (ii) brief washing with distilled water, and (iii) adjustment of restriction enzyme digestion mixture to compensate for the volume of the agarose. The cleaved DNA was electrophoresed horizontally to produce a DNA cleavage pattern. Of 19 restriction enzymes screened, 12 produced distinct DNA bands from the genomes of each of the five A. marginale isolates examined. The DNA cleavage pattern produced from each isolate with a given restriction enzyme was reproducible. However, the DNA cleavage patterns produced from different isolates with a given restriction enzyme were not necessarily identical. This procedure could be modified for general bacterial DNA isolation, in situ agarose digestion, and manipulations.

Restriction endonuclease analysis of DNA from Chlamydia trachomatis biovars

DNA from a total of 60 Chlamydia trachomatis isolates was examined by restriction endonuclease analysis. Strains from all established biovars and serovars were tested. There was great diversity between the mouse biovar and the lymphogranuloma venereum (LGV) and trachoma biovars. The LGV and trachoma biovar isolates generated similar fragment patterns; however, distinct fragments appeared to be unique to both biovars, thus allowing differentiation of these two major groups. In most cases, strains of the same serovar could be differentiated from one another when a battery of restriction enzymes was used. In addition, in some cases, certain restriction fragments appeared to be characteristic of strains from a particular geographical location. The DNA patterns generated by all C. trachomatis isolates differed greatly from the DNA patterns generated from the Chlamydia psittaci isolates tested, including TWAR, a human C. psittaci strain.

Chlamydia parasitism: ultrastructural characterization of the interaction between the chlamydial cell envelope and the host cell

Ultrastructural analysis of the growth cycles of Chlamydia trachomatis and Chlamydia psittaci showed that the chlamydial cell envelope became rigid and septated at the time of the reorganization from reticulate to elementary body. This process occurred in the immediacy of the inclusion membrane and in close proximity with the mitochondria or the endoplasmic reticulum of the host cell.

Comparison of Chlamydia psittaci isolates by restriction endonuclease and DNA probe analyses

DNAs from eight Chlamydia psittaci isolates (koala conjunctivitis, avian psittacosis, avian ornithosis, ovine abortion, ovine polyarthritis, sporadic bovine encephalomyelitis, and feline conjunctivitis) and one Chlamydia trachomatis isolate (lymphogranuloma venereum) were compared by restriction endonuclease and DNA probe analyses. Digestion with HindIII yielded a series of discrete fragments which allowed the differentiation of most isolates. A gene probe, pFEN207, which encodes the chlamydia-specific component of the lipopolysaccharide group antigen was used in Southern hybridizations. The probe was chlamydia specific and hybridized to a single BamHI fragment and multiple HindIII fragments in each isolate. The variation in size of the hybridizing fragments allowed easy differentiation of the isolates and may eventually lead to a meaningful subgrouping of the diverse group of disease agents presently included in the species C. psittaci.

The antichlamydial, antiviral, and antiproliferative activities of human gamma interferon are dependent on the integrity of the C terminus of the interferon molecule

The effects of recombinant human gamma interferon (rHuIFN-gamma; two identical monomers of 140 residues in length) and of two re-engineered C-terminal variants, rHuIFN-gamma Tetra-Ser (residues 129 to 132 replaced by serine) and rHuIFN-gamma 125 (two identical monomers of 125 residues each with the last 14 residues plus an additional alanine from the C terminus deleted), were compared in terms of several in vitro biological activities. By using three different human cell lines (HeLa 229, HEp-2, and A549), the interferons were tested for their ability to inhibit: (i) growth of Chlamydia trachomatis; (ii) replication of encephalomyocarditis virus; and (iii) cell growth. rHuIFN-gamma restricted the growth of chlamydiae to 50% of the non-IFN-treated control at concentrations ranging from 0.01 to 0.05 ng/ml, depending on the cell type assayed. One of the modified proteins, rHuIFN-gamma Tetra-Ser, also decreased the growth of chlamydiae, but it required a concentration of approximately 0.5 ng/ml to produce 50% inhibition. rHuIFN-gamma 125 had the lowest antichlamydial activity of the three IFN-gamma variants tested; concentrations of 1 to 20 ng/ml were needed to reduce the growth of C. trachomatis to 50% of that of the control. The relative antiviral and antiproliferative activities of the three IFN-gamma preparations paralleled their antichlamydial activities in these three cell lines. The antiencephalomyocarditis virus activities of rHuIFN-gamma Tetra-Ser and rHuIFN-gamma 125 were reduced by approximately 10-fold and 10(2)- to 10(3)-fold, respectively, compared with the antiviral activity of rHuIFN-gamma. Proliferation of the three cell lines was restricted to approximately 50% of the control with 0.5 to 10 ng of rHuIFN-gamma per ml. Inhibition of cell growth by rHuIFN-gamma Tetra-Ser was significant only at concentrations equal to or greater than 30 ng/ml, and the rHuIFN-gamma 125 variant did not significantly decrease the growth of any of the three cell lines at the concentrations tested. These results suggest that the C-terminal portion of rHuIFN-gamma is critical for maintaining the conformation necessary for inducing the antichlamydial, antiviral, and antiproliferative activities of the molecule.

Characterization of the new Chlamydia agent, TWAR, as a unique organism by restriction endonuclease analysis and DNA-DNA hybridization

Several molecular techniques were used for comparison of the novel Chlamydia agent, TWAR, with Chlamydia trachomatis and Chlamydia psittaci. Unlike all serotypes of C. trachomatis and most strains of C. psittaci, the eight TWAR isolates examined did not contain extrachromosomal DNA. TWAR was readily distinguished from C. trachomatis or C. psittaci by restriction endonuclease analysis, whereas identical or nearly identical restriction patterns were observed among the TWAR isolates. Southern blot analysis with a gene encoding a portion of the C. trachomatis serovar L2 major outer membrane protein as the probe showed that TWAR, like C. psittaci, contained sequences homologous to this gene. However, while the hybridization patterns were identical for all TWAR isolates, they differed from those of any of the other Chlamydia species tested. A PstI gene bank containing TWAR DNA was constructed in pUC19. Random fragments were purified and used for probing Chlamydia chromosomal digests. All of the five probes tested were TWAR specific, with the TWAR isolates showing identical patterns of homology. Qualitative studies of the DNA homology revealed that TWAR did not have significant homology to any of the Chlamydia strains assayed. Collectively, these results demonstrate that the TWAR isolates represent a single strain or closely allied genotypes and are clearly distinct from any of the other chlamydiae tested.

Automation in clinical microbiology: a new approach to identifying micro-organisms by automated pattern matching of proteins labelled with 35S-methionine

A new rapid automated method for the identification and classification of microorganisms is described. It is based on the incorporation of 35S-methionine into cellular proteins and subsequent separation of the radiolabelled proteins by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein patterns produced were species specific and reproducible, permitting discrimination between the species. A large number of Gram negative and Gram positive aerobic and anaerobic organisms were successfully tested. Furthermore, there were sufficient differences within species between the protein profiles to permit subdivision of the species. New typing schemes for Clostridium difficile, coagulase negative staphylococci, and Staphylococcus aureus, including the methicillin resistant strains, could thus be introduced; this has provided the basis for useful epidemiological studies. To standardise and automate the procedure an automated electrophoresis system and a two dimensional scanner were developed to scan the dried gels directly. The scanner is operated by a computer which also stores and analyses the scan data. Specific histograms are produced for each bacterial species. Pattern recognition software is used to construct databases and to compare data obtained from different gels: in this way duplicate "unknowns" can be identified. Specific small areas showing differences between various histograms can also be isolated and expanded to maximise the differences, thus providing differentiation between closely related bacterial species and the identification of differences within the species to provide new typing schemes. This system should be widely applied in clinical microbiology laboratories in the near future.

Molecular characterization of Chlamydia trachomatis and Chlamydia psittaci plasmids

Plasmids from Chlamydia trachomatis LGV-434 (serotype L2) and Chlamydia psittaci meningopneumonitis strain Cal-10 were cloned into the BamHI and EcoRI sites of pBR322, respectively. The recombinant plasmids pCTL2 and pCPMn, each containing an entire respective chlamydial plasmid, were transformed into Escherichia coli. The sizes of the plasmids of C. trachomatis and C. psittaci were 7.3 and 6.2 kilobases, respectively. The two plasmids were found to be distinct by restriction endonuclease analysis, DNA-DNA hybridization, and electron microscopic heteroduplex analysis. However, partial homology was observed between restriction fragments of pCTL2 and pCPMn by Southern blot analysis. Polypeptide products encoded by these plasmids were synthesized in vitro by an E. coli-directed transcription-translation system and in vivo in E. coli maxicells and minicells. None of these polypeptides was immunoreactive with anti-chlamydial sera by immunoblotting or immunoprecipitation. Based on the comparative analysis data, the C. trachomatis and C. psittaci plasmids were found to share little genetic relatedness.

Identification and properties of chlamydial polypeptides that bind eucaryotic cell surface components

An electroblotting technique was used to identify proteins of Chlamydia that bound surface-radioiodinated and Triton X-100-solubilized HeLa cell extracts. Two proteins, with apparent molecular masses of 18 and 32 kilodaltons (kDa), that bound HeLa cell surface components were identified on Chlamydia trachomatis L2 elementary bodies (EBs). Radioiodinated heparin, which disrupts chlamydial association with cultured cells, was also bound by these proteins. These two proteins were found on EBs but were absent or were present in reduced amounts on the noninfectious reticulate bodies. All C. trachomatis strains tested displayed two such proteins, although the apparent molecular weight of the larger protein varied with serotype in correlation with biotype and the disease that it caused. Two Chlamydia psittaci strains examined displayed only a single binding protein in the range of 17 to 19 kDa. All of the binding proteins stained intensely and distinctively on silver-stained sodium dodecyl sulfate-polyacrylamide gels and displayed an unusual sensitivity to reducing agents. The 32-kDa protein was not seen and did not bind 125I-labeled HeLa cell components if the EBs were solubilized in the presence of 2-mercaptoethanol. The 32-kDa protein was not affected by dithiothreitol, however. Similar to the effect of 2-mercaptoethanol, the 32-kDa protein was not visualized after treatment of EBs with the protease inhibitors tosyl-phenylalanine chloromethyl ketone (TPCK) or tosyl-lysine chloromethyl ketone (TLCK). TPCK and TLCK also abolished infectivity as did the alkylating agents N-ethylmaleimide and iodoacetamide, yet the latter two agents did not affect the appearance of the 32-kDa protein. These proteins were not detected in immunoblots with either rabbit antisera to C. trachomatis L2 EBs or by serum from a patient with lymphogranuloma venereum. The role of these proteins in the interaction of chlamydiae with host cells is not clear, but the binding of eucaryotic cell surface components and heparin, presence only during the infectious stage of the life cycle, variation between serotypes in correlation with disease, and sensitivity to reducing agents or protease inhibitors, collectively, suggest a role for these proteins in parasite-host interactions.

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.

Effect of proteolytic cleavage of surface-exposed proteins on infectivity of Chlamydia trachomatis

The proteolytic cleavage of Chlamydia trachomatis LGV-434 surface proteins and resultant effects on infectivity and association with cultured human epithelial (HeLa) cells have been examined. Of several proteases examined, trypsin, chymotrypsin, and thermolysin extensively cleaved the chlamydial major outer membrane protein (MOMP). Two proteases, trypsin and thermolysin, cleaved the MOMP to the extent that monomeric MOMP was not detectable by immunoblotting with monospecific polyclonal antibodies. In the case of thermolysin, not even antigenic fragments were detected. Surprisingly, infectivity toward HeLa cells was not diminished. In addition, the association of intrinsically 14C-radiolabeled elementary bodies (EBs) with HeLa cells or their dissociation by proteinase K was not measurably affected by prior trypsinization of the EBs. Trypsinization of lactoperoxidase surface-iodinated elementary bodies demonstrated that most of the 125I-labeled surface proteins were cleaved. In all cases, however, a number of proteolytic cleavage fragments remained associated with the EB surface after surface proteolysis. When trypsinized EBs were electrophoresed under nonreducing conditions and immunoblotted with either polyclonal or type-specific monoclonal MOMP antibodies, MOMP was found in a large oligomeric form that failed to enter the polyacrylamide stacking gel. Additionally, trypsinized viable EBs bound radioiodinated type-specific MOMP monoclonal antibody as efficiently as did the control nontrypsinized organisms. Taken together, the findings indicate that although the MOMP is highly susceptible to surface proteolysis, the supramolecular structure of the protein on the EB surface is apparently maintained by disulfide interactions. Thus, if surface-exposed chlamydial proteins are involved in the initial interaction of chlamydiae with eucaryotic cells, the functional domains of these proteins which mediate this interaction must be resistant to proteolysis and remain associated with the EB surface.

Partial amino acid sequence and molecular cloning of the encoding gene for the major outer membrane protein of Chlamydia trachomatis

The first 25 N-terminal amino acids of the major outer membrane protein of Chlamydia trachomatis serovar L2 were determined. The amino acid sequence was used to construct an oligonucleotide probe specific for the major outer membrane protein gene. Using this oligonucleotide as a hybridization major outer membrane protein gene. Using this oligonucleotide as a hybridization probe, we discovered one recombinant clone that produced a 15-kilodalton polypeptide which reacted with a monoclonal antibody directed against the major outer membrane protein type-specific epitope. In a separate set of experiments, we uncovered another recombinant clone that produced a 51-kilodalton polypeptide which was reactive with an anti-major outer membrane protein subspecies-specific monoclonal antibody. The expression of these recombinant DNA plasmids in Escherichia coli is discussed.

Characterization of Chlamydia trachomatis serotypes by human T-lymphocyte clones

T cells primed to Chlamydia trachomatis serotypes A, F, and K were cloned by limiting dilution. All T-lymphocyte clones obtained reacted only with C. trachomatis antigens. The proliferative capacity of 89 clones was studied with autologous non-T cells as antigen-presenting cells and the chlamydia serotypes A, B, D, F, K, and LGV-2 as antigens. Most of the clones reacted to several of the chlamydia strains, indicating common antigenic determinants. Other T-cell clones reacted with only a few serotypes. On the basis of the proliferation of the T-cell clones to the chlamydia strains and to interleukin-2, different reactivity patterns were obtained, which possibly can be used to differentiate among the chlamydia strains.

Comparison of Chlamydia psittaci isolates by DNA restriction endonuclease analysis

Preparations of DNA from 12 Chlamydia psittaci isolates and one Chlamydia trachomatis strain were compared by restriction endonuclease analysis. Polyacrylamide gel electrophoresis, followed by silver staining, resulted in optimal resolution of fragments generated by digestion. By this technique, four distinct electropherotypes were demonstrated when ovine abortion, ovine arthritis, and avian and Cal10 strains of C. psittaci were examined. Minor profile differences allowed the discrimination of avian isolates derived from psittacine and columbiforme species, and the Cal10 DNA electropherotype was shown to have features in common with these profiles. However, there were no detectable differences in the DNA patterns of eight ovine abortion isolates.

Monoclonal antibody against a genus-specific antigen of Chlamydia species: location of the epitope on chlamydial lipopolysaccharide

Monoclonal antibodies were prepared by the fusion of murine myeloma NS1 cells with spleen cells of BALB/c mice immunized with Formalin-killed elementary bodies of the Chlamydia trachomatis L2 serovar. The specificity of these monoclonal antibodies was determined with a solid-phase immunoassay in which HeLa 229 cells infected with C. trachomatis serovars D, G, H, I, L2 and the Chlamydia psittaci meningopneumonitis strain Cal-10 were used. An immunoglobulin G3 monoclonal antibody (L2I-6) was identified that reacted with both C. trachomatis- and C. psittaci-infected HeLa cells. The immunoreactivity of the genus-specific epitope was heat resistant (100 degrees C, 10 min) but was destroyed by sodium metaperiodate treatment. Further characterization of the chlamydial specificity of monoclonal antibody L2I-6 by microimmunofluorescence showed that it was reactive with all 15 C. trachomatis serovars and seven C. psittaci strains isolated from five different animal species. We undertook studies to identify the biochemical nature of the chlamydial component on which the genus-specific epitope was located. The immunoreactive component was isolated by hot phenol-water extraction of dithiothreitol-reduced chlamydial elementary bodies. The component was positive in the Limulus amoebocyte lysate test (results of Limulus amoebocyte lysate assay were identical with those of Salmonella typhimurium LT2 SAI 377 Re lipopolysaccharide [LPS]), contained 8.8% 2-keto-3-deoxyoctulosonic acid, was resistant to proteinase K, and possessed electrophoretic mobility and silver-staining characteristics in sodium dodecyl sulfate-polyacrylamide gel electrophoresis consistent with a rough LPS or glycolipid. On the basis of these findings, we conclude that the genus-specific epitope recognized by monoclonal L2I-6 is located on chlamydial LPS. We further characterized the antigenic properties of the chlamydial LPS epitope by examining the immunoreactivity of monoclonal antibody L2I-6 by immunoblotting analyses against isolated LPSs extracted from Neisseria gonorrhoeae, S. typhimurium, and Escherichia coli. Monoclonal antibody L2I-6 did not bind LPS of these organisms, demonstrating that the chlamydial genus-specific LPS epitope is apparently not shared by these gram-negative bacteria. We were able, however, to show that the chlamydial LPS does share antigenic determinants with LPS of gram-negative organisms. Polyclonal rabbit antisera raised against S. typhimurium Re LPS or lipid A showed intense immunological cross-reactivity with chlamydial LPS by immunoblotting.(ABSTRACT TRUNCATED AT 400 WORDS)