AN UNIDENTIFIED VIRUS PRODUCING ACUTE MENINGITIS AND PNEUMONITIS IN EXPERIMENTAL ANIMALS

Genetic and antigenic analysis of Chlamydia pecorum strains isolated from calves with diarrhea

Chlamydia pecorum (designated 22-58) was isolated in 2010 in HmLu-1 cells from the jejunum of a calf which died of necrotizing enterocolitis in Yamaguchi Prefecture, Japan. Immunohistochemical staining identified C. pecorum positive reactions in the jejunal villi. C. pecorum, designated 24-100, was isolated from the feces of a calf with diarrhea in another farm in Yamaguchi Prefecture in 2012. A significant increase in neutralizing antibody titers against C. pecorum was confirmed in paired sera. Nucleotide sequence identities of omp1 genes of the 2 isolates were 100%. The isolates were genetically and antigenically more closely related to C. pecorum Bo/Yokohama strain isolated from cattle with enteritis in Japan than to the other prototype strains, Bo/Maeda isolated from cattle with pneumonia and Ov/IPA isolated from sheep with polyarthritis. These results indicate that C. pecorum strains similar to 22-58 and 24-100 might be endemic in Yamaguchi Prefecture and cause enteric disease in cattle.

Chlamydia psittaci comparative genomics reveals intraspecies variations in the putative outer membrane and type III secretion system genes

Chlamydia psittaci is an obligate intracellular bacterium that can cause significant disease among a broad range of hosts. In humans, this organism may cause psittacosis, a respiratory disease that can spread to involve multiple organs, and in rare untreated cases may be fatal. There are ten known genotypes based on sequencing the major outer-membrane protein gene, ompA, of C. psittaci. Each genotype has overlapping host preferences and virulence characteristics. Recent studies have compared C. psittaci among other members of the Chlamydiaceae family and showed that this species frequently switches hosts and has undergone multiple genomic rearrangements. In this study, we sequenced five genomes of C. psittaci strains representing four genotypes, A, B, D and E. Due to the known association of the type III secretion system (T3SS) and polymorphic outer-membrane proteins (Pmps) with host tropism and virulence potential, we performed a comparative analysis of these elements among these five strains along with a representative genome from each of the remaining six genotypes previously sequenced. We found significant genetic variation in the Pmps and tbl3SS genes that may partially explain differences noted in C. psittaci host infection and disease.

Genome sequences of the zoonotic pathogens Chlamydia psittaci 6BC and Cal10

Chlamydia psittaci is a highly prevalent avian pathogen and the cause of a potentially lethal zoonosis, causing life-threatening pneumonia in humans. We report the genome sequences of C. psittaci 6BC, the prototype strain of the species, and C. psittaci Cal10, a widely used laboratory strain.

Multi locus sequence typing of Chlamydia reveals an association between Chlamydia psittaci genotypes and host species

Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses. Chlamydia trachomatis causes diseases such as trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Chlamydia pneumoniae is a common cause of community-acquired respiratory tract infections. Chlamydia psittaci, causing zoonotic pneumonia in humans, is usually hosted by birds, while Chlamydia abortus, causing abortion and fetal death in mammals, including humans, is mainly hosted by goats and sheep. We used multi-locus sequence typing to asses the population structure of Chlamydia. In total, 132 Chlamydia isolates were analyzed, including 60 C. trachomatis, 18 C. pneumoniae, 16 C. abortus, 34 C. psittaci and one of each of C. pecorum, C. caviae, C. muridarum and C. felis. Cluster analyses utilizing the Neighbour-Joining algorithm with the maximum composite likelihood model of concatenated sequences of 7 housekeeping fragments showed that C. psittaci 84/2334 isolated from a parrot grouped together with the C. abortus isolates from goats and sheep. Cluster analyses of the individual alleles showed that in all instances C. psittaci 84/2334 formed one group with C. abortus. Moving 84/2334 from the C. psittaci group to the C. abortus group resulted in a significant increase in the number of fixed differences and elimination of the number of shared mutations between C. psittaci and C. abortus. C. psittaci M56 from a muskrat branched separately from the main group of C. psittaci isolates. C. psittaci genotypes appeared to be associated with host species. The phylogenetic tree of C. psittaci did not follow that of its host bird species, suggesting host species jumps. In conclusion, we report for the first time an association between C. psittaci genotypes with host species.

A VIRUS FROM CASES OF ATYPICAL PNEUMONIA : RELATION TO THE VIRUSES OF MENINGOPNEUMONITIS AND PSITTACOSIS

From the lungs of two fatal cases and from the sputum of two non-fatal cases of atypical bronchopneumonia, a psittacosis-like virus was isolated by direct intranasal inoculation of mice. Intraperitoneal injection of the same human material into mice gave negative results. The virus has a relatively high virulence for mice by intranasal or intra-cerebral inoculation, but does not kill after intraperitoneal inoculation. Its virulence for Java ricebirds is low and it fails to produce a carrier state in mice and birds. Two cases showed an increase in complement-fixing antibodies to the new virus and to psittacosis. The virus is antigenically related to the viruses of meningopneumonitis and psittacosis by complement fixation and by active immunity tests in mice.

COMPARATIVE STUDY OF MENINGOPNEUMONITIS VIRUS, PSITTACOSIS OF PIGEON ORIGIN, AND PSITTACOSIS OF PARROT ORIGIN

Comparative morphological, histological, and biological studies suggest a close relationship between the meningopneumonitis virus of Francis and Magill and a virus recovered from thiamin-deficient pigeons. Both of these viruses are morphologically identical with typical psittacosis, and it seems probable that they are biologically modified strains of psittacosis. They both differ from typical psittacosis in that they are regularly more pathogenic for the pigeon after intracranial injection, and fail to produce hepatic necrosis after intraperitoneal injection in mice. A virus recently isolated from human cases of atypical pneumonia by Eaton, Beck, and Pearson may also be closely related to these two viruses. A number of psittacosis viruses of pigeon origin showed a similarly increased pathogenicity for pigeons by the intracerebral route, as compared with psittacosis viruses of parrot origin. The viruses of parrot origin, however, commonly produced latent infection in pigeons even when clinical illness was not evidenced. For the isolation of psittacosis of pigeon origin from human sputum the intracranial injection of mice or pigeons may be essential, although it is probable that the intranasal injection of mice would be successful. The intraperitoneal injection of mice may give negative results.

ISOLATION FROM NORMAL MICE OF A PNEUMOTROPIC VIRUS WHICH FORMS ELEMENTARY BODIES

1. A pneumotropic virus which forms elementary bodies has been isolated from apparently normal albino Swiss mice. 2. The antigenic relationship of this virus to those of meningopneumonitis, lymphogranuloma venereum, hamster pneumonia (7), and human pneumonitis (8) was established either by cross-immunity or complement fixation or both. 3. In spite of a relationship to other viruses, the virus could be differentiated from all the others studied by certain of its properties.

PROLONGED MAINTENANCE OF SPIROCHETES AND FILTRABLE VIRUSES IN THE FROZEN STATE

1. Observations are reported on the virulence of various types of spirochetes and filtrable viruses after storage at – 787deg;C. for periods up to 3 years. 2. Five specimens of Treponema pallidum belonging to 4 different strains, and 7 specimens of T. pertenue belonging to 5 different strains were tested after storage for approximately 3 years. With one exception each specimen contained actively motile treponemes, and all specimens were highly pathogenic for rabbits. Many other specimens of these spirochetes stored for shorter periods were also tested with similar results. 3. Relapsing fever spirochetes tested after storage from 6 months to 1 year showed active motility and were virulent for mice. 4. Leptospira icterohemorrhagiae was found to be actively motile after storage for 5, 6, and 10 months. The spirochete of rat bite fever, Spirillum minus, was virulent for mice after storage for 1 year. 5. The virus of human influenza, PR8 strain, tested after storage for approximately 3 years was fatal to mice in essentially the same dilution as was the same lot of material before freezing. Similar results were obtained upon testing the virus of meningopneumonitis after storage for 3 years. The virus of lymphogranuloma inguinale was pathogenic for mice after storage for 10 months.

A LATENT VIRUS IN NORMAL MICE CAPABLE OF PRODUCING PNEUMONIA IN ITS NATURAL HOST

1. A virus capable of producing fatal pneumonia in mice has been isolated repeatedly from the lungs of certain apparently healthy mice. Not all mice carry the virus. It was obtained only from mice supplied by three breeders although mice from eight different sources were studied. 2. The virus was avirulent as it occurred in normal mouse lungs and became virulent only after serial mouse lung passage. It was strictly pneumotropic for mice and produced pneumonia when given intranasally but showed no evidence of infection when given by other routes. The virus was non-infectious for ferrets and did not become pathogenic for this species after numerous serial passages. It was also non-pathogenic for rabbits, guinea pigs, rhesus monkeys, voles, deer mice, skunks, wood-chucks, opossums, and Syrian hamsters. 3. All strains of the virus which have been tested have been immunologically identical, as indicated both by cross immunity and cross neutralization tests in mice. 4. The virus was antigenic both in mice and in rabbits and was readily differentiated from viruses of human influenza and of swine influenza by means of either cross immunity or cross neutralization tests. 5. The virus was also neutralized by about 30 per cent of normal human sera tested. 6. The virus was extremely labile, and suspensions prepared in saline or broth became inactivated within a few hours at room temperature. The addition of normal horse serum to the virus suspensions, however, exerted a definite stabilizing effect. 7. Ultrafiltration results indicated that the virus particles have a diameter of about 100 to 150 millimicrons. 8. Evidence is presented which indicates that this virus is different from other viruses which various investigators have found in normal mouse lungs.

STUDIES ON LYMPHOGRANULOMA VENEREUM : II. THE ASSOCIATION OF SPECIFIC TOXINS WITH AGENTS OF THE LYMPHOGRANULOMA-PSITTACOSIS GROUP

Toxins, which resemble in most respects bacterial endotoxins, are associated with the agents of lymphogranuloma venereum, meningopneumonitis, and mouse pneumonitis as they grow in the yolk sac of the chick embryo. They are labile and are not readily separated from the bodies of the agent. They kill mice rapidly after intravenous, and in some cases after intraperitoneal, injection but the minimal lethal dose is relatively large and, in those freshly harvested yolk sacs which have been tested, has corresponded to about 36 million infective units. Characteristic lesions are produced in all mice except those which die very rapidly, and are found especially in the liver where necrosis of the midzone of the lobule occurs. Antitoxic sera which are effective against a few lethal doses of the toxin can be produced in rabbits or chickens by using either toxin or toxoid as antigen. Such sera behave in a manner analogous to antiendotoxins against bacterial endotoxins and they do not neutralize by the law of multiple proportions. Antitoxic sera can also be obtained from human beings convalescent from at least one of these diseases. The toxins and antitoxins appear to be highly specific and they may offer a useful tool in distinguishing between different members of this closely interrelated group.

THE RECOVERY FROM PATIENTS WITH ACUTE PNEUMONITIS OF A VIRUS CAUSING PNEUMONIA IN THE MONGOOSE

1. A virus capable of producing pulmonary consolidation in the wild mongoose (Herpestes griseus) has been isolated from throat washings obtained from four patients with a clinical syndrome termed acute pneumonitis. 2. The virus was not pathogenic for ferrets, mice, guinea pigs, rabbits, monkeys, voles, hamsters, deer mice, skunks, opossums, or woodchucks. 3. The virus was filterable through Berkefeld V and N candles, was not inactivated by glycerin or by freezing and drying in vacuum, and was propagated for at least 30 serial passages on the chorio-allantoic membrane of the developing chick embryo. 4. Normal mongooses placed in contact with infected mongooses developed pulmonary consolidation. 5. The virus was neutralized by the serum of mongooses convalescent from the infection but was not neutralized by normal mongoose serum. 6. Serum of human beings convalescent from acute pneumonitis also neutralized the virus, but serum obtained from the same individuals during the acute phase of the disease failed to do so. 7. The evidence so far obtained strongly suggests that this virus is the cause of acute pneumonitis in human beings. It differs from other viruses known to cause infections of the respiratory tract in man.

FURTHER LABORATORY STUDIES ON THE CLASSIFICATION OF PSITTACOSIS-LIKE AGENTS

1. It was demonstrated by pathogenicity and latency tests in mammals and birds that variations exist among a group of viruses, isolated from several sources and producing coccoid elementary bodies resembling those of psittacosis. 2. Active cross immunity tests emphasized these differences and confirmed their significance. 3. On the basis of the present experimental evidence the psittacosis-like viruses causing atypical pneumonia in man may be classified into three groups: psittacosis, ornithosis, and human pneumonitis (strain S-F) of undetermined origin.

THE ANTIGENIC RELATIONSHIP OF THE VIRUSES OF MENINGOPNEUMONITIS AND LYMPHOGRANULOMA VENEREUM

Animals recovered from infection with the viruses of lymphogranuloma venereum, meningopneumonitis, and psittacosis, were reinoculated in crossimmunity tests with these viruses. In mice immunized by intracerebral or intranasal inoculation a reciprocal partial cross-immunity between the viruses of lymphogranuloma venereum and meningopneumonitis was demonstrated. In preliminary experiments, similar cross-immunity between the agents of lymphogranuloma venereum and psittacosis was not definitely demonstrated. Hamsters, white rats, and kangaroo rats recovered from intracerebral or intranasal infection with the virus of lymphogranuloma venereum were more resistant than normal controls to inoculation with the virus of meningopneumonitis. Sera of animals immunized with the viruses of lymphogranuloma venereum and meningopneumonitis showed cross-reactions by complement fixation with antigens of these viruses. The results indicate an antigenic relationship between the viruses of lymphogranuloma venereum and meningopneumonitis.

Use of a nested PCR-enzyme immunoassay with an internal control to detect Chlamydophila psittaci in turkeys

Background

Laboratory diagnosis of Chlamydophila psittaci, an important turkey respiratory pathogen, is difficult. To facilitate the diagnosis, a nested PCR-enzyme immunoassay (PCR-EIA) was developed to detect the Cp. psittaci outer membrane protein A (ompA) gene in pharyngeal swabs.

Methods

The fluorescein-biotin labelled PCR products were immobilized on streptavidin-coated microtiter plates and detected with anti-fluorescein peroxidase conjugate and a colorimetric substrate. An internal inhibition control was included to rule out the presence of inhibitors of DNA amplification. The diagnostic value of the ompA nested PCR-EIA in comparison to cell culture and a 16S-rRNA based nested PCR was assessed in pharyngeal turkey swabs from 10 different farms experiencing respiratory disease.

Results

The sensitivity of the nested PCR-EIA was established at 0.1 infection forming units (IFU). Specificity was 100%. The ompA nested PCR-EIA was more sensitive than the 16S-rRNA based nested PCR and isolation, revealing 105 out of 200 (52.5%) positives against 13 and 74 for the latter two tests, respectively. Twenty-nine (23.8%) out of 122 ompA PCR-EIA negatives showed the presence of inhibitors of DNA amplification, although 27 of them became positive after diluting (1/10) the specimens in PCR buffer or after phenol-chloroform extraction and subsequent ethanol precipitation.

Conclusion

The present study stresses the need for an internal control to confirm PCR true-negatives and demonstrates the high prevalence of chlamydiosis in Belgian turkeys and its potential zoonotic risk. The ompA nested PCR-EIA described here is a rapid, highly sensitive and specific diagnostic assay and will help to facilitate the diagnosis of Cp. psittaci infections in both poultry and man.

Sequencing of the Chlamydophila psittaci ompA gene reveals a new genotype, E/B, and the need for a rapid discriminatory genotyping method

Twenty-one avian Chlamydophila psittaci isolates from different European countries were characterized using ompA restriction fragment length polymorphism, ompA sequencing, and major outer membrane protein serotyping. Results reveal the presence of a new genotype, E/B, in several European countries and stress the need for a discriminatory rapid genotyping method.

Host range of chlamydiaphages phiCPAR39 and Chp3

The host range of phiCPAR39 is limited to four Chlamydophila species: C. abortus, C. caviae, C. pecorum, and C. pneumoniae. Chp3 (a newly discovered bacteriophage isolated from C. pecorum) shares three of these hosts (C. abortus, C. caviae, and C. pecorum) but can additionally infect Chlamydophila felis. The ability to support replication was directly correlated with the binding properties of the respective bacteriophages with their host species. Binding studies also show that phiCPAR39 and Chp3 use different host receptors to infect the same host cells: cell binding is sensitive to proteinase K treatment, confirming that the chlamydiaphage receptors are proteinaceous in nature.

Biological properties and cell tropism of Chp2, a bacteriophage of the obligate intracellular bacterium Chlamydophila abortus

A number of bacteriophages belonging to the Microviridae have been described infecting chlamydiae. Phylogenetic studies divide the Chlamydiaceae into two distinct genera, Chlamydia and Chlamydophila, containing three and six different species, respectively. In this work we investigated the biological properties and host range of the recently described bacteriophage Chp2 that was originally discovered in Chlamydophila abortus. The obligate intracellular development cycle of chlamydiae has precluded the development of quantitative approaches to assay bacteriophage infectivity. Thus, we prepared hybridomas secreting monoclonal antibodies (monoclonal antibodies 40 and 55) that were specific for Chp2. We demonstrated that Chp2 binds both C. abortus elementary bodies and reticulate bodies in an enzyme-linked immunosorbent assay. Monoclonal antibodies 40 and 55 also detected bacteriophage Chp2 antigens in chlamydia-infected eukaryotic cells. We used these monoclonal antibodies to monitor the ability of Chp2 to infect all nine species of chlamydiae. Chp2 does not infect members of the genus Chlamydia (C. trachomatis, C. suis, or C. muridarum). Chp2 can infect C. abortus, C. felis, and C. pecorum but is unable to infect other members of this genus, including C. caviae and C. pneumoniae, despite the fact that these chlamydial species support the replication of very closely related bacteriophages.

Ferret respiratory diseases

Ferret behavior often brings them into close contact with potential respiratory pathogens and traumatic insults. Although respiratory disease accounts for a small percentage of cases, they are usually dramatic. Acute and chronic conditions occur, and many lesions are confined to the upper or lower respiratory tree but may not involve both. Pathogens such as influenza A account for a large percentage of upper respiratory infections and often mirror the "flu" season of humans. Traumatic insults to the head and chest are relatively common and account for many veterinary visits. Numerous diseases affecting the upper and lower respiratory systems are discussed, with suggestions for diagnostics and therapies.

Molecular characterization of a bacteriophage (Chp2) from Chlamydia psittaci

Comparisons of the proteome of abortifacient Chlamydia psittaci isolates from sheep by two-dimensional gel electrophoresis identified a novel abundant protein with a molecular mass of 61.4 kDa and an isoelectric point of 6.41. C-terminal sequence analysis of this protein yielded a short peptide sequence that had an identical match to the viral coat protein (VP1) of the avian chlamydiaphage Chp1. Electron microscope studies revealed the presence of a 25-nm-diameter bacteriophage (Chp2) with no apparent spike structures. Thin sections of chlamydia-infected cells showed that Chp2 particles were located to membranous structures surrounding reticulate bodies (RBs), suggesting that Chp2 is cytopathic for ovine C. psittaci RBs. Chp2 double-stranded circular replicative-form DNA was purified and used as a template for DNA sequence analysis. The Chp2 genome is 4,567 bp and encodes up to eight open reading frames (ORFs); it is similar in overall organization to the Chp1 genome. Seven of the ORFs (1 to 5, 7, and 8) have sequence homologies with Chp1. However, ORF 6 has a different spatial location and no cognate partner within the Chp1 genome. Chlamydiaphages have three viral structural proteins, VP1, VP2, and VP3, encoded by ORFs 1 to 3, respectively. Amino acid residues in the phiX174 procapsid known to mediate interactions between the viral coat protein and internal scaffolding proteins are conserved in the Chp2 VP1 and VP3 proteins. We suggest that VP3 performs a scaffolding-like function but has evolved into a structural protein.

Continuous isolation and characterization of Chlamydia pneumoniae from a patient with diffuse panbronchiolitis

We succeeded in isolating Chlamydia pneumoniae organisms continuously from a 70-year-old man who had received chemotherapeutic treatment with low dosages of erythromycin for five years to improve diffuse panbronchiolitis (DPB). He had two episodes of acute exacerbation of DPB and a total of six strains of C. pneumoniae were isolated at different stages during the past 13 months. The morphological properties and protein profiles of the elementary bodies of all the C. pneumoniae isolates were similar to each other. Interestingly, his serological response against C. pneumoniae in immunoblotting tests was differed between two episodes. The sera collected during the first episode reacted weakly to the major outer membrane protein (MOMP), whereas those collected during the second episode reacted strongly to the 60-kDa protein and weakly to MOMP. These facts suggest that the two different episodes occurred as a result of different mechanisms. Additionally, in spite of the low antibody titer by micro-immunofluorescence test in the second episode as compared with that of the first episode, the immune response against 60-kDa immunodominant protein increased markedly in the second episode, and we suspect that the second episode was due to an allergic reaction caused by this 60-kDa protein. These findings suggest that repeated or prolonged exposure to C. pneumoniae may be associated with acute exacerbations of chronic obstructive pulmonary disease, and that the patient should be noted as a possible source of C. pneumoniae infection.

Polymerase chain reaction for the detection of Chlamydia psittaci in the feces of budgerigars

The polymerase chain reaction (PCR) targeting the ompA gene of Chlamydia psittaci was evaluated for its ability to detect chlamydiae in fecal specimens of budgerigars as compared with isolation procedures using cell culture and embryonated egg inoculations. Several procedures for PCR template DNA preparation were compared so as to determine their detection levels for chlamydiae propagated in cell culture in the presence of fecal materials. Tween-20 and proteinase K treatments followed by centrifugation of the template DNA were found to be an appropriate procedure for DNA preparation for primary PCR. Subsequent nested PCR was shown to detect 4.8 IFU/ml or 84 particles/ml of chlamydiae. Chlamydiae in 50 fecal specimens from apparently healthy budgerigars were examined by nested PCR and several other methods. Nested PCR detected chlamydiae at a higher rate (12/50, 24%) than the isolation procedure in embryonated eggs (6/50, 12%). Primary PCR combined with the isolation procedure in cell culture gave a detection rate (5/50, 10%) similar to that of isolation from embryonated eggs. Detection rates by primary PCR (1/50, 2%) and in cell culture (0%) were inferior to the other procedures.

A new primer pair for detection of Chlamydia pneumoniae by polymerase chain reaction

In order to improve the detection and identification of Chlamydia pneumoniae, new primers for polymerase chain reaction (PCR) were designed based on the DNA base sequence within the 53-kDa protein gene, which is specific for C. pneumoniae. The primers permitted the identification of 24 C. pneumoniae strains collected from different geographical locations, but no reaction was observed with C. trachomatis, C. psittaci nor C. pecorum. The primers were unable to amplify the DNA of bacteria commonly related to respiratory tract infections. The positive amplification was achieved with only 9 EBs/assay. Therefore, the new primers seem to be useful in the diagnosis of C. pneumoniae infections.

Usefulness of omp1 restriction mapping for avian Chlamydia psittaci isolate differentiation

Sixty-five avian Chlamydia psittaci isolates collected worldwide, including 27 previously characterized reference strains, were analysed by restriction mapping of the major outer membrane protein gene (omp1) obtained after DNA amplification by PCR. They were compared to 2 ruminant isolates, a feline pneumonitis and a guinea pig inclusion conjunctivitis (GPIC) isolate. According to their omp1 restriction patterns, avian strains were heterogeneous in that they exhibited 6 and 4 distinct patterns using AluI and MboII restriction enzymes, respectively, thus defining 7 groups. However, 84% of the studied strains belonged to groups 1 to 4, which share a specific fragment triplet of 411, 282 and 102 base pairs in their AluI digestion patterns. Comparisons with serological classifications showed a strict correlation and allowed further intraserovar differentiation. Furthermore, this classification based upon a single gene (omp1) roughly correlated with the data obtained by RFLP of native DNA and DNA/DNA hybridization studies. There was no host or geographic specificity in the pattern exhibited by these strains. The ruminant, feline pneumonitis and GPIC C. psittaci isolates were clearly distinguished from each other and the avian strains. Moreover, this method was clearly able to identify dubiously designated strains as well as mixtures of isolates within a single sample. In conclusion, this PCR approach based upon omp1 restriction mapping enables the differentiation of avian C. psittaci isolates and can be proposed as a taxonomic and epidemiologic tool.

Characterization of a Chlamydia pneumoniae strain isolated from a 57-year-old man

The isolation of Chlamydia pneumoniae, especially from elderly persons, is generally not easy. Recently, we succeeded in isolating a chlamydial strain, which was designated KKpn-15, from a 57-year-old man suffering from acute bronchitis. It was compared with well established strains of C. pneumoniae, C. trachomatis and C. psittaci, and its biological properties, such as the morphology of elementary bodies (EBs) and inclusions, and the immunochemistry of EB proteins, were investigated. Based on the results obtained in the present study, it was confirmed that the new chlamydial strain, KKpn-15, is a member of the C. pneumoniae strain and that the organisms of KKpn-15 are useful as an antigen for the serodiagnosis and epidemiology of C. pneumoniae infection.

Characterization of Chlamydia pneumoniae species-specific proteins immunodominant in humans

Proteins of Chlamydia pneumoniae immunodominant in humans were characterized with the sera of 13 patients who were not likely to have been exposed to C. trachomatis or C. psittaci. The serological responses among these patients were similar on a qualitative basis, but some differences were found quantitatively. However, the serological responses of the patients who were infected with C. pneumoniae differed markedly from those of two patients who were infected with C. trachomatis and two who were infected with C. psittaci and those of mice that were transtracheally infected with C. pneumoniae. Among proteins immunodominant in the patients who were infected with C. pneumoniae, a 40-kDa major outer membrane protein was genus specific and 53-, 46-, and 43-kDa proteins were species specific in their reactions with the majority of the human sera used. A few sera reacted strongly with a 73-kDa protein genus specifically. Some proteins with weak immunogenicity exhibited species specificity. An antigenic analysis with human sera and murine monoclonal antibodies against the 53-kDa protein showed that hte antigenicities were strictly conserved among the seven strains of C. pneumoniae tested. The genus-specific 73-kDa protein was solubilized with octylglucoside. All of the species-specific immunodominant proteins were solubilized with sodium dodecyl sulfate, but the genus-specific major outer membrane protein was not. These results suggest that a serological diagnosis of C. pneumoniae infection could be achieved species specifically by comparison of the serum responses to sodium dodecyl sulfate- and octylglucoside-soluble fractions.

Evaluation of the sensitivity and specificity of polymerase chain reaction test kit, AMPLICOR Chlamydia trachomatis

The sensitivity and specificity of the polymerase chain reaction (PCR) test kit, AMPLICOR Chlamydia trachomatis, were examined by the use of purified elementary bodies (EBs), cells having inclusions containing reticulate bodies alone and 20 clinical isolates. The numbers of EB and inclusion of C. trachomatis at the detection limit were determined to be approximately 2 to 4 EBs and one inclusion per assay, respectively. No reaction occurred for C. psittaci and C. pneumoniae. All clinical isolates were positively reacted in the PCR assay.

Structures of and allelic diversity and relationships among the major outer membrane protein (ompA) genes of the four chlamydial species

DNA sequences coding for 81% of the ompA gene from 24 chlamydial strains, representing all chlamydial species, were determined from DNA amplified by polymerase chain reactions. Chlamydial strains of serovars and strains with similar chromosomal restriction fragment length polymorphism had identical ompA DNA sequences. The ompA sequences were segregated into 23 different ompA alleles and aligned with each other, and phylogenetic relationships among them were inferred by neighbor-joining and maximum parsimony analyses. The neighbor-joining method produced a single phylogram which was rooted at the branch between two major clusters. One cluster included all Chlamydia trachomatis ompA alleles (trachoma group). The second cluster was composed of three major groups of ompA alleles: psittacosis group (alleles MN, 6BC, A22/M, B577, LW508, FEPN, and GPIC), pneumonia group (Chlamydia pneumoniae AR388 with the allele KOALA), and polyarthritis group (ruminant and porcine chlamydial alleles LW613, 66P130, L71, and 1710S with propensity for polyarthritis). These groups were distinguished through specific DNA sequence signatures. Maximum parsimony analysis yielded two equally most parsimonious phylograms with topologies similar to the ompA tree of neighbor joining. Two phylograms constructed from chlamydial genomic DNA distances had topologies identical to that of the ompA phylogram with respect to branching of the chlamydial species. Human serovars of C. trachomatis with essentially identical genomes represented a single taxonomic unit, while they were divergent in the ompA tree. Consistent with the ompA phylogeny, the porcine isolate S45, previously considered to be Chlamydia psittaci, was identified as C. trachomatis through biochemical characteristics. These data demonstrate that chlamydial ompA allelic relationships, except for human serovars of C. trachomatis, are cognate with chromosomal phylogenies.

Establishment of a particle-counting method for purified elementary bodies of chlamydiae and evaluation of sensitivities of the IDEIA Chlamydia kit and DNA probe by using the purified elementary bodies

To evaluate the sensitivity of commercially available test kits for detection of chlamydiae, we established a method of purifying Chlamydia trachomatis and Chlamydia pneumoniae elementary bodies (EBs). We then subjected the purified EBs, together with the purified EBs of Chlamydia psittaci, to the IDEIA Chlamydia (IDEIA) and DNA probe test kits to determine the EB numbers at the detection limits. The sensitivities of the test kits were thus compared. The results can be summarized as follows. (i) Intact EBs in the purified preparations were present at 100, 96.3, and 97% for the C. psittaci Cal 10, C. trachomatis L2/434/Bu (L2), and C. pneumoniae TW-183 strains, respectively. The preparations of the L2 and TW-183 EBs contained a few EB envelopes, which reacted with antilipopolysaccharide monoclonal antibodies, as did the intact EBs, indicating that elimination of EB envelopes is not required for testing of the IDEIA kit's sensitivity. (ii) We established a method of counting intact EBs and EB envelopes under a scanning electron microscope after sedimentation of EBs on a coverslip by centrifugation. (iii) The EB numbers per assay at the cutoff level, which is set up in the IDEIA kit, were 9.6 x 10(2), 6.5 x 10(3), and 2.5 x 10(4) for the L2, TW-183, and Cal 10 strains, respectively. When the same EB preparations were applied to the DNA probe kit, the EB number at the cutoff level was 7.5 x 10(3) per assay for the L2 strain, but no reaction occurred for the Cal 10 and TW-183 strains at any EB number, indicating that the DNA probe kit is highly specific for C. trachomatis. Although the IDEIA kit designed for detection of C. trachomatis showed a sensitivity superior to that of the DNA probe, the chlamydial species was not determined by the IDEIA kit.

Cloning and sequence analysis of the major outer membrane protein gene of Chlamydia psittaci 6BC

The gene encoding the major outer membrane protein (MOMP) of the psittacine Chlamydia psittaci strain 6BC was cloned and sequenced. N-terminal protein sequencing of the mature MOMP indicated that it is posttranslationally processed at a site identical to the site previously identified in the MOMP of Chlamydia trachomatis L2. The nucleotide sequence of the C. psittaci 6BC MOMP gene was found to be 67 to 68% identical to those of human C. trachomatis strains, 73% identical to that of Chlamydia pneumoniae IOL-207, 79% identical to that of the C. psittaci guinea pig inclusion conjunctivitis strain, GPIC, and 83% identical to that of the C. psittaci ovine abortion strain S26/3. In contrast, the 6BC sequence was found to be greater than 99% identical to the sequences reported for two strains of C. psittaci, A22/M and Cal-10 meningopneumonitis, believed to be of nonpsittacine avian origin. Monoclonal antibody analysis confirmed the nonpsittacine avian origin of A22/M but identified the Cal-10 strain from which the MOMP gene was previously sequenced as a psittacine strain. These results confirm that psittacine and nonpsittacine avian strains of C. psittaci are closely related and distinct from the mammalian guinea pig inclusion conjunctivitis and ovine abortion strains of C. psittaci.

Serotyping of Chlamydia psittaci isolates using serovar-specific monoclonal antibodies with the microimmunofluorescence test

A panel of 10 serovar-specific monoclonal antibodies that could distinguish 10 distinct serovars of Chlamydia psittaci was prepared. The panel included one monoclonal antibody to each of the 10 serovars. Monoclonal antibodies were selected for their specificity in the indirect microimmunofluorescence test. Each of the monoclonal antibodies had a titer of 1:1,280 or higher to the homologous strain, with only two showing any cross-reactivity at a dilution of 1:10. Chlamydial antigen derived from organisms growing in tissue culture of one well of a 96-well multiwell dish was usually sufficient for the serotyping of an isolate. Infected yolk sac preparations were also suitable for serotyping. The panel of monoclonal antibodies was used to serotype 55 mammalian and avian strains. All except five of the strains were successfully serotyped; these five strains are presumed to represent at least two additional serovars. The use of a panel of monoclonal antibodies in the indirect microimmunofluorescence test provides a rapid and reliable method for serotyping new isolates. Monoclonal antibodies to new serovars can easily be added to the panel.

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.

Immunotyping of Chlamydia psittaci by indirect immunofluorescence antibody test with monoclonal antibodies

Monoclonal antibodies against pigeon and budgerigar strains of Chlamydia psittaci were used to classify the immunotypes of C. psittaci strains by an indirect immunofluorescence antibody (IFA) test. Thirty-three C. psittaci strains from pigeons and 24 from budgerigars were divided into three immunotypes (P-I, P-II, and P-III) and (B-I, B-II, and B-III), respectively. Two strains from human psittacosis patients were identified as P-III and B-I, coinciding with the epidemiological evidence of each human infection. Two strains from psittacine birds, a parrot and a parakeet, were identical to the B-II immunotype. Other mammalian strains were quite distinct from avian strains in their IFA reaction with the monoclonal antibodies.

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.

Monoclonal antibody typing of Chlamydia psittaci strains derived from avian and mammalian species

A total of 77 Chlamydia psittaci strains of avian, human, and mammalian origin were grouped into four serovars with 11 monoclonal antibodies recognizing the lipopolysaccharide and the major outer membrane protein antigens. The avian and human strains, which were closely related to each other, were distinct from the mammalian strains. Immunological typing of C. psittaci with monoclonal antibodies seems practical.

Identification of conserved regions for species and subspecies specific epitopes on the major outer membrane protein of Chlamydia trachomatis

Proteolytic peptides containing the serological epitopes present on the major outer membrane protein of Chlamydia trachomatis were studied by immunoblots. Monoclonal antibodies which have been defined by micro-immunofluorescence typing as serovar-, subspecies and species-specific were utilized. The reactivity of either serovar-specific or species-specific monoclonal antibodies in the immunoblots was similar to that in the micro-immunofluorescence test. However, monoclonal antibodies which demonstrated subspecies-specific reactivity by the micro-immunofluorescence test expressed species-specific reactivity by the immunoblot method. The serovar-specific epitope which was identified on the major outer membrane protein was lost after proteolytic digestion with Staphylococcus aureus V8 protease. Immunoblots of the proteolytic fragments identified the species-specific epitope on several peptides and the subspecies-specific epitope on fewer peptides than those in which the species-specific epitope was identified. In addition, both the species and subspecies epitopes were present on the same fragments of different serovars. The data indicate that the species epitope is on conserved regions of the major outer membrane protein and is structurally clustered with a subspecies-specific epitope.

Unique ultrastructure in the elementary body of Chlamydia sp. strain TWAR

The ultrastructure of two prototype strains (TW-183 and AR-39) of Chlamydia sp. strain TWAR was described. The TWAR elementary body (EB) demonstrated a unique morphology and structure distinct from those of other chlamydial organisms. It was pleomorphic but typically pear shaped. The average size was 0.38 micron, with a long axis of 0.44 micron, a short axis of 0.31 micron, and a ratio of the long to the short axes of 1.42. The cytoplasmic mass was round, with an average diameter of 0.24 micron. There was a large periplasmic space. Small, round electron-dense bodies (0.05 micron in diameter), which were attached to the cytoplasm by a stringlike structure, were seen in the periplasmic space. These features are in contrast to those of other chlamydiae, which are typically round with a narrow or barely discernible periplasmic space. The TWAR reticulate body (RB) was morphologically and structurally similar to those of other Chlamydia species, having an average diameter of 0.51 micron and being circular in shape. The ultrastructural observations of the intracellular growth of TWAR in HeLa cells revealed that TWAR underwent the same developmental cycle as do other chlamydiae, i.e., transformation of EB to RB, multiplication by binary fission, and maturation by transformation of RB to EB via the intermediate-form stage.

Identification of a new group of Chlamydia psittaci strains called TWAR

A new group of Chlamydia psittaci strains has been identified. They are called TWAR after the laboratory designation of the first two isolates. Twelve strains were isolated from pharyngeal swabs of different persons with acute respiratory disease in Seattle, Wash., during 1983 to 1986. One strain was obtained from the eye of a child during the trachoma vaccine study in Taiwan in 1965. Nine strains were characterized in this study. TWAR organisms formed intracytoplasmic inclusions in HeLa cells which were morphologically typical of C. psittaci and iodine stain negative (contained no glycogen). Immunological analysis with various chlamydia-specific monoclonal antibodies revealed that TWAR strains belong to the genus Chlamydia, are distinct from C. trachomatis, and are serologically unique among C. psittaci. All TWAR strains so far isolated appear identical serologically. TWAR organisms grew poorly in egg and cell cultures and demonstrated low virulence to mice by intracerebral, intranasal, and intravenous inoculation. Available data suggest that the TWAR strain is a primary human pathogen.

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.

Location of polysaccharide on Chlamydia psittaci by silver-methenamine staining and electron microscopy

Previous serological studies have indicated that the group antigen of chlamydial organisms is composed of an acidic polysaccharide and a lipid component. The present study was undertaken in an effort to locate this polysaccharide complex by use of electron microscopy and a silver-methenamine marker. The meningopneumonitis strain of Chlamydia psittaci was propagated in HeLa-M cell culture. Organisms were purified by differential centrifugation, treatment with Genetron, and by gel filtration. After fixation and embedding, sections were obtained for electron microscopy. Sections were stained for carbohydrates with silver-methenamine. A double layer of regularly spaced silver grains of uniform size was observed at the periphery of the sectioned organisms tracing the contours of the surface membrane (cell wall). This intensity of staining was observed only when sections were oxidized with periodate prior to silver-methenamine staining. Prior treatment with 1% sodium deoxycholate resulted in a significant reduction in staining. It is considered probable that the periodate-sensitive polysaccharide found at the periphery of the organisms represents, or is a component of, the group antigen of these organisms.