Comparative genomic analysis of Chlamydia trachomatis oculotropic and genitotropic strains

Chlamydia trachomatis infection is an important cause of preventable blindness and sexually transmitted disease (STD) in humans. C. trachomatis exists as multiple serovariants that exhibit distinct organotropism for the eye or urogenital tract. We previously reported tissue-tropic correlations with the presence or absence of a functional tryptophan synthase and a putative GTPase-inactivating domain of the chlamydial toxin gene. This suggested that these genes may be the primary factors responsible for chlamydial disease organotropism. To test this hypothesis, the genome of an oculotropic trachoma isolate (A/HAR-13) was sequenced and compared to the genome of a genitotropic (D/UW-3) isolate. Remarkably, the genomes share 99.6% identity, supporting the conclusion that a functional tryptophan synthase enzyme and toxin might be the principal virulence factors underlying disease organotropism. Tarp (translocated actin-recruiting phosphoprotein) was identified to have variable numbers of repeat units within the N and C portions of the protein. A correlation exists between lymphogranuloma venereum serovars and the number of N-terminal repeats. Single-nucleotide polymorphism (SNP) analysis between the two genomes highlighted the minimal genetic variation. A disproportionate number of SNPs were observed within some members of the polymorphic membrane protein (pmp) autotransporter gene family that corresponded to predicted T-cell epitopes that bind HLA class I and II alleles. These results implicate Pmps as novel immune targets, which could advance future chlamydial vaccine strategies. Lastly, a novel target for PCR diagnostics was discovered that can discriminate between ocular and genital strains. This discovery will enhance epidemiological investigations in nations where both trachoma and chlamydial STD are endemic.     

Comparison of Gen-probe transcription-mediated amplification, Abbott PCR, and Roche PCR assays for detection of wild-type and mutant plasmid strains of Chlamydia trachomatis in Sweden

The clinical performance of two nucleic acid amplification assays targeting the cryptic plasmid and two assays targeting rRNA molecules in Chlamydia trachomatis was examined. First-catch urine samples from Malmoe, Sweden, were tested for C. trachomatis with the Abbott real-time PCR assay m2000 and an in-house PCR for the new variant strain of C. trachomatis with a deletion in the cryptic plasmid. Aliquots of the urine samples were sent to Aarhus, Denmark, and further examined with the Roche COBAS Amplicor CT (RCA) PCR, the Gen-Probe Aptima Combo 2 assay (AC2) targeting the C. trachomatis 23S rRNA, and the Aptima C. trachomatis assay (ACT) targeting the 16S rRNA molecule. A positive prevalence of 9% (163/1,808 urine samples examined) was detected according to the combined reference standard. The clinical sensitivity and specificity of the four assays were as follows: for ACT, 100% (163/163) and 99.9% (1,643/1,645), respectively; for AC2, 100% (163/163) and 99.6% (1,640/1,645); for m2000, 68.7% (112/163) and 99.9% (1,644/1,645); for RCA, 63.8% (104/163) and 99.9% (1,643/1,645). The two Gen-Probe assays detected all mutant strains characterized by the in-house PCR as having the deletion in the cryptic plasmid, whereas the Roche and the Abbott PCRs targeting the plasmid were both unable to detect the plasmid mutant. The difference in clinical sensitivity between the plasmid PCR assays m2000 and RCA, on the one hand, and the rRNA assays AC2 and ACT, on the other, could be attributed almost exclusively to the presence of the plasmid mutant in about one-quarter of the Chlamydia-positive samples examined.     

Purification of Chlamydia trachomatis strains in mixed infection by monoclonal antibody neutralization.

A Chlamydia trachomatis D* serovariant strain was found to be mixed with an F serovar strain in a clinical specimen. By using a monoclonal antibody which neutralizes serovar F infectivity in hamster kidney cells, the D* variant strain was enriched until it could be cloned by limiting dilution. This newly described neutralization enrichment procedure can be used to purify a C. trachomatis serovar present in small numbers in a mixed culture or, potentially, to identify nonneutralizable mutants.     

High-resolution genotyping of Chlamydia trachomatis strains by multilocus sequence analysis

Genotyping of Chlamydia trachomatis is limited by the low sequence variation in the genome, and no adequate method is available for analysis of the spread of chlamydial infections in the community. We have developed a multilocus sequence typing (MLST) system based on five target regions and compared it with analysis of ompA, the single gene most extensively used for genotyping. Sequence determination of 16 reference strains, comprising all major serotypes, serotypes A to L3, showed that the number of genetic variants in the five separate target regions ranged from 8 to 16. The genetic variation in 47 clinical C. trachomatis isolates of representative serotypes (14 serotype D, 12 serotype E, 11 serotype G, and 10 serotype K strains) was analyzed; and the MLST system detected 32 variants, whereas 12 variants were detected by using ompA analysis. Specimens of the predominant serotype, serotype E, were differentiated into seven genotypes by MLST but into only two by ompA analysis. The MLST system was applied to C. trachomatis specimens from a population of men who have sex with men and was able to differentiate 10 specimens of one predominant ompA genotype G variant into four distinct MLST variants. To conclude, our MLST system can be used to discriminate C. trachomatis strains and can be applied to high-resolution molecular epidemiology.     

Salpingitis in mice induced by human strains of Chlamydia trachomatis

Human strains of Chlamydia trachomatis were inoculated unilaterally into the genital tracts of female TO, CBA, CBA/nu and C3H mice via the intrauterine route or under the ovarian bursa. Inflammatory changes were not seen in the oviducts or uterus of mice given two laboratory-adapted LGV serovars (L1 and L2), although chlamydiae were recovered from the lower genital tract. However, salpingitis and endometritis occurred after each of three chlamydial strains (serovars D and E) had been inoculated. Oviduct inflammation was seen for up to 6 weeks after inoculation but reached maximum severity usually after about 2 weeks, the lumen sometimes being occluded by exudate and necrotic debris. Pathological changes were seen often in both oviducts indicating canalicular spread of the organisms through the uterus. Pre-treatment of the mice with progesterone had an enhancing effect in that the lesions developed more rapidly; such treatment, in halting the oestrous cycle, probably made a larger number of target cells available for more efficient infection. Involvement of the oviduct on the uninoculated side occurred more rapidly in T-cell impaired nude mice than in immunologically normal mice, although there was little or no effect on the severity of the oviductal changes. There was evidence that the susceptibility of different strains of mice to chlamydial salpingitis varied. Thus, inflammatory changes in C3H mice were more severe than in TO mice and the changes in C3H and CBA strains were longer lasting than those in TO mice. This suggests that a possible genetic predisposition in the human situation should not be ignored. Finally, one chlamydial strain of low passage produced more severe salpingitis in mice than another strain of similar passage. By analogy different chlamydial strains may not be of equal pathogenicity in the human situation.     

Salpingitis in mice induced by human strains of Chlamydia trachomatis.

Human strains of Chlamydia trachomatis were inoculated unilaterally into the genital tracts of female TO, CBA, CBA/nu and C3H mice via the intrauterine route or under the ovarian bursa. Inflammatory changes were not seen in the oviducts or uterus of mice given two laboratory-adapted LGV serovars (L1 and L2), although chlamydiae were recovered from the lower genital tract. However, salpingitis and endometritis occurred after each of three chlamydial strains (serovars D and E) had been inoculated. Oviduct inflammation was seen for up to 6 weeks after inoculation but reached maximum severity usually after about 2 weeks, the lumen sometimes being occluded by exudate and necrotic debris. Pathological changes were seen often in both oviducts indicating canalicular spread of the organisms through the uterus. Pre-treatment of the mice with progesterone had an enhancing effect in that the lesions developed more rapidly; such treatment, in halting the oestrous cycle, probably made a larger number of target cells available for more efficient infection. Involvement of the oviduct on the uninoculated side occurred more rapidly in T-cell impaired nude mice than in immunologically normal mice, although there was little or no effect on the severity of the oviductal changes. There was evidence that the susceptibility of different strains of mice to chlamydial salpingitis varied. Thus, inflammatory changes in C3H mice were more severe than in TO mice and the changes in C3H and CBA strains were longer lasting than those in TO mice. This suggests that a possible genetic predisposition in the human situation should not be ignored. Finally, one chlamydial strain of low passage produced more severe salpingitis in mice than another strain of similar passage. By analogy different chlamydial strains may not be of equal pathogenicity in the human situation.     

Screening of volunteer students in Yaounde (Cameroon,Central Africa) for Chlamydia trachomatis infection and genotyping of isolated C. trachomatis strains

The prevalence of Chlamydia trachomatis infection was 3.78% out of 1,277 volunteer students screened by direct fluorescence assay and Cobas Amplicor PCR. The infection was associated with the nonuse or inconsistent use of condoms in women (P = 0.026) and a previous sexually transmitted infection in men (P = 0.023). The most frequent genotypes determined by sequencing the omp1 genes of 25 clinical isolates were E (44%) and F (20%), and some strains harbored mutations, but E genotype strains did not.     

IL-6对沙眼衣原体K血清型诱导细胞凋亡的影响

目的探讨IL-6对沙眼衣原体(Ct)K血清型诱导细胞凋亡的影响。方法用ELISA双抗体夹心法检测衣原体感染细胞分泌IL-6水平变化;用流式细胞仪(FCM)检测凋亡细胞百分率,DNA琼脂糖凝胶电泳检测细胞凋亡“梯状带”,观察anti-IL-6抗体拮抗IL-6活性对沙眼衣原体K血清型感染的McCoy细胞凋亡的影响。结果沙眼衣原体K血清型感染细胞分泌IL-6水平明显升高(P<0.05);感染同时加anti-IL-6抗体组在感染36、48、60 h细胞凋亡百分率均显著高于相应的无感染对照组及沙眼衣原体K血清型感染组(P<0.01),且呈时间依赖性(P<0.01)。结论IL-6可部分抑制沙眼衣原体K血清型诱导的McCoy细胞凋亡。     

Reactivation of Chlamydia trachomatis lung infection in mice by cortisone.

To study the latency, chronicity, and recurrent nature of chlamydial infection, we attempted to reactivate Chlamydia trachomatis lung infection in mice by immunosuppressive therapy with cortisone. Mice were treated with subcutaneous injections of cortisone acetate (125 mg/kg) every other day, starting on day 14 after intranasal inoculation of C. trachomatis serotype B (TW-5). C. trachomatis was recovered from the lungs beginning day 6 after the start of cortisone treatment until the end of the observation period on day 12 of treatment. Overall, the reactivation was successful in 8 of 55 mice treated with cortisone, in contrast to 0 of 41 inoculated, untreated mice (P = 0.009) and 0 of 35 uninoculated, treated mice. Cortisone treatment affected the ability of peritoneal exudate cells to respond to migratory inhibition after exposure to purified whole organisms of C. trachomatis serotype B (TW-5) but had little effect on serum antibody titers, indicating a possible role for cellular immunity in resistance against C. trachomatis infection in the lung.     

Chlamydia trachomatis infection inhibits both Bax and Bak activation induced by staurosporine

We have previously shown that Chlamydia trachomatis inhibits host cell apoptosis and blocks mitochondrial cytochrome c release. We now report that activation of both Bax and Bak, two proapoptotic members of the Bcl-2 family that regulate mitochondrial cytochrome c release, was inhibited in chlamydia-infected cells. This observation has provided new information on the mechanisms of chlamydial antiapoptotic activity.     

Experimental infection of the marmoset genital tract with Chlamydia trachomatis.

A strain of Chlamydia trachomatis isolated in McCoy cells from the urethra of a patient suffering from non-gonococcal urethritis was inoculated into the vagina of 8 female marmosets. Chlamydiae were isolated repeatedly for 10-42 days from the lower genital tract of 7 of the marmosets. Six of the infected animals developed an acute inflammatory reaction in the genital tract and chlamydial inclusions in epithelial cells were seen in smears from 2 of them. In addition, each of 6 infected marmosets examined developed humoral antibodies to C. trachomatis. In contrast, 3 control animals inoculated intravaginally with chlamydia-free McCoy cells showed no evidence of chlamydial infection. Since the marmoset is small and easily bred in captivity, it should provide a useful model for studying the mechanisms of chlamydial pathogenicity.     

Identification of Chlamydia trachomatis antigens by use of murine T-cell lines.

Chlamydia-specific short-term T-cell lines were used in conjunction with immunoblot techniques to examine Chlamydia trachomatis proteins for T-cell-stimulatory activity. This study was undertaken because of the known role of T cells in the resolution and pathogenesis of chlamydial infections. Therefore, determination of which chlamydial proteins are T-cell antigens and whether they evoke protective immunity or contribute to immunopathology is crucial. Immune lymph node cells were stimulated with whole chlamydial organism (elementary body) to derive predominantly CD4+ T-cell lines. Proteins from the elementary body and the outer membrane and cloned proteins were examined for antigenicity with these T-cell lines in a proliferation assay. Although a majority of the elementary body protein fractions were positive in this assay, only four of the outer membrane fractions were stimulatory. The cloned major outer membrane protein and outer membrane protein 2 were stimulatory in the assay and may account for the reactivity in three of the four positive outer membrane fractions. The C. trachomatis heat shock protein 60, examined because of its putative role in causing delayed-type hypersensitivity, was found to stimulate the CD4+ T cells. This approach with short-term T-cell lines with polyclonal reactivity was sensitive and specific in identifying chlamydial proteins as T-cell antigens.     

聚合酶链反应检测丝虫病患者泌尿道沙眼衣原体及解脲支原体的研究

本文采用聚合酶链反应方法,检测了５０ 例丝虫病患者尿中沙眼衣原体（ＣＴ） 及解脲支原体（ＵＵ）ＤＮＡ,同时选择３０ 例正常人作为对照。结果显示,丝虫病患者尿中ＣＴＤＮＡ、ＵＵ ＤＮＡ 和两者混合感染检出率分别为３０ ％ 、２５ ％ 和２０ ％ ,高于正常对３６３％ （Ｐ＜０－０１）,ＣＴ及ＵＵ 感染与病人的病情、病程有一定的关联。提示乳糜尿的发生、发展与泌尿道ＣＴ 和ＵＵ感染有关。     

Characteristics of Chlamydia trachomatis infection in hospitalized infants with lower respiratory tract infection.

BACKGROUND AND PURPOSE: To study the epidemiology, presentation and laboratory findings of Chlamydia trachomatis pneumonia in hospitalized infants younger than 6 months. METHODS: Between January 2001 and December 2005, infants younger than 6 months admitted to the children's medical center of Taipei Veterans General Hospital with the diagnosis of acute bronchiolitis, bronchopneumonia or pneumonia were prospectively studied. Chest radiograph findings were reviewed in all patients. Basic laboratory examinations performed included white blood cell count and eosinophil count. C. trachomatis was detected via enzyme-linked immunosorbent assay antigen test and the titers of immunoglobulin G and immunoglobulin M by indirect immunoperoxidase assay. RESULTS: A total of 60 infants, 32 males and 28 females, were included. C. trachomatis infection was detected in 30% of patients (18/60). The median age was 2.5 months (range, birth to 6 months). Fever was not detected in 72% of patients (13/18). Only 22% (4/18) of these patients had the characteristic staccato cough. The mean duration of symptoms before admission was 8 days (range, 1 day to 2 months). Rhinorrhea was a prodromal symptom in 67% (12/18) of patients, with a mean pre-onset duration of 7 days (range, 1 to 14 days). Eighty three percent (15/18) of the patients had tachypnea, with a mean duration of 3.2 days (range, 1 to 7 days). Conjunctivitis was noted before admission in 6 patients (33%). Only peripheral eosinophils showed statistically significant difference between Chlamydia-positive and -negative disease (p=0.046), and may be clinically useful in cases of suspected C. trachomatis infection. Mixed infection with other pathogens including adenovirus, respiratory syncytial virus, Mycoplasma pneumoniae, cytomegalovirus and Streptococcus pneumoniae was found in 27% (5/18) of patients. CONCLUSIONS: C. trachomatis is not infrequent and plays an important role in infants younger than 6 months old hospitalized due to lower respiratory tract infection.     

Induction of protective immunity against a Chlamydia trachomatis genital infection in three genetically distinct strains of mice

To establish the feasibility of inducing a protective immune response against a chlamydial genital infection in animals with different genetic backgrounds, groups of C3H/HeN (H-2k), BALB/c (H-2d) and C57BL/6 (H-2b) mice, were immunized intranasally with elementary bodies (EB) of the Chlamydia trachomatis mouse pneumonitis biovar. Following the intranasal immunization strong Chlamydia-specific humoral and cell-mediated immune (CMI) responses were detected in the three strains of mice. Eight weeks following immunization the animals were challenged with C. trachomatis in the genital tract. Vaginal cultures showed that the three strains of mice immunized with EB were significantly protected in comparison to the sham immunized animals. To determine the ability of this immunization protocol to protect against infertility six weeks after the genital challenge the animals were mated. Mice of the three strains immunized with EB showed significant protection as demonstrated by the number of animals that were fertile, and the number of embryos present in their uterine horns, in comparison to the sham immunized mice.