Comparative PCR-based restriction fragment length polymorphism analysis of the plasmid gene orf3 of Chlamydia trachomatis and Chlamydia psittaci

Infection of human monocytes by Chlamydia pneumoniae and Chlamydia trachomatis: an in vitro comparative study

Background

An increasing number of studies suggest that chlamydiae can infect immune cells. The altered immune cell function could contribute to the progression of several chronic inflammatory diseases.

The aim of this study was to comparatively evaluate Chlamydia pneumoniae (CP) and Chlamydia trachomatis (CT) interactions with in vitro infected human blood monocytes.

Results

Fresh isolated monocytes were infected with viable CP and CT elementary bodies and infectivity was evaluated by recultivating disrupted monocytes in permissive epithelial cells.

The production of reactive oxygen and nitrogen species was studied in the presence of specific fluorescent probes. Moreover, TNF-α, INF-α, INF-β and INF-γ gene expression was determined.

CT clearance from monocytes was complete at any time points after infection, while CP was able to survive up to 48 hours after infection. When NADPH oxydase or nitric oxide synthase inhibitors were used, CT infectivity in monocytes was restored, even if at low level, and CT recovery’s rate was comparable to CP one.

CT-infected monocytes produced significantly higher levels of reactive species compared with CP-infected monocytes, at very early time points after infection. In the same meanwhile, TNF-α and INF-γ gene expression was significantly increased in CT-infected monocytes.

Conclusions

Our data confirm that CP, but not CT, is able to survive in infected monocytes up to 48 hours post-infection. The delay in reactive species and cytokines production by CP-infected monocytes seems to be crucial for CP survival.

Evaluation of the new test VERSANT CT/GC DNA 1.0 assay for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in urine specimens

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) are the two most common sexually transmitted bacterial infections in developed countries. The purpose of the present study was evaluating a new system for CT/GC detection in urine specimens. A total of 700 urine specimens were obtained from patients attending the STD Outpatients Clinic of St. Orsola University Hospital, Bologna, Italy. Samples were tested by VERSANT® CT/GC DNA 1.0 Assay (Siemens Healthcare Diagnostics Inc., Tarrytown, NY), a multiplex Real-Time PCR assay, for simultaneous CT/GC detection. Results obtained by VERSANT assay were compared with those obtained by culturing genital secretions of the same patients. Moreover, urine specimens testing positive in VERSANT assay were retested by in-house PCR assays, used as confirmatory tests. VERSANT® CT/GC DNA 1.0 Assay performed with 99.4% and 99.2% of specificity for GC and CT detection, respectively, whereas sensitivity was 100% both for CT and GC. Culture methods were 100% specific, but far less sensitive than VERSANT assay. VERSANT® CT/GC DNA 1.0 Assay demonstrated to be a highly sensitive and specific technique for CT/GC detection.

Chlamydia psittaci genetic variants differ in virulence by modulation of host immunity

BACKGROUND

Psittacosis is a zoonosis caused by Chlamydia psittaci and is characterized by severe pneumonia and systemic infection. We sought to determine the basis of the 1000-fold difference in lethal dose of 2 C. psittaci 6BC strains in mice.

METHODS

Genomes of the strains were sequenced. Mice were infected intraperitoneally and the growth kinetics, immune responses, and pathology were compared.

RESULTS

The 2 strains differed by the presence of a 7.5-kb plasmid in the attenuated strain and 7 nonsynonomous single-nucleotide polymorphisms between the chromosomes, including a serine/threonine protein kinase gene pkn5. The plasmid was cured from the attenuated strain, but it remained nonlethal. Strains did not differ in growth kinetics in vitro or in vivo. Infection with the attenuated strain led to influx of activated macrophages with relatively minor organ damage. In contrast, the virulent strain caused an influx of nonactivated macrophages, neutrophils, and significant end organ damage. Mice infected with the virulent strain survived challenge when coinfected with either the plasmid-positive or plasmid-negative attenuated strain, indicating that an active process elicited by the attenuated strain reduces inflammation and disease.

CONCLUSIONS

C. psittaci modulates virulence by alteration of host immunity, which is conferred by small differences in the chromosome.

Chlamydia trachomatis serovar distribution and other concurrent sexually transmitted infections in heterosexual men with urethritis in Italy

The distribution of Chlamydia trachomatis serovars among 157 heterosexual male patients with urethritis and the presence of coinfections with other sexually transmitted infections were studied. One hundred seventeen (74.5%) patients, with a mean age of 33.7 years, were Italians, whereas 40 (25.5%) were immigrants coming from eastern European countries, Africa, and South America. All the immigrants and 82 (70.0%) Italian patients reported sex with prostitutes. Out of 157 patients, 73 (46.5%) were found positive for C. trachomatis in urethral secretions and eight different C. trachomatis serovars were identified. The most common serovars were E (n = 18; 24.7%), D (n = 15; 20.5%), G (n = 14;19.2%), and F (n = 12; 16.4%). The sequencing data showed a high degree of conservation of the omp1 gene. Thirty-six (46.7%) out of the 73 C. trachomatis-positive patients were coinfected with another sexually transmitted infection. The most common coinfection was gonorrhoea detected in 22 (30.1%) patients, followed by condyloma in eight (8.2%) patients, syphilis in five (6.8%), and HIV in three (4.1%).

Serological response to pgp3 protein in animal and human chlamydial infections

Specific antibodies to plasmid-encoded protein pgp3 are known to be encountered in human Chlamydia (C.) trachomatis infections. In order to verify whether antibodies to this protein could be developed in animals infected with plasmid-carrying chlamydial strains, 454 animal sera were examined using a home-made pgp3 protein ELISA and Western blots (WB) of recombinant pgp3 protein from Chlamydophila (Cp.) psittaci. Likewise, 50 human sera were tested by ELISA and WB of recombinant pgp3 from C. trachomatis. The reactivity against pgp3 protein was compared to the reactivity against chlamydial elementary bodies (EBs) detected by microimmunofluorescence (MIF) test. The presence of pgp3-specific antibodies was demonstrated in most ducks and pigeons with Cp. psittaci infection detected by MIF, as well as in the majority of symptomatic cats and pigs infected with Cp. felis and C. suis, respectively, which reacted at high titres to Cp. felis and C. suis EBs by MIF. Moreover, most of the sera collected from patients with C. trachomatis culture-confirmed infection and seropositive to C. trachomatis by MIF, presented antibodies specific to C. trachomatis pgp3 recombinant protein. Therefore, pgp3 protein could be a useful marker of chlamydial infections in animals, as well as in humans.

Antibodies from women urogenitally infected with C. trachomatis predominantly recognized the plasmid protein pgp3 in a conformation-dependent manner

Background

C. trachomatis organisms carry a cryptic plasmid that encodes 8 open reading frames designated as pORF1 to 8. It is not clear whether all 8 pORFs are expressed during C. trachomatis infection in humans and information on the functionality of the plasmid proteins is also very limited.

Results

When antibodies from women urogenitally infected with C. trachomatis were reacted with the plasmid proteins, all 8 pORFs were positively recognized by one or more human antibody samples with the recognition of pORF5 protein (known as pgp3) by most antibodies and with the highest titers. The antibody recognition of the pORFs was blocked by C. trachomatis-infected HeLa but not normal HeLa cell lysates. The pgp3 fusion protein-purified human IgG detected the endogenous pgp3 in the cytosol of C. trachomatis-infected cells with an intracellular distribution pattern similar to that of CPAF, a chlamydial genome-encoded protease factor. However, the human antibodies no longer recognized pgp3 but maintained recognition of CPAF when both antigens were linearized or heat-denatured. The pgp3 conformation is likely maintained by the C-terminal 75% amino acid sequence since further deletion blocked the binding by the human antibodies and two conformation-dependent mouse monoclonal antibodies.

Conclusion

The plasmid-encoded 8 proteins are both expressed and immunogenic with pgp3 as the most immunodominant antigen during chlamydial infection in humans. More importantly, the human anti-pgp3 antibodies are highly conformation-dependent. These observations have provided important information for further understanding the function of the plasmid-encoded proteins and exploring the utility of pgp3 in chlamydial diagnosis and vaccination.