Objective: We used reverse transcription-polymerase chain reaction (RT-PCR) assays to assess expression of genes from Chlamydia trachomatis in synovial tissues of patients with reactive arthritis (ReA)/Reiter's syndrome (RS) to determine viability/metabolic activity of the bacterium in joints of infected patients.
Methods: Synovial biopsies were obtained from 18 patients with ReA, RS, or other arthritides; nucleic acids from 16 samples were PCR positive for chlamydial chromosomal DNA. RT-PCR assays targeting primary transcripts from C. trachomatis rRNA operons, and mRNA from the bacterial omp1, hsp60, glyQS, and r-protein S5 and L5 genes, were used to characterize viability/metabolic activity. Host actin mRNA was assessed as control in each sample preparation.
Results: RT-PCR of host cell actin mRNA in the 18 patient samples confirmed the quality of all RNA preparations. RNA from 14/16 PCR positive samples was positive by RT-PCR for chlamydial rRNA primary transcripts. Each of these same 14 samples was also RT-PCR positive in assays targeting glyQS, r-protein S5 and L5, and hsp60 mRNA. However, none of the 14 samples showing chlamydial rRNA and mRNA was positive for omp1 transcripts.
Conclusion: Synovial chlamydia are viable/metabolically active, since primary rRNA transcripts and mRNA from chlamydial genes specifying components of the bacterial protein synthetic system were present in most patient samples assayed. Expression of omp1, encoding the major outer membrane protein, is strongly attenuated in persistently infecting synovial chlamydia, while that of hsp60, specifying a highly immunogenic heat shock protein of the organism, is not downregulated.