High prevalence of Chlamydia pneumoniae infection in cyclosporin A-induced post-transplant gingival overgrowth tissue and evidence for the possibility of persistent infection despite short-term treatment with azithromycin.

BACKGROUND Cyclosporin A (CsA) induces gingival overgrowth (GO) in up to a quarter of CsA-treated renal transplant recipients. A short-term therapy with azithromycin effectively reduces GO, indicating a possible involvement of microorganisms in the pathogenesis of CsA-induced GO. We aimed to determine if there could be any relationship between infection with Chlamydia pneumoniae and GO pathogenesis. In addition, we determined the long-term persistence rate of C. pneumoniae infection in residual GO tissue when azithromycin treatment failed to eliminate GO. METHODS Chlamydia pneumoniae IgG and IgM antibody titres were measured by microimmunofluorescence technique in sera of kidney recipients with (n = 11) and without (n = 89) GO. GOs were rated and gingivectomies were performed before treatment with 500 mg of azithromycin for 3 days and at months 6 and 12 post-treatment when C. pneumoniae titres were re-evaluated. Nested polymerase chain reaction was performed to identify C. pneumoniae-specific DNA in GO tissues. Results of C. pneumoniae antibody titres from patients with GO were compared with pair-matched controls without GO. RESULTS Chlamydia pneumoniae IgM titres were elevated in five of 11 patients with GO and in none without GO, whereas the difference of C. pneumoniae IgG titres between patients with GO and pair-matched controls did not reach significance (P<0.57). Chlamydia pneumoniae-specific DNA was found in 10 of 11 GO tissue samples pre-treatment. Azithromycin therapy effectively reduced GO and C. pneumoniae IgM titres. In residual GO, C. pneumoniae-specific DNA remained detectable after 1 year in all GO tissue samples despite azithromycin treatment. The C.pneumoniae IgM titres correlated with GO scores. CONCLUSION Chlamydia pneumoniae infection is highly prevalent in CsA-induced GO. The infection can persist over a long period in residual GO despite short-term azithromycin therapy. The results indicate that CsA immunosuppression enhances C. pneumoniae infection rates in non-cardiovascular tissue.