Background and aims of the study: Based on the concept of chronic persistent infections with Chlamydia pneumoniae among variable stressors for aortic valve degeneration, the study aim was to assess the presence of chlamydial heat shock protein (cHSP) 60 and its human homologue (hHSP60) in diseased valvular tissue.
Methods: Surgical specimens of high-grade stenosed, native (n = 33) and bioprosthetic (n = 10) aortic valves were examined immunohistochemically for the localization of cHSP60, hHSP60 and macrophages (CD68), supplemented by polymerase chain reaction (PCR) and electron microscopy to prove microbial presence.
Results: Degenerated valves showed specific immunostaining of cHSP60 in 27 cases (65%), of hHSP60 in 26 (63%), and of CD68 in 36 (84%). Both HSP60 homologues were predominantly detected in valvular fibrosa, consistently co-localized with macrophages and, quantitatively, showed a strong correlation (r = 0.81, p < 0.001). Presence of C. pneumoniae was demonstrated by PCR in a subset of 11 of 18 valves (61%). Microbial persistence was confirmed by ultrastructural analysis. Degenerated prosthetic valves revealed markedly higher macrophage infiltration and cHSP60 signaling compared with degenerated native valves (each p < 0.05).
Conclusion: Beyond detection of C. pneumoniae, the present data on co-localization and valvular predilection sites (fibrosa) of both HSP60 homologues indicate the presence of chronic persistent C. pneumoniae infection as well as regional stressor effects, and suggest their involvement in native and prosthetic valve degeneration.