Chlamydia pneumoniae immunoreactivity in coronary artery plaques of patients with acute coronary syndromes and its relation with serology

Background An association between Chlamydia pneumoniae (Cpn) infection and coronary artery disease has been reported and examined by different techniques. However, its immunoreactivity in coronary artery plaques of patients with acute coronary syndrome (ACS) and its relation with serology are less well defined. Methods We divided 40 coronary plaque specimens from 40 patients who underwent thrombectomy or directional coronary atherectomy into an ACS group (n = 22) and a non-ACS group (n = 18). Cpn in specimens was detected immunohistochemically and compared quantitatively. Serum immunoglobulin (Ig)A and IgG antibodies to Cpn and high-sensitivity C-reactive protein (hs-CRP) were measured. The relation between serology and immunohistochemical analysis was also investigated. Results Cpn immunopositive cells per square millimeter (Cpn+ cells/mm2) in the ACS group were significantly more numerous than in the non-ACS group (median 7.44 vs 1.50, P = .0018). Cpn IgA seropositivity rates and titers in the ACS group were significantly higher than those in the non-ACS group (86.3% vs 22.2%, P = .0002; median titer 1.403 vs 0.545, P = .003). There were no differences in IgG antibodies between the 2 groups. The hs-CRP values (in milligrams per liter) in ACS group were significantly higher than in non-ACS group (median 2.8 vs 1.2, P = .0019). Serum IgA titers in patients with at least 5 Cpn+ cells/mm2 in the specimens were significantly higher than in patients with fewer Cpn+ cells (median 1.52 vs 0.86, P = .026). There was no difference in serum hs-CRP values in patients with more Cpn+ cells but a trend to an increase. Conclusion Immunohistology frequently detected Cpn in coronary plaques; Cpn+ cells were more prevalent in plaques associated with ACS, and Cpn IgA but not IgG titers were increased with ACS and with high densities of Cpn+ cells within plaque.