Objective: To evaluate the prevalence of Chlamydia pneumoniae antibodies in an Italian population of HIV-infected and uninfected individuals in relation to the presence of HIV risk factors.
Design and methods: A prospective evaluation of C. pneumoniae microimmunofluorescence immunoglobulin (Ig) G and IgM titres, in relation to sex, age, HIV clinical stage, and the presence of different HIV acquisition risk factors.
Setting: The Department of Infectious and Tropical Diseases, a secondary and tertiary care institution in the 'La Sapienza' University of Rome, during 1994 and 1995.
Participants: HIV-infected and uninfected subjects (n = 322), all of them without respiratory symptoms.
Results: A statistically significant higher C. pneumoniae seroprevalence was found to be related, by multivariate analysis, to sex, age, and presence of HIV risk factor, but not to the presence of HIV infection itself. Among HIV-positive subjects, C. pneumoniae seroprevalence appeared to decrease with absolute CD4+ cell count and was low in Centers for Disease Control and Prevention (CDC) stage C of HIV infection. Furthermore, high C. pneumoniae IgG titres (> or = 1:512) were not found in subjects with CDC stage C disease or in those with low CD4+ cell count (< 200 x 10(6)/l).
Conclusion: C. pneumoniae seroprevalence is higher in injecting drug users and in subjects with promiscuous heterosexual activity. A previous report of a higher C. pneumoniae seroprevalence among HIV-1-infected subjects (in relation to the normal population) was probably due to the presence of HIV risk factor and not to the HIV infection itself. HIV-infected subjects seem to have progressively lost their C. pneumoniae IgG antibodies in middle and advanced stages of HIV infection. High C. pneumoniae IgG titres are rarely found in advanced stage HIV-infected patients.