Antipneumolysin antibody titers in HIV-seropositive injection drug users before and after pneumococcal bacteremia

Lower baseline antipneumolysin antibody (alpha -PLY) levels have been found in populations with a higher incidence of pneumococcal infections. To dete rmine whether predisease alpha -PLY titer is associated with invasive pneum ococcal disease in HIV-seropositive injection drug users (IDU), we utilized a prospective cohort of IDU in Baltimore to compare alpha -PLY titers befo re bacteremia in 28 HIV-seropositive IDU cases with alpha -PLY titers in 56 matched (CD4 and seroconversion date) HIV-seropositive IDU control subject s and 28 matched (calendar time) HIV-seronegative IDU control subjects rema ining free of pneumococcal disease. We also compared the post infection fol d-rise of alpha -PLY titers in cases relative to the change in alpha -PLY t iters in control subjects during the same interval; alpha -PLY titers were measured using quantitative ELISA, and functional activity was assessed usi ng antihemolysin assays. Predisease alpha -PLY titer did not differ between cases (66 units) and HIV-seropositive control subjects (70 units, p = 0.56 ) or HIV-seronegative control subjects (80 units, p = 0.10). There was a si gnificant difference in fold-rise of alpha -PLY titers postdisease between cases (1.18) and HIV-seronegative control subjects (0.76), p = 0.03. Baseli ne alpha -PLY titers do not differ significantly between HIV-seropositive I DU who develop pneumococcal bacteremia from HIV-seropositive and HIV-serone gative IDU control subjects remaining free of severe pneumococcal disease.