IMPAIRED NATURAL IMMUNITY TO PNEUMOLYSIN DURING HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION IN THE UNITED-STATES AND AFRICA

Human immunodeficiency virus (HIV) infection is associated with a sign ificantly increased incidence of pneumococcal pneumonia and concomitan t bacteremia. We hypothesized that the predisposition of HIV-infected patients to invasive pneumococcal infection may be related, in part, t o an impaired immune response to the pneumococcal antigen pneumolysin (PLY) because PLY facilitates bacterial invasion. We measured serum an ti-PLY antibodies in two separate populations of HIV-infected and HIV- seronegative controls, using both an enzyme-linked immunosorbent assay method and a functional assay of antibody inhibition of PLY-induced h emolysis and cytotoxicity. HIV-infected patients in the United States had significantly lower titers of anti-PLY antibodies by both methods than did seronegative control subjects. Moreover, HIV-infected patient s in Kenya who later developed pneumococcal bacteremia also had signif icantly lower anti-PLY antibody levels at baseline compared with seron egative control subjects. We conclude that lower baseline levels of an tibodies to PLY are associated with the higher incidence of bacteremic pneumococcal infections among HIV-infected patients.