Decreased serum opsonic activity against Streptococcus pneumoniae in Human Immunodeficiency Virus–infected Ugandan adults

Abstract

Type-specific immunoglobulin G (IgG) to pneumococcal capsular polysaccharide (CPS) and opsonic activity against Streptococcus pneumoniae were evaluated in serum samples from 36 Ugandan adults with community acquired pneumonia and 58 asymptomatic Ugandan adults with or without human immunodeficiency virus type 1 (HIV-1) infection. The levels of serum IgG to CPS were significantly higher in HIV-1–infected subjects than in HIV-uninfected subjects. Serum samples from HIV-1–infected subjects that had lower IgG titers demonstrated higher opsonic activity against type 3 (titers of 7) and type 9 (titers of 7–11) pneumococcal strains. Plasma HIV-1 load also correlated inversely with serum opsonic activity against these strains, and peripheral blood CD4+ lymphocyte numbers also tended to correlate with serum opsonic activity in asymptomatic HIV-1–infected adults. Our findings suggest that the opsonic activity of type-specific IgG is impaired in the serum of HIV-1–infected African adults, which may expose them to a serious risk of invasive pneumococcal infections.