Human immunodeficiency virus (HIV)-infected patients in Malawi have a high incidence of pneumococcal pneumonia. Since IgG2 is known to be protective against Streptococcus pneumoniae, we measured pneumococcal-specific IgG (IgG-pn), IgG1 (IgG1-pn), and IgG2 (IgG2-pn) in bronchoalveolar lavage (BAL) fluid to see if a quantitative deficit might explain this observation. IgG-pn, IgG1-pn, and IgG2-pn were measured to determine if there was a change in the ratio of immunoglobulin isoforms. Fifty-two BAL samples were collected from 26 HIV-infected HAART-naive Malawi patients and 26 HIV-negative volunteers. IgG-pn, IgG1-pn, and IgG2-pn were determined using sandwich ELISA techniques. ELISA wells were coated with pneumococcal vaccine (Pneumovax 23). Biotinylated IgG, IgG1, and IgG2 were used as the secondary antibodies. Data are expressed as ng/mL BAL ± SEM. Total IgG-pn was elevated in HIV+ patientss compared with HIV− patients (p = .0098), as were IgG2-pn (p = .0002) and IgG1 (p = .0067). HIV-infected patients did not have a statistically significant difference in IgG1/IgG2 ratio compared with HIV-negative patients (p = .3804). In conclusion, despite the high incidence of invasive pneumococcal disease in Malawi, HIV-infected Malawians had higher total IgG-pn-, IgG1-pn-, and IgG2-pn-specific antibodies in BAL than uninfected subjects. We speculate that this may be related to elevated proinflammatory cytokines in HIV BAL, including IFN-γ, which is known to stimulate IgG2 production in particular. These results suggest that the high incidence of pneumococcal pneumonia in Malawi is not due to a quantitative deficit in IgG levels but rather points to potential functional antibody defects.
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