ANTIBODY CLASS AND SUBCLASS RESPONSES TO PNEUMOCOCCAL POLYSACCHARIDESFOLLOWING IMMUNIZATION OF HUMAN IMMUNODEFICIENCY VIRUS-INFECTED PATIENTS

Antibodies of the IgM class and IgG2 and IgA2 subclasses are prominent in responses to pneumococcal polysaccharides (PPS) but may be decreas ed in human immunodeficiency virus (HIV)-infected patients, among whom invasive pneumococcal disease is common. After immunization of HIV-in fected and -seronegative subjects with pneumococcal vaccine, the numbe r of PPS-specific antibody-secreting cells (ASC) producing IgM was sig nificantly lower among HIV-infected subjects, whereas PPS-specific IgG and IgA ASC were more comparable. The subclass distribution of PPS-sp ecific IgG2-producing (similar to 80%) and IgA2-producing (similar to 50%) ASC and antibodies in serum were similar. However, before immuniz ation, the proportions of PPS-specific IgG2 for both serotypes 8 and 1 4 in baseline sera from HIV-infected patients were significantly decre ased compared with controls. Thus, the response to PPS among HIV-infec ted patients may be characterized by lower levels of specific IgG2 bef ore immunization and prominent defects in IgM responses soon after sti mulation.