Comparative protective activity of human monoclonal and hyperimmune polyclonal antibody against group B streptococci.

Group B streptococcal (GBS) infections cause significant morbidity and mortality in neonates and compromised hosts, who usually lack opsonic antibody to their infecting strain. Unfortunately, most conventional immunoglobulin preparations possess little GBS antibody. The protective activity of a human monoclonal antibody (HuMAb) and a human hyperimmune intravenous immunoglobulin (HivIg) were evaluated against these organisms and compared with a conventional intravenous immunoglobulin (ivIg). The HuMAb and the HivIg possessed significant protective activity (50%-95%) against extremely virulent strains of types I, II, and III GBS in doses as low as 4-20 mg/kg. In contrast, the conventional ivIg had little protective activity against some of these strains in doses as high as 500 mg/kg. The opsonic activity of the HuMAb and HivIg also usually exceeded that of the conventional ivIg. These studies suggest HivIg or HuMAb with markedly enhanced specific activity may provide optimal immunotherapy for GBS infections.