Use of Haemophilus influenzae b Vaccines in Evaluating Immunodeficiency

Abstract

Impaired antibody responses to polysaccharide compared to protein antigens are observed in several human humoral immunodeficiency disorders. In some of these disorders it is unclear whether there is an underlying developmental or fixed defect. Low IgG2 subclass levels may be associated with poor antibody response to polysaccharide antigens, but their association is probably not causal but secondary to an underlying immunoregulatory defect. Evidence of an immunoregulatory defect in some of these disorders comes from the observation that protein-conjugated polysaccharide vaccines can induce antibody responses in contrast to the polysaccharide vaccine. The FDA-licensed Haemophilus influenzae b polysaccharide and conjugated polysaccharide vaccine have proven useful in evaluating patients with these defects. Although the Haemophilus influenzae b polysaccharide is no longer licensed, it is available under IND status for this purpose.