Safety and immunogenicity of a polyvalent Klebsiella capsular polysaccharide vaccine in humans.

A polyvalent Klebsiella vaccine composed of six serotypes of capsular polysaccharides (K2, K3, K10, K21, K30, and K55) was developed and its safety and immunogenicity evaluated in humans. Highly purified capsular antigens were treated in 0.1 N NaOH in 95% ethanol to detoxify trace amounts of contaminating lipopolysaccharide (LPS). The vaccine was nontoxic and nonpyrogenic for animals. A total of 40 individuals received either 25 or 50 micrograms of each represented antigen subcutaneously. Reactions to vaccination, where noted, were transient and mild in nature. An immunizing dose of 50 micrograms of each antigen (300 micrograms total) elicited a fourfold or greater immunoglobulin G (IgG) response to all vaccine antigens in greater than 80% of vaccinees. Generally, the serospecificity of the antibody response was limited to those capsular antigens included in the vaccine. IgG isolated from the serum of vaccinees was found to be highly protective against fatal experimental Klebsiella K2 burn wound sepsis indicating that the functional antibody is elicited following vaccination.