Enhanced Antigenicity and Immunogenicity of Gonococcal Pilus - Lipopolysaccharide Conjugates

摘要

A gonococcal pilus vaccine protein was chemically conjugated to lipopolysaccharide (LPS) derived from serum-sensitive gonococcal strain F-62 and serum resistant strain 7134. Prior to the coupling reaction, the LPS were treated with alcoholic NaOH solution to release ester-linked, lipid A fatty acids. The available carboxyl groups of deacylated LPS (D-LPS) were converted into N-hydroxysuccinimide active esters and allowed to condense with free amino groups of gonococcal pili. As measured by the Limulus lysate assay, the D-LPS exhibited 1,000 fold reduced toxicity compared with native LPS. Quantitative carbohydrate analysis revealed 1.0 and 1.5 mol of F-62 and 7134 D-LPS bound per pilus subunit, respectively. Solid-phase radioimmunoassay inhibition data revealed that conjugation restored, as well as enhanced, LPS antigenicity lost during the detoxification reaction. Also solid-phase radioimmunoassay inhibition data indicated that the conjugates fully retained their capacity to bind with anti-pilus antibody. In complement-dependent serum bactericidal systems, the pilus-LPS conjugates, as well as D-LPS, were as effective as native LPS in inhibiting killing of gonococci. These serological studies indicate that the chemical techniques employed did not appreciably affect antigenic determinants of either pili or LPS. Immunization of mice with the pilus-LPS (F-62) conjugate induced an early response in anti-LPS antibody level similar to that of native LPS.