Bactericidal Antibody Response of Normal Human Serum to the Lipooligosaccharide of Neisseria gonorrhoeae

Abstract

Human antibody to lipooligosaccharide (LOS) from pooled normal human serum (NHS) and human immune serum globulin (HISG) was isolated by affinity chromatography from a Sepharose column to which Escherichia coli strain J-5 LOS had been conjugated. Fractionated antibody was tested for bactericidal activity against serum-resistant Neisseria gonorrhoeae strains 1W31, WR220, or 838 or serum-sensitive strains 1W31R or 1074. By enzyme-linked immunosorbent assay the eluate of antibody to LOS contained IgM, IgA, and IgO antibodies to both 1W31 and 1W31R LOS. The IgM fraction from NHS was bactericidal at 30 min for strains 1W31R and 1074 but failed to kill strains 1W31 and 838. An IgO fraction from HISO was bactericidal for strains 1W31 and WR220 yet failed to kill strain JW31R. The IgA fraction from NHS did not kill either strain JW31 or 1W31R. Blocking experiments indicated that IgA or IgG failed to prevent IgM-mediated killing of strain 1W31R, whereas IgA blocked the IgO-mediated killing of strain JW31.