Heterogeneity of molecular size and antigenic expression within lipooligosaccharides of individual strains of Neisseria gonorrhoeae and Neisseria meningitidis.

We determined the Mr of neisserial lipooligosaccharides (LOS) by using discontinuous sodium dodecyl sulfate-polyacrylamide gel electrophoresis, minimal loading concentrations, and Salmonella isogenic rough mutant LOS as Mr standards. Salmonella LOS were resolved into three components. The migration distance of each component was linearly related to its theoretical Mr (r = 0.99). Neisserial LOS also contained multiple components whose calculated Mr ranged from 3,200 to 7,100. The relative abundance of components and their MrS varied greatly among strains. Meningococcal LOS were composed almost exclusively of two closely migrating components; gonococcal LOS were more heterogeneous. LOS from a gonococcus selected for resistance to a Pseudomonas pyocin contained only a single component that was different from and of intermediate Mr among the three components of the parent strain. A monoclonal antibody directed against the meningococcal L8 LOS epitope was used to determine whether heterogeneity of antigen expression reflected Mr heterogeneity. Single components of the L8 meningococcal LOS and of the LOS of 3 of 19 gonococcal strains bound the monoclonal antibody. Gonococcal LOS components that expressed the L8 epitope were of a similar Mr (4,800). Smaller components of these same LOS did not express the epitope.