Phenotypic variation in epitope expression of the Neisseria gonorrhoeae lipooligosaccharide

Abstract

Gonococcal lipooligosaccharides (LOSs) are a series of antigenically complex heteropolymers. To investigate whether all members of clonally selected populations of Neisseria gonorrhoeae express antigenically similar LOS, we studied gonococcal strains 4505 and 220 with monoclonal antibodies 6B4 and 3F11 which have specificity for different oligosaccharide epitopes on the same or comigrating LOS unit(s) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fluorescent-antibody and immunoelectron microscopy studies indicated that all members of the clonally selected populations were not homogenous for the epitopes these antibodies recognized. Fluorescence-activated cell sorting studies of 3F11-coated strain 220 indicated that the density of epitope expression was a function of time of growth. The population could be separated into two broad groups corresponding to organisms staining strongly or weakly for the 3F11 epitope, and the epitope density decreased during the late-log and stationary phases of growth. Sequentially staining organisms on Formvar grids with 6B4 and 3F11, followed by staining with either 5- or 15-nm colloidal gold spheres conjugated to goat anti-mouse immunoglobulin M demonstrated the following populations of cells among organisms derived from a single clone: organisms which stained for both 6B4 and 3F11 epitopes and organisms which stained for either 6B4 epitopes alone or 3F11 epitopes alone. Immunofluorescence microscopy studies with rhodamine and fluorescein goat anti-mouse immunoglobulin M conjugates sequentially staining organisms on Formvar grids with 3F11 and 6B4 also demonstrated these three populations. Analysis of LOS preparations made over the last 5 years indicated no change in serotype antigen concentration or in sodium dodecyl sulfate-polyacrylamide gel electrophoresis migration pattern. These studies indicate that while clonally selected strains of Neisseria gonorrhoeae undergo phenotypic variation at the epitope level, the impact of this variation on the total LOS of the population has little overall effect on its antigenic or physicochemical properties.

Lipooligosaccharides (LOS) of Neisseria gonorrhoeae and Neisseria meningitidis have components that are immunochemically similar to precursors of human blood group antigens. Carbohydrate sequence specificity of the mouse monoclonal antibodies that recognize crossreacting antigens on LOS and human erythrocytes.

“…5 % was arbitrarily selected as the positive cutoff value. As each LOS is a mixture of different LOS components, relative binding reflects the relative proportion of LOS bearing the mAb-recognized epitope among all the LOS made by the population of that strain from which the LOS was extracted (64,65). Numbers in parentheses indicate minor serotypes (<50% inhibition of typing serum) (20) .…”

Repeat‐associated phase variable genes in the complete genome sequence of Neisseria meningitidis strain MC58

“…modifications, which affect adhesion (Stephens and McGee, 1981;Virji et al, 1991Virji et al, , 1993bRudel et al, 1992;Kupsch et al, 1993;McNeil et al, 1994;Nassif et al, 1994;Waldbeser et al, 1994;Jennings et al, 1998;Weiser et al, 1998), several surface proteins including Opas, Opc, PorA and iron binding proteins which have roles in adhesion, formation of surface pores and nutrient acquisition (Poolman et al, 1980;Stern et al, 1984;Sparling et al, 1986;Achtman et al, 1988;Tommassen et al, 1990;Bhat et al, 1991;Virji et al, 1992;1993a;Hopman et al, 1994;Sarkari et al, 1994;van der Ende et al, 1995;Chen et al, 1996;Lewis et al, 1999;Schryvers and Stojiljkovic, 1999) , and lipopolysaccharide (LPS) (Apicella et al, 1987;Schneider et al, 1988;Weel et al, 1989;van Putten and Robertson, 1995;Jennings et al, 1999). An increased rate of phase variation, associated with the loss of the Dam methylase, has been associated with some invasive disease isolates (Bucci et al, 1999).…”

Molecular analysis of lipooligosaccharide biosynthesis in Neisseria gonorrhoeae

“…Interestingly, FA5100 did not revert to reactivity with MAb 2-1-L8 at a detectable frequency. This is unusual, since phenotypic changes in LOS are seen in other gonococcal strains (1,24). We have analyzed this strain extensively and never found an MAb-reactive revertant of FA5100 (unpublished observations).…”

“…Gonococcal LOSs are heterogeneous glycolipids without repeating oligosaccharides (9) that show wide antigenic diversity among different strains (13). In studies using molecular sieve chromatography, fluorescence-activated cell sorter analysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) it was shown that, within a strain, LOS components differ in their relative concentrations and in the antigens they express (1,21,23,24). Furthermore, LOS expression undergoes antigenic variation (24) similar to that seen for pilus and Pll expression (27), although the mechanism that modulates this phenomenon is unknown.…”