The cell surface of Propionibacterium acnes: effect of specific chemical modifications on the ability of vaccines to produce splenomegaly in mice.

The surface of Propionibacterium acnes, VPI 0009, was studied using microelectrophoresis following chemical treatments intended to modify specific charged groups. The effect of specific modifications on ability of cells to induce splenomegaly, an indicator of stimulation of the reticuloendothelial system, was also determined. There was little difference between pH mobility curves of P. acnes VPI 0009 and other strains of propionibacteria which were not able to stimulate the reticuloendothelial system. Amino and carboxyl groups were found to be the sole ionizable groups at the cell surface and modification of these groups caused a substantial decrease in the ability of cells to stimulate the reticuloendothelial system. No phosphate groups were detected. Evidence for two types of amino groups was found: one type was present on protein moieties and their modification did not affect ability to stimulate the reticuloendothelial system, whereas modification of the other type, which was present on carbohydrate moieties, caused a loss of ability to stimulate the reticuloendothelial system. Mild oxidation with sodium metaperiodate caused abolition of reticuloendothelial system stimulation, but had no effect on surface charged groups, indicating it was acting on the unsubstituted linkages of sugar residues. Treatments with strong acids caused abolition of ability to stimulate the reticuloendothelial system and this was accompanied by release of polysaccharide material.