SALICYLATE-ENHANCED EXPOSURE OF KLEBSIELLA-PNEUMONIAE SUBCAPSULAR COMPONENTS

The capsular polysaccharide (CPS) of Klebsiella pneumoniae is an impor tant virulence factor. Salicylate, which inhibits CPS production, was used to expose subcapsular antigens and components that may play an im portant role in host defense. Salicylate treatment greatly increased p hagocytosis of five 01 serotypes by human polymorphonuclear leukocytes ,vith normal rabbit serum and rabbit antisera against purified 01 lipo polysaccharide (01LPS) as opsonins (p<0.01 or <0.05). Similar results were obtained with rabbit antiserum against a non-encapsulated isogeni c strain. To further determine how salicylate increases susceptibility to phagocytosis, the binding of monoclonal antibodies against 01LPS o r the LPS core and the binding of complement component C3b were measur ed by ELISA. The data indicate that salicylate reduced the barrier of CPS in serotypes 01:K1, 01:K10, and 01:K16 and unmasked subcapsular an tigenic components in serotypes 01:K2 and 01:K66 so that bound opsonin s could react with receptors on phagocytes. Serum bactericidal assays supported this conclusion. Therefore, decapsulating agents such as sal icylate accentuate phagocytosis of K. pneumoniae by making subcapsular antigens and components accessible to immune and nonimmune host defen ces and vaccination with subcapsular antigens may exhibit optimal prot ection against lethal infection when combined with salicylate therapy.