HUMAN CELL-MEDIATED IMMUNE-RESPONSES TO ANTIGENIC FRACTIONS OF SALMONELLA-TYPHI

The proliferative responses of peripheral blood mononuclear cells of 1 0 subjects that had typhoid fever, and healthy volunteers without hist ory of typhoid fever or immunization against disease, were analysed wi th antigen fractions from two protein extracts of Salmonella typhi. Fr actions from each extract were separated gy sodium dodecyl sulphate-po lyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis, transferr ed to nitrocellulose filters by electroblotting and processed to obtai n antigen-bearing nitrocellulose particles for use in lymphocyte cultu res. Although the individual proliferative responses were heterogenous we identified two main immunogenic regions of 29-32 x 10(3) MW for bo th extracts. Even though there was no one particular antigenic fractio n capable of stimulating lymphocytes from all individuals with a previ ous history of typhoid fever, the combination of three fractions 29-32 , 41-45, 63-71 x 10(3) MW could be stimulatory for cells of 90% of the se individuals. Also, four subjects that did not respond to unfraction ated antigens gave proliferative responses to several fractions of the same extract. We have identified the main immunogenic fractions of S. typhi that might play a role during typhoid infection and postinfecti on immunity, and merit further purification and characterization.