Antigenic analysis of Barber's protein antigen prepared from Salmonella typhi and demonstration of protein-specific antibodies in sera of typhoid patients.

A crude protein antigen (Barber's antigen) was prepared from Salmonella typhi by mild extraction with veronal buffer followed by repeated precipitation with trichloracetic acid according to the method of Barber. From serological studies and polyacrylamide gel electrophoresis, Barber's antigen was found to be highly heterogeneous and contain both the lipopolysaccharide and Vi antigens in addition to the protein antigens. Nevertheless antibodies specific to the proteins in the Barber's antigen were demonstrated in typhoid patients' sera by radioimmunoassay, indicating that proteins were also a major antigenic component of S. typhi and might play a role during typhoid infection.