Diversity of Vi-related antigens in the microcapsule of Salmonella typhi.

Two new antigenic acidic polysaccharides, Vi-P and Vi-C, were isolated from the microcapsule of Salmonella typhi by a very mild procedure. The antigens were purified to serological homogeneity, and it was found that each of them shares with Vi antigen one of its two serological determinants (a different one in each case). One of the antigens Vi-C, was also isolated from Escherichia coli B, which is not a Vi-producing strain.