Salmonella serogroup BO
antigen specific octasaccharides were isolated from phage P22 endo-rhamnosidase cleaved S. typhimurium O-
polysaccharide chains. The
O-antigen 4, 12 specific octasaccharide, covalently linked to different
carrier proteins, elicited both in rabbits and mice
antibodies with specificity for the S. typhimurium
O-antigens. Mice vaccinated with these octasaccharide-conjugates were protected against challenge
infections with O-antigenic homologous Salmonella. The importance of humoral immunity directed against the
O-antigen determinants was evidenced by the protective capacity of passively transferred antioctasaccharide
antibodies and also of
antibodies elicited by an
O-antigen 4 specific 3-O-alpha-abequopyranosyl-alpha-D-mannopyranoside-bovine
serum albumin conjugate. Also a purified outer
membrane protein preparation mediated, in vaccinated mice, protection against challenge
infection with S. typhimurium. Coupling of the octasaccharide to the outer
membrane proteins resulted in a
vaccine which protected mice against a double as high challenge dose than could either of the two components. In conclusion, the use of O-antigenic
oligosaccharides covalently attached to outer
membrane protein preparations raises the possibility of producing defined and atoxic
vaccines against
enterobacterial infections.