Antigenic and immunogenic differences in lipopolysaccharides of Escherichia coli J5 vaccine strains of different origins.

Escherichia coli strain J5 mutants of various origins have often been used as vaccines for induction of cross-reactive, cross-protective antibodies directed against the lipopolysaccharide (LPS) core region. The antigenic composition of LPS from J5 strains of different origin, i.e. strains J5(U), J5(UK), J5(2877) and J5(a), was investigated using monoclonal antibodies (mAbs) reactive only with LPS of a given chemotype, i.e. one specific for the incomplete E. coli core of the Rc chemotype, a second mAb reactive only with the E. coli R3 complete core, and a third specific for the O-antigen of E. coli serovar O111. The LPS of strains J5(U) and J5(a) is almost exclusively composed of LPS of the Rc chemotype, LPS of the J5(UK) strain is composed of Rc LPS and R3 complete core, while LPS of the J5(2877) strain contains Rc, R3 complete core and O-antigen. Growth of the bacteria in medium supplemented with galactose led to increased expression of complete core. The immune responses to the various strains were investigated. Antiserum to the J5 strain expressing the largest amount of R3 core [J5(UK)] had much higher anti-R3 LPS antibody titres compared to antiserum to the other strains. mAb 53, representative of the anti-R3 response to J5 strains containing complete core, bound to those E. coli LPS expressing the R3 core. Thus, the R3 LPS, present in some J5 vaccine strains is at least partially responsible for some of the cross-reactivities exhibited by some anti-J5 antisera.(ABSTRACT TRUNCATED AT 250 WORDS)