Escherichia coli strain J5 mutants of various origins have often been used as vaccines for induction of crossreactive, 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 Re 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 Re 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. The present findings may explain some of the discrepant outcomes reported for cross-protection studies with J5 antisera, where J5 strains of various origins grown under different culture conditions have been used as vaccines and where LPS or bacteria expressing various core types have been used for challenge.
To evaluate the suitability of Bacillus subtilis as a production host of heterologous proteins for pharmaceutical purposes, we assessed the biological activity of this bacterium and its major cell envelope components, lipoteichoic acid (LTA) and peptidoglycan–teichoic acid complex (PG–TA) in several eukaryotic effector assays. LTA and PG–TA were found to be non-toxic for mice and guinea-pigs in a short-term toxicity assay. PG–TA was weakly pyrogenic and weakly mitogenic. Both LTA and PG–TA acted as immunologic adjuvants in mice and when injected in mice, also caused an increase in the number of granulocyte–monocyte colony-forming cells in the bone marrow probably via stimulation of production of granulocyte–macrophage colony-stimulating factor.