MACROMOLECULAR ORGANIZATION OF RECOMBINANT YERSINIA-PESTIS F1 ANTIGENAND THE EFFECT OF STRUCTURE ON IMMUNOGENICITY

Yersinia pestis, the causative organism of plague, produces a capsular protein (fraction 1 or Fl antigen) that is one of the major virulence factors of the bacterium. We report here the production, structural a nd immunological characterisation of a recombinant Fl antigen (rF1). T he rF1 was purified by ammonium sulfate fractionation followed by FPLC Superose gel filtration chromatography. Using FPLC gel filtration chr omatography and capillary electrophoresis, we have demonstrated that r F1 antigen exists as a multimer of high molecular mass. This multimer dissociates after heating in the presence of SDS and reassociation occ urs upon the removal of SDS. Using circular dichroism, we have monitor ed the reassociation of monomeric rF1 into a multimeric form. Mice imm unised with monomeric or multimeric rF1 develop similar immune respons es, but mice immunised with monomeric rF1 were significantly less well protected against a challenge of 1 x 10(6) cfu of Y. pestis than mice immunised with multimeric rF1 (1/7 compared with 5/7). The significan ce of this result in terms of the structure and the function of rF1 is discussed. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.