O-ANTIGENIC DETERMINANTS IN SALMONELLA SPECIES OF SEROGROUP C-1 ARE EXPRESSED IN DISTINCT IMMUNOCHEMICAL POPULATIONS OF CHAINS

The O-antigenic specificities found amoung salmonellae of serogroup C- 1 are 0:6(1),7,0:6(1),6(2),7 and 0:6,7,14, as defined by classical ser ology. Factor 0:7 is the group-wide determinant while factors 0:6(1), 0:6(2) and 0:14 are found in some strains but not others. Strains of t he 0:6,,7 specificity are subject to lysogenic conversion by phages 6( 1) and 14 to the 0:6(1).7 and 0:6,7,14 specificities, respectively. To further delineate antigenic complexity and serological relationships among strains of this serogroup monoclonal antibodies (mAbs) were gene rated against the 0:6,,6,,7 polysaccharide of Salmonella thompson, Fiv e mAbs of either the 0:6, or the 0:6, specificities did not bind 0:6,7 .14 strains or LPS, showing that the 0:6 determinant in these strains is neither 0:6, nor 0:6,. Thus antigenic conversion of 0:6,,7 strains by phage 14 is accompanied by addition of 0:14 as well as loss of 0:6, . Three mAbs which demonstrated group-wide reactivity, and were thus s pecific for 0:7, recognized clearly separable epitopes hereby defined as sub-specificities, 0:7,, 0:7, and 0:7,. Immunoblotting of mAbs agai nst electrophoretically resolved LPS showed that factors 0:6, and 0:6, are expressed only in LPS molecules of high molecular mass whereas 0: 7, and 0:7, are expressed only in. relatively low-molecular-mass chain s. These results are consistent with the expression of different antig enic determinants in structurally distinct subpopulations of 0 chains. The implication of the existence of distinct subpopulation of chains is that the published structure of the 0:6,7 repeat unit is not fully representative of the O-antigenic structure of this group.