Serological cross-reaction between intact and chemically modified lipopolysaccharides of O1 Vibrio cholerae Inaba and non-O1 V. cholerae bio-serogroup Hakata.

Serological cross-reaction of intact as well as chemically modified LPS from O1 Vibrio cholerae 569B (Inaba) with non-O1 V. cholerae Hakata LPS, which contain alpha(1-->2)-linked N-acetyl perosamine-homopolymer constituting their O polysaccharide chain, was studied by passive hemolysis test by using their LPS as antigen for sensitizing sheep red blood cells (SRBC). The N-deacylation of the alpha(1-->2)-linked linear 3-deoxy-tetronyl perosamine-homopolymer constituting the O polysaccharide chain in 569B LPS resulted in virtual elimination of their serological reactivity with both homologous Inaba and heterologous Hakata antisera. Furthermore, when the resultant NH2 groups of the N-deacylated perosamine-homopolymers in 569B LPS were N-acylated with acetyl, propionyl or butanoyl groups, they markedly recovered the serological reactivity to a marked extent, in particular, their pronounced cross-serological reactivity with heterologous Hakata antiserum. These results are believed to be compatible with the interpretation that the Inaba antigen factor C possessed by the two bacteria studied is related to the common occurrence of the N-acyl groups, regardless of what the acyl groups are, residing in the perosamine residues of the perosamine-homopolymers constituting the O polysaccharide chain of their LPS.