Immunochemical characterization of an Ogawa-Inaba common antigenic determinant of Vibrio cholerae O1

Cholera remains an important public health problem in many parts of the wor ld and the availability of an effective cholera vaccine is important for th e prevention of cholera in the countries affected by this disease. Despite the apearance in 1992 of a new serogroup, O139, of Vibrio cholerae, most of the cholera outbreaks are still caused by V, cholerae O1 biotype El Tor. V accine trials in Asia from 1968 to 1971, and studies of the production of s erotype-specific antiserum in rabbits and of the protective activity of mon oclonal antibodies against diarrhoeal disease in neonatal mice, have led to the conclusion that the Ogawa serotype contains a specific antigenic deter minant whereas the Inaba serotype contains a different antigenic determinan t that cross-reacts with the Ogawa serotype. By studying the binding of ant i-Ogawa monoclonal antibodies to synthetic oligosaccharide fragments mimick ing the Ogawa O-specific polysaccharide, it has been shown that the termina l monosaccharide, bearing the 2-O-methyl group in the O-specific polysaccha ride, is most probably the serotype-specific determinant for the Ogawa stra in. However, study of the binding of a monoclonal antibody recognizing both Ogawa and Inaba serotypes suggested partial recognition of the core as wel l as of the O-specific polysaccharide of the LPS of V, cholerae O1, To furt her characterize this antigenic determinant that is common to the Ogawa and Inaba serotypes, the core and the O-specific polysaccharide linked to the core of V, cholerae O1 LPS were purified by preparative electrophoresis. Th e O-specific polysaccharide linked to the core was subjected to periodate o xidation to destroy sugars from the core. Binding studies of these purified saccharide fragments to a monoclonal antibody which is protective in mice and specific to the antigenic determinant common to Ogawa and Inaba serotyp es showed that both the core and the O-specific polysaccharide are involved in this common antigenic determinant. This explains how the presence or th e absence of the Ogawa-specific antigenic determinant would lead to the exp ression of two independent antigenic determinants of V. cholerae O1, one sp ecific to the Ogawa serotype and the other common to both Ogawa and Inaba s erotypes.