Bactericidal activity of the sera of rabbits immunized with Vibrio cholerae O1 whole cell extract

Abstract

24Vibrio cholerae serotype O1 causes diarrhea in many developing countries around the world. In most cases, cholera patients pose some sorts of immunity against the naturally occurring infection. In the present study, the bactericidal activity of the sera of rabbit immunized with whole cell extract of Vibrio cholerae O1 was investigated. The protein profile of the serotype exhibited 20 types of proteins of distinguished molecular weights. The western blot analysis revealed at least 10 proteins to be immunogenic. Interestingly, decomplementation of the sera was found to abolish the bactericidal activity. The bactericidal activity of non immunized rabbit sera was also investigated and the results revealed that the immunized sera were more effective than that of non immunized one.Bactericidal activity of the sera of rabbits immunized with Vibrio cholerae O1 whole cell extract assay Cholera is an acute, diarrheal illness caused by the infection of the intestine with the bacterium Vibrio cholerae. Serological classification of V. cholerae was first described by Gardner & Venkatraman in 1935 (1), on the basis of differences in the sugar composition of the heat-stable surface somatic "O" antigen. Currently the organism is classified into 206 "O" serogroups (2, 3).Cholera is usually characterized as a life-threatening secretory diarrhea induced by cholera enterotoxin (CT), secreted by virulent type of V. cholerae. Subsequent purification and structural analysis of the toxin showed the toxin consist of an A subunit and 5 smaller identical B subunits (4). The A subunit possesses a specific enzymatic function and acts intracellularly, raising the cellular level of cAMP and thereby changing the net absorptive tendency of the small intestine to one of net secretion. The B subunit helps the toxin to bind the eukaryotic cell receptor, ganglioside GM1. The binding of CT to epithelial cells is enhanced by neuraminidase. Apart from the obvious significance of CT in cholera pathogenesis, it is now clear that the production of CT by V. cholerae is important from the perspective of a serogroup having the potential to cause epidemics (5). This has become particularly evident since the emergence of V. cholerae O139. A dynamic 4.5 kb core region, termed the virulence cassette (6), has been identified in toxigenic V. cholerae O1 and O139 but is not found in non-toxigenic strains.Although both V. cholerae O1 and O139 elaborate a Received 12 February 2012/Accepted 21 April 2012 similar cholera toxin (7), they differ in the composition of their surface components as V. cholerae O139 produces a polysaccharide capsule (8). Thus previous exposure to V. cholerae O1 does not confer immunity against V. cholerae O139 (5, 9, 10). Antibodies against various cholera antigens such as lipopolysaccharides (LPS), outer membrane proteins, cholera toxin and toxin-coregulated pilus (TCP) have been detected in sera from individuals immunized with V. cholerae O1 or from convalescent patients (11)(12)(13)(14)(15).A thorough study of immune responses against v...