Vibriocidal antibody and antibodies to Vibrio cholerae lipopolysaccharide, cell-bound haemagglutinin and toxin in Thai population.

Vibriocidal antibody and antibodies to Vibrio cholerae lipopolysaccharide (anti-LPS), cell-bound haemagglutinin (anti-CHA) and toxin (anti-CT) were determined in Thai individuals of various age groups who lived in areas with high (H) and low (L) cholera endemicity. The enzyme-linked immunosorbent assay (ELISA) was performed to detect levels of class specific anti-LPS, anti-CHA and anti-CT. It was found that Thai individuals acquired the vibriocidal antibody early in life. Fifty percent of individuals aged 5 to 15 years old had detectable titre while more than 80% of adults had titres ranged from 1:5 to 1:125 or higher. Thai adults who lived in area with high cholera endemicity had significantly higher vibriocidal antibody levels than their counterparts who lived in area with low cholera endemicity. Lipopolysaccharide was not the only antigen responsible for stimulating the vibriocidal antibody production. Adult levels of all classes of anti-CHA from L were higher than those of H while the anti-LPS in the forms of total immunoglobulins, IgG and IgA were similar but IgM of L was higher than that of H. The levels of all classes of anti-CT from H seemed to increase with age except at the school age (5 years to 15 years old) when there were marked decreases of all antibody classes. Total immunoglobulin and IgM anti-CT at adult age of H and L were not different, although IgG anti-CT of L was higher than that of H and IgA anti-CT of H was higher than that of L.

Immunogenicity of soluble haemagglutinin-lipopolysaccharide complex of classical vibrio cholerae.

Soluble haemagglutinin-lipopolysaccharide complexes were found to be good antigens since it elicited high levels of the antibodies in the intestine especially of the IgA class. These specific antibodies sustained for a long period of time at the significantly high levels (longer than 6 months). The enteric memory primed by the antigens in the intestinal tract were longer than 3 months. Pools of intestinal fluids obtained from mice immunized with single dose of SH-LPS at 1 week, 1 month and 3 months after the antigen stimulation conferred protection against the homologous challenge. Better protection was found in the corresponding specimens collected from mice which received antigen booster at 3 months after the first stimulation. Multiple oral doses of the antigens (three doses at weekly intervals) did not have any advantage over the single dose immunization. The intestinal fluids obtained from the former group conferred similar degree of protection as those from the latter though the serum specimens offered higher PD50. The protection against cholera does not correlate with the levels of vibriocidal antibody in the body fluids which seems to confirm the hypothesis that the mechanism of protection against cholera by intestinal antibody is by reducing or preventing the attachment of the vibrios to the epithelium either via agglutinating process or via masking of the vibrio adhesive sites.