Spontaneous binding of Vibrio cholerae to human leucocytes

Various lymphocyte subpopulations have the capacity to bind different strains of Gram-negative bacteria. The capacity of a strain of Vibrio cholerae, biotype El Tor, isolated during an outbreak of cholera, to adhere to mononuclear cells isolated from peripheral blood was evaluated. V. cholerae binds to mononuclear cells in a dose-dependent manner. The binding was 76.1% at a cells/bacteria ratio of 1:200 and significantly decreased to 43.1% at a ratio of 1:1. The value of bound bacteria, a marker of the mean number of binding sites on the cell surface, decreased at lower cell/bacteria ratios. Studies on isolated cellular populations demonstrated that 51, 42 and 38%, respectively, of CD4+, CD8+ and B cells were bound by V. cholerae whereas monocytes exhibited a higher binding capacity. The data suggest that the percentage binding of V. cholerae to lymphocytes and monocytes was higher than the percentage found in previous studies with Gram-negative bacteria such as Yersinia enterocolitica, and Salmonella, but similar to Helicobacter pylori. The findings indicate that V. cholerae possesses multiple 'adhesins' such as fimbriae, flagella, haemagglutinins, lipopolysaccharides, and outer membrane proteins. The capacity to bind to blood lymphocytes may reflect the same capacity for the lymphocytes from the gastrointestinal associated lymphoid tissue. This cytoadherence may contribute to the uptake of V. cholerae from the gut and may contribute to activation of B cells and CD4+ lymphocytes.