Further evidence for cross-linking as a protective factor in experimental cholera: properties of antibody fragments.

Enzymic fragments of IgG antibody were tested for their protective abilities in the infant mouse cholera model. F(ab')2 retained the full protective activity of the parent IgG molecule despite losses in complement fixation and opsonic functions. Fab' and Fab fragments also contained significant protective activity but at a level of only 10% of the intact IgG or F(ab')2. Self-recombinant univalent F(ab')2 also contained about 10% of the protective activity of the divalent F(ab')2 parent molecule. These results are interpreted as evidence that cross-linking is an important mechanism by which specific antibody protects mucosal surfaces against experimental infection with Vibrio cholerae.