Does a monoclonal antibody reactive with the o139 antigen of e.coli would cross react with v.cholera o139?

Apparently not.: This does not seem likely because first that the v cholera is usually found in india and bangladesh while ecoli is usually in the U.S., mexico, and south america. Second, the mechanisms are different because the genes for toxicity on the e coli strains are not present in the v cholera. Third, there seems to be no information on any cross reaction of these two o 139 strains.

Nope: The o (somatic) antigens of each gram-negative bacilli are numbered specifically for the organism. Therefore, the o139 antigen of v. Cholerae is not the same as the o139 antigen of e. Coli.