Evaluation of monoclonal antibody F9-4 as immunological probe for Leptospira interrogans.

I assayed the lack of reactivity of monoclonal antibody (MAb) F9-4 with nonpathogenic leptospires. Of 47 saprophytic strains tested, 46 did not react in an enzyme immunoassay and 1 was recognized by MAb F9-4, as usually reported with pathogenic Leptospira strains. On the other hand, the MAb did not react with one pathogenic strain, thus showing that the ability of MAb F9-4 to discriminate between pathogenic and nonpathogenic leptospires is not absolute.