Affinity Constants of Anti‐Leptospira Monoclonal Antibodies, Numbers of Antigenic Determinants on Leptospiras, and Their Influence on the Microscopic Agglutination Test and ELISA

Abstract

The affinity constants of anti-canicola and anti-hebdomadis monoclonal antibodies and the numbers of antigenic determinants per organism of each serovar of leptospira were determined, and their influence on the results of microscopic agglutination test (MAT) and ELISA were examined. In the combinations of a monoclonal antibody and some serovar which showed higher affinity constants at levels of 107 to 108/m order, both MAT and ELISA were positive except for one combination, while in the combinations which gave lower affinity constants at levels of 106/m order, MAT was positive but ELISA was negative. The number of antigenic determinants seemed to have no significant influence on the results. The disagreement due to the difference in the threshold affinities of MAT and ELISA should be considered in the use of monoclonal antibodies in the taxonomy of leptospira.Many monoclonal antibodies against various serovars of leptospira interrogans have been produced since the first production described by Ono et al (15). Some were genus-specific (18) or species-specific (3), and others were serogroup-specific (2) or rather serovar-specific (15). Specificities of all monoclonal antibodies have been tested by MAT and/or ELISA. Terpstra et al (20) attempted to use monoclonal antibodies for leptospiral classification by MAT. However, differences in results obtained by MAT and ELISA were found in some monoclonal antibodies; MAT was positive but ELISA was negative, or vice versa (9, 11, 15). These differences cause confusion in the taxonomy of leptospiras by monoclonal antibodies.The present paper deals with the determination of the binding affinities of anti-canicola and anti-hebdomadis monoclonal antibodies for various serovars and the number of antigenic determinants per leptospiral organism in order to explain the difference in the results obtained by MAT and ELISA.

Application of Monoclonal Antibodies in a Rapid Sandwich Dot-Enzyme Linked Immunosorbent Assay for Identification and Antigen Detection ofLeptospiraSerovars

“…Similar discrepancies in cross-reactivity of MAbs in MAT and ELISA have also been reported by other researchers. (29,(31)(32)(33)(34) These differences have been attributed to the differential threshold affinities of MAT and ELISA. (32) Monoclonal antibodies have been generated mostly against the serovars or strains belonging to serogroup icterohaemorrhagiae and have been found useful in providing more clear identity of the organisms at strain, serovar, or species level.…”

“…(29,(31)(32)(33)(34) These differences have been attributed to the differential threshold affinities of MAT and ELISA. (32) Monoclonal antibodies have been generated mostly against the serovars or strains belonging to serogroup icterohaemorrhagiae and have been found useful in providing more clear identity of the organisms at strain, serovar, or species level. Kobayashi and co-workers (14) using MAbs against serovars icterohaemorrhagiae and copenhageni could infer that serovar tonkini probably does not belong to serogroup icterohaemorrhagiae.…”