Antigenic epitopes on Mycobacterium tuberculosis recognized by antibodies in tuberculosis and mouse antisera

The effect of sodium periodate and proteolytic enzyme treatments on the antibody binding capacity of Mycobacterium tuberculosis antigen (Ag) was studied by ELISA. Treatment with sodium periodate resulted in a marked decrease in the capacity of M. tuberculosis Ag to bind antibodies in human TB sera, but had no effect on the reactivity with antibodies in mouse. In contrast, treatment with proteolytic enzymes (trypsin and chymotrypsin) had no effect on the reactivity of M. tuberculosis Ag with human TB sera but reduced substantially the reactivity to antibodies in mouse antisera. These results indicate that anti-M. tuberculosis antibodies in human TB sera react predominantly with carbohydrate determinants and not with protein epitopes sensitive to trypsin and chymotrypsin. The bulk of murine antibodies on the other hand were directed against protein determinants and not the carbohydrate epitopes.