Immunogenicity of rifamycins

The presence of anti-rifamycin antibodies in sera of rabbits injected with a rifamycin-protein conjugate or with some unconjugated rifamycin derivatives, was assayed by equilibrium dialysis. The conjugate was effective in eliciting the production of rifamycin specific antibodies. This capacity also was exhibited by the derivatives P and S/TA. The possible mechanism of the formation of potentially immunogenic rifamycin-protein complexes in the organism is discussed. Competition experiments were performed in order better to clarify the haptenic moiety of rifamycins. We conclude that the antigenic determinant of the rifamycin molecule includes part of the chromophore together with part of the ansa chain.