SUPPRESSION OF THE ANTIVENOM ANTIBODY-RESPONSE BY SERUM THERAPY

1. The antivenom antibody response of mice injected with Bothrops jara raca venom and receiving specific serum therapy was studied under diff erent experimental conditions. Balb/c mice (18-22 g) injected with ven om (1.75 mg/kg) presented the clinical symptoms observed in patients b itten by B. jararaca and a high and long-lasting antivenom antibody re sponse. 2. Injection of 0.1 ml of horse antiserum to venom 15 min afte r venom administration abolished the symptoms induced by the venom and induced an almost completely suppressed production of mouse antivenom antibodies. The extent of suppression of the antivenom antibody respo nse depended on the dose of horse antiserum administered and was great er the sooner the serum therapy was applied after envenomation. 3. Inj ection of antiserum into envenomed mice that received an unrelated ant igen (KLH) did not suppress the antibody response to KLH antigen thoug h it inhibited production of antivenom antibodies. 4. Envenomed mice r eceiving an equivalent dose of F(ab')(2) fragments obtained by pepsin digestion of horse antiserum presented the same extent of suppression of the antivenom antibody response as mice injected with the non-treat ed antiserum. 5. Mice whose antibody response was suppressed, when rec hallenged with venom, presented a primary antibody response. 6. These results suggest that suppression of the antivenom antibody response pr esented by envenomed patients submitted to serum therapy is due to the masking of the venom epitopes by horse antibodies as well as to the r apid elimination of the venom epitopes.