Immunity in trypanosomiasis

Abstract

Antibody-resistant strains are less sensitive to suramin and antrycide than antibody-sensitive strains. When living trypanosomes were exposed to suramin and antrycide in vitro, antibody-resistant strains needed 50 times more drugs than antibody-sensitive trypanosomes in order to make them non-infectious to mice. In therapeutic experiments in mice the minimal therapeutic dose of drugs for antibody-sensitive strains was 0·1 mg. but for resistant strains it was 0·3 mg./20 g. mice. Rabbits treated prophylactically with suramin resisted infection with the antibody-sensitive strain for a period of 4 months, but failed to resist infection with the antibody-resistant strain after 2 months.Rabbits treated prophylactically with antrycide pro-salt, resisted infection with antibody-sensitive strains for a period of 2 months, but failed to resist infection with the antibody-resistant strain even 1 month after injection with the drug. Although trypanosomes can become drug resistant without being antibody resistant it is suggested that, under natural conditions, drug-resistant strains in animals and man develop from antibody-resistant strains, particularly when trypanostatic drugs are used. It is suggested in conclusion from these experiments that strains of trypanosomes which are exposed for some time to antibodies and become antibody resistant after passage through animals like rabbits, as well as those strains frequently passaged through mice, should be used in all tests for the efficiency of chemotherapeutic drugs.