Studies on Larval Antigens Derived by Cultivation of Some Parasitic Nematodes in Simple Media: Protection Tests in Laboratory Animals

Abstract

Antigens prepared from in vitro cultures of some parasitic nematodes have been found to be highly effective in protecting guinea pigs against infection and mortality from Dictyocaulus viviparus and Trichostrongylus colubriformis; rabbits were similarly protected against infection with Strongyloides papillosus. Two injections of antigen administered at an interval of 21 days were required for maximum protection. At intervals of 14 days or less protection was markedly reduced. With some preparations as little as 100 to 125 larval equivalents of antigen were found to be effective in stimulating resistance. Aluminum hydroxide adjuvant was found to have a significant enhancing effect when used at threshold levels of antigen. Lyophilized antigens showed little loss of activity when stored at either room or refrigerator temperatures for 6 to 9 months. Antigens prepared from Haemonchus contortus and T. colubriformis were effective at high levels of dosage in protecting guinea pigs against infection with D. viviparus. In contrast, only homologous antigens were found to be capable of protecting guinea pigs against infection with T. colubriformis. Nonspecific antigens prepared from tapeworms and a bacterium were not able to induce resistance to either nematode.