Serodiagnosis of Toxocaral Larval Migrans in Monkeys by Enzyme-Linked Immunosorbent Assay (ELISA) with Somatic Adult and Secretory Larval Antigens

Abstract

With the introduction of an enzyme-linked immunosorbent assay (ELISA) for the diagnosis of toxocaral larva migrans syndrome in human and experimental animals (Cypes et al., 1977, J. Inf. Dis. 135: 633-640; Ruitenberg and Knapen, 1977, J. Inf. Dis. 136 (suppl.): 267-273) one of the problems in the serodiagnosis of this infection was solved, namely the lack of a sensitive method. The use of a wide variety of antigens of somatic origin of different stages of the parasite's life cycle resolved the problem of specificity. The demonstration by de Savigny (1975, J. Parasitol. 61: 781-782) that excretory/secretory (ES) antigens obtained from in vitro-maintained L2 larvae were very specific for toxocara antibody contributed to better serodiagnosis of toxocariasis. This prompted us to reexamine sera of monkeys experimentally infected and subsequently immunized with Toxocara canis with ELISA using ES antigen. Monkeys (Macaca fasciolaris) were infected orally with 2 x 104 embryonated T. canis eggs and were later immunized by three injections of 1.5 mg adult T. canis antigen intramuscularly as was described in detail by Ruitenberg and Knapen (1977, loc. cit.). The ES antigens were obtained by in vitro maintenance of L2 larvae as described by de Savigny (1975, loc. cit.) and de Savigny and Tizard (1977, Trans. Roy. Soc. Trop. Med. Hyg. 71: 501-507). ELISA was carried out as a micro assay. For the somatic antigens the procedure was described earlier by Ruitenberg and Knapen (1977, loc. cit.), whereas for the ES antigen the following modifications were applied. The ES antigen concentration used was empirical. In our system a 1:1,000 dilution in carbonate