IMMUNOLOGICAL STUDIES ON TRICHINELLA SPIRALIS INFECTION WITH EMPHASIS ON TIME COURSE STUDIES OF ANTIBODY RESPONSE AGAINST MUSCLE LARVAE

Fischer rats were experimentally infected with Trichinella spiralis and class-specific antibody response against the infection was followed up until 32 weeks after infection by means of indirect ELISA, immunoelectron microscopy (IEM), and western blotting. By indirect ELISA, the titer of specific IgG against crude antigen of T. spiralis muscle larvae increased from 2 weeks after infection, and kept high levels up to 32 weeks, but the titer of specific IgM was very low through the infection course. On the other hand, the titer of specific IgG against excretion and secretion antigen of muscle larvae began to increase from 4 weeks onward, and specific IgM was detectable from 3 weeks onward. These results indicate that different kinetics of antibody response (both IgG and IgM) are induced by different antigens, which was also confirmed by the following two methods. One method is immunoelectron microscopy using resin-embedded larvae as a substrate and infected sera as a staining antibody, which clearly revealed that there are two types of antigen : rapid responding antigens, and slow responding antigens. G class antibodies against the former including the cuticle inner layer, hypodermis, cord, hemolymph, intestinal gland cell granules, glycogen aggregates, discrete areas of genital primordial cell cytoplasm, and midgut occupying substance, were detectable from earlier phase of infection, while G class antibodies against the latter including the cuticle surface, stichocyte granules, and esophagus occupying substance, were detectable from relatively late phase of infection. M class antibodies against rapid responding antigens were undetectable or weak if any, but reactivity of M class antibody against slow responding antigens increased appreciably. The same tendency was observed by the other method, namely western blotting. The rapid responding antigens included ones from bands of pⅠ 4.4～4.7, 4.9～5.4 and 6.3～6.5 ; the slow responding antigens included ones from bands of pⅠ 4.0 and 5.4. The present contribution established that muscle larvae of T. spiralis contain two major types of antigens (rapid responding antigens and slow responding antigens) and the chronology of class-specific antibody response against each antigen is described, which will be indispensable for analysing any Trichinella-related immune response, especially for application to immunodiagnostic method of the disease