Application of immunofluorescence and immunoenzyme methods in the serodiagnosis of Trichinella spiralis infection.

To detect antibodies to T. Spiralis in sera, the IF methods with the cuticle of T. spiralis larvae (the tube test) was compared to the cryostat method. In the latter method, cryostat sections were prepared from isolated T. spiralis larvae or from tongue or diaphragm musculature in which encysted T. spiralis larvae were present. In this case, both cuticle and internal structures were employed as antigenic sites. The cryostat method proved to be more sensitive than the tube test. With the cryostat method, specific antibodies were detected in sera of experimentally infected mice 14 days after infection, whereas with the tube test, antibodies were detected on Day 24 postinfection and consistently thereafter. The enzyme-linked immunosorbent assay (ELISA) was then studied. Quantitation of specific antibodies was achieved with alkaline phosphatase- or peroxidase-labeled antispecies immunoglobulin in antigen-coated tubes. The enzyme that remained in the tube after washing provided a measure of the amount of specific antibodies in the serum. A saline extract of T. spiralis larvae served as the antigen. In the experimental models studied (T. spiralis-infected rabbits and pigs), ELISA proved to be more sensitive than IF. At Day 3 postinfection and thereafter, specific antibodies could be detected. ELISA was modified to satisfy requirements for routine application.