Trichinella spiralis: antigen-antibody interaction assayed by radioactive iodinated antigen

A radioactive iodine labeled microprecipitin (RAMP) assay was developed for measuring the binding of antigen by antibody in trichinosis.Fifteen of 18 sera from trichinosis patients were reactive in this assay. No reactions were obtained with 71 sera from healthy persons and with 98 sera from individuals with proven viral, bacterial, mycotic, parasitic, or degenerative diseases. In experimentally infected rats and rabbits, all but one of 75 infected animals gave positive reactions in this assay, whereas all of 104 uninfected controls failed to react. Serum pools from infected and normal rabbits tested at different times with different lots of radioactive antigen gave highly reproducible results. Heating or reduction and alkylation of the immune sera destroyed or markedly reduced the antibody reactions in the RAMP assay. Rabbit immune serum was absorbed with goat antirabbit IgE antiserum. When tested after absorption, the reactivity of the serum in the RAMP assay was significantly reduced and the reactivity in the PCA test was eliminated. However, the titer in the soluble antigen fluorescent antibody test was not reduced. These studies indicate that the RAMP assay can reliably measure antibodies to T. spiralis belonging primarily to the immunoglobulin E class.