Cholesterol-Lecithin Slide (TsSF) and Charcoal Card (TsCC) Flocculation Tests Using an Acid Soluble Fraction of Trichinella spiralis Larvae

Abstract

Two simple sensitive flocculation tests were developed employing acid soluble T. spiralis larvae antigen absorbed onto cholesterol-lecithin crystals. Washing of the emulsion greatly increased the sensitivity of the antigen in the slide flocculation test. The addition of charcoal to the antigen emulsion permitted its use in a simple card test using serum or minute amounts of plasma collected from finger puncture. Absorption of reactive sera with a single dose of washed, packed, and essentially dry antigen-cholesterol-lecithin complex resulted in a complete removal of serologically detectable antibody indicating that the tests were based upon a true antigen-antibody system. Sensitivity of both tests was excellent. In the slide flocculation test, 64 sera from 68 patients were reactive, 2 were weakly reactive and 2 were nonreactive. All 21 sera from trichinosis patients were reactive in the charcoal card test. The tests also appear to be relatively specific. Only 3 sera from a total of 96 normal persons and patients with other diseases were reactive in the slide flocculation test; 13 sera showed weak reactions. With the charcoal card test 3 reactions were obtained with sera from a total of 64 normal individuals and patients with other diseases. The tests are especially well suited to small laboratory and field conditions because they are simple to perform and utilize antigenic emulsions which may be kept for prolonged periods without apparent loss of reactivity. Slide flocculation tests are among the simplest procedures for the serodiagnosis of infections. These techniques have not yet found wide application in the field of parasitology primarily because of the difficulty in many instances of combining the parasitic antigens with the carrier (cholesterol, latex, or bentonite). Suessenguth and Kline (1944) found that an aqueous extract of Trichinella larvae coated onto cholesterol crystals could be used as antigen in a simple and rapid flocculation slide test for trichinosis. They reported that this test was more sensitive than the complement fixation test (Suessenguth et al., 1957). However, other investigators have presented evidence indicating that this test lacks the specificity of other serological tests for trichinosis (Bozicevich et al., 1951; Sadun and Norman, 1955a; Greene and Brazeale, 1951). Recently Anderson (1960) developed a slide Received for publication 26 April 1963. flocculation test for schistosomiasis using antigen prepared by coating a buffered saline extract of cercariae onto cholesterol-lecithin particles and subsequently washing this complex to remove the excess antigen. This method has been shown to be one of the most sensitive and specific serodiagnostic procedures for schistosomiasis (Anderson, 1960; Anderson and Naimark, 1960; Jachowski and Anderson, 1961). Following the development of the rapid plasma reagin card test (Portnoy et al., 1962) for syphilis, the schistosome slide flocculation te t antigen was adapted to the card procedure and evaluated under laboratory and field conditions (Sadun et al., 1963). The card test in schistosomiasis gave results comparable to those obtained with the standard slide flocculation procedure and permitted the test to be completed within a few minutes on plasma obtained by finger puncture. The purpose of the current study was to determine whether similar procedures would provide a slide flocculation test for trichinosis