A Hemagglutination Test for Toxoplasmosis

Abstract

The importance of adequate serological tests for toxoplasmosis is accentuated by the tremendous gains in knowledge concerning this infection, which stemmed from the description of the in vitro dye test by Sabin and Feldman in 1948. In the less than 8 years since this discovery, the serology of toxoplasmosis has been characterized and forms of the infection not previously known have been described and proved (Siim, 1951; Jacobs, Cook, and Wilder, 1954; Jacobs, Fair, and Bickerton, 1954). Together with the complement fixation tests, also developed by Sabin and his co-workers, the dye test offers the best means of diagnosis other than demonstration of the parasites. Dye test antibodies appear earlier than c.f. antibodies and persist longer; these differences, properly interpreted, have aided in the diagnosis of many clinical cases. It is unfortunate, however, that the dye test is not as satisfactory from a standpoint of practice as it is technically. It requires live parasites, which are dangerous to handle, microscopic reading of the tests, and considerable care in most of the manipulations involved. Only a few laboratories in this country now perform the dye test, and it is unlikely that it will gain wider acceptance because of these difficulties. The same is true in other countries, where the additional difficulty is reported that normal serum for the necessary accessory factor substance is difficult to obtain (fide Desmonts). Now, especially because the results of dye test studies have revealed and publicized various symptomatic forms of toxoplasmosis, the index of suspicion in fevers of undetermined origin, neonatal disease, and uveitis has been increased. The demand for the test by pediatricians, internists, and ophthalmologists exceeds existing facilities, and points up the need for a diagnostic procedure which can be practiced more generally. This need has stimulated explorations for various other means of serological testing. The studies of Middlebrook and Dubos (1948), Boyden (1950-1951), Keogh et al. (1948), Alexander et al. (1950), Stavitsky (1954), and others have demonstrated the applicability of the hemagglutination test to a variety of antigens, both polysaccharide and protein in nature. The technique has already been tested in parasitic infections, such as schistosomiasis and trichinosis, by Kagan (1955-1956). In an effort to devise a test for toxoplasmosis which could be generally adopted, we have explored the applicability of this procedure. The following report presents preliminary results of these studies.