The application of a haemagglutination technique to the study of Trichomonas vaginalis infections.

Although there is an extensive literature on the subject of trichomoniasis, reports on the serological investigation of Trichomonas vaginalis infections are scanty and the results inconclusive, the emphasis in serological work having been on bovine infections with Trichomonas foetus rather than on human infections with T. vaginalis. Riedmuller in 1932 (quoted by Trussell, 1947) tested the sera of a number of women for complement-fixing antibody using T. foetus as antigen. His results were uniformly negative irrespective of the presence or absence of trichomonas infection. Wendlberger (1936) carried out complement fixation tests with an alcoholic extract of a culture of T. vaginalis as antigen. The culture employed for the production of this antigen contained bacterial contaminants. Positive results were observed in 22 out of 32 sera taken from known cases of trichomoniasis, while 16 sera from apparently healthy women were negative. A series of 400 sera was examined by Trussell, Wilson, Longwell, and Laughlin (1942) by a complement fixation technique with a washed suspension of T. vaginalis as antigen. The test was positive with 52 out of 110 sera from known cases of trichomoniasis (47%). Of 290 " normal " female sera tested, 48 were positive (16%). The results recorded in the latter two papers provide the only evidence for the occurrence of serum antibodies in human trichomoniasis at present known to the author. A micro-agglutination technique was introduced in 1941 by Robertson working with T. foetus. This test was shown to give valuable information in the investigation of T. foetus infections of cattle (Kerr and Robertson, 1941; Pierce, 1947). Trussell (1946) applied a similar technique to human infections with T. vaginalis. Having established that the method would give successful results in experimentally immunized rabbits, 200 human sera were examined, but over 90% of these were recorded as negative and the remainder gave only low titre positive reactions. Both complement fixation and micro-agglutination methods for the detection of antibody to T. vaginalis were tested in this laboratory, but they gave only weak reactions with human serum. A new approach to the problem was suggested by the observations of Muniz (1950), who used a haemagglutination technique similar to that employed by Middlebrook and Dubos (1948) in their studies on tubercle bacilli. He applied it to investigations on trypanosomiasis, sensitizing erythrocytes with a polysaccharide fraction of Schizotrypanum cruzi, and observing lysis rather than agglutination as evidence of positive reactions. An attempt was therefore made to apply the technique of agglutination of sensitized red cells for the detection of circulating antibodies in human trichomoniasis. The results are recorded below.