Characteristics of the Toxoplasma Hemagglutination Test Antigen

Abstract

Toxoplasma hemagglutination test antigen, which is a lysate of washed parasites, loses potency rapidly when stored in the liquid state. It is stable for long periods when kept frozen or when lyophilized or precipitated by acetone and dried from ether. The dry powders are stable at 37° C and 56° C for at least five months and one month respectively. Potency is lost on filtration through a No. 02 Selas candle. The antigen elicits a skin reaction in toxoplasmin-sensitive patients. It also produces antibodies demonstrable by dye test when injected into mice. The antigen appears to be mainly protein in nature, with a high concentration of ribonucleoprotein. Nitrogen content seems to be correlated with potency. The hemagglutination test has presented difficulties with small animal sera, but has given consistently good results with human sera. It lags about four days behind the dye test in the demonstration of antibodies in early cases of human toxoplasmosis, but agrees very well with the dye test in late stages of the infection. The test has been performed satisfactorily with red blood cells of sheep or of “O” rH negative humans, and with formalinized cells.