IDENTIFICATION OF ANTIGENS OF PATHOGENIC FREE-LIVING AMEBAS BY PROTEIN IMMUNOBLOTTING WITH RABBIT IMMUNE AND HUMAN SERA

Prominent antigens of pathogenic and nonpathogenic free-living amoebae were identified by using polyclonal rabbit immune sera in immunoblot assays. The intent was to determine if prominent epitopes identified w ith rabbit immune sera could also be recognized by human sera. With ra bbit sera, the development of immunoreactive bands was restricted to m olecular masses of greater than 18.5 kDa for Naegleria, Hartmannella, and Vahlkampfia antigens. Two or more broad bands of less than 18.5 kD a were prominent features in three different Acanthamoeba species. Few cross-reactive antibodies could be detected between representative sp ecies of the three different subgroups of Acanthamoeba. Naegleria anti gen was likewise serologically distinct, as were Hartmannella and Vahl kampfia antigens. The relative lack of cross-reacting antibodies betwe en the pathogenic amoebae suggested that it would be desirable to use a panel of amoebic antigens to represent the range of serologically di stinct antigens far assessing reactive antibodies in human sera. In po oled human serum (10 serum specimens per pool), the appearance of mini mally reactive bands ranging from 32.5 to 106 kDa was a common feature of all six antigens. A prominent band of less than 18.5 kDa was ident ified in the Acanthamoeba culbertsoni antigen lane in 2 of the 10 huma n serum specimen pools. When the sera from each of the two groups were tested individually by immunoblotting, the reaction with the A. culbe rtsoni antigen could be associated with one individual. By using a pan el of amoebic antigens, this method could prove useful in recognizing undiagnosed amoebic infections by revealing specific reactive antibodi es.