Immunization with live amoebae, amoebic lysate and culture supernatant in experimental Naegleria meningoencephalitis.

Immunization with two doses of live Naegleria fowleri produced a survival of 34% of mice compared to 0% in unimmunized controls, whereas multiple doses of live N. fowleri resulted in loss of protective immunity. In contrast, multiple doses of N. fowleri lysate produced a survival of 30%, and multiple doses of N. fowleri culture supernatant produced a survival of 67 to 78%. Fractionation of the culture supernatant by column chromatography showed that all six fractions contained protective antigens, but the best protection occurred from immunization with the high molecular weight fraction (greater than 200,000 daltons).