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

Abstract

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).

Intranasal Coadministration of the Cry1Ac Protoxin with Amoebal Lysates Increases Protection againstNaegleria fowleriMeningoencephalitis

“…routes in mice receiving four doses of amoebal lysates, but other groups have obtained lower rates (30%) after five i.p. immunizations with higher doses of amoebal lysate protein (0.5 mg) than the one used in this work (32).…”

“…Even if supernatants of N. fowleri culture medium used as immunogen achieve similar protection to that attained with lysates plus Cry1Ac, the procedure is much more laborious and the amount of antigen recovered is much smaller than that obtained from total amoebal lysates. On the other hand, the protection rates obtained with supernatants appear to be highly variable, since the five fractions tested yielded a 31% protection average (range, 18 to 57%) (32).…”

“…In general, total protective immunity was not achieved in mice except when five doses of a fraction of N. fowleri culture fluid were injected i.p. (32). Even if supernatants of N. fowleri culture medium used as immunogen achieve similar protection to that attained with lysates plus Cry1Ac, the procedure is much more laborious and the amount of antigen recovered is much smaller than that obtained from total amoebal lysates.…”

“…Several attempts have been made to induce protective immunity against experimental N. fowleri in mice, but the study of immunity in experimental and natural infections has been limited to the analysis of serum antibody responses (3,9,10,19,32). The immunization protocols used to induce protection against intranasal challenge with N. fowleri amoebae in mice, including different antigens-such as N. fowleri amoebal lysates, live and fixed amoebae, and culture medium-administered by the intranasal (i.n.…”

“…), intravenous, and intraperitoneal (i.p.) routes, have led to variable results with partial protective immunity (3,9,10,19,32). Therefore, additional strategies are clearly needed to achieve total protective immunity against experimental primary amoebic meningoencephalitis.…”