Efficacy of immune therapy in early experimental Naegleria fowleri meningitis.

Naegleria fowleri meningoencephalitis is usually fatal in humans despite treatment. As a new approach, we tested intracisternal passive immune therapy in rabbits with amebic meningoencephalitis by using antinaegleria immune serum, an immunoglobulin G fraction, and a newly developed monoclonal antibody to N. fowleri. Both the immune serum and an immunoglobulin G fraction isolated from it by affinity chromatography provided a consistent, although temporary, protective effect, shown by prolongation of survival (P = 0.001). Multiple doses of immune serum further prolonged survival (P = 0.005). The protective effect of serum was retained after heating to 56 degrees C. We then developed a monoclonal antibody to N. fowleri which provided similar protection. Passive intracisternal antibody therapy might serve as an adjunctive component in the treatment of amebic meningoencephalitis.