Identification of Immunogenic Antigens of Naegleria fowleri Adjuvanted by Cholera Toxin.

The intranasal administration ofNaegleria fowlerilysates plus cholera toxin (CT) increases protection againstN. fowlerimeningoencephalitis in mice, suggesting that humoral immune response mediated by antibodies is crucial to induce protection against the infection. In the present study, we applied a protein analysis to detect and identify immunogenic antigens fromN. fowleri, which might be responsible for such protection. A Western blot assay ofN. fowleripolypeptides was performed using the serum and nasal washes from mice immunized withN. fowlerilysates, either alone or with CT after one, two, three, or four weekly immunizations and challenged with trophozoites ofN. fowleri.Immunized mice withN. fowleriplus CT, after four doses, had the highest survival rate (100%). Nasal or sera IgA and IgG antibody response was progressively stronger as the number of immunizations was increased, and that response was mainly directed to 250, 100, 70, 50, 37, and 19 kDa polypeptide bands, especially in the third and fourth immunization. Peptides present in these immunogenic bands were matched by nano-LC-ESI-MSMS with different proteins, which could serve as candidates for a vaccine againstN. fowleriinfection.