Immunoblot analysis of IgA antibodies to Naegleria fowleri in human salivaand serum

The objective of this study was to evaluate the secretory IgA (SIgA) antibo dy response to Naegleria fowleri (Nf) in individuals living in a parasite e ndemic area. Saliva and serum samples were obtained from both healthy subje cts and patients suffering from a respiratory illness (chronic bronchitis o r rhinitis) and were analyzed by immunoblot assay. SIgA from the patients' samples recognized more intensely a greater number of Nf proteins than did SIgA from the healthy control group. The proteins more frequently recognize d were those with a molecular weight of 171, 107, 102, 62, 50, 46, and 10 k Da. Some IgA antibodies recognized proteins from Nf and Entamoeba histolyti ca (Eh) of similar molecular weight. These results suggest that some of tho se antibodies could have been elicited by a previous intestinal infection w ith Eh. Through the common mucosal immune system the IgA B-cells activated by Eh antigens can be disseminated to all the mucosae, including the nasal mucosa. SIgA antibodies recognizing Nf proteins, induced either by specific immunization or by cross-reaction, could participate in the resistance to the infection, probably by inhibiting the adherence of Nf trophozoites to t he nasal mucosa.