EXCRETORY-SECRETORY AND SOMATIC ANTIGENS IN THE DIAGNOSIS OF HUMAN FILARIASIS

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 56  (3) , 567-576
Abstract
In order to compare the immunodiagnostic value of excretory-secretory (E-S) antigens derived from adult Brugia malayi worms with somatic antigens derived from adults, microfilariae (Mf) and infective [3rd stage] larvae (L3) of these parasites, well defined serum pools form patients with filarial (Brugia, Wachereria bancrofti, Loa and Dipetalonema perstans) and nonfilarial (Ascaris, Strongyloides, Toxocara, Echinococcus, Cysticercus and Schistosoma) helminth infections were tested against antigen derived from these different life cycle stages of B. malayi in a Staphylcoccus aureus radioimmunoprecipitation assay (S. aureus RIA). The adult brugia antigens proved significantly more discriminatory than those of the other parasite stages, with the homologous brugia serum pool also showing greater reactivity to adult than to L3 and Mf antigens. Similar results were obtained when individual sera from patients (rather than serum pools) were tested in the same assay. The most surprising finding was the minimal reactivity seen between the adult filarial antigens and the non-filarial serum pools despite the presence in these pools of strong antibody reactivity with their homologous antigens. The reasons underlying the unexpected specificity of this S. aureus RIA for discriminating among sera from filarial and nonfilarial infections were analyzed qualitatively by immunoprecipitation techniques. The use of the chloramine-T method for radioiodination resulted in preferential labeling of the low MW proteins (10,000-70,000 daltons) in the B. malayi adult somatic antigen and these antigens were bound primarily by the filarial and not the nonfilarial serum pools. Apparently, lower MW helminth antigens may show greater species specificity than those with higher MW, and those with higher MW greater crossreactivity. If substantiated by further analysis, such results would have important implications for the subsequent isolation of diagnostically important filarial parasite antigens.