Comparison of immunoblot and immunoprecipitation methods for analyzing cross-reactive antibodies to filarial antigens.

Qualitative analysis of antibody responses in helminth infections is essential not only for developing better immunodiagnostic antigens but also for understanding immune recognition and its relevance to immunopathogenesis and protective immunity. In this study 2 qualitative analytic methods (immunoprecipitation and immunoblotting) were compared for the ability to define the extent of cross-reactivity in the serum antibodies from patients with various forms of filariasis (caused by Brugia malayi, Wuchereria bancrofti, Loa loa and Tetrapetalonema perstans) or other non filarial helminth infections (ascariasis, strongyloidiasis, trichinosis, echinococcosis and schistosomiasis). Our results demonstrated that the spectrum of cross-reactive antibodies identified by immunoprecipitation was limited because of the selective radiolabeling of particular filarial antigens, while immunoblotting was able to detect a much wider range of cross-reactive antibodies in both filarial and non-filarial serum pools. In addition, this latter procedure was easily adapted for simultaneous analysis of different antibody isotopes (e.g., IgE and IgG) to the same antigens in individual sera. Immunoblotting thus provides an excellent tool for studying the spectrum of antibodies of different isotypes evoked during helminth infections and for discriminating between those responses that are species-specific and those that are cross-reactive.