Strongyloides stercoralis: characterization of immunodiagnostic larval antigens.

Forty-one-, 31-, and 28-kDa proteins of Strongyloides stercoralis filariform larvae have previously been demonstrated to be sensitively and specifically recognized by serum IgG in individuals with strongyloidiasis. Characteristics of these proteins, their immunodominant epitopes, and reactive antibodies are described here. The proteins are soluble in aqueous as well as detergent extracts. The immunodominant epitopes are present in S. stercoralis but not in S. cebus or S. ratti. Epitopes on the three proteins are not shared, as determined by cross-adsorption of serum with each of the size components on nitrocellulose. In most sera from strongyloidiasis patients there was reactivity to each of the proteins by IgG1 and IgG4, but reactivity by IgG2 or IgG3 was detectable only in a minority. A rabbit antiserum raised to a 41-kDa size fraction of S. stercoralis larvae reacted against a doublet of 41-kDa which was distinct from the immunodiagnostic 41-kDa protein.