Identification of a 26-kDa protein fraction as an important antigen for application in the immunodiagnosis of strongyloidiasis

Strongyloidiasis caused by the intestinal nematode Strongyloides stercoralis typically occurs in the asymptomatic form. The definitive diagnosis is usually done by detection of larvae on fecal samples. However, as the parasite load is often low in most cases, microscopy is not usually sensitive and specific, and diagnosis becomes extremely difficult. Thus, development of reliable serological methods is imperative. In the present study, a diversity of epitopes from S. stercoralis larva were characterized by analysis of reactivity with serum samples obtained from individuals with and without the infection by using Western blot technique. A total of 91 serum samples belonging to 5 groups were analyzed. Different reactivity profiles were observed, representing recognition of proteins with molecular mass varied from 6 to 129 kDa. A protein band of approximately 26 kDa presented a high frequency of reactivity with serum samples from the strongyloidiasis patients group (18/23). Reactivity with this protein band was also observed in only 7 of 64 non-infected individuals or individuals infected with other helminthes. Reactivity with 2 other bands, 1 of approximately 33 kDa and a duplet of approximately 21 kDa, were also found in high frequency (17/23 and 9/23, respectively). However, reactivity with these bands was also observed in all the other serum groups studied. The results indicate that the 26-kDa band maybe be an important tool for the development of diagnostic techniques for strongyloidiasis.