Recombinant dissection of myosin heavy chain of Toxocara canis shows strong clustering of antigenic regions

Myosins from nematode parasites elicit strong humoral and cellular immune r esponses and have been investigated as vaccine candidates. In this study we cloned and sequenced a cDNA coding for myosin heavy chain from Toxocara ca nis, a nematode parasite of canids which may also infect humans and cause v arious unspecific symptoms. To determine the major antigenic regions the my osin heavy chain was systematically dissected into ten overlapping recombin ant fusion polypeptides which were purified by metal chelate chromatography . Single fragments were then tested for their IgG reactivity in sera from t oxocarosis patients and healthy probands. Two regions, one region at the mi d to carboxy-terminal end of the head domain and one region in the rod doma in, were identified as major antigens, which in combination were positive w ith 86% of the sera. The other domains were less reactive. This shows that the patients' IgG reactivity was not directed evenly against all parts of t he molecule, but was rather clustered in few regions.