CYSTEINE PROTEASE OF THE NEMATODE NIPPOSTRONGYLUS-BRASILIENSIS PREFERENTIALLY EVOKES AN IGE IGG1 ANTIBODY-RESPONSE IN RATS/

Some cysteine proteases such as papain and those of mites and schistos omes have potent allergenic properties. To clarify the allergenicity o f nematode cysteine proteases, the enzyme was purified from the intest inal nematode Nippostrongylus brasiliensis using cation exchange chrom atography and gel filtration chromatography. The purified protease, of 16kD and pi 8.5, showed maximum enzyme activity at pH 5.5 and substra te preference for Z-Phe-Arg-MCA. The specific inhibitors of cysteine p rotease leupeptin, iodoacetic acid, and E-64, completely suppressed th e activity, indicating that the purified enzyme belongs to the cystein e protease family. Cysteine protease activity was found not only in so matic extract, but also in the excretory-secretory (ES) product of the nematode. When anti-cysteine protease immunoglobulin isotypes were ex amined in sera from rats infected with N. brasiliensis, a high level o f IgG1 and a lower level of IgE antibody were detected. Depletion of I gG antibodies from the sera using protein G affinity columns resulted in a marked increase in reactivity of anti-cysteine protease IgE with the antigen, possibly due to the removal of competing IgG antibodies. In contrast to IgE and IgG1, production of anti-cysteine protease IgG2 a was negligible. These results indicate that the nematode cysteine pr otease preferentially evokes an IgE/IgG1 antibody response.