SECRETION AND PURIFICATION OF HEPATITIS-C VIRUS NS1 GLYCOPROTEIN PRODUCED BY RECOMBINANT BACULOVIRUS-INFECTED INSECT CELLS

Recombinant baculoviruses that produce a putative non-structural prote in 1 (NS1) of hepatitis C virus (HCV), predicted to be the second enve lope glycoprotein, were constructed. The recombinant NS1 protein (re-N S1) produced in infected insect cells was localized on the cell surfac e and was apparently glycosylated, because it was susceptible to treat ment with both tunicamycin and N-glycanase. Furthermore, re-NS1 was ef fectively secreted into the culture supernatant when the putative NS1 signal peptide (SP) was replaced by the SP of rabies virus G protein, and the C-terminal hydrophobic region was eliminated. The secreted re- NS1 was tagged with six His residues at the C terminus and purified si mply by native Ni2+-nitrilotriacetic acid (Ni2+-NTA) affinity column c hromatography. An enzyme-linked immunosorbent assay (ELISA) was develo ped for the serological diagnosis of HC using purified re-NS1. Anti-NS 1 antibody (Ab) was detected in 55 of 60 patients (92%) with chronic H C liver diseases. Thus, this ELISA for Ab directed against HCV re-NS1 produced in insect cells is useful for the detection of chronic HC pat ients.