Dot blot analysis of HCV proteins binding to IgG from patient sera. HCV proteins were obtained from tissue culture fluid. Protein preparations were serially diluted (1, 10-1, 10-2, 10-3) and were dot blotted onto a nitrocellulose membrane. These blots were then treated with patient antibodies. The figure shows (A) Reactions of patient IgG against dilutions of IgG depleted patient sera, CIMM-HIV cell culture supernatants from different cell lines (HCV infected B-cells, HCV infected human neuronal precursor T and M cells), or commercial antigens (NS4 and Core antigen), or uninfected B-cells. (B) Reactions of patient IgG against dilutions of various HCV isolates grown in vitro as described before. All HCV isolates were from the first transfer to fresh B cells (T1) except for isolates 314T2 (second transfer) and PCLBT4 (fourth transfer). These infected cells have been in culture for varying periods of time, including over three years for PCLBT4.