Immunogenic properties of chimeric potato virus X particles displaying the hepatitis C virus hypervariable region I peptide R9.

The immunogenic properties of chimeric potato virus X (PVX) particles engineered to display the synthetic R9 peptide have been evaluated. The R9 peptide is a consensus sequence derived from diverse variants of the hypervariable region 1 from the hepatitis C virus (HCV) envelope protein E2. Two different constructs were designed, with the R9 peptide expressed either as an indirect fusion via the ribosomal skip 2A (PVX(R9-2A)CP) sequence or as a direct PVX coat protein fusion (PVX(R9)CP). Systemic infection of Nicotiana benthamiana plants was only achieved with PVX(R9-2A)CP constructs, and the presence of the R9 peptide was detected in extracts from these plants by ELISA, Western blot and electron microscopy using specific anti-R9 antibodies. The virus particles were recovered at yields of up to 125mg/kg from leaf material. BALB/c mice immunized with purified PVX(R9-2A)CP particles developed specific anti-R9 IgG titers of up to 1:50,000. Monoclonal anti-R9 antibodies were obtained from the spleen of a mouse immunized with PVX(R9-2A)CP particles and characterized by Western blot and electron microscopy. Sera from patients infected chronically with HCV were found to react specifically with PVX(R9-2A)CP particles in 35% of cases.