Development of a plant-derived subunit vaccine candidate against hepatitis C virus.

Hepatitis C virus (HCV) is a major cause of acute and chronic hepatitis with over 180 million cases worldwide. Vaccine development for HCV has been difficult. Presently, the virus cannot be grown in tissue culture and there is no vaccine or effective therapy against this virus. In this research, we describe the development of an experimental plant-derived subunit vaccine against HCV. A tobamoviral vector was engineered to encode a consensus sequence of hypervariable region 1 (HVR1), a potential neutralizing epitope of HCV, genetically fused to the C-terminal of the B subunit of cholera toxin (CTB). This epitope was selected from among the amino acid sequences of HVR1 "mimotopes" previously derived by phage display technology. The nucleotide sequence encoding this epitope was designed utilizing optimal plant codons. This mimotope is capable of inducing cross-neutralizing antibodies against different variants of the virus. Plants infected with recombinant tobacco mosaic virus (TMV) engineered to express the HVR1/CTB chimeric protein, contained intact TMV particles and produced the HVR1 consensus peptide fused to the functionally active, pentameric B subunit of cholera toxin. Plant-derived HVR1/CTB reacted with HVR1-specific monoclonal antibodies and immune sera from individuals infected with virus from four of the major genotypes of HCV. Intranasal immunization of mice with a crude plant extract containing the recombinant HVR1/CTB protein elicited both anti-CTB serum antibody and anti-HVR1 serum antibody which specifically bound to HCV virus-like particles. Using plant-virus transient expression to produce this unique chimeric antigen will facilitate the development and production of an experimental HCV vaccine. A plant-derived recombinant HCV vaccine can potentially reduce expenses normally associated with production and delivery of conventional vaccines.

Nucleotide sequence of the 3'-terminal region of the RNA of the El Amar strain of plum pox potyvirus.

The nucleotide sequence of the 3'-terminal 4773 nucleotides of the RNA of a widely divergent, aphid-transmissible strain of plum pox potyvirus isolated from Egypt (PPV-El Amar) was determined. The sequenced region covers the carboxy terminus of the cylindrical inclusion (CI) gene, and the putative 6K protein, the NIa protease, the NIb RNA polymerase and the coat protein genes, linked together as one large open reading frame (ORF) in a fashion similar to the canonical genomic organization of other potyviruses. The large ORF encoding the polyprotein is followed by a 217 nucleotide non-coding region and a poly(A) tail. However, whereas the three PPV strains previously sequenced show levels of identity in excess of 98%, PPV-El Amar shows levels of heterogeneity of 20% in the nucleotide sequence and 10% in the amino acid sequence, when compared with these previously sequenced strains. The N-terminal region of the capsid protein, postulated to be involved in the aphid transmission mechanism of the virus, was found to be the region which differed most between PPV-El Amar and the other strains.