DNA Virus Vectors for Vaccine Production in Plants: Spotlight on Geminiviruses

Abstract

Plants represent a safe, efficacious and inexpensive production platform by which to provide vaccines and other therapeutic proteins to the world's poor. Plant virus expression vector technology has rapidly become one of the most popular methods to express pharmaceutical proteins in plants. This review discusses several of the state-of-the-art plant expression systems based upon geminiviruses that have been engineered for vaccine production. An overview of the advantages of these small, single-stranded DNA viruses is provided and comparisons are made with other virus expression systems. Advances in the design of several different geminivirus vectors are presented in this review, and examples of vaccines and other biologics generated from each are described.

Keywords: geminivirus; plant; vaccine; virus expression vector.

Figure 1

(a) Genomic organization of geminiviruses. An example of a mastrevirus is provided. Top; circular version, bottom; linearized version of genome. MP; movement protein, CP; coat protein, LIR and SIR; long and short intergenic regions; (b). Geminivirus expression constructs of past and present. Schematic representations of expression vector constructs based on geminiviruses. Top; example of an earlier expression vector. Middle; vector for co-expression of two different proteins, or complex multimeric protein such as monoclonal antibodies. Bottom; foreign gene is expressed in the form of two exons, and protein expression can only take place upon intron processing. In this case, Rep is expressed from an additional construct. GOI; gene of interest, 35S; 35S CaMV promoter, T; terminator. Hatched box; Rep gene could be present in cis in this construct, or expressed in trans from another construct. (middle construct sourced from [15], bottom construct sourced from [16]).