Viruses recombinant protein expression system

The first hurdle encountered during the development of alfalfa as a recombinant protein production system was the relative inefficiency of the available expression cassettes. A study in which a tomato proteinase inhibitor I transgene was expressed in tobacco and alfalfa under the control of the cauliflower mosaic virus (CaMV) 35S promoter showed that 3-4 times more protein accumulated in tobacco leaves compared to alfalfa leaves [5]. Despite the low efficiency of the CaMV 35S promoter in alfalfa, bio-pharmaceutical production using this system has been reported in the scientific literature. Such reports include expression of the foot and mouth disease virus antigen [6], an enzyme to improve phosphorus utilization [7] and the anti-human IgG C5-1 [8]. In this last work, the C5-1 antibody accumulated to 1% total soluble protein [8]. 

Within each species, individual promoters resulted in distinct, tissue-dependent accumulation patterns. The cauliflower mosaic virus (CaMV) 35S promoter, for example, led to high-level accumulation in callus and leaves whereas the maize ubiqui-tin-1 promoter was the best choice for producing recombinant proteins in cereal seeds even though it is not in itself seed-specific [23]. The lack of such comparative studies for proteins other than rAbs makes it difficult to generalize an optimal expression strategy for all proteins. Tables 7.1 and 7.2 list recombinant proteins expressed in plants and provide details of the production system, promoters and other regulatory elements used in each case. 

Several soluble antigens that have been produced in plants using plant viruses as expression systems have shown immunogenic and protective properties in test animals [11]. The plant-derived proteins, which include known immunogens from pathogens or allergens from plants [38], have been tested either as crude plant extracts containing recombinant protein or as purified material from the infected plants. 

Recombinant plant viruses have been used as expression vectors because the infections are rapid and systemic, leading to high levels of recombinant protein produc-... 

Two types of expression systems based on plant RNA viruses have been developed for production of immunogenic peptides and proteins in plants epitope presentation systems (short antigenic peptides fused to the CP that are displayed on the surface of assembled viral particles) and polypeptide expression systems (these systems express the whole unfused recombinant protein that accumulates within the plant). 

Blasey HD, Lundstrom K, Tate S, Bernard AR (1997), Recombinant protein production using the Semliki Forest Virus expression system, Cytotechnology 24 65-72. 

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