The therapeutic potential of plant-derived vaccines and antibodies.

The production of recombinant proteins in plants is reviewed with a particular focus on plant-derived vaccines and antibodies for human healthcare. Issues relating to foreign gene expression, such as protein yield, localisation and glycosylation are also considered. Emphasis is placed on reporting progress with preclinical and clinical evaluation of plant-derived vaccines and antibodies. An assessment is made of the likely future direction of research and development in this area.

Plant-derived vaccine protects target animals against a viral disease.

The successful expression of animal or human virus epitopes on the surface of plant viruses has recently been demonstrated. These chimeric virus particles (CVPs) could represent a cost-effective and safe alternative to conventional animal cell-based vaccines. We report the insertion of oligonucleotides coding for a short linear epitope from the VP2 capsid protein of mink enteritis virus (MEV) into an infectious cDNA clone of cowpea mosaic virus and the successful expression of the epitope on the surface of CVPs when propagated in the black-eyed bean, Vigna unguiculata. The efficacy of the CVPs was established by the demonstration that one subcutaneous injection of 1 mg of the CVPs in mink conferred protection against clinical disease and virtually abolished shedding of virus after challenge with virulent MEV, demonstrating the potential utility of plant CVPs as the basis for vaccine development. The epitope used occurs in three different virus species-MEV, canine parvovirus, and feline panleukopenia virus- and thus the same vaccine could be used in three economically important viral hosts-mink, dogs, and cats, respectively.

Potential of chimaeric plant virus particles as novel, stable vaccines.

Technology has been developed for the expression of multiple copies of epitopes from human and animal pathogens on the surface of assembled particles of a plant virus (cowpea mosaic virus). The technology, termed the Chimaeric Virus Particle (CVP) Technology, can be exploited for the production of vaccines in plants. Each chimaeric virus particle contains 60 copies of the foreign peptide which are expressed in highly exposed positions on the surface of the virus particle. Viral and bacterial epitopes have been expressed as CVPs in an immunologically active form. CPMV is stable at temperatures up to 65 degrees C and a chimaera expressing an HIV epitope survives exposure to a protease and to pH values as low as 1.0.

Effect of glycerol on thermolysin-catalyzed peptide bond synthesis.

The effect of glycerol on the hydrolytic activity of thermolysin (EC 3.4.24.4) has been compared with the effect on the condensation of N-benzyloxycarbonyl-L-aspartic acid with L-phenylalanine methyl ester to form N-benzyloxycarbonyl-L-aspartyl-L-phenylalanine methyl ester (Z X Asp X Phe X OMe), the precursor to the sweet-tasting compound L-aspartyl-L-phenylalanine methyl ester. Hydrolytic activity was measured by the degradation of azocasein and furylacryloyl-L-glycyl-L-leucinamide. Increasing concentrations of glycerol reversibly inhibited the hydrolytic activity of the enzyme toward both substrates. The inclusion of glycerol in the synthetic medium facilitated the production of Z X Asp X Phe X OMe in a water-soluble system but reduced the initial rate of peptide synthesis. Glycerol stabilized thermolysin against thermal denaturation.