Recombinant Vaccines

Traditional vaccines, built from a weakened or killed whole pathogen, have real limitations — variable quality, side effects and, for some pathogens, safety concerns about handling live material. Recombinant DNA technology has produced several newer vaccine classes that are more uniform and generally gentler. Subunit recombinant vaccines use only a purified component of the pathogen — a protein, peptide or piece of DNA — rather than the whole organism, giving a pure, stable and safe preparation; the recombinant hepatitis B vaccine, made by cloning the HBsAg surface-antigen gene into the yeast Saccharomyces cerevisiae, was the world's first synthetic vaccine (launched in 1997, marketed as Recombivax and Engerix-B), and India became only the fourth country after the USA, France and Belgium to develop its own indigenous hepatitis B vaccine. Attenuated recombinant vaccines genetically modify a pathogenic bacterium or virus so it can no longer cause disease but can still be used live to trigger immunity. DNA vaccines, a technique dating to 1990, work differently again: a gene encoding an antigenic protein is inserted into a plasmid and delivered into the target animal's own cells, which then display the antigen and provoke an antibody response — since only a few pathogen genes are present, the DNA vaccine itself cannot cause disease, and it is comparatively cheap and easy to design. A fourth class, edible vaccines, are produced by molecular pharming: the relevant gene is introduced into a plant, w …