DNA shuffling: Induced molecular breeding to produce new generation long-lasting vaccines

The paradigm for classic vaccines has been to mimic natural infection, and their success relies mostly on the induction of neutralizing antibodies followed by long-lasting immunity. The outcome of aggressive chronic infections such as HIV and HCV, the reappearance of fastidious diseases such as tuberculosis and the progression of cancer growth suggest that natural immune responses are definitely insufficient in many cases. A new paradigm is needed to design and develop a new high-efficiency generation of vaccines ideally able to surpass the capabilities of natural immune responses. In vitro evolution is a new, important laboratory method to evolve molecules with desired properties, which appears as an appealing alternative to achieve this goal. In its battle against disease, the vertebrate immune system triggers a series of well-known molecular events in order to produce protective neutralizing antibodies. This natural in vivo response shares remarkable similarities with the in vitro technique known as molecular breeding or "DNA shuffling." This method exploits the recombination between genes to dramatically accelerate the rate at which genes can be evolved under selection pressure in the laboratory, producing optimized high-efficiency mutant proteins. Since new generation vaccines are aimed to overcome natural selection and environmental pressures to fully inactivate rapidly developing pathogen variants, they could be engineered, developed and selected through the application of directed DNA shuffling procedures. This review highlights the potential of the procedure in the complex context of natural immune responses and the equilibrium and interaction existing in nature between hosts and pathogens.