Researchers at Peking University have been working to develop vaccines that use modified, live viruses such that they cannot replicate in human cells, yet still elicit an appropriate immune response. This feat was accomplished by engineering cells that contained "artificial" amino acids not normally found in our genetic code. Viruses were then exposed to the cells and modified such that they could replicate in this new cell line by utilizing the synthetic amino acids. However, since these synthetic amino acids don't exist in our bodies, the viruses wouldn't be able to cause disease in humans, even in their live forms.
Yesterday, the Peking University team published a paper in Science, which details the team's success in developing an Influenza A vaccine that uses these "Live but Replication-Incompetent Viruses." They found that mice vaccinated with cells containing the modified virus gained full protection against the influenza. Vaccines using live viruses are normally more effective, yet riskier than those which contain "inactivated" viruses. This is because live viruses, even weakened, have the potential to mutate back to a pathogenic form and cause disease. However, since the modified viruses in this study can't replicate in normal cells, using a live virus didn't cause any vaccine-acquired infections. This implies that we can now develop more effective, yet equally safe, vaccines in the future.
The success from this study highlights the potential for other vaccines to be developed using the same technology.
Link to article: http://www.genengnews.com/gen-news-highlights/engineered-flu-virus-a-replicative-dud-but-stays-live/81253494