A group of scientists from Hyderabad now plans to develop a virus that is partly alive and partly dead in an attempt to wipe polio off the country’s map.
The city-based Ella Foundation, which bagged a grant of $1 lakh from the Bill and Melinda Gates Foundation, is set to start work on a virus that is “disabled” but effective enough to prevent new polio cases. Viruses are pathogens that can only reproduce inside cells.
Ella Foundation scientists propose to halt one or more of the processes required for reproduction of poliovirus inside cells. They anticipate the virus to reproduce partly and thus be partly alive, but at the same time since it cannot complete its circle of life, is therefore partly dead.
“Because the ‘disabled’ virus does not reproduce, and hence cannot spread, it also cannot cause vaccine-derived polio,” said Dr Krishna Ella, co-founder of Ella Foundation. At present, polio vaccines are given through oral drops (live but attenuated virus administered) and injected (killed virus vaccine).
The new virus will have benefits of both polio vaccines, Dr Krishna said. He said: “Once (we reach the time when) there are no polio cases reported, the live vaccine can no longer be used due to two reasons. First, live virus spreads within the body and can go around in the environment to spread to other people. Second, in rare cases, it can cause disease: the so-called vaccine-derived polio.
“Therefore, the world is moving towards using killed vaccine.” However, there are several problems in using a killed vaccine. First, it does not reproduce itself in the body and, thus, does not induce all body defence. Besides, large doses are required for killed virus to produce the required defence mechanisms. The requirement for large doses also takes more resources to manufacture enough doses to cover large populations.
But killed virus vaccine is neither associated with spread within the community nor does it cause disease.