New Delhi, Feb. 25: The bird flu virus may be a global threat but another poultry killer is a possible friend-in-waiting for humans.

Two India-born scientists in the US have befriended the Newcastle Disease virus, popularly known in India as Ranikhet virus, to seek a better cure for deadly cancers.

Siba Samal and Elankumaran Subbiah, who have their roots in Orissa and Tamil Nadu, have unravelled the mechanism by which the virus rips open tumour cells while leaving normal, healthy cells intact.

This knowledge has helped the duo — both work with the Virginia-Maryland Regional College of Veterinary Medicine — design a modified Newcastle Disease (ND) virus that can seek and destroy cancer cells in laboratory conditions.

“We have identified the reason the ND virus does not replicate in normal cells but only in tumour cells,” Subbiah told The Telegraph.

The reason is that interferon, a natural protein that protects cells from foreign bodies, clamps down on the virus as it tries to replicate in normal cells.

Tumour cells have a defective interferon response system. So the virus thrives in these cells, triggering apoptosis — a programmed cell death or cell suicide.

The Indian researchers’ exploits with the altered ND virus won them a grant from the US National Institutes of Health.

The novel element in their work is the use of reverse genetics to alter the ND virus. Reverse genetics is the process of generating a recombinant virus by putting together copies of complementary DNA. Such designer viruses have specific properties that make them attractive as biotechnological tools, live vaccines and cancer therapies.

Samal and Subbiah plan to use the money to test the modified ND virus system on animal models to generate safety and efficacy data so that it can be taken to the next level of clinical trials in humans.

“But we are several years away from human clinical trials,” Subbiah said. The first disease they intend to target with the new therapy is prostrate cancer, though their research has demonstrated its effectiveness against many others.

Cancer-killing viruses, once found effective and safe for use, can either replace or work along with existing forms of tumour treatment such as chemotherapy and radiotherapy, both of which have pronounced side effects.

The ND virus belongs to a class of viruses that scientists call oncolytic. These viruses can selectively infect and destroy cancer cells and leave normal cells unharmed. Another oncolytic virus is the polio virus.

The use of poultry viruses in cancer therapy poses no threat to humans, Subbiah said. “The host’s immune system will respond to the virus and eventually clear it.”

“The ND virus is 101 per cent safe for humans, though it affects unvaccinated birds with a varying degree of fatality,” said S.V. Vaidya, an independent poultry consultant in Pune.