Washington, Aug 26 : Scientists have made a new discovery that could help explain how influenza B is limited to humans, and why it cannot be as virulent as A strains that incorporate new genes from influenza viruses that infect other species.

The discovery by researchers at Rutgers University and the University of Texas at Austin could also help scientists develop drugs to fight seasonal influenza epidemics caused by the common influenza B strain.

The researchers have determined the three-dimensional structure of a complex between an influenza B virus protein and one of its human protein targets, resulting in suppression of the cell's natural defences to the infection and paving the way for the virus to replicate efficiently.

"Our study shows the basis by which non-structural protein 1 of influenza B, or NS1B, binds to a human host protein, immobilizing it to prevent it from fighting the virus," said Gaetano Montelione, a lead author and professor of biochemistry and molecular biology, School of Arts and Sciences, at Rutgers.

That human protein, known as interferon-stimulated gene 15 protein or ISG15, is an essential part of the defence mechanism that human cells use to protect themselves from viral infections.

Chemicals that block the binding of NS1B to ISG15 may have antiviral potential against influenza B virus.

The study, led by professors Montelione and Robert Krug at the University of Texas at Austin, also reveals why NS1B cannot bind ISG15 molecules in other species, such as dogs or mice.

Only human and non-human primate ISG15 proteins have a unique molecular sequence in a small part of the protein that makes it possible to bind to the NS1B protein. So far, influenza B virus has been found only in humans.

The findings were published in the most recent issue of PNAS (Proceedings of the US National Academy of Sciences). (ANI)