WASHINGTON, (Reuters) – An antibody being developed  by a Dutch drug company chokes off both seasonal flu and the  H5N1 avian flu virus and might offer a way to develop better  treatments and vaccines, researchers reported yesterday.

Crucell NV’s antibody, a naturally occurring immune system  protein, grabs onto a hidden part of flu viruses, stopping them  from infecting cells, they reported in the journal Science.

It is the second report in a week to find antibodies that  can interfere with a range of strains of flu — one of the  hardest viruses to fight because it mutates so much.

“This is very exciting because it marks the first step  toward the Holy Grail of influenza vaccinology — the  development of a durable and cross-protective universal  influenza virus vaccine,” Ian Wilson, a researcher at he  Scripps Research Institute in La Jolla, California, who helped  lead the research, said in a statement.

“Such a flu vaccine could be given to a person just once  and act as a universal protectant for most subtypes of  influenza, even against pandemic viruses.”

On Sunday, another research team said they had found a  batch of antibodies that do something similar.
Flu vaccines and drugs focus on proteins found on the  surface of the flu virus called hemagglutinin and  neuraminidase, which give influenza A viruses their names, as  in H5N1 or H1N1.

Hemagglutinin is a lollipop-shaped structure with a big,  round head. This head is so large that it attracts most of the  immune system antibodies — which then slip off when it  mutates.