By Susanne Rust
Sifting through thousands of proteins, researchers have identified an antibody that not only prevents the influenza virus from taking hold of its victims' cells, but also cures already infected animals.
And by examining the cell and virus in their crystalline, or 3-D forms, the researchers were able to identify how this antibody effectively neutralized the virus.
The antibody grabs hold of a particular structure on the virus - a structure the virus uses to latch onto its victim's cells.
And while researchers had known how critical that structure is for the virus, they had deemed it too small for an antibody to effectively get a hold of.
This focused binding "using only a single loop on the antibody has never been seen before, and it's really fascinating," said Ian Wilson, lead author and a professor of structural biology at the Scripps Research Institute. "It gives us some good idea about designs for vaccines and therapies."
The report appears in today's edition of the journal Nature.
The work got started by a team of researchers from the Scripps Research Institute in La Jolla and Sea Lane Biotechnologies, a biotech company in Silicon Valley.
Because bone marrow serves as an archeological repository for all the antibodies a person has ever made, the team began collecting bone marrow from people who had been exposed to particular strains of the flu. The researchers knew the antibodies they were looking for would be in there.
Then using all of the samples they collected, both domestically and internationally, they were able to create a library of billions of flu antibodies. Winnowing the collection down to just those antibodies that could bind to influenza A viruses, they landed on C05.
They found that if they put C05 in a petri dish, with some healthy cells and influenza A, the C05 protected the cells from being infected.
The cells also prevented mice from getting the flu.
And finally, the scientists discovered that if they gave mice that had been exposed to the deadly flu a small dose of C05, 100 percent were cured.
The scientists also looked at the structure of the antibody to figure out how it was doing its job, and that's when they saw that it literally blocked the flu from latching onto its host's cells.
Because this structure on the flu virus is so important for the virus' survival, it doesn't change much among strains, therefore the antibody is effective against several, including H1, H2, H3 and H9.
"Clearly, the holy grail is a universal flu vaccine, and this is another important step toward that. It gives us another target to focus on," Wilson said referring to other research that has shown a target area in the stem of the influenza virus. This antibody, C05, focuses on the head region of the virus.
"If we can figure out how to induce this sort of antibody in a vaccine, we would have something that's very useful," said Lawrence Horowitz, the CEO of Sea Lane Biotechnologies and co-author of the study.