Effective Vaccines are Key to Bush’s New Flu Plan

President Bush’s rollout yesterday of a plan to protect the public against a flu pandemic covers several facets. One of the most important ones, if not the cornerstone of the entire plan, is a series of measures aimed at making lots of vaccines in the shortest possible time.

It has been a major challenge until now for several reasons, particularly because of the way flu vaccines currently are made.

“If bird flu erupts into a pandemic, the world will need a lot of vaccine in a hurry,” writes LA Times reporter Charles Piller. “That would be virtually impossible with the current flu-vaccine manufacturing method, which is little changed since the 1940’s.

Indeed, the current predominant method involves an unusually labor-intensive process in which the flu vaccines are grown in million of fertilized chicken eggs --- a process that requires at least six months. This time-consuming process also makes it hard for vaccine makers to keep up with new flu strains as they evolve.

The good news is that pharmaceutical companies are stepping forward with two new techniques that could make turnaround a lot faster.

One approach is reverse genetics. This involves taking apart the genes that make up two viruses --- one deadly, one not so harmful --- and reassembling them into a new, weakened virus that when administered through a vaccine provides immunity from the deadly virus. When the vaccine is injected into an animal or person, it tricks the body into thinking it’s been infected.

In the case of an H5N1 vaccine, the body’s natural immune system would detect the H5 protein and dispatch an army of protective particles, known as antibodies, to latch onto the virus and prevent it from entering a target cell.

Supporters of the reverse genetics approach liken it to advances the Hepatitis B vaccine in the 1980s, when scientists learned how to insert the genetic material for hepatitis B proteins into yeast cells.

Some researchers argue that reverse genetics is the only way to produce vaccines for the current strain of avian flu known as H5N1.

From the standpoint of mass production, another approach involving DNA vaccines may turn out to be even more promising. One biochemist, for example, estimates that the technology could yield 500 million doses of vaccine from a single lab in as little as three weeks. One company even believes it may enable them to develop a vaccine that would protect against all types of flu strains, pandemic or seasonal.

Producing such a vaccine would involve inserting the genetic instructions for making the H5 protein within the deadly bird flu strain into a small ring of DNA extracted from E.coli, a common intestinal bacteria. A vaccine containing this tiny bit of DNA then would be injected into a cell triggering an immune system response in the same way a conventional vaccine does.

Posted by Jim Langcuster at November 2, 2005 02:09 PM | TrackBack