Ou Medicine

Out-Guessing the Flu

It says something about the survival instinct of influenza virus that the batch of vaccine being cooked up this summer isn't designed for the flu we might catch this fall but for the flu we had last winter.

Gillian Air, PhD and her colleagues were first to determine the shape of the influenza enzyme, which led to development of the antiviral drugs Relenza® and Tamiflu®.

By the time we roll up our sleeves in late October, these amazing escape artists will have done it again, mutating just enough to shrug off our natural defenses, reproduce by the trillions and make a lot of people very sick.

On another front in the flu war, tens of millions of dollars are being spent studying avian flu strains in hopes of heading off a pandemic like the one in 1918 that left 50 million people dead.

Neither of these efforts - vaccinating against last year's flu or focusing on bird virus whose human-to-human spread is limited to blood relatives - seems to Gillian Air, Ph.D., as the best way to fight influenza.

The world-renowned authority on flu viruses is instead focused on finding a way to predict how the virus will mutate between one flu season and the next with the goal of "getting the vaccine made for the right year, instead of the year before."

"Basically," Air said, "we have to do in the lab what's happening in the world, but we have to do it a bit faster."

The George Lynn Cross Research Professor of Biochemistry is charting new scientific territory, just has she has done before with historic results.

In the late 1970s, while working in the lab of Nobel laureate Fred Sanger in the Laboratory of Molecular Biology in England and studying the bacterial virus phiX174, Air produced the first-ever sequence of a mutant gene. The process Air used was developed by Sanger and won him a second Nobel in 1980 for the complete sequence of phiX174.

Air modestly says of her discovery, "The joke is that the technology was really bad back then, and when I looked at the result, I couldn't see what was going on and left it on someone else's desk. He said, ‘Aha, there's the mutation!' It was a mess, and I couldn't see it until he showed me where it was."

A similar gel showing now-familiar bands of DNA is thumb-tacked to her bulletin board along with other items, but there's no label boasting the significance of her work.
Air is similarly modest about her critical contribution to the development of flu therapies Relenza® and Tamiflu®, which came in the early 1980s while working in her native Australia with Graeme Laver, whom she calls "one of the real gurus of flu."

The two researchers and an X-crystallographer determined the three-dimensional structure of the flu enzyme neuraminidase. Neuraminidase is the "N" used in identifying a flu strain, as in H1N1, the 1918 flu, or H2N2, the so-called Asian flu.

Neuraminidase and its partner, hemagglutinin, are glycoprotein "spikes" that sit on the surface of the influenza virus. While hemagglutinin gains the virus entrance into the cell where it replicates, it is neuraminidase that chemically snips the offspring viruses free from the cell and allows them to infect and destroy all the cells that line the upper respiratory tract and sometimes the lungs as well.

Gillian Air, Ph.D., center, checks progress in the tissue culture area where research assistants Lyuba Popova, left, and Shelly Gulati are working.

The discovery by Air and her colleagues that neuraminidase has an enzyme-active pocket on its surface allowed developers of Relenza® and Tamiflu® to target the pocket, block enzyme activity and prevent the replicated virus from escaping the cell.

Air's current effort to predict how a virus will mutate relies on single human antibodies developed by Patrick Wilson, Ph.D., at the Oklahoma Medical Research Foundation. "These antibodies will stop the virus from replicating unless the virus mutates," Air said.

When Wilson's antibodies were mixed with the Wisconsin strain used in last winter's vaccine, the virus did mutate, Air said. The amino acid that mutated in the hemagglutinin of the Wisconsin strain was the same site that mutated naturally to give rise to the "Brisbane" flu variant being used in the 2008 flu vaccine for the Southern Hemisphere.

"The virus is actually changing. When we add antibody, the virus we get out is not the same as the virus we put in. This is how different variants come up every winter," Air said. "These new variants have arisen from the same mechanism ... there was antibody selection."

She continued, "Humans make a lot of different antibodies, and what we've never known is how the virus can mutate in the face of a whole lot of different antibodies," Air said.

"The answer seems to be that we don't make so many different antibodies at all. We make a very limited selection, and that's how the virus escapes. We thought we made antibodies against the whole of the surfaces of the proteins that are antigenic.

Now it seems that at any one time, only one part of that protein is antigenic.

"So if we look at the antibodies that people are making against this year's virus and use those in the lab, we might be able to select out the mutants that are going to be selected in the world," Air explained.

And voila, a vaccine that targets the right virus.

Unfortunately, such a vaccine may be years away, Air said. Meanwhile, people will continue being vaccinated against a combination of three strains that affected humans the year before, but that's not all bad. "Because there is cross-reactivity, the antibodies you make against this year's vaccine will still 35give you some protection against next year's virus," Air said. "Just not as much as you'd like."

Air's lab is also trying to determine how the virus recognizes the cells it will infect and how it enters them, and in this puzzle lies the debate over bird flu.

Those who believe humans are at risk maintain that if bird flu learns to recognize the sugars in the human respiratory tract, it will spread through human populations, Air explained.

"That's the dogma. The truth is more complicated and that's why we're working on it. I don't think it has anything to do with the (sugar) specificity," Air said.

"We've had cells in the lab that had all the right receptors on the surface, and in fact, the virus can get in but doesn't make new viruses, so it doesn't spread."

Only several hundred humans have contracted bird flu in the world to date, "but the virus hasn't mutated in those people. It can get from a bird to a person, and what is not happening is person-to-person transmission except in a couple of isolated cases. It's always within blood relatives, so it's got to be genetic."

How long before Air or someone else figures out how to win the war against flu? "Well, I started working on it in the 1970s, and the idea right from the start was to try to get a better vaccine," Air said. "We've been working very hard and we know more about what's needed for a better vaccine, but it's surprising how little we know about what mutations will allow a new variant to spread around the world."