

Influenza is no longer the scourge it once was thanks to modern medicine, and specifically, annual vaccination efforts. The flu vaccine isn’t perfect, though. Influenza mutates rapidly, which means a new vaccine formulation is needed every year. An international team of researchers has identified a new antibody that might give us the edge in this yearly arms race. It bypasses the constantly changing surface markers and attacks a different part of the virus membrane.

So why is influenza such a tricky virus to vaccinate against? The virus has a jumble of proteins on its surface called hemagglutinin and neuraminidase that is uses to enter cells. The pattern of these proteins is different in every strain of influenza, which allows it to evade your immune system even if you’ve been infected with the flu before. Basically, you don’t have antibodies that recognize the new patterns on the virus (known as antigens) until you’ve encountered the new strain.

When your body has become sensitized to a pathogen, it can prepare an adaptive immune response. Each antibody can only detect a single antigen. But when it does find its match, the alarms are sounded: The antibody binds to the surface of the virus particle, marking it for destruction by the immune system, and also preventing it from entering your cells. As the immune response picks up, more antibodies are pumped out and other immune cells swing into action to clear virus-infested cells and combat the infection.

antibody antigen recognitionA vaccine provides a template of antigens to train the immune response to recognize the new strains of influenza each year. There’s a certain amount of guess work involved, though. Doctors have to predict which strains will be most prevalent in the upcoming flu season to formulate the vaccine, and sometimes they get it wrong.

The newly isolated antibody, known as CT149, could vastly improve treatment. It bypasses the mixed-up pattern of proteins on the surface of virus particles. Instead, CT149 binds to the hemagglutinin stem region, which is identical on multiple strains of the virus, and it doesn’t mutate every year.

This antibody was isolated from the blood of patients infected with the pandemic H1N1 influenza virus in 2009. To test its activity, researchers injected mice with doses of CT149, and then exposed them to four powerful strains of the flu. The mice were protected from all four, one of which was the 2009 H1N1 strain.

binding site

The discovery of this antibody could point the way to new targets for vaccine research. If the hemagglutinin stem region can be exploited, future vaccines might provide better protection, or even last for more than a year. Maybe one day you’ll be able to get a single vaccine that offers years of protection against the most dangerous strains of the flu. The CT149 antibody itself may also be of use for acute treatment of influenza for already infected individuals — and stopping outbreaks before they become pandemics.