Natural Immunity May Hold Vaccine Clues.

• Position: FLU INFECTION - Brief article

People with higher levels of antibodies against the stem portion of the influenza virus hemagglutinin (HA) protein have less viral shedding when they get the flu, but do not have fewer or less-severe signs of illness, according to a study published in mBio.

HA sits on the surface of the influenza virus to help bind it to cells and features a head and stem region. Scientists only recently discovered that humans naturally generate anti-HA stem antibodies in response to flu infection, and this is the first study of its kind to evaluate preexisting levels of these specific antibodies as a predictor of protection against influenza.

The study team from the National Institute of Allergy and Infectious Diseases has explored immune responses to two influenza surface proteins: HA--the main target of traditional seasonal flu vaccines--and neuraminidase (NA). The head region of HA is changing constantly, which is why influenza vaccine strains must be updated each year. The HA stem region, however, is less susceptible...