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Common Antibodies Found for Multi-Virus Flu Vaccine

Vaccination

(U.S. Centers for Disease Control and Prevention)

22 July 2016. A team at National Institutes of Health discovered three types of antibodies that can neutralize a variety of influenza viral strains infecting humans. Researchers from National Institute of Allergy and Infectious Diseases and National Human Genome Research Institute published their findings yesterday in the journal Cell (paid subscription required).

The team led by Peter Kwong, John Mascola, and Adrian McDermott at NIAID are seeking a more robust strategy for flu vaccine design, which today requires creating a new vaccine formula every year to meet anticipated mutations in flu viruses. Because vaccines need a long lead time to develop a new formulation, manufacture sufficient quantities, and ship inventories were needed, health authorities often must guess well in advance at the precise targets for each year’s flu vaccine.

Most seasonal flu vaccines in the U.S. cover 3 or 4 strains or lines of the virus. In recent years those strains include H1N1 and H3N2 among the influenza A viruses, and 1 or 2 influenza B lines. Influenza A viruses have 11 different strains, while influenza B viruses have 2 main varieties. People older than 65 usually get a higher dose of the vaccine since between 80 and 90 percent of flu related deaths have occurred in people 65 years and older.

In the paper, the researchers took blood samples from 6 participants in a clinical trial testing a vaccine protecting against the H5N1 or avian flu virus, a strain of influenza A. From the samples, the team identified white blood cells, called B cells, in the immune system producing antibodies that reacted to the test vaccine. The researchers then genetically analyzed the antibodies from these reacting B cells.

Results of the analysis reveal 3 classes of antibodies capable of addressing a wide range of influenza A sub-types, from a common characteristic in their hemagglutinin proteins — the “H” in the influenza strain code. The stem in the crystalline protein structure of the hemagglutinin stem had a common binding area for antibodies. Thus various strains of influenza A viruses may have different protein structures, but the binding regions in the stems overlapped.

The researchers point out that a common binding region in the flu virus stem was found before, but only in humans developing antibodies resulting from a natural flu virus infection. These new findings indicate a common binding region covering a wide range of influenza strains could be induced with a vaccine.

As a result, the authors recommend using the sequencing data from these B cells as a benchmark for measuring the breadth of immune responses in future vaccine trials.

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