H1N1 antibodies may help develop universal influenza vaccine
MedWire News: Human antibodies produced in response to infection with or vaccination against the pandemic H1N1 influenza virus may hold the key to developing a more universal influenza vaccine, say Canadian researchers.
They explain that the pandemic H1N1 antibodies are unusual in that they target the stem of the influenza hemagglutinin (HA) protein rather than the head, which is targeted by seasonal influenza antibodies.
"Current flu vaccines target the head of the HA to prevent infections, but because the flu virus mutates very quickly, this part of the HA changes rapidly, hence the need for different vaccines every flu season," commented lead study author John Schrader (University of British Columbia, Vancouver) in a press statement.
Schrader explained that the H1N1 antibodies, which are largely encoded by the IGHV1-69 gene, have the potential to neutralize many if not all of the different strains of influenza, as "the stem plays such an integral role in penetrating the cell that it cannot change between different variants of the flu virus."
Writing in Frontiers in Immunology, the team found that the H1N1 antibodies were able to neutralize various strains of the virus, including 2009 pandemic H1N1, seasonal influenza H1N1, and avian H5N1, by inhibiting HA-mediated membrane fusion.
They say they also tested the ability of these antibodies to treat lethal, heterologous H5N1 infections in mice with great success.
The researchers correlated the dominant response of the pandemic H1N1 antibodies against the HA stem with a relative lack of memory B cells against the HA head of the pandemic H1N1 virus. They say that this allows the memory B cells triggered by seasonal influenza that are specific to the HA stem to "compete for T-cell help."
Schrader and colleagues conclude: "The demonstration that a conventional vaccine given safely to millions of humans induces a dominant, cross-protective antibody response against the HA stem… points to a readily testable vaccination strategy for inducing broad-spectrum protective antibodies against influenza by vaccinating successively with conventional vaccines or live attenuated viruses based on influenza viruses with an 'antigen-shifted' HA that humans have not been exposed to."
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By Helen Albert