Influenza virus-specific CD4+T-helper cells were cloned that recognized a virus strain isolated in 1981, but that failed to recognize more recent strains. The HLA-DR*1601-restricted epitope recognized was located in the hemagglutinin (HA99-113) and the naturally occurring A → V substitution at position 106 was responsible for abrogating the recognition by HA99-113-specific CD4+T-cells. This amino acid substitution was found in influenza A/H3N2 viruses that circulated between 1999 and 2005 and did not affect recognition by virus-specific antibodies. It was speculated that influenza viruses could evade recognition by virus-specific CD4+T-cells, at least temporarily.

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Virus Research
Erasmus MC: University Medical Center Rotterdam

Berkhoff, E., Geelhoed-Mieras, M., Jonges, M., Smith, D. J., Fouchier, R., Osterhaus, A., & Rimmelzwaan, G. (2007). An amino acid substitution in the influenza A virus hemagglutinin associated with escape from recognition by human virus-specific CD4+ T-cells. Virus Research, 126(1-2), 282–287. doi:10.1016/j.virusres.2007.02.018