Structure and applications of novel influenza HA tri-stalk protein for evaluation of HA stem-specific immunity.

September 27, 2018 By:
  • Lu IN
  • Kirsteina A
  • Farinelle S
  • Willieme S
  • Tars K
  • Muller CP
  • Kazaks A.

Long alpha helix (LAH) from influenza virus hemagglutinin (HA) stem or stalk domain is one of the most conserved influenza virus antigens. Expression of N-terminally extended LAH in E. coli leads to assembly of alpha-h elical homotrimer which is structurally nearly identical to the corresponding region of post-fusion form of native HA. This novel tri-stalk protein was able to differentiate between group 1 and 2 influenza in ELISA with virus-infected mice sera. It was also successfully applied for enzyme-linked immunospot assay to estimate the number of HA stem-reactive antibody (Ab)-secreting cells in mice. An in-house indirect ELISA was developed using a HA tri-stalk protein as a coating antigen for evaluation of HA stem-specific Ab levels in human sera collected in Luxembourg from 211 persons with occupational exposure to swine before the pandemic H1N1/09 virus had spread to Western Europe. Our results show that 70% of these pre-pandemic sera are positive for HA stem-specific Abs. In addition, levels of HA stem-specific Abs have positive correlation with the corresponding IgG titers and neutralizing activities against pandemic H1N1/09 virus.

2018 Sep. PLoS One.13(9):e0204776.
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