title: Hemagglutinin Sequence Conservation Guided Stem Immunogen Design from Influenza A H3 Subtype.
abstract: Seasonal epidemics caused by influenza A (H1 and H3 subtypes) and B viruses are a major global health threat. The traditional, trivalent influenza vaccines have limited efficacy because of rapid antigenic evolution of the circulating viruses. This antigenic variability mediates viral escape from the host immune responses, necessitating annual vaccine updates. Influenza vaccines elicit a protective antibody response, primarily targeting the viral surface glycoprotein hemagglutinin (HA). However, the predominant humoral response is against the hypervariable head domain of HA, thereby restricting the breadth of protection. In contrast, the conserved, subdominant stem domain of HA is a potential "universal" vaccine candidate. We designed an HA stem-fragment immunogen from the 1968 pandemic H3N2 strain (A/Hong Kong/1/68) guided by a comprehensive H3 HA sequence conservation analysis. The biophysical properties of the designed immunogen were further improved by C-terminal fusion of a trimerization motif, "isoleucine-zipper", or "foldon". These immunogens elicited cross-reactive, antiviral antibodies and conferred partial protection against a lethal, homologous HK68 virus challenge in vivo. Furthermore, bacterial expression of these immunogens is economical and facilitates rapid scale-up.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science , Bangalore , India.
authors.forename: V Vamsee Aditya
authors.initials: VV
authors.lastname: Mallajosyula
authors.affiliation: Merck Research Laboratories , West Point, PA , USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Citron
authors.affiliation: Viral Pseudotype Unit, Medway School of Pharmacy, University of Kent , Chatham, Kent , UK.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ferrara
authors.affiliation: Viral Pseudotype Unit, Medway School of Pharmacy, University of Kent , Chatham, Kent , UK.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Temperton
authors.affiliation: Merck Research Laboratories , West Point, PA , USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Liang
authors.affiliation: Merck Research Laboratories , West Point, PA , USA.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Flynn
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science , Bangalore , India.
authors.forename: Raghavan
authors.initials: R
authors.lastname: Varadarajan
keywords: Escherichia coli; antibody response; hemagglutinin stalk; pre-fusion conformation; protein minimization; subunit vaccine