Heterosubtypic Protection Against Influenza A Induced by Adenylate Cyclase Toxoids Delivering Conserved HA2 Subunit of Hemagglutinin

Antiviral Res. 2013 Jan;97(1):24-35. doi: 10.1016/j.antiviral.2012.09.008. Epub 2012 Oct 2.


The protective efficacy of currently available influenza vaccines is restricted to vaccine strains and their close antigenic variants. A new strategy to obtain cross-protection against influenza is based on conserved antigens of influenza A viruses (IAV), which are able to elicit a protective immune response. Here we describe a vaccination approach involving the conserved stem part of hemagglutinin, the HA2 subunit, shared by different HA subtypes of IAV. To increase its immunogenicity, a novel strategy of antigen delivery to antigen presenting cells (APCs) has been used. The HA2 segment (residues 23-185) was inserted into a genetically detoxified adenylate cyclase toxoid (CyaA-E5) which specifically targets and penetrates CD11b-expressing dendritic cells. The CyaA-E5-HA2 toxoid induced HA2(93-102), HA2(96-104) and HA2(170-178)-specific and Th1 polarized T-cell responses, and also elicited strong broadly cross-reactive HA2-specific antibody response. BALB/c mice immunized with three doses of purified CyaA-E5-HA2 without any adjuvant recovered from influenza infection 2days earlier than the control mock-immunized mice. More importantly, immunized mice were protected against a lethal challenge with 2LD(50) dose of a homologous virus (H3 subtype), as well as against the infection with a heterologous (H7 subtype) influenza A virus. This is the first report on heterosubtypic protection against influenza A infection mediated by an HA2-based vaccine that can induce both humoral and cellular immune responses without the need of adjuvant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylyl Cyclases / genetics
  • Adenylyl Cyclases / immunology*
  • Animals
  • Antibodies, Viral / blood
  • Cross Protection*
  • Dendritic Cells / immunology
  • Disease Models, Animal
  • Female
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • Hemagglutinin Glycoproteins, Influenza Virus / immunology*
  • Influenza A virus / genetics
  • Influenza A virus / immunology*
  • Influenza Vaccines / administration & dosage
  • Influenza Vaccines / genetics
  • Influenza Vaccines / immunology*
  • Mice
  • Mice, Inbred BALB C
  • Orthomyxoviridae Infections / immunology
  • Orthomyxoviridae Infections / prevention & control
  • Protein Subunits / genetics
  • Protein Subunits / immunology
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Survival Analysis
  • Th1 Cells / immunology
  • Toxoids / genetics
  • Toxoids / immunology*
  • Vaccines, Synthetic / administration & dosage
  • Vaccines, Synthetic / genetics
  • Vaccines, Synthetic / immunology


  • Antibodies, Viral
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Influenza Vaccines
  • Protein Subunits
  • Recombinant Proteins
  • Toxoids
  • Vaccines, Synthetic
  • Adenylyl Cyclases