title: Increased Protein Degradation Improves Influenza Virus Nucleoprotein-Specific CD8+ T Cell Activation In Vitro but Not in C57BL/6 Mice.
abstract: Due to antigenic drift of influenza viruses, seasonal influenza vaccines need to be updated annually. These vaccines are based on predictions of strains likely to circulate in the next season. However, vaccine efficacy is greatly reduced in the case of a mismatch between circulating and vaccine strains. Furthermore, novel antigenically distinct influenza viruses are introduced into the human population from animal reservoirs occasionally and may cause pandemic outbreaks. To dampen the impact of seasonal and pandemic influenza, vaccines that induce broadly protective and long-lasting immunity are preferred. Because influenza virus-specific CD8+T cells are directed mainly against relatively conserved internal proteins, like nucleoprotein (NP), they are highly cross-reactive and afford protection against infection with antigenically distinct influenza virus strains, so-called heterosubtypic immunity. Here, we used modified vaccinia virus Ankara (MVA) as a vaccine vector for the induction of influenza virus NP-specific CD8+T cells. To optimize the induction of CD8+T cell responses, we made several modifications to NP, aiming at retaining the protein in the cytosol or targeting it to the proteasome. We hypothesized that these strategies would increase antigen processing and presentation and thus improve the induction of CD8+T cell responses. We showed that NP with increased degradation rates improved CD8+T cell activation in vitro if the amount of antigen was limited or if CD8+T cells were of low functional avidity. However, after immunization of C57BL/6 mice, no differences were detected between modified NP and wild-type NP (NPwt), since NPwt already induced optimal CD8+T cell responses.
  
  
  OBJECTIVE
  Due to the continuous antigenic drift of seasonal influenza viruses and the threat of a novel pandemic, there is a great need for the development of novel influenza vaccines that offer broadly protective immunity against multiple subtypes. CD8+T cells can provide immunity against multiple subtypes of influenza viruses by the recognition of relatively conserved internal antigens. In this study, we aimed at optimizing the CD8+T cell response to influenza A virus by making modifications to influenza A virus nucleoprotein (NP) expressed from the modified vaccinia virus Ankara (MVA) vaccine vector. These modifications resulted in increased antigen degradation, thereby producing elevated levels of peptides that can be presented on major histocompatibility complex (MHC) class I molecules to CD8+T cells. Although we were unable to increase the NP-specific immune response in the mouse strain used, this approach may have benefits for vaccine development using less-immunogenic proteins.
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Arwen F
authors: AF
authors: Altenburg
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Carolien E
authors: CE
authors: van de Sandt
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Stella E
authors: SE
authors: van Trierum
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Heidi L M
authors: HLM
authors: De Gruyter
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Peter R W A
authors: PRWA
authors: van Run
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Ron A M
authors: RAM
authors: Fouchier
authors: Medical Biotechnology Center, VIB, Ghent, Belgium.|Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
authors: Kenny
authors: K
authors: Roose
authors: Medical Biotechnology Center, VIB, Ghent, Belgium.|Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
authors: Xavier
authors: X
authors: Saelens
authors: Institute for Infectious Diseases and Zoonoses, LMU University of Munich, Munich, Germany.|German Centre for Infection Research (DZIF), Braunschweig, Germany.
authors: Asisa
authors: A
authors: Volz
authors: Institute for Infectious Diseases and Zoonoses, LMU University of Munich, Munich, Germany.|German Centre for Infection Research (DZIF), Braunschweig, Germany.
authors: Gerd
authors: G
authors: Sutter
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands.
authors: Rory D
authors: RD
authors: de Vries
authors: Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands g.rimmelzwaan@erasmusmc.nl.|ViroClinics Biosciences BV, Rotterdam, the Netherlands.
authors: Guus F
authors: GF
authors: Rimmelzwaan
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000378:metabolism; D000956:Antigens, Viral / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002645:Chickens; D003429:Cross Reactions / Q000276:immunology; D004285:Dogs; D005260:Female; D006367:HeLa Cells; D006801:Humans; D009980:Influenza A virus / Q000276:immunology* / Q000378:metabolism*; D007252:Influenza Vaccines / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D061985:Madin Darby Canine Kidney Cells; D051379:Mice; D008810:Mice, Inbred C57BL; D019590:Nucleocapsid Proteins; D009976:Orthomyxoviridae Infections / Q000821:virology; D059748:Proteolysis; D016601:RNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D014611:Vaccination / Q000379:methods; D014616:Vaccinia virus / Q000276:immunology; D014758:Viral Core Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D007252:Influenza Vaccines; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins