title: Amplified and persistent immune responses generated by single-cycle replicating adenovirus vaccines.
abstract: Replication-competent adenoviral (RC-Ad) vectors generate exceptionally strong gene-based vaccine responses by amplifying the antigen transgenes they carry. While they are potent, they also risk causing adenovirus infections. More common replication-defective Ad (RD-Ad) vectors with deletions of E1 avoid this risk but do not replicate their transgene and generate markedly weaker vaccine responses. To amplify vaccine transgenes while avoiding production of infectious progeny viruses, we engineered "single-cycle" adenovirus (SC-Ad) vectors by deleting the gene for IIIa capsid cement protein of lower-seroprevalence adenovirus serotype 6. In mouse, human, hamster, and macaque cells, SC-Ad6 still replicated its genome but prevented genome packaging and virion maturation. When used for mucosal intranasal immunization of Syrian hamsters, both SC-Ad and RC-Ad expressed transgenes at levels hundreds of times higher than that of RD-Ad. Surprisingly, SC-Ad, but not RC-Ad, generated higher levels of transgene-specific antibody than RD-Ad, which notably climbed in serum and vaginal wash samples over 12 weeks after single mucosal immunization. When RD-Ad and SC-Ad were tested by single sublingual immunization in rhesus macaques, SC-Ad generated higher gamma interferon (IFN-γ) responses and higher transgene-specific serum antibody levels. These data suggest that SC-Ad vectors may have utility as mucosal vaccines.
  
  
  OBJECTIVE
  This work illustrates the utility of our recently developed single-cycle adenovirus (SC-Ad6) vector as a new vaccine platform. Replication-defective (RD-Ad6) vectors produce low levels of transgene protein, which leads to minimal antibody responses in vivo. This study shows that replicating SC-Ad6 produces higher levels of luciferase and induces higher levels of green fluorescent protein (GFP)-specific antibodies than RD in a permissive Syrian hamster model. Surprisingly, although a replication-competent (RC-Ad6) vector produces more luciferase than SC-Ad6, it does not elicit comparable levels of anti-GFP antibodies in permissive hamsters. When tested in the larger rhesus macaque model, SC-Ad6 induces higher transgene-specific antibody and T cell responses. Together, these data suggest that SC-Ad6 could be a more effective platform for developing vaccines against more relevant antigens. This could be especially beneficial for developing vaccines for pathogens for which traditional replication-defective adenovirus vectors have not been effective.
authors.affiliation: Virology and Gene Therapy Graduate Program, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Crosby
authors.affiliation: Department of Veterinary Sciences, The University of Texas M. D. Anderson Cancer Center, Bastrop, Texas, USA.
authors.forename: Pramod
authors.initials: P
authors.lastname: Nehete
authors.affiliation: Department of Immunology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA Department of Veterinary Sciences, The University of Texas M. D. Anderson Cancer Center, Bastrop, Texas, USA.
authors.forename: K Jagannadha
authors.initials: KJ
authors.lastname: Sastry
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota, USA Translational Immunovirology and Biodefense Program, Mayo Clinic, Rochester, Minnesota, USA Department of Immunology, Mayo Clinic, Rochester, Minnesota, USA Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, USA mab@mayo.edu.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Barry
mesh_terms: D000260:Adenoviruses, Human / Q000235:genetics* / Q000502:physiology; D000281:Administration, Intranasal; D000286:Administration, Sublingual; D000818:Animals; D000906:Antibodies / Q000032:analysis / Q000097:blood; D004337:Drug Carriers / Q000008:administration & dosage*; D005260:Female; D005822:Genetic Vectors; D018928:Immunity, Mucosal; D007371:Interferon-gamma / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008253:Macaca mulatta; D008647:Mesocricetus; D051379:Mice; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000276:immunology*; D014621:Vagina / Q000276:immunology; D014779:Virus Replication
chemical_list: D000906:Antibodies; D004337:Drug Carriers; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D007371:Interferon-gamma