Nasal delivery of an adenovirus-based vaccine bypasses pre-existing immunity to the vaccine carrier and improves the immune response in mice

PLoS One. 2008;3(10):e3548. doi: 10.1371/journal.pone.0003548. Epub 2008 Oct 29.


Pre-existing immunity to human adenovirus serotype 5 (Ad5) is common in the general population. Bypassing pre-existing immunity could maximize Ad5 vaccine efficacy. Vaccination by the intramuscular (I.M.), nasal (I.N.) or oral (P.O.) route with Ad5 expressing Ebola Zaire glycoprotein (Ad5-ZGP) fully protected naïve mice against lethal challenge with Ebola. In the presence of pre-existing immunity, only mice vaccinated I.N. survived. The frequency of IFN-gamma+ CD8+ T cells was reduced by 80% and by 15% in animals vaccinated by the I.M. and P.O. routes respectively. Neutralizing antibodies could not be detected in serum from either treatment group. Pre-existing immunity did not compromise the frequency of IFN-gamma+ CD8+ T cells (3.9+/-1% naïve vs. 3.6+/-1% pre-existing immunity, PEI) nor anti-Ebola neutralizing antibody (NAB, 40+/-10 reciprocal dilution, both groups). The number of INF-gamma+ CD8+ cells detected in bronchioalveolar lavage fluid (BAL) after I.N. immunization was not compromised by pre-existing immunity to Ad5 (146+/-14, naïve vs. 120+/-16 SFC/million MNCs, PEI). However, pre-existing immunity reduced NAB levels in BAL by approximately 25% in this group. To improve the immune response after oral vaccination, the Ad5-based vaccine was PEGylated. Mice given the modified vaccine did not survive challenge and had reduced levels of IFN-gamma+ CD8+ T cells 10 days after administration (0.3+/-0.3% PEG vs. 1.7+/-0.5% unmodified). PEGylation did increase NAB levels 2-fold. These results provide some insight about the degree of T and B cell mediated immunity necessary for protection against Ebola virus and suggest that modification of the virus capsid can influence the type of immune response elicited by an Ad5-based vaccine.

Publication types

  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / immunology*
  • Administration, Intranasal
  • Animals
  • Antibody Formation / physiology
  • Bronchoalveolar Lavage Fluid / chemistry
  • Bronchoalveolar Lavage Fluid / immunology
  • Drug Delivery Systems / methods*
  • Ebola Vaccines / administration & dosage*
  • Ebola Vaccines / immunology*
  • Ebolavirus / immunology
  • Hemorrhagic Fever, Ebola / immunology
  • Hemorrhagic Fever, Ebola / pathology
  • Hemorrhagic Fever, Ebola / veterinary
  • Immunity, Mucosal / drug effects
  • Immunity, Mucosal / physiology*
  • Immunotherapy, Active / methods*
  • Mice
  • Mice, Inbred C57BL
  • Polyethylene Glycols / chemistry
  • Polyethylene Glycols / pharmacology
  • Survival Analysis
  • Virosomes / immunology


  • Ebola Vaccines
  • Virosomes
  • Polyethylene Glycols