title: Bolstering Components of the Immune Response Compromised by Prior Exposure to Adenovirus: Guided Formulation Development for a Nasal Ebola Vaccine.
abstract: The severity and longevity of the current Ebola outbreak highlight the need for a fast-acting yet long-lasting vaccine for at-risk populations (medical personnel and rural villagers) where repeated prime-boost regimens are not feasible. While recombinant adenovirus (rAd)-based vaccines have conferred full protection against multiple strains of Ebola after a single immunization, their efficacy is impaired by pre-existing immunity (PEI) to adenovirus. To address this important issue, a panel of formulations was evaluated by an in vitro assay for their ability to protect rAd from neutralization. An amphiphilic polymer (F16, FW ∼39,000) significantly improved transgene expression in the presence of anti-Ad neutralizing antibodies (NAB) at concentrations of 5 times the 50% neutralizing dose (ND50). In vivo performance of rAd in F16 was compared with unformulated virus, virus modified with poly(ethylene) glycol (PEG), and virus incorporated into poly(lactic-co-glycolic) acid (PLGA) polymeric beads. Histochemical analysis of lung tissue revealed that F16 promoted strong levels of transgene expression in naive mice and those that were exposed to adenovirus in the nasal cavity 28 days prior to immunization. Multiparameter flow cytometry revealed that F16 induced significantly more polyfunctional antigen-specific CD8+ T cells simultaneously producing IFN-γ, IL-2, and TNF-α than other test formulations. These effects were not compromised by PEI. Data from formulations that provided partial protection from challenge consistently identified specific immunological requirements necessary for protection. This approach may be useful for development of formulations for other vaccine platforms that also employ ubiquitous pathogens as carriers like the influenza virus.
authors.affiliation: †Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Jin Huk
authors.initials: JH
authors.lastname: Choi
authors.affiliation: †Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Schafer
authors.affiliation: ‡Department of Pathology, The University of Texas Medical Branch, Galveston, Texas 77555, United States.
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Freiberg
authors.affiliation: †Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, United States.|§Center for Infectious Disease, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Croyle
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000276:immunology*; D000257:Adenoviridae Infections / Q000276:immunology*; D000818:Animals; D002478:Cells, Cultured; D046129:Ebola Vaccines / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000276:immunology; D029043:Ebolavirus / Q000276:immunology*; D005822:Genetic Vectors / Q000276:immunology; D057809:HEK293 Cells; D006367:HeLa Cells; D019142:Hemorrhagic Fever, Ebola / Q000276:immunology / Q000517:prevention & control*; D006801:Humans; D007113:Immunity, Innate; D007117:Immunization, Secondary; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D059085:Nasal Sprays; D019076:Transgenes / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000737:chemistry / Q000276:immunology
chemical_list: D046129:Ebola Vaccines; D059085:Nasal Sprays; D014614:Vaccines, Synthetic
keywords: Ebola virus; adenovirus serotype 5; formulation; multifunctional CD8+ T cell response; nasal vaccine; pre-existing immunity