Oral administration of an adenovirus vector encoding both an avian influenza A hemagglutinin and a TLR3 ligand induces antigen specific granzyme B and IFN-γ T cell responses in humans

Abstract

PurposeTo test the safety and immunogenicity of an orally delivered avian influenza vaccine. The vaccine has a non-replicating adenovirus type 5 vector backbone which expresses hemagglutinin from avian influenza and a TLR3 ligand as an adjuvant. MethodsForty-two subjects were randomized into 3 groups dosed with either 1×1010, 1×109, or 1×108IU of the vaccine administered in capsules. Twelve subjects were vaccinated with identical capsules containing placebo. A portion of the 1×109 dose group were immunized a second time 4 weeks after the first immunization. The safety of the vaccine was assessed by measuring the frequency and severity of adverse events in placebo versus vaccine treated subjects. IFN-γ and granzyme B ELISpot assays were used to assess immunogenicity. ResultsThe vaccine had a positive safety profile with no treatment emergent adverse events reported above grade 1, and with an adverse event frequency in the treated groups no greater than placebo. Antigen specific cytotoxic and IFN-γ responses were induced in a dose dependent manner and cytotoxic responses were boosted after a second vaccination. ConclusionThis first in man clinical trial demonstrates that an orally delivered adenovirus vectored vaccine can induce immune responses to antigen with a favorable safety profile. Clinical Trial Registration number: NCT01335347.