Ols and procedures were approved by the Institutional Animal Care and Use Committee at the Center for Biologics Evaluation and Research (protocol #1991-06) and conducted in an SPF animal facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International. All experiments were performed according to institutional guidelines. During influenza challenge studies, animals that had lost 25 of their initial body weight were humanely euthanized to avoid further suffering.Influenza virusesHighly virulent, mouse-adapted virus A/Fort Monmouth/1/ 47-ma (H1N1) [A/FM] has been previously described [35] and was kindly provided by Earl Brown, University of Ottawa, Canada. It was prepared as a pooled homogenate of lungs from BALB/c mice infected with the virus by the intranasal (i.n.) route 4 days earlier.Adenovirus vectorsPan Adenovirus type 3 (PanAd3) was isolated from a stool specimen collected from a bonobo (Pan paniscus). The PanAdisolate was amplified and the virus genome was then cloned in a plasmid vector and fully sequenced. As shown in a phylogenetic tree based on hexon sequences [34], PanAd3 is a member of adenovirus species C, closely related to 
species C human and chimpanzee adenoviruses already used in preclinical and clinical trials (human Ad5, ChAd3). PanAd3 vectors were constructed by homologous recombination in E. coli strain BJ5183 by co-transformation with PanAd3 purified viral DNA and a PanAd3-EGFP shuttle vector. Homologous recombination between pIX genes, right ITR DNA sequences present at the ends of linearized PanAd3-EGFP shuttle and viral genomic DNA allowed its insertion in the plasmid vector, simultaneously replacing the E1 region with a human inhibitor cytomegalovirus (HCMV) Autophagy promoter-driven EGFP expression cassette containing the bovine growth hormone polyadenylation signal (BGH polyA), generating pPanAd3DE1-EGFP. The E3 region (nucleotides 28684 to 32640) was then deleted through several cloning and homologous recombination steps to generate the pPanAd3DE1DE3 backbone, which was propagated in HEK 293 cells. Expression cassettes containing consensus sequences of NP and M1 plus the human cytomegalovirus promoter and bovine growth hormone polyadenylation signal 1081537 were constructed. The influenza expression cassette contains consensus sequences of NP and M1. Influenza A NP and M1 sequences were obtained from the NCBI Influenza Virus Resource database (http://www.ncbi.nlm.nih. gov/genomes/FLU/FLU.html). Protein sequences were chosen from among different subtype strains isolated between 1990 and 2009 that caused infection in humans worldwide. The NP consensus sequence was derived by alignment of all non-identical sequences (H1N1: 88 of 629 sequences, H1N2: 5 of 26, H3N2: 244 of 1557, H5N1: 50 of 121) using 
MUSCLE version 3.6, and applying the majority rule. Further, the NP sequence used in the PanAd3 vaccine lacks the Nuclear Localization Signal residing in aa 6? (TKR mutated to AAA), which results in increased cytoplasmic accumulation. The M1 consensus sequence was similarly derived by the alignment of non-identical sequences (H1N1: 51 of 808 sequences, H1N2: 3 of 34, H3N2: 115 of 2150, H5N1: 23 of 145). NP and M1 sequences were spaced by a flexible linker (GGGSGGG). The resulting NPM1 sequence was codonoptimized for expression in eukaryotic cells. A diagram of the insert and its full sequence are given in Figure 1. The NPM1 expression cassette was inserted into the PanAd3DE1DE3 backbone via homol.Ols and procedures were approved by the Institutional Animal Care and Use Committee at the Center for Biologics Evaluation and Research (protocol #1991-06) and conducted in an SPF animal facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International. All experiments were performed according to institutional guidelines. During influenza challenge studies, animals that had lost 25 of their initial body weight were humanely euthanized to avoid further suffering.Influenza virusesHighly virulent, mouse-adapted virus A/Fort Monmouth/1/ 47-ma (H1N1) [A/FM] has been previously described [35] and was kindly provided by Earl Brown, University of Ottawa, Canada. It was prepared as a pooled homogenate of lungs from BALB/c mice infected with the virus by the intranasal (i.n.) route 4 days earlier.Adenovirus vectorsPan Adenovirus type 3 (PanAd3) was isolated from a stool specimen collected from a bonobo (Pan paniscus). The PanAdisolate was amplified and the virus genome was then cloned in a plasmid vector and fully sequenced. As shown in a phylogenetic tree based on hexon sequences [34], PanAd3 is a member of adenovirus species C, closely related to species C human and chimpanzee adenoviruses already used in preclinical and clinical trials (human Ad5, ChAd3). PanAd3 vectors were constructed by homologous recombination in E. coli strain BJ5183 by co-transformation with PanAd3 purified viral DNA and a PanAd3-EGFP shuttle vector. Homologous recombination between pIX genes, right ITR DNA sequences present at the ends of linearized PanAd3-EGFP shuttle and viral genomic DNA allowed its insertion in the plasmid vector, simultaneously replacing the E1 region with a human cytomegalovirus (HCMV) promoter-driven EGFP expression cassette containing the bovine growth hormone polyadenylation signal (BGH polyA), generating pPanAd3DE1-EGFP. The E3 region (nucleotides 28684 to 32640) was then deleted through several cloning and homologous recombination steps to generate the pPanAd3DE1DE3 backbone, which was propagated in HEK 293 cells. Expression cassettes containing consensus sequences of NP and M1 plus the human cytomegalovirus promoter and bovine growth hormone polyadenylation signal 1081537 were constructed. The influenza expression cassette contains consensus sequences of NP and M1. Influenza A NP and M1 sequences were obtained from the NCBI Influenza Virus Resource database (http://www.ncbi.nlm.nih. gov/genomes/FLU/FLU.html). Protein sequences were chosen from among different subtype strains isolated between 1990 and 2009 that caused infection in humans worldwide. The NP consensus sequence was derived by alignment of all non-identical sequences (H1N1: 88 of 629 sequences, H1N2: 5 of 26, H3N2: 244 of 1557, H5N1: 50 of 121) using MUSCLE version 3.6, and applying the majority rule. Further, the NP sequence used in the PanAd3 vaccine lacks the Nuclear Localization Signal residing in aa 6? (TKR mutated to AAA), which results in increased cytoplasmic accumulation. The M1 consensus sequence was similarly derived by the alignment of non-identical sequences (H1N1: 51 of 808 sequences, H1N2: 3 of 34, H3N2: 115 of 2150, H5N1: 23 of 145). NP and M1 sequences were spaced by a flexible linker (GGGSGGG). The resulting NPM1 sequence was codonoptimized for expression in eukaryotic cells. A diagram of the insert and its full sequence are given in Figure 1. The NPM1 expression cassette was inserted into the PanAd3DE1DE3 backbone via homol.