title: Increased viral loads and exacerbated innate host responses in aged macaques infected with the 2009 pandemic H1N1 influenza A virus.
abstract: In contrast to seasonal influenza virus infections, which typically cause significant morbidity and mortality in the elderly, the 2009 H1N1 virus caused severe infection in young adults. This phenomenon was attributed to the presence of cross-protective antibodies acquired by older individuals during previous exposures to H1N1 viruses. However, this hypothesis could not be empirically tested. To address this question, we compared viral replication and the development of the immune response in naïve young adult and aged female rhesus macaques infected with A/California/04/2009 H1N1 (CA04) virus. We show higher viral loads in the bronchoalveolar lavage (BAL) fluid and nasal and ocular swabs in aged animals, suggesting increased viral replication in both the lower and upper respiratory tracts. T cell proliferation was higher in the BAL fluid but delayed and reduced in peripheral blood in aged animals. This delay in proliferation correlated with a reduced frequency of effector CD4 T cells in old animals. Aged animals also mobilized inflammatory cytokines to higher levels in the BAL fluid. Finally, we compared changes in gene expression using microarray analysis of BAL fluid samples. Our analyses revealed that the largest difference in host response between aged and young adult animals was detected at day 4 postinfection, with a significantly higher induction of genes associated with inflammation and the innate immune response in aged animals. Overall, our data suggest that, in the absence of preexisting antibodies, CA04 infection in aged macaques is associated with changes in innate and adaptive immune responses that were shown to correlate with increased disease severity in other respiratory disease models.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, USA.
authors.forename: Laurence
authors.initials: L
authors.lastname: Josset
authors.forename: Flora
authors.initials: F
authors.lastname: Engelmann
authors.forename: Kristen
authors.initials: K
authors.lastname: Haberthur
authors.forename: Sara
authors.initials: S
authors.lastname: Kelly
authors.forename: Byung
authors.initials: B
authors.lastname: Park
authors.forename: Yoshi
authors.initials: Y
authors.lastname: Kawoaka
authors.forename: Adolfo
authors.initials: A
authors.lastname: García-Sastre
authors.forename: Michael G
authors.initials: MG
authors.lastname: Katze
authors.forename: Ilhem
authors.initials: I
authors.lastname: Messaoudi
mesh_terms: D056704:Adaptive Immunity; D000375:Aging; D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology*; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D056738:Cross Protection; D016207:Cytokines / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology* / Q000502:physiology*; D008213:Lymphocyte Activation; D008253:Macaca mulatta; D017817:Nasal Lavage Fluid / Q000821:virology; D009976:Orthomyxoviridae Infections / Q000276:immunology* / Q000821:virology*; D058873:Pandemics; D012137:Respiratory System / Q000821:virology; D019562:Viral Load
chemical_list: D000914:Antibodies, Viral; D016207:Cytokines