Influenza virus directly infects, inflames, and resides in the arteries of atherosclerotic and normal mice

Objective: Influenza can trigger heart attacks, and vaccination against influenza reduces the risk of cardiovascular events. Currently, it is believed that influenza virus in general does not disseminate to extra-pulmonary tissues. We assessed the vascular effects of influenza infection and whether the virus can directly infect atherosclerotic arteries in mice. Methods/Results: We intranasally infected 4 different types of mice-atherosclerotic apo E-deficient (our primary model), LDL receptor knockout, C57BL/6, and outbred Swiss,-with influenza A/HK (H3/N2) virus. On day 7 after infection, we cultured viable virus from lung, aorta, and heart tissue, but not from the blood of apo E-deficient mice. Immunofluorescence studies showed influenza A virus NP1 protein and real time polymerase chain reaction (PCR) assay showed RNA in the aorta of infected apo E-deficient mice. Infected mice had significantly higher blood levels of chemokines and cytokines than control mice. At the local level, gene expression for several chemokines and cytokines was increased and eNOS expression was decreased. Infected mice had a higher density of macrophages in plaque than did control mice. Conclusions: We have shown for the first time that influenza virus can directly infect and reside in atherosclerotic arteries and that infection was associated with systemic and arterial-level proinflammatory changes. (C) 2009 Elsevier Ireland Ltd. All rights reserved.