Increased interleukin-6 levels in nasal lavage samples following experimental influenza A virus infection

Interleukin-6 (IL-6) is a pleotropic cytokine implicated in the pathogenesis of local inflammation during viral upper respiratory infections. This study determined if experimental influenza A virus infection causes local IL-6 production. Seventeen healthy, adult subjects were intranasally inoculated, by course drops, with a safety-tested strain of influenza A/Kawasaki/86 (H1N1) virus. Nasal lavage samples were collected, symptoms were recorded, and expelled nasal secretions were weighed once before and then daily for 8 days after the virus inoculation. Lavage samples were submitted for virus culture and were examined for IL-6 and IL-4 by enzyme-linked immunosorbent assay. The IL-6, but not IL-4, levels were significantly increased in the nasal lavage samples of the 12 subjects who shed virus but not in those of the 5 subjects who did not shed virus. Moreover, the elevations in IL-6 levels were related temporally to the development of nasal symptoms and secretions but not to systemic symptoms. These results suggest a role for locally produced IL-6 in the pathogenesis and expressed symptomatology of influenza A virus infection.