Tohoku J. Exp. Med., 2014 April, 232(4)

Increased Levels of Plasma Galectin-9 in Patients with Influenza Virus Infection

SHIGEKI KATOH,¹ MASAKI IKEDA,¹ HIROKI SHIMIZU,¹ KEIJI MOURI,¹ YASUSHI OBASE,¹ YOSHIHIRO KOBASHI,¹ KIYOYASU FUKUSHIMA,² MISTUOMI HIRASHIMA³ and MIKIO OKA¹

¹Department of Respiratory Medicine, Kawasaki Medical School, Kurashiki, Okayama, Japan
²Division of Respiratory Disease, Japanese Red Cross Nagasaki Genbaku Isahaya Hospital, Isahaya, Nagasaki, Japan
³Department of Immunology and Immunopathology, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan

Galectin-9 (Gal-9) is a β-galactoside-binding protein involved in various biologic processes, including cell aggregation, adhesion, chemoattraction, and apoptosis. Little is known, however, about the regulation mechanisms of Gal-9 production. Recent studies reported high plasma Gal-9 levels in humans infected with human immunodeficiency virus-1 and dengue virus. Viral respiratory infections such as influenza are common human illnesses. A synthetic double-stranded RNA, polyinosinic-polycytidylic acid (PolyIC), mimics the effects of viruses in various cell types and induces the expression of Gal-9 in endothelial cells. To examine the potential link between viral infection and Gal-9 expression, we measured plasma Gal-9 concentrations in patients with influenza. Subjects were 43 patients with influenza virus infection, 20 with pneumococcal pneumonia, and 20 healthy adults. Gal-9 concentrations in the plasma and in culture supernatants of human airway epithelial cells were measured using an enzyme-linked immunosorbent assay. Plasma Gal-9 concentrations were higher in patients with influenza infection than in patients with pneumococcal pneumonia and healthy subjects (p < 0.05). Patients with influenza were effectively differentiated from those with pneumococcal pneumonia or healthy subjects, based on the plasma levels of Gal-9 (p < 0.0001). Furthermore, using a human airway epithelial cell line, we showed that the presence of PolyIC but not lipopolysaccharides increased the Gal-9 concentration in the culture medium (p < 0.05), suggesting that PolyIC enhanced Gal-9 production. These findings support our proposal that Gal-9 production is induced by influenza virus infection in humans. In conclusion, plasma Gal-9 could be a new biomarker for patients with influenza infection.

keywords —— airway epithelial cells; double-stranded ribonucleic acid; galectin-9; human; influenza

© 2014 Tohoku University Medical Press

===============================

Tohoku J. Exp. Med., 2014, 232, 263-267

Correspondence: Shigeki Katoh, M.D., Ph.D., Department of Respiratory Medicine, Kawasaki Medical School, 577, Matsushima, Kurashiki, Okayama 701-0192, Japan.

e-mail: kshigeki@med.kawasaki-m.ac.jp