Frequency and role of NKp46 and NKG2A in hepatitis B virus infection

• Published in: PLOS ONE Vol. 12; no. 3; p. e0174103
• Main Authors: Yoshioka, Teppei, Tatsumi, Tomohide, Miyagi, Takuya, Mukai, Kaori, Nishio, Kumiko, Nishio, Akira, Yokoyama, Yoshinobu, Suda, Takahiro, Kegasawa, Tadashi, Shigekawa, Minoru, Hikita, Hayato, Sakamori, Ryotaro, Takehara, Tetsuo
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science (PLoS) 22.03.2017; Public Library of Science
• Subjects: Adult; Aged; Aged, 80 and over; Analysis; Biology and life sciences; Cell activation; Cell culture; Cell Line, Tumor; Chronic infection; Coculture Techniques; Coculture Techniques - methods; Cytolysis; Cytometry; Cytotoxicity; Deoxyribonucleic acid; Development and progression; DNA; DNA, Viral; DNA, Viral - genetics; Female; Flow cytometry; Gastroenterology; Genetic aspects; Health aspects; Hep G2 Cells; Hepatitis; Hepatitis B; Hepatitis B virus; Hepatitis B virus - genetics; Hepatitis B, Chronic; Hepatitis B, Chronic - metabolism; Hepatology; Humans; Infections; Interferon; Interferon-gamma; Interferon-gamma - metabolism; Killer cells; Killer Cells, Natural; Killer Cells, Natural - metabolism; Ligands; Liver; Lymphocyte Activation; Lymphocyte Activation - physiology; Lymphocytes; Male; Medicine; Medicine and health sciences; Middle Aged; Natural Cytotoxicity Triggering Receptor 1; Natural Cytotoxicity Triggering Receptor 1 - metabolism; Natural killer cells; NK Cell Lectin-Like Receptor Subfamily C; NK Cell Lectin-Like Receptor Subfamily C - metabolism; NKG2 antigen; Pathogenesis; Patients; Peripheral blood; Physiological aspects; Polymerase chain reaction; Q; R; Research and Analysis Methods; Research Article; Science; Stat1 protein; T cell receptors; Toxicity; TRAIL protein; Trends; University graduates; Viral infections; Virus Replication; Virus Replication - genetics; Viruses; γ-Interferon; Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0174103

Natural Killer (NK) cells are involved in the control of viral infection. However, the role of NK cells in chronic hepatitis B (CHB) remains unclear. This study investigated the frequencies and roles of NK cells in CHB, with a focus on activating receptor NKp46 and inhibitory receptor NKG2A. Peripheral blood lymphocytes were obtained from 71 CHB patients and 37 healthy subjects (HS). The expressions of NKp46 and NKG2A were analyzed using flow cytometry. The role of NKp46-ligand was assessed using an in vitro co-culture system. Cytotoxicity and IFN-γ production in NK cells were evaluated using RT-PCR and flow cytometry. CHB patients were classified into treatment-naïve patients with low HBV DNA titer (CHB-L; n = 28), high HBV DNA titer (CHB-H; n = 24) by the cut-off level of serum HBV DNA 4 log copies/ml, and patients receiving nucleos(t)ide analogue (CHB-NA; n = 19). The expressions of NKp46 and NKG2A were higher in CHB-H than in HS/CHB-L/CHB-NA. HepG2.2.15 had higher NKp46-ligand expression than HepG2. When NK cells from HS were co-cultured with HepG2.2.15, inhibition of the NKp46 and NKp46-ligand interaction by anti-NKp46 antibody significantly reduced cytolysis of HepG2.2.15 and IFN-γ production. However, those reductions were not observed in co-culture with HepG2. Additionally, NK cells that highly expressed NKp46 also highly expressed NKG2A (NKp46highNKG2Ahigh subset). The frequencies of NKp46highNKG2Ahigh subset in CHB-H were higher than those in HS/CHB-L/CHB-NA. Among treatment-naïve CHB patients, the frequencies of NKp46highNKG2Ahigh subset were positively correlated with serum ALT (P<0.01, r = 0.45) and HBV DNA (P<0.01, r = 0.59) levels. The expressions of Fas-L, STAT1, TRAIL and CD107a were higher and IFN-γ expression was lower in the NKp46highNKG2Ahigh subset than in the other subsets. The NKp46 and NKp46-ligand interaction contributes to NK cell activation. A novel NK cell subset, the NKp46highNKG2Ahigh subset, may be associated with liver injury and HBV replication.