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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Teppei
http://orcid.org/0000-0002-3608-0554
T
Yoshioka
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Tomohide
T
Tatsumi
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Takuya
T
Miyagi
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Kaori
K
Mukai
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Kumiko
K
Nishio
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Akira
A
Nishio
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Yoshinobu
Y
Yokoyama
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Takahiro
T
Suda
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Tadashi
T
Kegasawa
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Minoru
M
Shigekawa
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Hayato
H
Hikita
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Ryotaro
R
Sakamori
Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Tetsuo
T
Takehara
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D045744:Cell Line, Tumor; D018920:Coculture Techniques / Q000379:methods; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000235:genetics; D019694:Hepatitis B, Chronic / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007694:Killer Cells, Natural / Q000378:metabolism; D008213:Lymphocyte Activation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D055654:NK Cell Lectin-Like Receptor Subfamily C / Q000378:metabolism*; D055627:Natural Cytotoxicity Triggering Receptor 1 / Q000378:metabolism*; D014779:Virus Replication / Q000235:genetics
D004279:DNA, Viral; C112260:NCR1 protein, human; D055654:NK Cell Lectin-Like Receptor Subfamily C; D055627:Natural Cytotoxicity Triggering Receptor 1; D007371:Interferon-gamma