Hepatitis B virus surface antigen(HBsAg),a specific antigen on the membrane of Hepatitis B virus (HBV)-infected cells,provides a perfect target for therapeutic drugs.The development of reagents with high affinity and specificity to the HBsAg is of great significance to the early-stage diagnosis and treatment of HBV infection.Herein,we report the selection of RNA aptamers that can specifically bind to HBsAg protein and HBsAg-positive hepatocytes.One high affinity aptamer,HBs-A22,was isolated from an initial 115 mer library of ～1.1×1015 random-sequence RNA molecules using the SELEX procedure.The selected aptamer HBs-A22 bound specifically to hepatoma cell line HepG2.2.15 that expresses HBsAg but did not bind to HBsAg-devoid HepG2 cells.This is the first reported RNA aptamer which could bind to a HBV specific antigen.This newly isolated aptamer could be modified to deliver imaging,diagnostic,and therapeutic agents targeted at HBV-infected cells.

To better understand the effect of a new split variant of human asialoglycoprotein receptor (ASGPR H1b) on ASGPR ligands' binding ability, we established a functional cell line which expresses ASGPR. The full lengths of ASGPRH1a and H2c fragments from human liver were amplified by reverse transcript PCR (RT-PCR) and inserted into eukaryotic expression vector pIRES2EGFP, pCDNA3.1 (Zeo+) respectively. The recombinants were co-transfected into HeLa cells. After selection by using Neocin and Zeocin, a stably transfected cell line was established, which was designated 4-1-6. The transcription and expression of ASGPRH1a and H2c in 4-1-6 were confirmed by RT-PCR, Western blotting and immunofluorescence. The endocytosis function of the artificial "ASGPR" on the surface of 4-1-6 was tested by FACS. It was found that the cell line 4-1-6 could bind ASGPR natural ligand molecular asialo-orosomucoid (ASOR). After the eukaryotic plasmid H1b/pCDNA3.1 (neo) was transfected into cell line 4-1-6, H1b did not down-regulate the ligand binding ability of ASGPR. The eukaryotic expression plasmid H1b/pcDNA3.1 (neo) and H2c/pcDNA3.1 (neo) were co-transfected transiently into Hela cell. Neither single H1b nor H1b and H2c could bind ASOR. In conclusion, a functional cell line of human asialoglycoprotein receptor (ASGPR) which expresses both H1a and H2c stably was established. The new split variant H1b has no effect on ASGPR binding to ASOR. ASGPRH1b alone can't bind to ASOR, it yet can't form functional complex with ASGPRH2c.

OBJECTIVETo explore the effect of the cytoplasmic DNA sensor DAI on replication of hepatitis B virus (HBV) and its possible mechanism.

METHODSThe hepatocyte-derived cell line HepG2 was co-transfected with DAI siRNA and the HBV1.3 replicative plasmid PHY106, and the cells were divided into two experimental groups. Six hours later, total RNA was extracted from the first group of cells and expression of IFIT1 and IL-6 were detected by real-time RT-PCR. The second group of cells was incubated for 4 days, after which the cell supernatant was collected and the HBV surface antigen (HBsAg) and envelope antigen (HBeAg) were detected by ELISA. In addition, HBV core particles were extracted and applied to southern blot assay to detect the intracellular HBV replication intermediates (rcDNA, dlDNA and ssDNA). Next, the HepG2 cells were triple transfected with siRNA targeting the type I interferon pathway molecule TBK1 and DAI simultaneously and HBV1.3, after which HBV viral proteins were detected. Two-group comparisons were made using the independent sample t-test, and more-than-2-group comparisons were made using ANOVA.

RESULTSDAI gene expression was down-regulated in response to DAI siRNA transfection. Cells with down-regulated DAI showed inhibited HBV replication (in a dose-dependent manner), accompanied by reduced levels of HBsAg (0.0195+/-0.0050 vs.

CONTROL0.3150+/-0.0200, P less than 0.05, t = 14.77) and HBeAg (0.0140+/-0.0040 vs.

CONTROL0.01235+/-0.0135, P less than 0.05, t = 7.777). No effect of down-regulated DAI was observed for the expression of IFIT1 of IL-6. siRNA-mediated down-regulation of TBK1 and DAI simultaneously led to reduced expression of HBsAg and HBeAg.

CONCLUSIONDown-regulation of DAI gene expression inhibited HBV replication and HBV protein expression, but the underlying mechanism was not related to the type I interferon or NF-kB signaling pathway.

Carrier Proteins ; metabolism ; DNA-Binding Proteins ; genetics ; metabolism ; Down-Regulation ; Gene Expression Regulation ; Hep G2 Cells ; Hepatitis B Surface Antigens ; isolation & purification ; Hepatitis B e Antigens ; isolation & purification ; Hepatitis B virus ; physiology ; Humans ; Interleukin-6 ; metabolism ; NF-kappa B ; metabolism ; Plasmids ; RNA, Small Interfering ; genetics ; Signal Transduction ; Transfection ; Virus Replication

To better understand the effect of a new split variant of human asialoglycoprotein receptor (ASGPR Hlb) on ASGPR ligands' binding ability, we established a functional cell line which expresses ASGPR. The full lengths of ASGPRH 1 a and H2c fragments from human liver were amplified by reverse transcript PCR (RT-PCR) and inserted into eukaryotic expression vector plRES2EGFP,pCDNA3.1 (Zeo+) respectively. The recombinants were co-transfected into HeLa cells. After selection by using Neocin and Zeocin, a stably transfected cell line was established, which was designated 4-1-6. The transcription and expression of ASGPRHla and H2c in 4-1-6 were confirmed by RT-PCR,Western blotting and immunofluorescence. The endocytosis function of the artificial "ASGPR" on the surface of 4-1-6 was tested by FACS. It was found that the cell line 4-1-6 could bind ASGPR natural ligand molecular asialo-orosomucoid (ASOR). After the eukaryotic plasmid H lb/pCDNA3.1 (neo)was transfected into cell line 4-1-6, Hlb did not down-regulate the ligand binding ability of ASGPR.The eukaryotic expression plasmid Hlb/pcDNA3.1 (neo) and H2c/pcDNA3.1 (neo) were co-transfected transiently into Hela cell. Neither single Hlb nor Hlb and H2c could bind ASOR. In conclusion, a functional cell line of human asialoglycoprotein receptor (ASGPR) which expresses both Hla and H2c stably was established. The new split variant Hlb has no effect on ASGPR binding to ASOR. ASGPRHlb alone can't bind to ASOR, it yet can't form functional complex with ASGPRH2c.