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本帖最后由 bigben446 于 2013-6-10 02:27 编辑
1 RNAi目前没有一个成功的先例，且不看好
2 “目前最重要的步骤还是，作用乙肝聚合酶生成RC-DNA或者阻止乙肝分泌出细胞的药物，而非研究能够作用cccDNA的药物。”
------核苷药物就是很有效的阻断pgRNA生成RC-DNA的，虽然不能彻底阻断，但是效果足够好了，但核苷药物的HBsAg转阴概率太低。阻止乙肝分泌出细胞的药物，如果不同时阻断HBV的复制的话，贸然阻断HBV的分泌，会使HBV病毒产物在细胞内累积，有可能导致肝细胞损害。
"在常年吃药的过程中，致使cccDNA被消耗干净。"
--------------------------------------------------------------核苷药物使用这么多年，结果还是HBsAg转阴的概率那么低，从结果看也知道cccDNA很难被核苷药物控制清除（PS：临床不少结果表明HBsAg的量是和cccDNA正相关的）。
3 HBV慢性化终生感染的原因除了cccDNA很稳定，半衰期很长外，还有一个关键原因是：
cccDNA在细胞内有一个自我扩增补充的机制，只要有合成好的RC-DNA，cccDNA少的话，会优先补充cccDNA库（涉及到大膜蛋白对cccDNA的调节）
贴几个ref：
Title: Formation of the pool of covalently closed circular viral DNA in hepadnavirus-infected cells.
Author: Tuttleman, J. S.; Pourcel, C.; Summers, J.
Source: Cell, 1986, 47(3): 451-460
Abstract:
Covalently closed circular (CCC) double-stranded DNA believed to be the transcriptional template for duck hepatitis B virus (DHBV) is amplified in aging primary cultures of hepatocytes from congenitally infected ducklings. Analysis of 5-bromodeoxyuridine-labeled heavy/light CCC DNA shows that the relaxed circular DNA synthesized in the cytoplasm by reverse transcription is the predominant precursor to the amplified pool of nuclear viral CCC DNA. In vitro infection of uninfected hepatocyte cultures with DHBV demonstrates that a similar 50-fold amplification of CCC DNA occurs during an early stage in the infection before virus production. This amplification allows the establishment of a pool of transcriptional templates in the cell without the need for semiconservative replication or multiple rounds of infection. This process may account for the ability of hepadnavirus-infected cells persistently to produce virus particles in the absence of stable integration of viral DNA.
Title: In hepatocytes infected with duck hepatitis B virus, the template for viral RNA synthesis is amplified by an intracellular pathway.
Author: Wu, T. T.; Coates, L.; Aldrich, C. E. (...)
Source: Virology, 1990, 175(1): 255-261
Abstract:
During the productive phase of chronic hepadnaviral infections, virion DNA synthesis occurs in the cytoplasm of the infected hepatocyte, but viral RNA is synthesized in the nucleus, apparently from a covalently closed, circular (CCC) viral DNA. J. Tuttleman, C. Pourcel, and J. Summers (1986a, Cell 47, 451-460) have shown that the intracellular levels of CCC DNA can increase during initiation of infection of duck hepatocytes in vitro with duck hepatitis B virus and during long term culture of infected duck hepatocytes in vitro. This amplification of CCC DNA occurs through the reverse transcription pathway. To distinguish between an entirely intracellular process of amplification and amplification due to multiple infections by extracellular virus in the virus producing cultures, suramin was added to the infected cultures to block superinfection. We found that CCC DNA amplification occurred at least as efficiently in the presence of suramin as in its absence. First, there was a net increase in the total amount of CCC DNA in the cultures both in the presence and in the absence of suramin. Second, synthesis of CCC DNA in the presence and absence of suramin was observed by density labeling of this viral DNA by growth of the cultures in medium containing BUdR. Amplification was also demonstrable in the presence of neutralizing duck antibodies. These results support the hypothesis of Tuttleman et al. (1986a) that CCC DNA amplification in chronically infected cultures and, by inference, the mechanism of persistent infection involves primarily intracellular regulatory mechanisms.
Title: Coordinate regulation of replication and virus assembly by the large envelope protein of an avian hepadnavirus.
Author: Lenhoff, R. J.; Summers, J.
Source: J Virol, 1994, 68(7): 4565-4571
Abstract:
We have used linker scanning and site-directed mutagenesis in an attempt to distinguish among the known functions of the duck hepatitis B virus large envelope protein, p36. We found that linker-encoded amino acid substitutions in at least one region of the pre-S envelope protein p36 produced defects in both the production of enveloped virus and the regulation of covalently closed circular DNA (cccDNA) synthesis. Most linker substitutions, typically in the 5' two-thirds of the pre-S region of the p36 gene did not affect either cccDNA regulation or enveloped virus production but did destroy the infection competence of the enveloped particles produced. Single amino acid substitutions of residues 128 and 131 demonstrated a similar correlation between defects in the ability of p36 to support enveloped virus production and to control cccDNA levels. We concluded from these studies that virus production and cccDNA regulation probably require a common activity of p36.
最后，清除HBV，以HBsAg向HBsAb为表征，实质是机体免疫系统控制清除肝细胞内的cccDNA。
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楼主: lifflefield
发表于 2013-5-27 23:08
