标题: [Corrections by Studyforhope] How REP 9AC works. [打印本页] 作者: StephenW 时间: 2011-8-13 17:15 标题: [Corrections by Studyforhope] How REP 9AC works.
I had given some wrong interpretations on this forum about how REP 9AC works to inhibit the entry/exit of HBV. I want to share the explanations, kindly provided to me by Studyforhope on MedHelp, on how REP 9AC actually works. I don't know who Studyforhope is, but to me, he/she is very knowledgeable and I am very grateful to him/her for the explanation.
Your questions:
1.Does REP 9AC block the release/PRODUCTION/FORMATION of spherical and elongated particles(no viral dna and is non-infectious) of HBsAg from infected liver cells?
YES
2.Does REP 9AC block the release of Dane particles from infected liver cells?
NO
3. Or does REP 9AC block the formation of Dane particles?
NO
The measurement of viral load is done by extrating DNA from the lysed Dane particles. Since the HBv genome is present once per viron, a Dane particle count can be easily calculated from the DNA amount found in the patient serum.
Surface antigen is produced from the HBV cccDNA (circular, closed coiled) by transcription in the nucleus where the cccDNA resides a a minichromosome. The messenger RNA moves to the cytosol for translation and the surface antigen protein is primarily inserted (HERE IS THE BLOCK BY REPLICOR) in the endoplasmatic reticulum membrane and later processed into vesicles for export.
Dane particle HBV DNA is synthesized from the progenomic RNA ( made by transcription from the intranuclear permanent cccDNA) inside partially formed cores inside the cystosol, which close by self assembly to a closed sphere while this happens, causing the partial singlestrandedness (incompleteness) of the second so called HBV genomic plus strand. The cores are later covered with a surface antigen/membranecoat, that is fastened to the core by inward directed preS1 loops, while the outward, myristylated preS1 loops of the Dane particles are the ones that make later (after release of the virion from the hepatozyte into the circulation) contact for infection to the targeted liver cell membrane receptor, causing entry to the hepatozyte. When an artificillay introduced pres1 peptide molecule is already stuck on these receptors (importantly, a small receptor percentage is enough to block!!!) (HERE IS THE BLOCK BY MYRCLUDEX!) then the Dane particle membrane cannot get close enough to the cell membrane to FUSE, thus NO ENTRY, no reinfection, a cleaner liver, day by day....
作者: tonychant 时间: 2011-8-13 19:11
can you speak chinese?作者: StephenW 时间: 2011-8-13 20:37
tonychant 发表于 2011-8-13 19:11
can you speak chinese?
Yes, I can read but not write (except by using Google Translate). Why ask? 作者: 灰天 时间: 2011-8-13 21:02
Some more explanations from studyforhope. [UND - I think it means undetectable]
1. REP 9AC is best used with an antiviral (that reduces viral load and thus re-infection)?
A difficult question, because a reduction in viral load by the antiviral is also often followed by lower immune activity, that might delay the reawakening of the immune response to the surface antigen after it has been blocked by REp9AC from flooding the system.
Nevertheless, the capacity of HBV to grow back against the reawakened surface epitope Tcell mediated clearance effect should be much weaker with an antiviral in place. HBV is a dynamic disease and the dramatic reduction by antivirals of the replicative capacity of HBV should help the clearance dynamics.
The blockage of reinfection by antivirals might not be as effective as one might think. The virus overproduces virions tens of thousandfold over the amount needed to fully reinfect. Not only is the UND status misleading insofar as the detection methods still have limited sensitivity and UND could still mean a production of eg 50000 dane particles a day, but yet another critical effect has to be considered. Freshly produced virions in particular will readily infect a neighboring hepatocyte cell from the space of Disse, but also circulating virions will be rapidly absorbed and removed by the liver by its affinity to the preS1myr binding receptor at the hepatocyte surface. To put it simple, the liver will act like a gigantic affinity absorbing column/mass, removing/ clearing Dane particles from the circulation until it is saturated. Thus even real UND with more sensitive methods might not mean that there is still a large amount of reinfection/remnant virion production going on.
2. REP 9AC is best used with an entry inhibitor like Myrcludex?
This could be an ideal combination, because any freshly produced or cleared cell will be protected from reinfection, allowing slow but consistent reduction of viral infestation of the liver.
Here is however another critical argument regarding the replacement of immune cleared cells by fresh uninfected hepatocytes; While the mainstream thinking is that hepatocytes are replaced by division from so called satellite cells embedded in the liver ( 'liver stem cells") others think that regular hepatocytes will divide once the regnerative impulse/signal from Hepatocyte Growth Factor is sensed to replace a shrinking liver mass. The dividing "mother" cell is likely infected, and since there are typically 10 to 30 HBV cccDNA molecules in the nucleus, these will be distributed into the daughter cells, which then, bingo, are already infected from their "birth".
Antivirals typically reduce the amount of cccDNA, but nor dramatically, at best about 10 times.This might still help in this scenario.
3. REP 9AC, by reducing the number of HBsAg particles, is sufficient to allow the immune system to do its job in clearing hbv?
This will depend on the vigor and breath of the anti surface Tcell (cd8 - cytotoxic/killer as well as cd4 helper Tcells) and later B cell response. It has been tolerized by oversupply with antigen for a long time, most clones will be exhausted or lost. Thus a less than perfect SVR rate can be explained by an insuffcient recovery of that system. It will take time to regenerate, reawake, possibly by the novo supply from the thymus. Some think that the surface antigen mainly acted as a suppressor of innate immunity, that this innate immunity will restart once the mitigating protein hasd disappeared from the circulation. Chisari and the majority of HBV immunology specialist place more emphasis on the adaptive, specific response, since it allows targeted removal of HBV protein producing infected cells. In reality, innate immunity is the danger sensing promotor of adaptive imunity, the two work in intimate collaboration and therefore both need to be quite functional for a successful clearance event.
4. What is the method used to deliver REP 9AC into the liver cells?
From what was heard at the European meeting, it is by weekly infusion.