HAPS HEPATITIS B VIRUS (HBV) CAPSID INHIBITORS AFFECT CORE PROTEIN INTERACTION WITH THE MINICHROMOSOME AND TARGET CCCDNA FUNCTION
HAPS乙型肝炎病毒(HBV)衣壳蛋白抑制剂影响核心蛋白的相互作用的微小染色体目标cccDNA的功能
L. Belloni1,2,3*, L. Li4, G.A. Palumbo1,2, S.R. Chirapu5, L. Calvo1, M. Finn5, A. Zlotnick4, M. Levrero1,2,3
1Dip. di Medicina Interna (DMISM), 2EAL Inserm U 785, 3Life Nanosciences Laboratory, Sapienza University, Rome, Italy, 4Dept of Molecular & Cellular Biochemistry, Indiana University, Bloomington, IN, 5Dept Chemistry, Scripps Research Inst, La Jolla, CA, USA. *[email protected]
Background: HBV capsid assembly is critical for RNA packaging, reverse transcription, and intracellular trafficking and represents an attractive new therapeutic target. Core proteins (Cp) have been shown to bind the nuclear cccDNA, possibly contributing to the regulation of its function and stability. Hetero-aryl-dihydropyrimidines (HAPs), a new class of antivirals inhibiting HBV replication in vitro and in vivo, enhance the rate and the extent of core protein (Cp) assembly and, at high concentration, stabilize preferentially non-capsid polymers of Cp. Here we investigated the impact of HAP12 on cccDNA formation, levels and transcription as part of its antiviral activity against HBV.
Methods: Capsid-associated HBV-DNA (TaqMan real-time PCR), cccDNA (TaqMan real-time PCR) and pgRNA levels (quantitative real-time PCR with specific primers), were assessed in: a) HepG2 cells transfected with full length HBV genomes; b) the HepG2 H1.3 HBV stable clone; c) the inducible AD38 stable HBV cell line, left untreated or treated with the hetero-aryl-dihydropyrimidine HAP12 at 1-5 microM.
Results: HAP12 treatment of cells transfected with wild type linear HBV genomes showed a complete suppression of HBV replication at 72 and 96 hrs with a peak >50% reduction of pgRNA transcription at 96 hours, without significant changes in cccDNA levels. The strong HAP12 inhibitory effect on pgRNA transcription and HBV replication as well as the lack of significant effect on steady state cccDNA levels was confirmed in both the HepG2 H1.3 stable cell line and in the AD38 HBV inducible cell line. We confirmed, using the cccDNA ChIP assay that HBc is recruited onto the cccDNA in HBV replicating cells. HAP12 treament strongly inhibits cccDNA HBc occupancy in HepG2 H1.3 cells and, in agreement with the inhibition of cccDNA transcription and pgRNA production, a sharp decrease in cccDNA-bound H3 histone acetylation.
Conclusions: HAPs binding to HBV capsid, in addition to conformational change resulting in a core protein that does not support HBV replication, also target the nuclear cccDNA. We show that inappropriate assembly and effective cytoplasmic trapping of Cp induced by HAPs affects Cp interaction with the HBV minichromosome and cccDNA function.
Assigned speakers:
Dr. Laura Belloni, Sapienza University , Rome , Italy
Assigned in sessions:
25.04.2013, 09:00-18:00, Poster Session, P01-07a, Category 07a: Viral Hepatitis B & D: Experimental, Poster Area
Biotechnology company adds new investor in its fight against Hepatitis B virus
March 25, 2013 6:17 pm by Stephanie Baum | 0 Comments
deal, agreementA biotechnology company seeking to eradicate the Hepatitis B virus has added a new investor to its backers to close a $25 million Series A round.
Novira Therapeutics in Radnor, Pennsylvania added Versant Ventures — a venture firm that backs early stage life science companies, according to a company statement. Versant will invest $7.5 million in Novira as part of the deal. The investment follows an initial close of the Series A round in August last year.
Novira is developing capsid inhibitors that attack the shell protecting the virus’ genetic material. It is also developing other Hepatitis B treatments. It is expecting to start clinical trials in 2014.
In an e-mail to clarify the financing, Chief Scientific Officer and President Osvaldo Flores said the financing round followed a two-step closing model in which investors 5AM and Canaan led the first closing in August with a partial syndicate. That was followed by a second closing announced after Versant agreed to be part of the syndicate. Flores added that the financing round was increased to $25 million from $23 million because the slot for the third venture group was increased to match that of the lead investors. The $25 million amount also takes into account the participation of seed investors in the round.
Newborns, young children and immunocompromised patients frequently become chronically infected with Hepatitis B. About 400 million people worldwide suffer from chronic HBV infection. Up to 25 percent with chronic cases of Hepatitis B die from carcinoma or liver cancer, according to the Centers for Disease Control. Vaccinations for infants and non-vaccinated children under 18 is the most common way to prevent transmission. The most common ways the virus is transmitted are through unprotected sex and blood transfusions. About 600,000 people die each year from the virus, according to the World Health Organization.
In an interview last August Flores told MedCity News: “’We believe our drug either alone or in combination with others has the potential to lead to better cure rates” than the treatments that are currently available.
I don't understand the abstract myself. Initially, scientists think HAP reduces viral load by interfering with the capsid made of HBc protin that is essential for forming a new virion. The scientists now discover that HAP also indirectly interferes with the transcription of cccDNA, thereby further reduces production of new virions.
Just my own understanding. 作者: 宁静温泉 时间: 2013-4-16 13:31