The objectives of the proposed research are to understand the mechanisms for the generation and emergence of variants during chronic infection with hepadnaviruses. Variants are thought to be important in the pathogenesis or persistence of HBV infections in humans, and are known to be responsible for the development of drug resistance during antiviral therapy and for infection in vaccinated individuals and liver transplant recipients. However, because chronic infection is due to persistent infection at the cellular level, and the liver is a relatively quiescent tissue, it is not clear how variants that are generated during a chronic infection emerge as the dominant species of virus. The research we propose is designed to clarify the mechanisms for emergence of virus strains. Understanding the processes that result in evolution of the virus population in a chronically infected liver requires gaining new fundamental information about the nature of chronic infections; i.e. about how the progeny of the infecting viruses and variants are distributed in the liver, how much viral and cellular turnover occurs during chronic infection, and how virus lineages are segregated in different populations of hepatocytes where selection of individual variants can occur. Because these questions cannot be addressed experimentally in human HBV infections, we will use the duck hepatitis B virus (DHBV) model. DHBV, a member of the hepadnavirus family, closely resembles HBV in virus structure, genome replication, persistence, and tissue tropism. DHBV is the only member of this family of viruses that can be genetically manipulated in vitro and tested conveniently in animal infections. The five specific aims are (1) to measure the spontaneous mutation frequency in a single round of transcription and reverse transcription of the DHBV genome, (2) to determine the nature of mixed infections of the liver at the cellular level, particularly the frequency of doubly and singly infected hepatocytes, cell-to-cell variation in covalently closed circular DNA (cccDNA) copy number, and the effects of liver growth and regeneration on these properties, (3) to measure the dynamic state of in vivo chronic infections, (4) to describe the process of replacement of a cytopathic strain by a noncytopathic reverant in vivo, and (5) to determine the spatial distribution of virus strains in mixed infections.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA084017-02
Application #
6377639
Study Section
Experimental Virology Study Section (EVR)
Program Officer
Cole, John S
Project Start
2000-07-01
Project End
2005-06-30
Budget Start
2001-07-01
Budget End
2002-06-30
Support Year
2
Fiscal Year
2001
Total Cost
$637,016
Indirect Cost
Name
University of New Mexico
Department
Physiology
Type
Schools of Medicine
DUNS #
829868723
City
Albuquerque
State
NM
Country
United States
Zip Code
87131
Zhang, Yong-Yuan; Theele, Daniel P; Summers, Jesse (2005) Age-related differences in amplification of covalently closed circular DNA at early times after duck hepatitis B virus infection of ducks. J Virol 79:9896-903
Bill, Colin A; Summers, Jesse (2004) Genomic DNA double-strand breaks are targets for hepadnaviral DNA integration. Proc Natl Acad Sci U S A 101:11135-40
Zhang, Yong-Yuan; Summers, Jesse (2004) Rapid production of neutralizing antibody leads to transient hepadnavirus infection. J Virol 78:1195-201
Summers, Jesse; Mason, William S (2004) Residual integrated viral DNA after hepadnavirus clearance by nucleoside analog therapy. Proc Natl Acad Sci U S A 101:638-40
Zhang, Yong-Yuan; Zhang, Bai-Hua; Theele, Daniel et al. (2003) Single-cell analysis of covalently closed circular DNA copy numbers in a hepadnavirus-infected liver. Proc Natl Acad Sci U S A 100:12372-7
Srivastava, R; You, L; Summers, J et al. (2002) Stochastic vs. deterministic modeling of intracellular viral kinetics. J Theor Biol 218:309-21
Pult, I; Abbott, N; Zhang, Y Y et al. (2001) Frequency of spontaneous mutations in an avian hepadnavirus infection. J Virol 75:9623-32