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另一个角度: Viral Quasi-Species 病毒准种
Gastroenterology. 2007 Sep;133(3):951-958. Epub 2007 Jun 20.
Viral Quasi-Species Evolution During Hepatitis Be Antigen Seroconversion.
Lim SG, Cheng Y, Guindon S, Seet BL, Lee LY, Hu P, Wasser S, Peter FJ, Tan T,
Goode M, Rodrigo AG.
Department of Gastroenterology and Hepatology, National University Hospital,
Singapore; Department of Medicine, Yong Yoo Lin School of Medicine, National
University of Singapore, Singapore; Immunovirology Group, Agency for Science,
Technology and Research, Singapore; Collaborative Anti-Viral Research Lab,
Institute of Molecular and Cell Biology, Biopolis, Singapore.
Background & Aims: Although viral quasi-species evolution may be related to
pathogenesis of disease, little is known about this in hepatitis B virus (HBV);
consequently, we aimed to evaluate the evolution of HBV quasi-species in
patients with well-characterized clinical phenotypes of chronic hepatitis B.
Methods: Four cohorts of well-defined clinical phenotypes of chronic hepatitis
B, hepatitis Be antigen (HBeAg) seroconverters (spontaneous seroconverters and
interferon-induced seroconverters) and nonseroconverters (controls and
interferon nonresponders) were followed during 60 months on average. Serum from
4 to 5 time points was used for nested polymerase chain reaction, cloning, and
sequencing of the precore/core gene (20 clones/sample). Only patients with
genotype B were used. Sequences were aligned using Clustal X, then serial-sample
unweighted pair grouping method with arithmetic means phylogenetic trees were
constructed using Pebble 1.0 after which maximum likelihood estimates of
pairwise distances under a GTR + I + G model was assessed. Viral diversity and
substitution rates were then estimated. Results: Analysis of 3386 sequences
showed that HBeAg seroconverters had 2.4-fold higher preseroconversion viral
sequence diversity (P = .0183), and 10-fold higher substitution rate (P < .0001)
than did nonseroconverters, who had persistently low viral diversity (3.6 x
10(-3) substitutions/site) and substitution rate (2.2 x 10(-5)
substitutions.site(-1).month(-1)). After seroconversion, there was a striking
increase in viral diversity. Most seroconverters had viral variants that showed
evidence of positive selection, which was seen mainly after seroconversion.
Conclusions: The high viral diversity before a reduction in HBV DNA and before
HBeAg seroconversion could either be related to occurrence of stochastic
mutations that lead to a break in immune tolerance or to increased immune
reactivity that drives escape mutations.
PMID: 17854598 [PubMed - as supplied by publisher] |
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