The Molecular Biology of Human Caliciviruses

  1. Derek Chadwick and
  2. Jamie A. Goode
  1. Ian N. Clarke and
  2. Paul R. Lambden

Published Online: 7 OCT 2008

DOI: 10.1002/0470846534.ch11

Gastroenteritis Viruses: Novartis Foundation Symposium 238

Gastroenteritis Viruses: Novartis Foundation Symposium 238

How to Cite

Clarke, I. N. and Lambden, P. R. (2001) The Molecular Biology of Human Caliciviruses, in Gastroenteritis Viruses: Novartis Foundation Symposium 238 (eds D. Chadwick and J. A. Goode), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/0470846534.ch11

Author Information

  1. Virus Group, Division of Cell and Molecular Medicine, University of Southampton Medical School, Southampton, UK

Publication History

  1. Published Online: 7 OCT 2008
  2. Published Print: 16 MAY 2001

Book Series:

  1. Novartis Foundation Symposia

Book Series Editors:

  1. Novartis Foundation

ISBN Information

Print ISBN: 9780471496632

Online ISBN: 9780470846537



  • gastroenteritis;
  • calicivirus;
  • electron microscopy;
  • Norwalk-like viruses;
  • ORF1;
  • capsid;
  • viral-like particles;
  • Sapporo-like viruses;
  • molecular;
  • structure


Within the last decade molecular analyses of the genome of Norwalk-like viruses (NLVs) have confirmed that this important group of infectious agents belongs to the Caliciviridae family. NLVs have a positive-sense, single-stranded RNA genome of approximately 7700 nucleotides excluding the polyadenylated tail. The genome encodes three open reading frames: ORF 1 is the largest (∼1700 amino acids) and is expressed as a polyprotein precursor that is cleaved by the viral 3C-like protease; ORF 2 encodes the viral capsid (550 amino acids); and ORF 3 encodes a small basic protein of unknown function. Comparative sequencing studies of human caliciviruses have revealed a second distinct group of viruses known as Sapporo-like viruses (SLVs). SLVs also have a single-stranded, positive-sense RNA genome of approximately 7400 nucleotides and the small 3′ terminal ORF (NLV-ORF3 equivalent) is retained. Phylogenetic analyses of NLV and SLV genomic sequences have assigned these viruses to two different genera with each genus comprised of two distinct genogroups. The fundamental difference in genome organization between NLVs and SLVs is that the polyprotein and capsid ORFs are contiguous and fused in SLVs. Progress in understanding the molecular biology of human caliciviruses is hampered by the lack of a cell culture system for virus propagation. Studies on viral replication and virion structure have therefore relied on the expression of recombinant virus proteins in heterologous systems. Norwalk virus capsid expressed in insect cells assembles to form virus-like particles (VLPs). Structural studies have shown that Norwalk virus VLPs are comprised of 90 dimers of the capsid protein.