Molecular Biology of Porcine Circoviruses
from: Animal Viruses: Molecular Biology (Edited by: Thomas C. Mettenleiter and Francisco Sobrino). Caister Academic Press, U.K. (2008)
Porcine Circoviruses (PCV) are the smallest viruses replicating autonomously in eukaryotic cells. The virions are non-enveloped and spherical with a diameter of 16-18 nm and the covalently closed and single-stranded DNA genomes comprise less than 1800 nucleotides. The genomes encode only two major open reading frames. The gene products Rep, Rep' and Cap are involved in viral replication, regulation of transcription and capsid formation. Due to their highly limited coding capacity, circoviruses are supposed to rely principally on the host's machinery for synthesis of macromolecules. Two types of PCV are known, which differ with respect to their pathogenicity. Porcine circovirus type 1 (PCV1) is not linked with a disease, while porcine circovirus type 2 (PCV2) is the etiological agent of Postweaning Multisystemic Wasting Syndrome (PMWS), a new emerging and multifactorial disease in swine. PCV1 and PCV2 show a high degree of sequence homology and a similar genomic organisation; nevertheless, the basis of the distinct pathogenicity has not yet been unravelled. Here the molecular biology of PCV1 and PCV2 is described read more ...