IS THE MAJOR CAPSID PROTEIN OF IRIDOVIRUSES A SUITABLE TARGET FOR THESTUDY OF VIRAL EVOLUTION

Iridoviruses are large cytoplasmic DNA viruses that are specific for d ifferent insect or vertebrate hosts. The major structural component of the non-enveloped icosahedral virus particles is the major capsid pro tein (MCP) which appears to be highly conserved among members of the f amily Iridoviridae, Phycodnaviridae, and African swine fever virus. Th e amino acid sequences of the known MCPs were used in comparative anal yses to elucidate the phylogenic relationships between different cytop lasmic DNA viruses including three insect iridoviruses (Tipula iridesc ent virus, Simulium iridescent virus, Chile iridescent virus), seven v ertebrate iridoviruses isolated either from fish (lymphocystis disease virus, rainbow trout virus, European catfish virus, doctor fish virus ), amphibians (frog virus 3), or reptiles (turtle virus 3, turtle viru s 5), one member of the family Phycodnaviridae (Paramecium bursaria Ch lorella virus type 1), and African swine fever virus. These analyses r evealed that the amino acid sequence of the MCP is a suitable target f or the study of viral evolution since it contains highly conserved dom ains, but is sufficiently diverse to distinguish closely related irido virus isolates. Furthermore the results suggest that a substantial rev ision of the taxonomy of iridoviruses based on molecular phylogeny is required.