Parvovirus Classification Kevin E Brown Immunisation and Diagnosis Unit Virus Reference Department Centre for Infections

Classification of Viruses Prior to 1966 an array of different names/classifications Moscow 1966 – International Congress of Microbiology International Committee on Taxonomy of Viruses (ICTV) A single taxonomic scheme for all viruses Naming and classification 70 Study Groups who provide the information Regular reports (currently 8 th )

ICTV classification ‘a virus species is a polythetic class of viruses that constitute a replicating lineage and occupy a particular ecological niche’ (7 th report) Polythetic class - several properties in common, but not necessarily a single common defining property Hierarchy of recognised viral taxa: (Order); Family; (Subfamily); Genus; Species ‘Other groupings (from clade to super-family), may communicate useful descriptive information in some circumstances but they have no formally recognized taxonomic meaning’ (8 th report, p4)

Demarcation criteria: When is a new virus a new virus? Pairwise sequence identity profiles: well resolved peaks between strains, species and genera. Different virus families show similar overall patterns. Genetic analysis should provide validation of taxonomic assignments. Since viruses are polythetic, multiple demarcation criteria are needed to reliably delineate different species. Sequence comparisons are an increasingly dominant (but not the only) criteria.

Parvoviridae Non-enveloped 22-24nm icosahedral virion kb ss linear DNA genome ITRs at 5’ and 3’ ends Encode no polymerase Dependant on cellular/other viral proteins for DNA replication 2 large ORF NS (or Rep) proteins VP (or Cap) proteins

Parvovirus Classification Host range -2 subfamilies Densovirinae – insects Parvovirinae – vertebrates Autonomous/dependant replication +, –, or +/- strand packaging Identical or different 5’ and 3’ ITRs 1, 2 or 3 promoters Sequence phylogeny

Parvovirus Taxonomy + +

Erythrovirus Genus Encapsidate equivalent numbers of + and – strand upon extraction anneal to form ds DNA Long palindromic ITR (~383 nt) ‘Identical’ ITR at 5’ and 3’ ends Single mRNA promoter Polyadenylation signals mid genome and 3’ end Efficient replication in erythroid precursors

Human Parvovirus B19 (B19V) Type member of the Erythrovirus family First identified in 1974 (CPHL, London) ~ 22 nm icosahedral virion Linear ss DNA ~ 5600 nucleotides Long (383nt) terminal hairpin seq Complex transcription map Single promoter (p6) 1 non-spliced non-structural protein 2 capsid proteins (VP1 & VP2) -alt splicing Small proteins of unknown function VP2 self assembles to form VLP Erythrotropic Does not grow in standard tissue culture Replicates in erythroid progenitors Rare cell lines (UT7/Epo; KU812Ep6)

Servant et al. J. Virol 2002 V9 A6 Phylogenetic tree of VP1u region

Phylogenetic analysis of capsid proteins of the Parvovirinae

Phylogenetic analysis of non-structural proteins of the Erythroviruses

Percent Identity NS proteins Genus Species Strains

List of species in Erythrovirus genus Type species – human parvovirus B19 Accepted species Human parvovirus B19 (B19V) B19V-A6, B19V-Au, B19V-LaLi, B19V-V9, B19V-Wi Pig-tailed macaque parvovirus (PmPV) Rhesus macaque parvovirus (RmPV) Simian parvovirus (SPV Tentative species Bovine parvovirus type 3 (BPV-3) Chipmunk parvovirus (ChpPV)

Human Parvoviruses Parv4/5

Parvovirus Study Group Peter Tattersall, Max Bergoin, Marshall Bloom, Kevin Brown, Michael Linden, Nick Muzycka, Colin Parrish and Peter Tijssen Dr Anne Field ( )