Primate erythroparvovirus 1, generally referred to as B19 virus, parvovirus B19or sometimes erythrovirus B19, was the first (and until 2005 the only) known human virus in the family Parvoviridae, genus Erythroparvovirus; it measures only 23–26 nm in diameter. The name is derived from Latin, parvum meaning small, reflecting the fact that B19 ranks among the smallest DNA viruses. B19 virus is most known for causing disease in the pediatric population; however, it can also affect adults. It is the classic cause of the childhood rash called fifth disease or erythema infectiosum, or "slapped cheek syndrome Erythroviruses belong to the Parvoviridae family of small DNA viruses. It is a non-enveloped, icosahedral virus that contains a single-stranded linear DNA genome of approximately 5,600 base pairs in length. The infectious particles may contain either positive or negative strands of DNA. The icosahedral capsid consists 60 capsomeres, consisting of two structural proteins, VP1 (83 kDa) and VP2 (58 kDa), which are identical except for 227 amino acids at the amino-terminal of the VP1-protein, the so-called VP1-unique region. VP2 is the major capsid protein, and comprises approximately 95% of the total virus particle. VP1-proteins are incorporated into the capsid structure in a non-stochiometrical relation (based on antibody-binding analysis and X-ray structural analysis the VP1-unique region is assumed to be exposed at the surface of the virus particle. At each end of the DNA molecule there are palindromic sequences which form "hairpin" loops. The hairpin at the 3' end serves as a primer for the DNA polymerase. It is classified as erythrovirus because of its capability to invade red blood cell precursors in the bone marrow. Three genotypes (with subtypes) have been recognised.

The nucleotide substitution rate for total coding DNA has been estimated to be 1.03 (0.6-1.27) x 10⁻⁴ substitutions/site/year. This rate is similar to that of other single stranded DNA viruses. VP2 codons were found to be under purifying selection. In contrast VP1 codons in the unique part of the gene were found to be under diversifying selection. This diversifying selection is consistent with persistent infection as this part of the VP1 protein contains epitopes recognised by the immnune system.

Like other nonenveloped DNA viruses, pathogenicity of parvovirus B19 involves binding to host cell receptors, internalization, translocation of the genome to the host nucleus, DNA replication, RNA transcription, assembly of capsids and packaging of the genome, and finally cell lysis with release of the mature virions. In humans the P antigen (also known as globoside) is the cellular receptor for parvovirus B19 virus that causes erythema infectiosum (fifth disease) in children. This infection is sometimes complicated by severe aplastic anemia caused by lysis of early erythroid precursors

With Regards,
Nancy Ella
Managing Editor
Drug Designing: Open Access