Human Parvovirus B-19

Parvoviridae, parvovirinae

Computer model of HPV B-19 capsid.[14]

The Erythrovirus

Child with Fifth Disease.[14]
Human Parvovirus B-19 is most well-known for causing the childhood disease erythema infectiosum, better known as Fifth Disease. The disease primarily manifests itself as a red rash on the cheeks and trunk, and clears up in a week or so. The virus has a fairly short incubation period of around 4 to 14 days. Only children get Fifth Disease; adults may display flu-like symptoms characteristic of any viral infection. In both adults and children, HPV B-19 has been known to induce arthritic symptoms in joints and synovial fluid, both acute and chronic arthropathy. It's believed that this is caused by VP2, as this structural protein can induce the production of autoantibodies for keratin, collagen, and cardiolipin due to cross-reactivity.

HPV B-19 virus infects and lyses erythroid progenitor cells in the bone-marrow (hence the name erythrovirus), which are the precursors for red-blood- cells (remember, parvovirus can only infect cells that are actively replicating, as the virus has no way of forcing the cell into mitosis). The virus uses the blood group cell receptor P antigen found on erythroblasts, megakaryoblasts, endothelial cells, and fetal myocardial cells. In most adult cases, the infection is relatively painless. However, in immuno-compromised individuals whose immune system cannot properly clear the infection, infection can lead to a depletion of RBC precursors and lead to chronic hemolytic anemia and pure- red-cell-aplasia, a low red-blood-cell count. B-19-specific IgG immunoglobulin prophylaxis and/or RBC transfusion are used to aid immuno-compromised patients in clearance of the infection.

There is also risk associated with infection of B-19 in pregnant women. The virus can cause an intra-uterine infection that can lead to hydrops fetalis and abortion. Intra-uterine blood transfusions have been performed in order to protect the fetus in infected mothers.

Presently, there is no vaccine for human parvovirus B-19. However, a new cell-line has been recently developed that can produce inactivated B-19 viral capsid protein, specifically VP1 (VP2 is ineffective at inducing an antibody response), as it is the primary antigen specificity during native viral infections. This vaccine will help to prevent outbreaks of Fifth disease in schools as well as eliminate any risk associated with infection of B-19 during pregnancy.

Hydrops fetalis in infant.[14]