John Libbey Eurotext

Hématologie

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B19 parvovirus and human hematopoiesis Volume 1, issue 6, Novembre - Décembre 1995

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Unité de virologie, service de microbiologie, hôpital Saint-Louis, Université Paris VII, 1, avenue Claude-Vellefaux, 75475 Paris Cedex 10.

Human B19 parvovirus was discovered in 1975 in blood donor sera. It is a member of the Parvovirus genus within the Parvoviridae family. Like other members of the family, it is a small non enveloped icosahedral particle containing a single-stranded DNA genome. However, it is the only member of this virus family that causes diseases in humans. The pattern of B19 parvovirus disease following infection is the result of a balance among virus replication and the host immune response. B19 parvovirus exhibits an extreme tropism for human erythroid cells. In vitro B19 parvovirus replication is directly cytolytic, it strongly inhibits erythroid colony formation of the late erythroid progenitor cells (CFU-E). This selective tropism explains the occurrence in vivo, in patients with underlying haemolytic disease of transient aplastic crisis, an abrupt cessation of erythropoisis characterised by absent erythroid precursors in the bone marrow, reticulocytopenia and severe anaemia. Acute disease can be treated by blood transfusion. The fetus is a target for B19 parvovirus replication. Most in utero parvovirus infections have an asymptomatic course. In some cases, it causes non immune hydrops fetalis which may be resolved by intrauterine transfusion. Persistent B19 parvovirus infection occurs in immunocompromised patients, anaemia is severe and may be intermittent with periods of viraemia and remission with temporary disappearance of virus from the circulation. Chronic disease can be controlled by administration of immune globulin. If a safe and effective vaccine were available, it would be a welcome choice in all these clinical situations to reduce both morbidity and mortality, as well as to improve the management of these diseases. The most common illness caused by B19 parvovirus infection is childhood fifth disease or erythema infectiosum. In normal adults, B19 infection is asymptomatic in about 20 % of the cases. In others, particularly in women, it causes arthritis alone or in combination with a rash. These clinical syndromes appear when the viraemia stage has largely passed. Indeed the immune response produces this symptoms, probably by immune complex formation and deposition.