Parvovirus B19 and the new century.

Since the discovery of parvovirus B19 by Ivonne Cossart 25 years ago, the knowledge of infection due to this virus has evolved from self-limiting erythema in-fectiosum in immunocompetent children to lethal cytopenia in immunocompro-mised patients. Now, it is possible to prevent these life-threatening parvovirus B19–mediated diseases [2, 3]. In this issue of Clinical Infectious Diseases , Lindblom et al. [1] comment on how parvovirus B19 infection causes severe cytopenia and can mimic a leukemic relapse or therapy-induced pancytopenia in children with acute lymphoblastic leu-kemia, causing significantly longer periods without chemotherapy and a higher number of blood transfusions in parvovirus B19 DNA–positive children, compared with parvovirus B19 DNA–negative patients (). In their cohort of 99 pan p 99 tients, 18 were parvovirus B19 DNA positive at the time of diagnosis or during therapy, and only 1 child was infected after chemotherapy. The number of days of un-wanted treatment interruption was significantly higher for parvovirus B19–positive patients than for parvovirus B19–negative patients and was associated with poor prognosis. The parvovirus B19–positive patients, who received multiple courses of systemic chemotherapy, required longer hospital stays, frequent blood sampling, obtain-ment of multiple bone marrow specimens, multiple transfusions of RBCs or platelets, and cessation of maintenance chemother-apy for у3 weeks. To avoid subsequent uncertain diagnoses, an assay to detect parvovirus B19 should be performed at diagnosis of leukemia and during treatment of parvovirus B19–seronegative patients who exhibit unexplained cytopenia. Modern diagnostic analysis of parvo-virus B19 infection usually includes measurement of parvovirus B19 IgG and IgM antibodies in blood samples and parvo-virus B19 DNA in blood or tissue samples and especially in bone marrow samples (by quantitative PCR [4]). Morphologically , bone marrow aspirate samples do not show mature erythroid precursors but do show characteristic giant pronormob-lasts at the time of acute infection [2]. In the past, parvovirus B19 was identified as an uncommon virus (with very little interest for the medical studies) and has attracted relatively little attention from clinicians and immunologists. Usually, adults presenting with symptomatic par-vovirus B19 infection rapidly develop cellular immune responses with multiple specificities, which rise to high levels and are maintained for many months. In a few cases, parvovirus B19 DNA was detected in peripheral blood cells for 16 months [5]. It is also possible that viral antigen is retained (e.g., on skin and follicular den-dritic cells) following the extremely high burden that appears during acute infection. Alternatively, subgenomic particles may …