PRIMARY AND SECONDARY INFECTIONS BY HUMAN PARVOVIRUS B19 FOLLOWING BONE-MARROW TRANSPLANTATION - CHARACTERIZATION BY PCR AND B-CELL MOLECULAR IMMUNOLOGY

Due to the preparative regimen necessary, bone marrow transplantation (BMT) consistently results in severe immunedeficiency, often associate d with anaemia, leukopenia and thrombocytopenia. Parvovirus B19 replic ates in red blood cell precursors in the bone marrow and causes erythe ma infectiosum ('fifth disease'), anaemia, arthritis and foetal death. We assessed the significance of B19 infections as a cause of post-BMT complications. Over 900 serial serum samples from 201 allogeneic bone marrow recipients were studied by polymerase chain reaction (PCR) and by modern serodiagnostic methods. During the first 6 months after tra nsplantation all BMT recipients remained B19 PCR-negative. Antibody sc reening for B19 infections was performed up to 36 months post-transpla ntation. Three cases of acute B19 infection were diagnosed during the second year post-BMT. To characterize the adoptively transferred immun e system we measured subclasses and avidity of anti-VP1 IgG and epitop e-type specificity (ETS) of anti-VP2 IgG, which allowed functional dif ferentiation of primary and secondary B-cell responses long after BMT. The profile of the immune response was that of a primary infection in 1 and of reinfection in 2 of the 3 acute cases. Both types were clini cally mild. Infection by human parvovirus B19 is not a frequent cause of post-BMT cytopenias. The findings with the new B19 antibody markers support the concept that the donated marrow determines the type of an tiviral B-cell responses.