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Human parvovirus B19 can be transmitted by coagulation factor concentrates and is highly resistant to virucidal methods. To evaluate whether the additional removal of virus by chromatographic methods during the manufacture of high-purity concentrates reduces the risk of B19 transmission, we have prospectively evaluated the rate of anti-B19 seroconversion in two groups of susceptible (anti-B19 negative) hemophiliacs infused with high-purity, heated (pasteurized) or solvent-detergent-treated factor VIII concentrates. Both products infected a relatively high proportion of patients (nine of 20).

Peripheral blood leukocytes from immunocompetent and immunocompromised individuals were analyzed for human polyomarivus BK and JC DNA presence. A nested polymerase chain reaction which amplify the transcriptional control region of the genome of both viruses was employed. The immunocompromised patients included bone marrow transplantation recipients and AIDS patients. BKV sequences were detectable in 52.8-62.5% of the individuals included in this study, whereas the percentage of individuals with JCV sequences in peripheral blood lymphocytes varied from 38.8% to 50%. The frequency of reactivations of BKV and JCV were also determined by detection of shedding in urine of viral DNA. The highest frequency of reactivations of either BKV or JCV was demonstrable in the group of bone marrow transplantation recipients, but reactivations occurred also in immunocompetent individuals. JCV sequences amplified from urine samples showed a restriction pattern similar to the archetype one, whereas sequences obtained from lymphocytes showed rearranged pattern as well as archetype pattern. Finally all JCV sequences from cerebrospinal fluid seemed to be rearranged. These observations suggest that peripheral blood lymphocytes have a fundamental role in the persistence of polyomaviruses infection and in the dissemination at least of JCV within the organism allowing that rearranged variants, better adapted to grow in brain tissue, emerge.

Two forms of human polyomavirus JC (JCV) genome are known based upon the structure of the transcriptional control region (TCR) of the virus : the archetypal form, which is commonly detected in urine, and the rearranged form, which was first detected in brain tissue from progressive multifocal leukoencephalopathy (PML) patients. The latter actually includes a group of TCR variants that, relative to the former, are characterized by various deletions and/or duplications. The aim of this study was to establish whether or not a correlation exists among the TCR type, the spreading of the virus within the host and its ability to cause PML. JCV TCR sequences from peripheral blood leukocytes (PBL) and cerebrospinal fluid (CSF) obtained from various groups of patients were compared. JCV with archetypal TCR was detected in CSF and PBL specimens from patients without neurological disorders or who eventually received a diagnosis of a non-PML neurological disorder. Rearranged TCR sequences were detected in all the CSF and PBL specimens from PML patients. The high similarity observed between the TCR structure detected in PBL and CSF specimens from individual patients could strengthen the hypothesis that PBL has a role in spreading JCV to the brain. Moreover, heterogeneous TCR patterns have been shown in individual PBL specimens from PML patients. This supports the hypothesis that, in PBL, JCV may replicate and undergo rearrangements of the TCR. The detection of JCV DNA by PCR in CSF independently from PML, although rare, could suggest that this assay is not sufficient for a virological diagnosis of PML. Further studies are required to assess the usefulness of quantitative assays or TCR typing in combination with PCR for diagnostic purposes.

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