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The ability of cultured human synovial cells derived from synovial membrane and cartilage to support the replication of human parvovirus B19 was assessed. No viral DNA synthesis nor viral antigens were detected suggesting that B19 virus is not capable of replicating in synovial cells. The significance of this finding in relationship to the pathogenesis of parvovirus arthritis is discussed.
Human parvovirus B19 is a member of the autonomous parvoviridae but in contrast to other members of the genus has not been shown to agglutinate red blood cells. We now report that the virus agglutinates red cells of primate origin, though with plasma-derived virus this activity is masked by the presence of an IgM-like inhibitor. This observation is consistent with the presence on the erythroid precursor target cell of a specific receptor for parvovirus B19.
A chemiluminescence dot blot hybridization assay was used for the detection of B19 parvovirus DNA in human sera by using digoxigenin-labeled probes. The probes were revealed immunoenzymatically by use of anti-digoxigenin Fab fragments conjugated with alkaline phosphatase. The chemiluminescence signal was obtained by reacting the labeled probe-target complex with an enzyme-triggerable dioxetane substrate. The emitted photons were detected with instant photographic films. In the search for B19 parvovirus DNA, 2,808 serum samples were analyzed.
To produce parvovirus B19 antigen for diagnostic purposes, partially overlapping segments covering the genes encoding the viral structural proteins VP1 and VP2 were cloned into expression vectors. The constructs were induced in Escherichia coli, resulting in the expression of beta-galactosidase fusion proteins. In immunoblotting experiments with sera from patients with erythema infectiosum, immunoglobulin G (IgG) and IgM antibodies bound to a single polypeptide of 235 amino acids at the N terminus of VP1. The DNA fragment encoding this polypeptide was amplified by the polymerase chain reaction and cloned into an expression vector. The viral capsid antigen expressed in E. coli was purified by preparative agarose gel electrophoresis and used in IgG and IgM solid-phase enzyme immunoassays. Comparison with reference gamma- and mu-capture radioimmunoassays using whole virus antigen showed that these antibody tests are suitable for the serodiagnosis of human infections caused by parvovirus B19.
A 59 year old woman presented with an influenza-like illness preceding signs and symptoms strongly suggestive of systemic lupus erythematosus (SLE), which progressed over several months. Owing to these influenza-like symptoms, a viral cause of her illness was sought. Human parvovirus B19 serology was positive and antibodies to DNA were detected by two different methods. This patient is believed to be the first report of human parvovirus B19 infection coinciding with the onset of SLE. The evidence for B19 virus and the part it plays in autoimmunity and arthritis is discussed.
AIMS: To compare the use of biotinylated and digoxigenin labelled probes for diagnosis of human fetal parvovirus B19 infection in formalin fixed, paraffin wax embedded tissues; and to assess the cellular distribution of the virus in positive cases. METHODS: Sections of lung tissue from 23 cases of anatomically normal non-immune fetal hydrops presenting between 1984 and 1989, and from 13 control cases of hydrops due to chromosomal abnormality were probed for B19 DNA by in situ hybridisation using both biotinylated and digoxigenin labelled probes. The distribution of the virus was then investigated in all cases of fetal B19 infection confirmed in this laboratory to date (n = 11) by combining in situ hybridisation for viral DNA (using the digoxigenin system) with immunohistological labelling for a range of cellular antigens. RESULTS: Five unequivocal cases of B19 infection were identified among the 23 fetuses with unexplained hydrops using both probe labels. When combined with data from previous studies of the period 1974-1983, the results indicate that B19 infection was responsible for 27% of cases of anatomically normal non-immune hydrops and 8% of all cases, of non-immune hydrops presenting to this hospital over 15 years. False positive signal was seen in an additional three cases, using biotinylated probes. Digoxigenin labelled probes gave greater specificity and permitted detailed investigation of tissues high in endogenous biotin. Though most cells containing B19 DNA colabelled as erythroid precursors, viral DNA was frequently detected within mononuclear-phagocytic cells. In three cases viral signal was also found within occasional myocardial cells labelled by antibody to desmin. CONCLUSIONS: A relatively high proportion of cases of anatomically normal, non-immune hydrops are caused by B19 infection. Digoxigenin is a more reliable probe label than biotin for in situ hybridisation in archival fetal tissues. Double labelling for cellular antigens and viral nucleic acid is a powerful technique for investigating virus-host cell interactions, and provides evidence that cell types other than those of erythroid lineage may have a role in human fetal parvovirus infection.
Parvovirus B19 DNA can be detected by polymerase chain reaction with double primer pairs (nested PCR). Recent infection was documented by a retrospective serological study using Parvoscan-B19 enzyme linked immunosorbent assay (EIA) for detection of B19 human parvovirus IgM and IgG antibodies in serum or plasma specimens. In 3 families B19 outbreaks caused aplastic crises necessitating blood transfusion in 5 children and 1 adult with hereditary sphaerocytosis. Four members from 2 of the families had clinically overt haemolytic anaemia prior to the event. Two members in another family presented with an aplastic crisis disclosing the underlying chronic haemolytic disease. All 7 patients were identified as PCR positive in serum samples taken 3-14 days after the onset of symptoms. Comparison with dot blot hybridization revealed detectable DNA in only 2/3 PCR positive patients. Thus, nested PCR is more sensitive than the dot blot hybridization method and is therefore a suitable complement to the antibody assay for identifying recent B19 infection.
A case of bone marrow necrosis associated with a serologically documented recent Parvovirus B 19 infection which preceded the development of PH1+ acute lymphoblastic leukemia is reported. No conclusions can be drawn on the basis of a single case but the question of the role of human Parvovirus B19 in the pathogenesis of bone marrow necrosis is discussed. It is suggested that the virus may act as a co-factor for the induction of bone marrow necrosis, in some cases.
A seven months old boy was admitted to hospital for investigation and treatment of severe anaemia. The final diagnosis was hereditary spherocytosis. When, six weeks later, he developed an aplastic crisis, serological criteria provided evidence of recent human parvovirus B19 infection. The same disease was detected in the family. Human parvovirus B19 is shown to be of particular interest in aplastic crisis.
The pathogenic human parvovirus B19 has extreme tropism for human erythroid progenitor cells and has resisted cultivation in conventional cell lines. We report first propagation of this virus in an erythropoietin-dependent strain of a megakaryoblastic leukemia cell line called UT-7. Virus protein was present in about 5% of cells after 1 week of culture. Appropriate ratios of major and minor capsid proteins were determined by immunoblot, and newly synthesized capsid protein was detected by immunoprecipitation of radioactively labeled cell lysates. High molecular weight monomer and dimer intermediates were detected by Southern analysis, indicating active viral replication. Approximately 1,000 genome copies were present per infected cell, and at the optimal multiplicity of infection 20- to 50-fold more virus was produced than inoculated. Virus propagation only occurred in UT-7 cells that were adapted to growth in erythropoietin; virus signal was not detected in UT-7 cells adapted for growth in granulocyte-macrophage colony-stimulating factor or interleukin-3, even with exposure to erythropoietin for several days. Infectious virus was detected in cultures as long as 3 months after inoculation. Despite persistence, there was no evidence of viral integration on Southern analysis. This cell line may prove useful for the production of infectious virus and in the analysis of B19 parvovirus persistence, cytotoxicity, and permissivity.
The human parvovirus B19 agent causes infectious erythema (fifth disease). However, a wide range of other pathological manifestations may also be seen: atypical exanthema, ARD (also obstructive forms, e.g. bronchiolitis), acute gastroenteritis, chronic anemia or aplastic crises (in constitutional or malignant hematological diseases or immunological deficiency), arthralgia/arthritis (e.g. rheumatoid arthritis, jcA), diseases of the central nervous systems (e.g. febrile convulsions in young children), lymphadenopathies (e.g. lymphadenitis mesenterialis or pseudoappendicitis); prenatal infection can lead to fetal death (not malformations!). Infection occurring concomitantly with vaccination may suggest complications of the latter. To clarify the true etiological situation, modern laboratory investigations are then required. Vaccination against parvovirus B19 (initially indicated in the case of non-immune girls and women wanting children) is a desirable future development.
Antibodies against H-1 and X14 parvoviruses were found 13.71 and 9.14%, respectively, of 350 sera from women affected by repeated abortions or still-births. On the contrary, only 2.66 and 1.66% of 300 control sera were positive to the two viruses. The difference in the incidence of antibodies appears highly significant (p greater than 0.001). Therefore a possible role of the parvoviruses in inducing abortions or still-births in humans is suggested.
Monoclonal antibody technologies were applied to the study of early events in porcine parvovirus (PPV) infections in vitro. Balb/c mice were immunized with whole swine testicle cells and hybridomas were produced following fusion with myeloma cells. Resultant clones were screened firstly in an ELISA system, to detect monoclonal antibody recognition of swine testicle cells, and secondly, in a fluorescent antibody test to detect monoclonal antibody which inhibited production of PPV antigen. One clone, 1H11, which satisfied these screening requirements, recognized proteins present in cell lines both permissive and non-permissive for porcine parvovirus replication and inhibited the production of virus progeny of several PPV isolates. A linear staining pattern of cross-linked plasma membranes, indicative of monoclonal antibody binding at the cell membrane, was demonstrated by indirect immunofluorescence assays. In immunoblotting experiments, 1H11 recognized a polypeptide of approximately 40 kDa in size, present in both permissive and non-permissive cell lines.
DNA sequences between 0 and 98.8 genome map units (m.u.) from canine parvovirus (CPV) and feline panleukopenia virus (FPV) were cloned into plasmid vectors to form infectious molecular clones. Those plasmids were transfected into permissive cells and viruses recovered were shown to contain intact genomes, having regenerated the complete viral 5' ends up to 100 m.u. The viruses derived from the plasmids were compared to the original viruses, and shown to be indistinguishable in antigenic type, hemagglutination (HA) type and host range. The plasmid origin of the viruses was shown by preparing recombinant clones between CPV and FPV, and demonstrating the recombinant nature of the resulting viruses by restriction mapping and by sequencing viral DNA across the recombination sites. The sequences of our wild-type isolates CPV-d and FPV-b were completed, revealing 50 nucleotide sequence differences, of which 16 determined coding changes--5 in NS-1,2 in NS-2, and 9 in VP-2 protein. The sequences of the 5' ends (95.3-100 m.u.) of both viruses were also determined. Analysis of recombinant viruses mapped both CPV- and FPV-specific antigenic epitopes, the pH dependence of HA, and sequences affecting canine host range of the viruses within the VP-1 and VP-2 structural protein genes. Most of the specific changes were shown to be either on, or within one amino acid of, the surface of the virus capsid, indicating that the exposed surface of the parvovirus capsid plays an important role in determining a number of virus functions. The specific epitopes were affected by differences in a raised area on the capsid ("threefold spike"), while the pH dependence of HA difference was adjacent to a depression in the surface of the capsid at the twofold axis of symmetry.
In the parvovirus H-1 P38 promoter, there are sequences identified as a TATA box, an SP1 site, and a trans-activation responsive element (tar). It was previously shown that the parvovirus H-1 nonstructural protein NS1 positively regulates the expression of the P38 promoter for the viral capsid protein gene via the tar. To characterize the tar element further, a series of single-point mutations of the tar was constructed and the mutants were compared to wild-type for the trans-activation of the P38 promoter using a cat reporter gene. Most of the tar mutations had a negative effect on the P38 promoter and some of them reduced activity as much as 70%. However, when several mutants with multiple-point mutations in the tar were tested, no significant additive effect was observed. We examined the function of the SP1 site in the trans-activation of the P38 promoter by replacing the wild-type SP1 sequence with synthetic DNA fragments, OSP1 or 2SP1, containing no SP1 or two SP1 sites respectively, in a P38 construct with a cat reporter gene. The results indicate that P38 expression varies in proportion to the number of SP1 sites, suggesting a role for the SP1 site during trans-activation by NS1. The role of the TATA box on the P38 promoter was also examined by mutagenizing TATA to CACG. The activity of this promoter was reduced to 43%. When a construct mutated at both the SP1 and TATA box sites was tested for its activity, about 22% of the wild-type activity remained, implying that this remaining activity was contributed largely by the tar element. A model is proposed for how the tar element activates the wild-type and SP1-TATA minus promoters in the presence of NS1.
Porcine parvovirus is an autonomous parvovirus which normally infects pigs and multiplies in porcine cells in vitro. In this report, we describe the properties of a variant designated P2, which has extended its host range to include canine cells. The variant was able to produce cytopathic effects (CPE) in canine cells, unlike the prototype NADL-2 strain. The variant also produced higher viral antigen and infectivity titers in canine cells than the NADL-2 strain, whereas both strains produced CPE and similar titers in porcine cells. Generation of recombinant plasmids between the P2 variant DNA and an infectious clone of NADL-2, and analysis of the properties of the virus stocks produced from these recombinant plasmids, indicated that two changes were necessary for this extension in the host range. One change was located in the nonstructural protein coding region and the other in the capsid coding region.
The human parvovirus B19 is now known to be one of the causative agents of nonimmune hydrops fetalis and spontaneous abortions in pregnant women. The presence of the viral proteins and antibodies in fetuses of B19-infected women suggests that the virus can cross the placental barrier. In order to gain an insight into the mechanism of intrauterine fetal infection and the virus-induced hydrops fetalis, we examined whether human umbilical cord blood cells were permissive for B19 replication. Cord blood cells were infected with B19 in vitro, and Southern blot analyses of low M(r) DNA isolated from these cells revealed the presence of the characteristic replicative intermediates of B19 DNA. In addition, B19 genome expression in cord blood cells was detected by Northern blot analysis. Quantitative DNA dot blot analysis of culture supernatants documented complete assembly and release of B19 progeny virions in these cells. The progeny virions were biologically active in secondary infections of normal human bone marrow cells. The human umbilical cord blood cells may be a useful alternative to bone marrow and fetal liver culture systems for further studies on B19 since the need for bone marrow donors is obviated and, unlike fetal tissues, there are no ethical questions associated with the experimental use of cord blood because it is normally discarded. These studies also suggest that the umbilical cord blood may be a site for active replication of parvovirus B19 in vivo and may thus provide a means for transmission of the virus during intrauterine fetal infections.
The parvovirus H-1 P38 promoter contains a trans-activation responsive element (tar). It was previously shown that the parvovirus H-1 nonstructural protein NS1 positively regulates the expression of the P38 promoter for the viral capsid protein gene via the tar (Rhode and Richard, 1987, J. Virol. 61, 2807-2515). To characterize the mechanism of trans-activation by the tar, we used gel shift assays to demonstrate that there exist proteins in virus-infected cellular extracts which have higher binding activity than that found in mock-infected extracts. These observations in vitro are consistent with the expression by P38 constructs with the wild-type promoter linked to a reporter gene, chloramphenicol acetyl transferase (cat), in vivo. We also provide evidence that the protein(s)-tar complex has a molecular mass of approximately 75 kDa in an SDS-polyacrylamide gel, which is less than NS1, and this complex cannot be precipitated by NS1 antibody, which suggests that NS1 mediates the trans-activation by inducing an alteration in the binding activity of some cellular protein(s) in an indirect manner. These data support our previous hypothesis for the activation of the P38 promoter, in which the trans-activator(s) interacts with the tar effectively in the presence of NS1, leading to the formation of the transcription initiation complex by protein-protein associations (Gu, Chen, and Rhode, 1992, Virology 187, 10-17).