Molecular, cellular and clinical aspects of parvovirus B19 infection

Association of parvovirus B19 genome in children with myocarditis and cardiac allograft rejection: diagnosis using the polymerase chain reaction

BACKGROUND

Inflammatory diseases of the heart, including myocarditis and cardiac transplant rejection, are important causes of morbidity and mortality in children. Although viral infection may be suspected in either of these clinical conditions, the definitive etiology is often difficult to ascertain. Furthermore, the histology is identical for both disorders. Coxsackievirus has long been considered the most common cause of viral myocarditis; however, we previously demonstrated by polymerase chain reaction (PCR) analysis that many different, and sometimes unexpected, viruses may be responsible for myocarditis and cardiac rejection. In this study, we describe the association of parvovirus genome identified through PCR analysis of cardiac tissue in the clinical setting of myocarditis and cardiac allograft rejection.

METHODS AND RESULTS

Myocardial tissue from endomyocardial biopsy, explant, or autopsy was analyzed for parvovirus B19 using primers designed to amplify a 699-base pair PCR product from the VP1 gene region. Samples tested included those obtained from patients with suspected myocarditis (n=360) or transplant rejection (n=200) or control subjects (n=250). Parvoviral genome was identified through PCR in 9 patients (3 myocarditis; 6 transplant) and no control patients. Of the 3 patients with myocarditis, 1 presented with cardiac arrest leading to death, 1 developed dilated cardiomyopathy, and the other gradually improved. Four of the 6 transplant patients had evidence of significant rejection on the basis of endomyocardial biopsy histology. All transplant patients survived the infection.

CONCLUSIONS

Parvovirus is associated with myocarditis in a small percentage of children and may be a potential contributor to cardiac transplant rejection. PCR may provide a rapid and sensitive method of diagnosis.

Experimental infection of cynomolgus monkeys with simian parvovirus

Simian parvovirus is a recently discovered parvovirus that was first isolated from cynomolgus monkeys. It is similar to human B19 parvovirus in terms of virus genome, tropism for erythroid cells, and characteristic pathology in natural infections. Cynomolgus monkeys were infected with simian parvovirus to investigate their potential usefulness as an animal model of human B19 parvovirus. Six adult female cynomolgus monkeys were inoculated with purified simian parvovirus by the intravenous or intranasal route and monitored for evidence of clinical abnormalities; this included the preparation of complete hematological profiles. Viremia and simian parvovirus-specific antibody were determined in infected monkeys by dot blot and Western blot assays, respectively. Bone marrow was examined at necropsy 6, 10, or 15 days postinfection. All of the monkeys developed a smoldering, low-grade viremia that peaked approximately 10 to 12 days after inoculation. Peak viremia coincided with the appearance of specific antibody and was followed by sudden clearance of the virus and complete, but transient, absence of reticulocytes from the peripheral blood. Clinical signs were mild and involved mainly anorexia and slight weight loss. Infection was associated with a mild decrease in hemoglobin, hematocrit, and erythrocyte numbers. Bone marrow showed marked destruction of erythroid cells coincident with peak viremia. Our findings indicate that infection of healthy monkeys by simian parvovirus is self-limited and mild, with transient cessation of erythropoiesis. Our study has reproduced Koch's postulates and further shown that simian parvovirus infection of monkeys is almost identical to human B19 parvovirus infection of humans. Accordingly, this animal model may prove valuable in the study of the pathogenesis of B19 virus infection.

Detection of parvovirus B19-specific IgM by antibody capture radioimmunoassay

A solid phase IgM-capture radioimmunoassay (MACRIA) for the detection of parvovirus B19-IgM is described (Cohen et al., 1983, J. Hyg. Camb. 91, 113-130). IgM from a dilution of patients serum is 'captured' onto a solid phase coated by anti-human IgM. To determine whether any of the IgM is specific for parvovirus B19, B19 antigen is added followed by a detector system. In the MACRIA described here the detector system comprises a mouse monoclonal antibody to parvovirus B19 and a 125I-labelled anti-mouse antibody. A calibration curve derived from a standard B19 IgM serum is used to quantify B19 IgM using a single dilution of test sera. The purpose of the protocol is the diagnosis of recent acute infection with parvovirus B19.

Dot immunoperoxidase assay for detection of parvovirus B19 antigens in serum samples

We describe a simple and rapid dot immunoperoxidase assay for the direct detection of parvovirus B19 capsid antigens in human sera. The assay was performed with serum specimens dotted onto nylon membranes. VP1 and VP2 B19 antigens, which represent 4 and 96% of the capsid, respectively, were detected with a pool of monoclonal antibodies directed against the two proteins, and the complex was visualized by immunoperoxidase staining. The assay could be performed in about 4 h, and positive results were revealed at the end of the reaction as dark blue spots on the nylon membrane at the site of positive specimens. A total of 541 serum samples from different subjects and with different laboratory evaluations with regard to B19 infection were analyzed. The results obtained by the dot immunoperoxidase assay were compared with the results obtained for the presence of B19 DNA by dot blot hybridization and nested PCR. With optimized working conditions, the dot immunoperoxidase assay was able to detect the presence of B19 with a sensitivity comparable or slightly higher than that achieved by dot blot hybridization but less than that achieved by nested PCR. Since the level of sensitivity of the dot immunoperoxidase assay proved to be appropriate for the detection of acute B19 infection, and since the cost, time to a result, and versatility of the assay are important issues, from our evaluation, the dot immunoperoxidase assay described may be particularly suitable for large-scale screening of samples and a good alternative to DNA detection methods in the routine laboratory evaluation of B19 infection.

Quantitation of parvovirus B19 DNA sequences by competitive PCR: differential hybridization of the amplicons and immunoenzymatic detection on microplate

A competitive PCR assay was developed to quantify B19 DNA sequences. Target and internal standard sequences were co-amplified by the same set of primers. The internal standard competitor was constructed by recombinant PCR and differed from the original genome sequence in a 21-bp mutagenized fragment, internal to the region amplified by the same set of primers. The internal standard competitor was cloned in a plasmid vector and the cloned fragment used in all the experiments. Target and internal standard sequences were labelled with digoxigenin during the co-amplification reaction and the different amplicons were detected in two separate hybridization reactions by biotinylated probes specific for the original 21-bp sequence or the mutagenized one. Hybridized amplicons were captured onto streptavidin-oated microtitre wells and detected by anti-digoxigenin antibodies conjugated to peroxidase. The chromogenic reaction for peroxidase was quantitatively evaluated by optical density determination. The titration curve subsequently developed showed a linear relationship over the range 10(2) to 10(5) genome copies, thus obtaining an exact quantitative evaluation over a wide range together with good sensitivity. Nine reference serum samples positive for B19 DNA and eight negative serum samples were tested by the competitive PCR assay for the quantitation of B19 DNA sequences.

Toxoplasmosis and parvovirus B19

Pregnant women might well improve their chances for a successful pregnancy outcome by following the advice of W. C. Fields: avoid contact with small children and animals whenever possible. Failing widespread acceptance of this philosophy, management of T. gondii and parvovirus B19 infections continues to be a challenge for the foreseeable future.

Parvovirus B19 in human disease

Parvovirus B19, the only known human pathogenic parvovirus, is associated with a wide range of disease manifestations. In healthy individuals, the major presentation of B19 infection is erythema infectiosum. In patients with underlying hemolytic disorders, infection is the primary cause of transient aplastic crisis. In immunosuppressed patients, persistent infection may develop that presents as pure red cell aplasia and chronic anemia. In utero infection may result in hydrops fetalis or congenital anemia. Diagnosis is based on examination of bone marrow and virologic studies. Much is known of the pathophysiology of the virus, and studies are in progress to develop a vaccine to prevent this widespread infection.

Virus-receptor interactions in the enteric tract. Virus-receptor interactions

Expression of specific virus receptors on the surface of intestinal epithelial cells or M cells can determine whether or not a animal is susceptible to infection with an enterotropic virus. Receptors for many animal viruses have been identified. The specificity of virus-receptor interactions clearly affects the species specificity of virus infection, and in some instances may be an important determinant of viral tissue tropism. In this paper, the specificity of coronavirus-receptor interactions is summarized. Porcine and human coronaviruses utilize aminopeptidase N as their receptors, but in a species-specific manner. Mouse hepatitis virus uses several rodent glycoproteins in the carcinoembryonic antigen family as receptors. In addition, some coronaviruses can interact with carbohydrate moieties on the cell surface. Understanding the molecular mechanisms of virus-receptor interactions may lead to development of novel strategies for the control of enteric viral diseases.

Cryo-electron microscopy studies of empty capsids of human parvovirus B19 complexed with its cellular receptor

The three-dimensional structures of human parvovirus B19 VP2 capsids, alone and complexed with its cellular receptor, globoside, have been determined to 26 resolution. The B19 capsid structure, reconstructed from cryo-electron micrographs of vitrified specimens, has depressions on the icosahedral 2-fold and 3-fold axes, as well as a canyon-like region around the 5-fold axes. Similar results had previously been found in an 8 angstrom resolution map derived from x-ray diffraction data. Other parvoviral structures have a cylindrical channel along the 5-fold icosahedral axes, whereas density covers the 5-fold axes in B19. The glycolipid receptor molecules bind into the depressions on the 3-fold axes of the B19:globoside complex. A model of the tetrasaccharide component of globoside, organized as a trimeric fiber, fits well into the difference density representing the globoside receptor. Escape mutations to neutralizing antibodies map onto th capsid surface at regions immediately surrounding the globoside attachment sites. The proximity of the antigenic epitopes to the receptor site suggests that neutralization of virus infectivity is caused by preventing attachment of viruses to cells.

Parvovirus B19 infection. Associated diseases, common and uncommon

Parvovirus B19 infection is common worldwide but is often asymptomatic. However, the virus has been implicated in numerous disorders, including aplastic crisis in patients with chronic hemolytic anemia, erythema infectiosum, arthropathy, arthritis, and fetal infections. Diagnostic tests are not routine, but several are available through commercial reference laboratories. Treatment ranges from analgesics and antipyretics for mild and self-limited illness to administration of commercial immunoglobulin preparations and blood transfusion for more serious conditions.

Diverse hematologic effects of parvovirus B19 infection

Human parvovirus B19 is linked with a broadening spectrum of hematologic disorders, including aplastic crises in the context of hemolytic anemias, neutropenia, thrombocytopenia, and hemophagocytic syndromes. Children with any of these cytopenias should be screened for the presence of B19 because treatment with intravenous gamma globulin may provide resolution of abnormal blood counts if other therapeutic options, such as transfusion, are not adequate or desired.

Detection of parvovirus B19 DNA in bone marrow cells by chemiluminescence in situ hybridization

A chemiluminescence in situ hybridization method was developed for the search of B19 parvovirus DNA in bone marrow cells, employing digoxigenin-labeled B19 DNA probes, immunoenzymatically detected with a highly sensitive 1,2-dioxetane phosphate as chemiluminescent substrate. The light emitted from the in situ-hybridized probe was analyzed and measured by a high-performance luminograph connected to an optical microscope and to a personal computer for the quantification of the photon fluxes from the single cells and for image analysis. The chemiluminescence in situ hybridization was applied to bone marrow cell smears of patients with aplastic crisis or hypoplastic anemia, who had been previously tested by in situ hybridization with colorimetric detection, dot blot hybridization, and nested PCR. The chemiluminescent assay provided an objective estimation of the data, proved specific, and showed an increased sensitivity in detecting B19 DNA compared with in situ hybridization with colorimetric detection.

Parvoviruses and bone marrow failure

Parvovirus B19, the only known human pathogenic parvovirus, is highly tropic to human bone marrow and replicates only in erythroid progenitor cells. The basis of this erythroid tropism is the tissue distribution of the B19 cellular receptor, globoside (blood group P antigen). In individuals with underlying hemolytic disorders, infection with parvovirus B19 is the primary cause of transient aplastic crisis. In immunocompromised patients, persistent B19 infection may develop that manifests as pure red cell aplasia and chronic anemia. B19 infection in utero can result in fetal death, hydrops fetalis or congenital anemia. Diagnosis is based on examination of the bone marrow and B19 virological studies. Treatment of persistent infection with immunoglobulin leads to a rapid, marked resolution of the anemia.

Parvovirus B19 infection

Human parvovirus B19, discovered in 1974, is a single-stranded DNA virus which causes erythema infectiosum, arthralgia, aplastic crisis in patients with red cell defects, chronic anaemia in immunocompromised patients, and fetal hydrops. Seroprevalence in developed countries is 2-10% in children less than 5 years, 40-60% in adults more than 20 years, and 85% or more in those over 70 years. The virus may be transmitted by the respiratory route and by transfusion of infected blood and blood products. After an incubation period of six to eight days, viraemia occurs, during which reticulocyte numbers fall dramatically resulting in a temporary drop in haemoglobin of 1 g/dl in a normal person. Clearance of viraemia is dependent on development of specific antibody to the B19 structural proteins, VP1 and VP2. The red cell receptor for the virus is blood group P antigen. Diagnosis in immunocompetent persons depends on detection of specific IgM in serum. Diagnosis in immunocompromised persons depends on detection of B19 antigen or DNA in serum. There is no specific treatment for B19 infection; however, human normal immunoglobulin may be used as a source of specific antibody in chronically infected persons. A recombinant parvovirus B19 vaccine is under development.

Follow-up study of clinical and immunological findings in patients presenting with acute parvovirus B19 infection

This study was undertaken to examine the natural history of parvovirus B19 infection in persons without a known immune defect in terms of both clinical symptoms and immune responsiveness to the virus. Fifty-three patients with acute B19 infection (positive for serum anti-B19 IgM) were studied; symptoms at acute infection were rash and arthralgia (n = 26), rash (n = 7), arthralgia (n = 16), aplastic crisis (n = 3), and intrauterine fetal death (n = 1). Patients were followed for 26-85 months (mean 57 months) and reassessed for persistent symptoms, anti-B19 antibodies, and antibodies to the unique region of B19 VP1. There were 23 cases of arthralgia persisting for longer than 1 year after acute infection. One of these patients, a 48-year-old woman at follow-up, had had persistent arthralgia for 4 years following acute B19 infection, had rheumatoid factor at a titre of 1920 IU/ml detected at follow-up, and had been independently diagnosed as having rheumatoid arthritis at the time of follow-up. All 53 patients were positive for serum anti-B19 IgG compared to 45 of 53 age- and sex-matched control patients, a significant difference (two-tailed P value = 0.008). All test patients at follow-up and control patients were negative for serum anti-B19 IgM and antibodies to the unique region of B19 VP1. Serum from acute infection from 33 of 53 test patients was tested for antibodies to the unique region of VP1, and 16 of these were positive. The presence of this antibody did not correlate with subsequent duration of symptoms but did correlate with a short interval between symptom onset and blood sampling. The unique region of B19 VP1 is known to be crucial for a successful humoral response to the virus, and it seems that the antigenic role played by this region is important only during the acute phase of B19 infection.

Autoantibodies following parvovirus B19 infection

This study was undertaken to assess the incidence and significance of autoantibody production following B19 infection, 53 patients with acute B19 infection (positive for serum anti-B19 IgM) were studied; symptoms were rash and arthralgia (n = 26), rash (n = 7), arthralgia (n = 16), aplastic crisis (n = 3), and intrauterine death (n = 1). These patients were followed for 26-85 months (mean 57 months) and re-assessed for persistent symptoms, serum anti-B19 antibodies, and serum autoantibodies. At follow-up, 14 test and two control patients had one or more serum autoantibodies (anti-nuclear antibody, anti-smooth muscle antibody, gastric parietal cell antibody, anti-reticulin antibody, anti-mitochondrial antibody, rheumatoid factor) at a titre of > or = 40 (P = 0.004). Seven test patients and no control patients had serum autoantibody at a titre > or = 160. Of these seven test patients, only one had persistent symptoms. At follow-up assessment, this woman was 48-year-old, had persistent arthralgia for 4 years following acute B19 infection, rheumatoid factor at a titre of 160 (1920 IU/ml), and had been independently diagnosed as having rheumatoid arthritis. In conclusion, results of the present study showed that low titre autoantibody production was common following symptomatic B19 infection, however, while interesting from a virological standpoint, this finding may be of little significance for future development of autoimmune disease.

Parvovirus B19 promoter at map unit 6 confers autonomous replication competence and erythroid specificity to adeno-associated virus 2 in primary human hematopoietic progenitor cells

The pathogenic human parvovirus B19 is an autonomously replicating virus with a remarkable tropism for human erythroid progenitor cells. Although the target cell specificity for B19 infection has been suggested to be mediated by the erythrocyte P-antigen receptor (globoside), a number of nonerythroid cells that express this receptor are nonpermissive for B19 replication. To directly test the role of expression from the B19 promoter at map unit 6 (B19p6) in the erythroid cell specificity of B19, we constructed a recombinant adeno-associated virus 2 (AAV), in which the authentic AAV promoter at map unit 5 (AAVp5) was replaced by the B19p6 promoter. Although the wild-type (wt) AAV requires a helper virus for its optimal replication, we hypothesized that inserting the B19p6 promoter in a recombinant AAV would permit autonomous viral replication, but only in erythroid progenitor cells. In this report, we provide evidence that the B19p6 promoter is necessary and sufficient to impart autonomous replication competence and erythroid specificity to AAV in primary human hematopoietic progenitor cells. Thus, expression from the B19p6 promoter plays an important role in post-P-antigen receptor erythroid-cell specificity of parvovirus B19. The AAV-B19 hybrid vector system may also prove to be useful in potential gene therapy of human hemoglobinopathies.

Parvovirus B19 infection and hematopoiesis

Parvovirus B19, the only known human pathogenic parvovirus, is highly tropic to human bone marrow and replicates only in erythroid progenitor cells. The basis of this erythroid tropism is the tissue distribution of the B19 cellular receptor, globoside (blood group P antigen). In individuals with underlying hemolytic disorders, infection with parvovirus B19 is the primary cause of transient aplastic crisis (TAC). In immunocompromised patients, persistent B19 infection may develop that manifests as pure red cell aplasia and chronic anemia. B19 infection in utero can result in fetal death, hydrops fetalis, or congenital anemia. Diagnosis is based on examination of the bone marrow and B19 virological studies. Treatment of persistent infection with immunoglobulin leads to a rapid marked resolution of the anemia.

Human parvovirus B19 can infect cynomolgus monkey marrow cells in tissue culture

The human pathogenic parvovirus B19 cannot be grown in standard tissue culture but propagates in human bone marrow, where it is cytotoxic to erythroid progenitor cells. We now show that parvovirus B19 can replicate in cynomolgus bone marrow. Cynomolgus monkeys may be a suitable animal model for pathogenesis studies of parvovirus B19.

Genetic diversity in the non-structural gene of parvovirus B19 detected by single-stranded conformational polymorphism assay (SSCP) and partial nucleotide sequencing

A homologous region in the parvovirus B19 non-structural gene (B19 nt 1399-1682) was examined in 50 samples from patients with a wide variety of B19-related disease from various countries by PCR amplification, single-stranded conformational polymorphism (SSCP) assay and nucleotide sequencing. Five SSCP types were confirmed by nucleotide sequence analysis. Of a total of 6 mutations, all were silent. Types 3 and 4 accounted for 92% of strains. There was no correlation between genome type and either clinical illness or patient age. However, there was a correlation between SSCP type and country of origin. Type 3 strains predominated in Japan (18/26) and the UK (6/8), whereas type 4 predominated in the USA (9/12). Notably, type 3 strains also predominated among females (14/18), whereas there were approximately equal numbers of strain types 3 (7/17) and 4 (8/17) among males; an observation which remains unexplained. Within the Japanese group, although type 3 strains predominated overall, strains isolated from 1981 to 1987 consisted of types 1 (2/15), 2 (1/15), 3 (8/15), and 4 (4/15), whereas strains isolated from 1990 to 1994 consisted almost entirely of type 3 (10/11).

B19 parvovirus

B19 parvovirus is pathogenic in man and causes a variety of clinical illnesses, among them several haematological diseases. Acute infection of a host with underlying haemolysis produces transient aplastic crisis; of the midtrimester fetus, hydrops fetalis; and of an immunocompromised patient, pure red cell aplasia. The target of B19 parvovirus infection is the human erythroid progenitor cell. Infection is cytotoxic due to expression of the viral nonstructural protein. The virus can be propagated in cultures of human bone marrow, blood, and fetal liver. Humoral immunity normally terminates infection, and commercially available immunoglobulin can be used to treat persistent infection. Recombinant capsids, produced in a baculovirus system, are suitable as a vaccine reagent.

Parvovirus B19 infection--persistence and genetic variation

53 patients with acute B19 infection were studied; symptoms at acute infection were rash and arthralgia (n = 26), rash (n = 7), arthralgia (n = 16), aplastic crisis (n = 3), and intrauterine fetal death (n = 1). These patients were followed for 26-85 months (mean 57 months) and re-assessed for persistent symptoms, anti-B19 antibodies, and B19 DNA. At follow-up, 7 individuals were positive for serum B19 DNA, compared with none of the controls (2-tailed p value = 0.016). All 7 of those persistently infected were women, 3 of whom had symptoms; 1 had a chronic haemolytic anaemia (initial presentation was aplastic crisis); 1 had persistent arthralgia in both knees (initial presentation was bilateral knee arthralgia); and 1 had arthralgia in one knee and chronic fatigue syndrome (initial presentation was bilateral arthralgia in knees and shoulders). For the 7 persistently infected patients, serum from the time of diagnosis of acute B19 infection was available for 4, all of which contained B19 DNA. With single-stranded conformational polymorphism (SSCP) assay of these 11 PCR products, identical SSCP types were demonstrated in 5 of 7 follow-up isolates. In 2 of the 4 cases for which both acute and follow-up PCR product was available, the SSCP type of the follow-up product was different from that of the acute product. Two B19 virus types were demonstrated in one patient (with persistent arthralgia and chronic fatigue syndrome) at follow-up assessment.