Outbreak of aplastic crises in sickle cell anaemia associated with parvovirus-like agent

Human parvovirus B19 infection: clinical and epidemiological study of 24 cases

From March 1994 to November 1995 24 cases of human parvovirus B19 infection were seen at the Infectious Diseases Department of the Hospital Universitário Antônio Pedro, Niterói-RJ. Serum samples for IgM detection (capture enzyme immunoassay) were positive from the 1st to the 27th day after the onset of the exathema. The classical features of erythema infectiosum (slapped cheecked syndrome) were observed in 8 (33.3%) cases all of them children. Eight patients (6 adults and 2 children) presented a symmetrical polyartropathy, seen more frequently in women. These results show that B19 infection diagnosis is difficult when the disease does not present the classical features and because of the frequent involvement of the joints this infection should be considered in the differential diagnosis of early rheumatoid arthritis.

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.

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.

Improved survival in homozygous sickle cell disease: lessons from a cohort study

OBJECTIVE

To examine whether simple interventions in a sickle cell clinic improve survival in sickle cell disease.

DESIGN

Survival curve analysis and hazard ratios in a cohort study followed from birth.

SETTING

MRC Laboratories (Jamaica) at the University of the West Indies, and Victoria Jubilee Hospital, Kingston, Jamaica.

SUBJECTS

315 patients with homozygous sickle cell disease detected during the screening of 100,000 consecutive non-operative deliveries between June 1973 and December 1981 at the main government maternity hospital, Kingston, Jamaica.

INTERVENTIONS

Prophylactic penicillin to prevent pneumococcal septicaemia, parental education in early diagnosis of acute splenic sequestration, close monitoring in sickle cell clinic.

MAIN OUTCOME MEASURES

Survival.

RESULTS

Survival appeared to improve, the log rank test for trend comparing the first, second, and last third of the study reaching borderline significance (P = 0.05). Combined deaths from acute splenic sequestration and pneumococcal septicaemia-meningitis declined significantly (test for trend, P = 0.02).

CONCLUSION

Early diagnosis and simple prophylactic measures significantly reduce deaths associated with homozygous sickle cell disease.

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 in pregnancy

Human parvovirus is an often unrecognized but potentially deadly infection when contracted by childbearing women who are seronegative. Although maternal symptoms and sequelae are mild, the exposed fetus quickly can develop nonimmune hydrops fetalis and die. Health care providers can prepare for appropriate maternal and fetal management by reviewing the history, disease process, and transmission mode of parvovirus.

Life-threatening infection in two children with hemoglobin S-beta-thalassemia

Life-threatening infections with Streptococcus pneumoniae and parvovirus occurred in two patients with hemoglobin S-beta-thalassemia. We recommend that acute febrile illnesses in the presence of any hemoglobinopathy be considered potentially life threatening, and managed accordingly.

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.

Peptides derived from the unique region of B19 parvovirus minor capsid protein elicit neutralizing antibodies in rabbits

B19 parvovirus is pathogenic in humans. The virus propagates in the bone marrow, where it is cytotoxic to erythroid progenitor cells. Antibodies appear in blood after infection and neutralize virus in vitro; infection appears to confer lasting immunity. The predominant immune response on immunoblot is to the minor capsid protein (VP1), which differs from the major capsid protein (VP2) by an additional 227 amino acids. We previously demonstrated that antisera directed to a fusion protein containing this unique region or to more limited fusion peptides of 50-100 amino acids each neutralized virus. In the current work, we tested synthetic peptides of about 20 amino acids derived from the VP1 unique region for their ability to elicit a neutralizing antibody response in rabbits. Individual peptides were covalently linked to a lysine core to produce a multivalent antigen. Animals produced antibodies to all 13 synthetic peptides, as determined by ELISA. At 12 weeks, animals injected with one of three peptides--two from the far amino terminus and the third from the center of the unique region--had produced antibodies that completely neutralized virus; by 16 weeks, antisera elicited with another four peptides also were effective. In summary, we identified regions containing neutralizing epitopes within the first 80 amino acids and amino acids 148-205 of the unique region. Our data suggest that synthetic peptides might be useful vaccine reagents for protection against parvovirus infection in humans.

In situ hybridisation and in situ polymerase chain reaction detection of parvovirus B19 DNA within cells

Modification of an in situ polymerase chain reaction (ISPCR) technique is described for the detection of B19 parvovirus infection. Specific amplification of B19 DNA inside fixed cells was followed by hybridisation with a digoxigenin-labelled probe and then visualised by immunochemical reaction. The assay had higher sensitivity compared to direct in situ hybridisation and still allowed cellular localisation and characterisation of infected cells. This assay can be used as a confirmatory method for PCR in tissues and will allow further identification of tissues permissive for B19 parvovirus infection.

Human parvovirus B19 serology with recombinant VP1 and VP2 antigens: diagnosis of acute infections by detecting B19-specific IgM and IgA antibodies

BACKGROUND

The availability of immunoassays for the laboratory diagnosis of human parvovirus B19 (B19) infection, which is commonly associated with erythema infectiosum in children and arthropathy and arthralgia in adults has been hampered by the lack of native B19 antigen. The production of abundant supplies of recombinant (r) B19 proteins, through the cloning of the B19 genome into expression vectors, has led to a proliferation of assays for detecting B19-specific antibodies.

OBJECTIVES

This study was undertaken to evaluate serological assays for detecting B19-specific IgM and IgA antibodies using rVP1 and rVP2 B19 viral coat proteins. Their suitability in the diagnosis of acute B19 infections and the incidence of non-specific reactivity were determined.

STUDY DESIGN

A panel of sera consisting of B19-specific IgM-positive and -negative samples was tested for B19-specific IgM and IgA antibodies in an indirect IFA using rVP1 antigen. These samples and a further panel collected from patients with other virus infections and samples containing rheumatoid factor were tested for B19-specific IgM in an antibody-capture ELISA and an indirect ELISA, both of which utilized rVP2 antigen.

RESULTS

Data from the two ELISAs using rVP2 antigen and the IFA with rVP1 antigen all showed significant correlation (P >/= 0.001) with a reference RIA using native B19 antigen. Non-specific reactions were observed with Paul-Bunnell-positive and rubella virus-specific IgM antibody-positive sera in the ELISAs but not in the IFA. B19-specific IgA antibodies were detected in all sera containing B19-specific IgM antibodies but were also found in a small number of sera collected from healthy blood donors with no history of recent B19 infection.

CONCLUSION

This study demonstrates the usefulness of assays employing rVP1 and rVP2 B19 antigens for detecting B19-specific antibodies. The use of IgM-specific ELISAs allows the processing of large numbers of samples and the absence of non-specific reactivity in the IFA may indicate a role for this assay as a confirmatory test.

Parvovirus B19 outbreak on an adult ward

In November and December 1992, an outbreak of parvovirus B19 infection occurred among patients and staff on an adult mixed surgical ward at a large hospital in London. Three patients and 15 staff members were serologically confirmed as acute cases. The attack rate among susceptible members of staff was 47%. In those infected, arthralgia (80%) and rash (67%) were the most common symptoms. Of six susceptible in-patients on the ward, three became infected. One of the in-patients who had carcinoma of the mouth was viraemic for more than 10 days with marrow suppression resulting in the postponement of chemotherapy until intravenous immunoglobulin was given and he was no longer viraemic. Control measures taken included closure of the ward to new admissions, transfer of only immune staff to the ward, and restriction of the ward nursing staff to working only on that ward. Although no specific exposure was conclusively identified as a risk factor, there was a suggestion of an increased risk of acquiring parvovirus B19 infection among those staff who did not adopt strict hand washing procedures after each physical contact with a patient (RR = 2.33; P = 0.07). Knowledge of parvovirus B19 among interviewed health care workers was poor: only 42% reported knowing about parvovirus B19 and only 38% could name a patient category at risk of a severe outcome following infection. This is the first report of a nosocomial outbreak affecting an adult ward and of possible transmission of parvovirus B19 infection from staff to in-patients. Hospital control of infection teams should include parvovirus B19 in their outbreak containment plans.

Parvovirus B19 infection in HIV-1 infected patients with anemia

Serum samples were analysed for IgM and IgG antibodies to parvovirus by ELISA and for parvovirus B19 DNA by polymerase chain reaction (PCR) in 69 HIV-1 infected Swedish patients with anemia and in 37 HIV-1 infected subjects without anemia. In 5/69 anemic patients, parvovirus B19 DNA was detected despite the lack of IgM antibody activity to the virus. The detection of parvovirus B19 DNA was significantly correlated to the degree of anemia in the anemic patients. In two patients who had a chronic anemia, a persistent parvovirus infection was detected by PCR, but not by serology, for 1 and 1.5 years, respectively. The results suggest that persistent parvovirus infection is a rare cause of anemia, but important to identify, since the infection is potentially treatable with intravenous immunoglobulin.

Application to immunoglobulin M capture hemadherence assays of hemagglutination of monkey erythrocytes by native and recombinant human parvovirus B19 antigens

Human parvovirus B19 recently was shown to agglutinate baboon and human erythrocytes. We have now demonstrated that both recombinant and native B19 antigens agglutinate rhesus, cynomolgus, and Saimiri monkey erythrocytes. Using cynomolgus erythrocytes and the recombinant antigen, we developed an immunoglobulin M (IgM) antibody capture hemadherence test (MACHAT) for the detection of specific B19 IgM antibodies in human sera. The results obtained with MACHAT were compared with those obtained with an IgM capture enzyme immunoassay (MACEIA) employing the native antigen routinely used in our laboratory. For 229 patient serum samples, we found 96% agreement between the results of the two assays. There was some evidence that MACHAT was slightly more sensitive than MACEIA. Our results add to the range of erythrocytes that can be agglutinated by B19 virus and show that native as well as recombinant antigens may be used in MACHAT.

Persistent erythema infectiosum-like rash as a prodrome of acute lymphocytic leukemia

A 7-year-old boy had erythema infectiosum with typical manifestations. Over more than 40 days, these lesions showed no sign of regression, and chronic anemia became progressively more severe. Electron microscopic examination performed 20 days after onset showed abnormal Sezary-like lymphocytes. Bone marrow biopsy, which was performed to evaluate the anemia, was consistent with acute lymphocytic leukemia. Persistent parvovirus B19 infection may be connected with immunosuppression. Therefore, early electron microscopic study and bone marrow biopsy may be helpful for early diagnosis of hematologic malignancies.

[Extensive bone marrow necrosis and major sickle cell syndromes]

Three cases of extensive bone marrow necrosis in patients with sickle cell disease are reported. All three patients presented severe bone pains with severe anaemia (haemoglobin value less than 5 g/dl) and high increased of LDH serum values (upper than 20 fold normal value). Bone marrow aspirate and biopsy showed typical signs of necrosis. The extent of necrosis was evaluated by reticuloendothelial scan obtained with 111In chloride. Treatment required transfusions of phenotyped red blood cell concentrates. Favourable outcome was observed in all patients.

Brachial neuritis after human parvovirus B19 infection

This case report presents the clinical picture of a patient with brachial neuritis who was investigated and found to have infection with human parvovirus B19. The clinical presentations and prevalence of human parvovirus infection are discussed, as is the prognosis for brachial neuritis. It is recommended that viral serologic testing, including that for human parvovirus, be carried out in cases of brachial neuritis. (J Shoulder Elbow Surg 1993;2:321-3).

Detection of human parvovirus B19-specific IgM and IgG antibodies using a recombinant viral VP1 antigen expressed in insect cells and estimation of time of infection by testing for antibody avidity

Sera from patients with symptoms of recent human parvovirus B19 (B19) infection were tested for B19-specific IgM in an immunofluorescence assay (IFA) using insect cells expressing B19 recombinant VP1 coat protein as an antigen. A highly significant correlation (P < 0.001) was found between titres obtained in the IgM IFA and the units obtained in an IgM antibody-capture RIA using plasma derived native B19 antigen. An IgG IFA using the recombinant antigen was performed on 57 sera and the antibody avidity determined. There was a highly significant correlation (P < 0.001) between the relative amounts of low avidity B19-specific IgG antibodies and time after onset of illness. This finding allows the detection of IgG to be used for diagnosing acute infection.

Electron microscopic identification of parvovirus virions in erythroid and granulocytic-line cells in a patient with human parvovirus B19 induced pancytopenia

In this short report we describe a patient with human parvovirus B19 (HPV B19)-induced transient pancytopenia. Parvovirus virions were seen by electron microscopy in both erythroid and granulocytic precursors. Erythroid cells are not the only targets in these cases. We draw attention to this disorder so that physicians involved with hematological disorders and transplantation be more aware of this infection.

Human parvovirus infection in homozygous sickle cell disease

We studied the epidemiology of human parvovirus B19 infection in 308 children with homozygous sickle cell (SS) disease and 239 controls with a normal haemoglobin (AA) genotype followed from birth in a cohort study. Annual serum samples identified the time and frequency of B19 infection, which did not differ between SS and AA children, about 40% of each group developing specific IgG by age 15. B19 infection followed an epidemic pattern similar to that observed for aplastic crises; accounted for all 91 aplastic crises that occurred; and was found in an additional 23 SS patients, of whom 10 showed mild haematological changes and 13 no changes. The magnitude or duration of IgG response did not differ between these groups. No patient had 2 attacks of aplasia and no patient nor control had 2 attacks of B19 infection. Following B19 infection, serial specific IgG concentrations remained high after 5 years in only 45% of SS patients, although the rarity of recurrent aplasia suggests lifelong immunity. B19 infection accounts for most if not all aplastic crises in SS disease, but at least 20% of infections do not result in aplasia. An effective vaccine against B19 might make an important contribution to the management of sickle cell disease.

Thrombocytopenia induced by human parvovirus B19 infections

Human parvovirus B19 (B19) has a remarkable tissue-tropism for erythroid elements--from erythroid precursors (BFU-E, CFU-E) to erythroblasts. B19 is thought to be incapable of propagating in cells other than erythroid progenitors. Leukocytopenia and thrombocytopenia sometimes occur in addition to erythrocytopenia in patients with B19 infection. We retrospectively investigated the possible cause of thrombocytopenia by B19 infection in 23 patients with thrombocytopenia admitted to our hospital in the past 5 years. Two patients were found to be infected by B19. Mild thrombocytopenia in both cases was thought to be an early event in B19 infection.

Acute splenic sequestration together with aplastic crisis caused by human parvovirus B19 in patients with sickle cell disease

Three children with homozygous sickle cell disease, 22 months and 8 and 10 years of age, had clinical and hematologic manifestations of aplastic and splenic sequestration crisis simultaneously. They had an acute drop in hemoglobin level (16, 20, and 45 gm/L), reticulocytopenia (0.1%, 0.6%, and 0.3%), and sudden splenic enlargement. Evidence of recent parvovirus infection was demonstrated.

Characterization of a nested polymerase chain reaction assay for detection of parvovirus B19

The characterization and application of a nested polymerase chain reaction (PCR) assay for the detection of human parvovirus B19 DNA is described. The assay was evaluated with 149 diagnostic serum samples (collected up to 150 days after the onset of symptoms) previously tested by dot blot hybridization for B19 DNA and by class-specific capture radioimmunoassays for the detection of B19 immunoglobulin M (IgM) and IgG. B19 DNA was detectable by the PCR in 70% of the sera. There was a statistically significant association between the detection of B19 DNA by PCR and high B19 IgM values (P < 0.005), low B19 IgG values (P < 0.05), and a short interval between onset of symptoms and serum collection (P < 0.005). Serial serum samples, throat swabs, and peripheral blood mononuclear cells collected from 10 individuals during an outbreak of parvovirus B19 were also tested by the nested PCR. B19 DNA was detectable in the throat swabs at the time of the clinical illness and in the peripheral blood mononuclear cell fraction up to the end point of the study 6 months after infection. The location of the B19 DNA could not be determined in cytocentrifuge preparations of peripheral blood mononuclear cells with nonisotopic in situ hybridization and immunolabelling.

The clinical features of sickle cell disease

Evidence from structural studies of DNA suggest that the sickle cell mutation has arisen on at least three separate occasions in Africa and as a fourth independent mutation in the Eastern Province of Saudi Arabia or India. The pathophysiology of sickle cell disease is essentially similar in these different areas although the frequency and severity of complications may vary between areas. Generally, the chronic haemolysis and resulting anaemia is well tolerated, although serious morbidity and occasionally mortality may be associated with the aplastic crisis or cholelithiasis. Exacerbation of anaemia below steady state levels occurs with chronic glomerular damage and renal failure, especially in older patients. Most of the morbidity of the disease arises from bone marrow necrosis in the painful crisis or from vaso-occlusive manifestations. Changes in the splenic circulation result in life-threatening episodes of acute splenic sequestration, the chronic morbidity of hypersplenism, and splenic dysfunction renders children prone to pneumococcal septicaemia. Chronic organ damage contributes to chronic leg ulceration in adolescence and progressive renal, pulmonary, and occasionally cardiovascular impairment in later life. The clinical spectrum of homozygous sickle cell disease varies widely between patients. Factors contributing to this variability include alpha-thalassaemia, persistence of high HbF levels, haematology, social circumstances, and geographical and climatic variation. Many of the causes of mortality may be prevented or more effectively treated, leading to increased survival and an increased quality of life in affected subjects.

DNA replication of parvovirus B 19 in a human erythroid leukemia cell line (JK-1) in vitro

A major limitation of studies on the parvovirus B 19, a causative agent of transient aplastic crisis, has been the absence of appropriate cell lines permissive for the virus. In the present study, a human erythroid leukemia cell line (JK-1) was shown to support B 19 virus DNA replication in vitro. Forty-eight hours after virus inoculation of JK-1 liquid cell cultures, the average number of B 19 genome copies was estimated at 3,000 per cell by DNA dot blot analysis. The addition of erythropoietin increased B 19 copy number to 10,000 per cell. The presence of replicative forms of the B 19 virus genome was genome was demonstrated by Southern blot analysis. Although persistent infection of B 19 virus was not observed in JK-1 cells, this culture system will be of value in elucidating the molecular basis of the erythroid specificity of parvovirus B 19.

Human parvovirus B19-associated arthritis in children

Human parvovirus B19 (HPV B19) infection has been associated with chronic joint complaints in adult patients. We now report 22 children with joint complaints associated with recent HPV B19 infection. These children had either erythema infectiosum or serologic evidence of recent infection. Twenty children had arthritis; two had arthralgias. Eleven children had associated constitutional symptoms. Laboratory findings were generally normal. The duration of joint symptoms was less than 4 months in 14 children; however, six children have had persistent arthritis for 2 to 13 months, which would fulfill criteria for the diagnosis of juvenile rheumatoid arthritis. Although HPV B19 is usually associated with acute arthritis of brief duration, in some children infection with HPV B19 may be associated with the development of chronic arthritis.

Successful replication of parvovirus B19 in the human megakaryocytic leukemia cell line MB-02

The pathogenic human parvovirus B19 has been shown to undergo productive replication in the erythroid lineage in primary normal human hematopoietic progenitor cells. However, none of the established erythroleukemia cell lines has allowed B19 virus replication in vitro. The remarkable erythroid tissue tropism of B19 virus was evaluated with a human megakaryocytic leukemia cell line, MB-02, which is dependent on the growth factor granulocyte-macrophage colony-stimulating factor but can be induced to undergo erythroid differentiation following treatment with erythropoietin (Epo). Whereas these cells did not support B19 virus DNA replication in the presence of granulocyte-macrophage colony-stimulating factor alone, active viral DNA replication was observed if the cells were exposed to Epo for 5 to 10 days prior to B19 virus infection, as detected by the presence of the characteristic B19 virus DNA replicative intermediates on Southern blots. No replication occurred if the cells were treated with Epo for 3 days or less. In addition, complete expression of the B19 virus genome also occurred in Epo-treated MB-02 cells, as detected by Northern blot analysis. B19 progeny virions were released into culture supernatants that were biologically active in secondary infection of normal human bone marrow cells. The availability of the only homogeneous permanent cell line in which induction of erythroid differentiation leads to a permissive state for B19 virus replication in vitro promises to yield new and useful information on the molecular basis of the erythroid tissue tropism as well as parvovirus B19-induced pathogenesis.

Human parvovirus B19 and rheumatoid arthritis

Human parvovirus B19 infections have been linked with the development of a short-lived symmetrical polyarthritis and, rarely, a more persistent arthritis. We prospectively looked for serological evidence of recent B19 infection in 25 early synovitis patients presenting within 12 weeks of symptom onset and compared them with 21 controls seen over the same time period. None of the control patients had evidence of recent B19 infection while 3 of the early synovitis patients had raised IgM anti-B19 antibody levels. Two had a transient arthritis and 1 developed persistent seropositive rheumatoid arthritis.

Recombinant parvovirus B19 capsids as a new substrate for detection of B19-specific IgG and IgM antibodies by an enzyme-linked immunosorbent assay

A new enzyme-linked immunosorbent assay for the detection of B19-specific IgG and IgM antibodies was established using B19 capsids synthesized in a baculovirus expression system. These B19 capsids, consisting of either coat protein VP2 alone or of both VP1 and VP2, have been shown to be similar to native virus in size and appearance. The results obtained for the detection of B19-specific antibodies showed good correlations with a radioimmunoassay which uses native B19 virus and an immunofluorescence assay based on insect cells expressing coat protein VP1. The course of the antibody response could be followed by determining the titers of sequential serum samples taken after a recent B19 infection. Both types of recombinant capsids form an excellent source of antigen for the detection of both B19 IgG and IgM antibodies and are a very promising substitute for native virus.

Parvovirus B19 replication in human umbilical cord blood cells

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.

Parvovirus B19 infection and bone marrow transplantation

Parvovirus B19 lytically infects erythroid progenitor cells and thereby causes cessation of erythropoiesis in infected individuals. Anemia develops only if red cell turnover is increased, as in patients with chronic hemolysis (transient aplastic crisis). In addition to transient marrow failure, B19 can cause chronic anemia and, rarely, pancytopenia in immunodeficient patients who are not able to mount an adequate immune response to clear the virus. Bone marrow transplantation, although causing significant immunosuppression, is rarely complicated by symptomatic B19 infection. This is probably due to effective passive immunotherapy by immunoglobulin infusions immediately after transplantation and early reconstitution of antibody responses after uncomplicated transplantation.

Viruses and the blood

Haematological syndromes attributed to viruses demonstrate geographical variations in incidence and great dependence on host factors. Severe haematological disease is the exception rather than the rule in dengue virus infection, and probably depends at least in part on the host immune response to the virus. The increased incidence of hepatitis-associated aplasia in east Asia may reflect distribution of an infectious agent, an environmental toxin, or genetic predisposition, but probably represents some combination of these factors. Agents with apparently universal distribution, such as parvovirus B19 and Epstein-Barr virus, are associated with bone marrow failure only in a very narrow range of hosts. These examples teach us that viral causes cannot automatically be excluded from the differential diagnosis of syndromes whose occurrence is rare or apparently sporadic. Further investigation of these syndromes should include more detailed characterization of host factors, particularly immunological characteristics, and possible infectious and toxic cofactors which are associated with morbidity.

Restriction of porcine parvovirus replication in nonpermissive cells

Swine testicle (ST) cells and Madin-Darby canine kidney (MDCK) cells differ in their ability to support replication of porcine parvovirus (PPV). Viral replication events in ST cells, a permissive cell type, and MDCK cells, a nonpermissive cell type, were compared in an attempt to elucidate putative mechanisms of restrictive virus replication. Radiolabeled PPV bound to the cell surface of both cell types equally well and the binding was shown to be PPV specific, indicating that the restriction was not at the cell surface level. In contrast, profound differences in intracellular events in PPV replication were observed between these two cell types. Synthesis of viral DNA was limited in MDCK cells in that the percentage of cells with replicative-form DNA as determined by strand-specific probe in situ hybridization was approximately 100-fold lower in MDCK cells than in ST cells at the same multiplicity of infection. Northern (RNA) blot analysis, using oligonucleotide probes derived from both structural and nonstructural protein-coding regions of the PPV genome, revealed four PPV mRNA transcripts from infected ST cells. Comparatively, RNA species from the structural protein coding region were actively transcribed in MDCK cells, but synthesis of RNA species from the nonstructural protein coding region was negligible. Immunoprecipitation of viral polypeptides revealed the three characteristic structural polypeptides, VP1, VP2, and VP3, along with the nonstructural polypeptide, NS-1 from ST cells. In contrast, neither viral structural or nonstructural polypeptides nor progeny virions were produced from MDCK cells. The data suggest that mechanisms controlling permissiveness of cells to PPV infection are associated with the level of viral DNA replication, RNA transcription, and viral antigen expression but not absorption to the cell surface.

Prokaryotic expression of a VP1 polypeptide antigen for diagnosis by a human parvovirus B19 antibody enzyme immunoassay

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.

Replication of parvovirus B19 in hematopoietic progenitor cells generated in vitro from normal human peripheral blood

Erythroid progenitor cells generated in vitro from peripheral human blood in the presence of interleukin-3 and erythropoietin were infected with human parvovirus B19. B19 virus DNA replication was highest 48 to 72 h after infection, and maximum levels of B19 virus proteins were detected in culture supernatants at 72 to 96 h after infection. B19 virus propagated in vitro was infectious. This cell culture system with peripheral blood cells facilitates studies in vitro of B19 virus replication.

Polymerase chain reaction with double primer pairs for detection of human parvovirus B19 induced aplastic crises in family outbreaks

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.

Acute parvovirus B19 infection mimicking myelodysplastic syndrome of the bone marrow

A 36-year-old, previously healthy woman was referred to our institution with pancytopenia and splenomegaly for suspected acute leukemia. Bone marrow aspiration showed marked dysplastic changes, excess of blasts, and only spurious red blood cell precursors. Action was taken to prepare allogeneic bone marrow transplantation from an HLA identical sibling for myelodysplastic syndrome. Repeat cytological examination of the bone marrow revealed striking hyperplasia of the red cell line with presence of abnormal giant proerythroblasts. Acute parvovirus B19 infection was suspected and confirmed by detection of anti-B19 IgM and B19 DNA. The underlying disease for this transient aplastic crisis was a formerly unknown hereditary spherocytosis.

Chemiluminescence dot blot hybridization assay for detection of B19 parvovirus DNA in human sera

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.