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

Preliminary X-ray crystallographic investigation of human parvovirus B19

Crystals that diffract X rays to at least 8 A resolution have been grown from human B19 parvovirus empty capsids. These particles consist of VP-2 derived from a baculovirus expression system. This is possibly the first time that a self-assembled empty viral capsid, grown in other than normal host cells, has been crystallized. Partial X-ray diffraction data have been collected using synchrotron radiation. The space group is P2(1)3 with a = 362 A. The particle position in the crystal cell is given, at least roughly, from packing considerations.

Evaluation of a synthetic-peptide enzyme-linked immunosorbent assay for immunoglobulin M to human parvovirus B19

A synthetic peptide corresponding to a part of the virus protein 1-virus protein 2 overlapping region of human parvovirus B19 was used in an indirect enzyme-linked immunosorbent assay. Antibodies of the immunoglobulin (Ig) M class were measured in serum samples from patients with erythema infectiosum and controls. In comparison with an IgM assay using native B19 viral antigen, the peptide antigen assay was 92% sensitive and 87% specific. B19 IgM reactivities were seen in a limited number of children with other viral diseases. Specific IgM reactivities to short synthetic viral peptides have previously been reported only with Epstein-Barr virus. Since other sources of viral antigen are limited, the peptide antigen assay may be a useful alternative for the diagnosis of B19-associated disease in human beings.

Viruses and bone marrow failure

Many agents are associated with bone marrow failure, including toxins, inherited metabolic defects, ionizing radiation, and viral infection. In most cases, the etiologic agent is unknown. Many of these unclassified cases have symptomatic, immunologic, or epidemiologic similarities to viral infections. Viruses from different taxonomic families have been implicated in bone marrow failure syndromes, and they appear to cause hematosuppression by a variety of mechanisms. Some of the viruses involved in relatively well characterized suppressive interactions will be reviewed, including parovovirus B19, dengue, hepatitis viruses, Epstein-Barr virus, cytomegalovirus and the human immunodeficiency virus.

Recent advances in pediatric infectious diseases and their impact on dermatology

The past five years have seen numerous advances in the field of pediatric infectious diseases, and many of these have a substantial impact on the practice of dermatology. We review some of these advances and discuss their implications on etiology, diagnosis, therapy and complications of some relatively common conditions. The etiologic agent of exanthum subitum (roseola infantum) has been clearly implicated as a herpesvirus-6. Although in the classically described situation high fever in a young child is followed by defervescence and rash, two new scenarios have been described associated with this virus. The first is fever without rash and the second is rash without fever. The etiologic agent of erythema infectiosum ("slapped cheek") has been shown to be a human parvovirus B19. The virus has also been associated with aplastic crises (in hemoglobinopathies), hydrops fetalis, and a syndrome of subacute arthralgias in women. The etiologic agent in cat-scratch disease has recently been shown to be a small pleomorphic bacillus that also can produce pyogenic granuloma-like lesions in patients with acquired immunodeficiency syndrome. The number of cases of congenital syphilis, particularly in large cities, is increasing tremendously. Many of these infants have received no prenatal care because of drug abuse problems in their parents. Finally, we describe the changing etiology of impetigo that is predominantly associated with Staphylococcus aureus. We further describe the growing resistance to erythromycin and several new erythromycin drug-drug interactions.

Human parvovirus B19 infected fetal liver as a source of antigen for a radioimmunoassay for B19 specific IgM in clinical samples

A radioimmunoassay for human parvovirus B19 IgM was developed using virus antigen derived from infected fetal liver obtained post mortem. The specificity and sensitivity of this assay, compared with an established radioimmunoassay using serum antigen, was determined by testing 126 sera by both techniques. The results obtained demonstrated close concordance. False negative results were not obtained using fetal liver antigen in 58 tests on known B19 IgM negative sera. Sixty-four IgM positive sera gave positive results using fetal liver derived antigen and the results obtained were quantitatively similar. Four sera gave false positive results using liver antigen but at a very low level. In view of these results we were able to establish a routine diagnostic service for B19 IgM using fetal liver derived antigen, and the results obtained on the first 459 clinical specimens are presented.

In situ hybridization for the detection of human parvovirus B19 nucleic acid sequences in paraffin-embedded specimens

Parvovirus infection of pregnant women leading to a transplacentar infection of the fetus may result in hydrops fetalis, and ultimately in intrauterine death of the fetus. In situ hybridization with a biotinylated as well as with a 35S-labeled probe for human parvovirus B19 was performed on formalin-fixed paraffin-embedded (FFPE) tissue from a fetus suffering from non-immunologic hydrops fetalis. Histology was suggestive of viral infection probably with human parvovirus. Parvovirus DNA could be detected and precisely localized mainly in the nuclei of erythroid precursors cells within fetal blood vessels of all organs examined. There was no detection of B19 nucleic acid in parenchymal cells of the placenta or the fetal organs, nor within maternal blood cells. These findings are in agreement with the well-known properties of animal parvoviruses to replicate exclusively in proliferating cells. Taking into consideration the problems in diagnosing human parvovirus infection by light microscopy, we conclude that in situ hybridization with an appropriate non-radioactive probe is a valuable, rapid and safe complementary detection method for the diagnosis and study of human parvovirus infections. The 35S-labeled probe is more sensitive than the biotinylated probe, but has the disadvantages of lower resolution of the signal, longer duration of the assay, the hazard of radioactivity and the shorter shelf-life of the probe.

Rheumatologic manifestations of human parvovirus B19 infection in adults. Initial two-year clinical experience

During 1987 and 1988, we identified 9 adults at the Medical and Rheumatology Services of the University of Iowa Hospitals and Clinics who had a clinical diagnosis of fifth disease; 8 of the 9 had symptoms of joint involvement. Another 12 adults with serologic positivity for anti-parvovirus B19 IgM antibody presented with polyarthralgia/polyarthritis. Patients were usually found to be seronegative for rheumatoid factor, and none developed nodules or erosive disease. Many patients with chronic disease met criteria for a diagnosis of rheumatoid arthritis. A diagnosis of parvovirus B19 infection should be considered during the initial visit of patients with polyarthralgia/polyarthritis.

An immunofluorescence assay for the detection of parvovirus B19 IgG and IgM antibodies based on recombinant viral antigen

An indirect immunofluorescence assay for serum IgG and IgM antibodies to human parvovirus B19 was established using recombinant B19 viral antigen, the capsid protein VP1, which had been produced in a baculovirus expression system. This protein gives a strong and characteristic signal in the immunofluorescence assay, making it a suitable candidate for this test system. The test results showed a good correlation with results obtained with a solid-phase capture radioimmunoassay (Cohen et al., 1983). 76% of sera from a random selection of blood donors were positive for B19 IgG which agrees with previous findings. The course of the IgM and IgG antibody response to B19 infection could be followed with the immunofluorescence assay by determining the titers of series of sera taken after a recent B19 infection. Investigation of 24 sera containing rubella-specific IgM showed no cross-reactivity with the recombinant B19 VP1 used in this test system. The test described here has the advantage of being based on a renewable source of antigen and will be further evaluated for routine diagnostic use in comparison with radioimmunoassay.

B19 parvovirus infection causing aplastic crisis in 3 out of 5 family members with hereditary spherocytosis

B19 parvovirus infection is a principal cause of transient bone marrow suppression in patients with chronic haemolytic anaemias. Acute infection is described in a family of five individuals with hereditary spherocytosis; three of them developed marked hypoplastic anaemia.

Antigenic parvovirus B19 coat proteins VP1 and VP2 produced in large quantities in a baculovirus expression system

Two baculovirus expression vectors derived from Autographica californica nuclear polyhedrosis virus (AcNPV) were prepared containing the complete 2.5 kb coding region for parvovirus B19 coat protein VP1 (AcB19VP1L) and the 1.8 kb coding region for VP2 (AcB19VP2L), placed under the control of the polyhedrin promoter. The recombinant viruses were used to infect Spodoptera frugiperda cells and the proteins expressed were analysed using appropriate antibodies. AcB19VP1L-infected cells produced B19 VP1 as shown by its reaction with 13 human sera containing B19-specific antibodies in Western blot analysis and indirect immunofluorescence. The signal seen with VP1 in immunofluorescence makes it suitable for the development of a diagnostic assay based on this technique. VP1 also reacted with two monoclonal antibodies (mAbs) specific for the B19 protein part of a 196 kDa beta-galactosidase B19 fusion protein expressed in E. coli. Cells infected with AcB19VP2L produced B19 VP2 which reacted with the same human sera in indirect immunofluorescence and with five of the 13 sera in Western blots. VP2 did not react with the fusion protein-specific mAbs. The large amounts of viral antigen produced in this system means the development of widely available diagnostic tests for B19 infection and the further characterization of the B19 structural proteins are within reach.

Adeno-associated parvoviruses inhibit growth of cells derived from malignant human tumors

Infection of freshly established malignant human tumor cells with the adeno-associated viruses AAV-2 or AAV-5 inhibits cell proliferation. Normal human fibroblasts are also affected, but appear to partially escape the inhibition. In cell cultures of permanent lines of human and rodent origin, cell number reduction could not be observed. The AAV-mediated influence on cell growth is not due to helper-independent replication of the virus, since neither of the cell cultures supported AAV propagation in the absence of a viral helper.

Detection of human parvovirus B19 DNA by using the polymerase chain reaction

The polymerase chain reaction (PCR) was investigated for detecting human parvovirus B19 (B19) DNA in sera. Three pairs of oligonucleotides were evaluated as primers. The best oligonucleotide pair spanned 699 nucleotides, including the region common to VP1 and VP2. After PCR amplification of B19 DNA in serum, a 699-nucleotide DNA fragment was detected on agarose gels. This DNA fragment was B19 DNA, because after Southern transfer it hybridized to a 19-nucleotide internal probe and contained a single PstI cleavage site. Dot blot hybridization with a radiolabeled cloned portion of the B19 genome as a probe was compared with PCR. PCR was 10(4) times more sensitive than dot blot hybridization and, with an internal radiolabeled probe, 10(7) times more sensitive than dot blot hybridization. Of 29 serum specimens from 18 patients with proven B19 infections, 24 were PCR positive. None of 20 serum samples from uninfected controls were positive. Of 22 serum samples positive for immunoglobulin M to B19, PCR detected B19 DNA in 17. Seven serum samples lacking immunoglobulin M were PCR positive. PCR detected B19 DNA in urine, amniotic fluid, pleural fluid, ascites, and leukocyte extracts. PCR is a rapid and simple method for diagnosing infections with human parvovirus B19 but must be combined with serologic tests for immunoglobulin M to B19, especially when testing only a single serum sample.

The six classic childhood exanthems: a review and update

The six classic exanthems of childhood have many similar physical findings. Familiarity with them, as well as with important laboratory data, allows early and accurate diagnosis of these often confusing diseases. Recognition and treatment of possible sequelae also improve prognosis. In this review we discuss epidemiology, etiology, clinical manifestations, pathologic and laboratory findings, differential diagnosis, therapy, and prevention of each of the exanthems.

Construction of a recombinant human parvovirus B19: adeno-associated virus 2 (AAV) DNA inverted terminal repeats are functional in an AAV-B19 hybrid virus

To facilitate genetic analysis of the human pathogenic parvovirus B19, we constructed a hybrid B19 viral genome in which the defective B19 inverted terminal repeats were replaced with the full-length inverted terminal repeats from a nonpathogenic human parvovirus, the adeno-associated virus 2 (AAV). The hybrid AAV-B19 genome was rescued from a recombinant plasmid and then the DNA was replicated upon transfection into adenovirus 2-infected human KB cells in the presence of AAV genes coding for proteins required for AAV DNA replication (AAV-Rep proteins). In addition, in the presence of AAV genes coding for the viral capsid proteins (AAV-Cap proteins), the rescued/replicated hybrid AAV-B19 genomes were packed into mature AAV progeny virions, which were subsequently released into culture supernatants. The recombinant AAV-B19 progeny virions were infectious for normal human bone marrow cells and strongly suppressed erythropoiesis in vitro. The availability of an infectious recombinant B19 virus should facilitate the mutational analysis of the viral genome, which, in turn, may yield information on individual viral gene functions in B19-induced pathogenesis. The hybrid AAV-B19 genome may also prove to be a useful vector for gene transfer in human bone marrow cells.

A genetically engineered cell line that produces empty capsids of B19 (human) parvovirus

B19 parvovirus is pathogenic in humans, causing the common childhood exanthem fifth disease and bone-marrow failure, both acute (transient aplastic crisis of hemolysis) and chronic (pure erythrocyte aplasia in immunodeficiency). The virus is tropic for a human red cell progenitor cell, and failure to culture B19 in a cell line has limited its clinical study. We cotransfected the right half of the cloned B19 genome and a minigene derived from the human dihydrofolate reductase gene (DHFR) into dhfr--Chinese hamster ovary cells and screened selected clones by RNA analysis; after amplification in methotrexate, clones were tested for capsid protein expression. A cell line, designated 3-11-5, stably expressed nearly full-length transcripts for the two capsid proteins. These cells produced the major and minor structural protein species in natural proportions that self-assembled into virion capsids. Capsids from 3-11-5 cells could be separated from virions by sucrose gradient sedimentation and had the density on cesium chloride isopycnic sedimentation of empty parvovirus capsids. Capsid protein was present in both nuclei and cytoplasm on immunofluorescence study but fractionated with the cytosol on purification. Empty capsid production was equal to or greater than virion production by infected bone-marrow cells, 1000-2000 capsids per cell, but cell growth was not diminished by capsid production. This cell line will be useful in developing practical assays for B19 parvovirus antibody and a vaccine for the virus, as well as potentially serving as a packaging cell line for gene therapy.

Fifth disease in children living in Belém, Brazil

Acute sera from two children suffering from an illness with an erythematous rash were positive for B 19 virus specific IgM antibody, as tested by a capture radioimmunoassay. The first patient, a two year old boy, presented with a cutaneous rash of six days duration, the second was a four year old girl, sister of the first patient, who was examined at the same time and had a three day history of cutaneous rash.

Analysis of parvovirus infections using strand-specific hybridization probes

The autonomous parvoviruses cause a broad spectrum of acute and chronic infections of animals and man. The discrimination of sites of viral replication from sites of viral sequestration is an important goal in elucidating the pathogenesis of these diseases. It is possible to employ strand-specific RNA hybridization probes in such analyses because a 'plus' sense probe will react with single stranded virion DNA and duplex replicative form DNA, but a 'minus' sense probe will react preferentially with obligate replicative intermediates (duplex replicative form DNA and mRNA). Strand-specific RNA hybridization probes were developed for the Aleutian mink disease parvovirus (ADV) and were used to study acute and chronic infections of mink. Such probes were capable of differentiating replicative intermediates (duplex replicative form DNA and mRNA) from single-stranded virion DNA in Southern blot analysis and in strand-specific in situ hybridization. ADV infection of seronegative newborn mink kits causes an acute, cytopathic infection of type II alveolar cells. Replication in these cells is highly permissive and is characterized by high levels of replicative intermediates and virion DNA. A fatal respiratory distress syndrome and hyaline membrane formation result from impaired surfactant production by the infected type II cells. On the other hand, ADV infection of adult mink is associated with a persistent infection and a disorder of the immune regulation. The target cells for viral replication in adult mink are confined to the lymphoid system and the bone marrow. Replication in these cells, which are probably lymphocytes, is restricted, and characterized by greatly reduced levels of replicative intermediates and virion DNA. It, therefore, seems that disease in the infected adult mink results from a restricted infection by ADV. Large amounts of virion DNA can also be demonstrated in locations where replication cannot be detected and apparently represents sequestration of virion particles by elements of the reticuloendothelial system. Thus, replication and sequestration can, in fact, be distinguished by the strand-specific in situ hybridization. These studies indicate that strand-specific in situ hybridization is a potentially valuable method for studying the pathogenesis of parvovirus infections.

Human parvovirus B19 infection among hospital staff members after contact with infected patients

In the spring and summer of 1988, two separate outbreaks of an illness with a rash resembling erythema infectiosum occurred among members of the nursing staff of the Children's Hospital of Philadelphia. The sources were two adolescent patients with sickle cell disease and aplastic crisis who had unsuspected parvovirus infection. Tests for IgM and IgG antibodies to parvovirus B19 were positive in both patients, and electron microscopical examination showed parvovirus-like particles in the early serum samples. Of 40 health care workers exposed to infected patients, 12 (30 percent) were infected, 2 (5 percent) were possibly infected, 8 (20 percent) had evidence of a past infection with B19, and 18 (45 percent) remained seronegative. Attack rates among the susceptible contacts were 36 percent in the first outbreak and at least 38 percent in the second. Clinical symptoms began a mean of 12.6 days after exposure and included malaise, rash, and joint pain. We conclude that hospital workers are at risk of contracting nosocomial erythema infectiosum from patients with parvovirus-associated aplastic crisis. We recommend that all patients with hereditary hemolytic anemias who are admitted with a febrile illness be evaluated for aplasia and promptly placed in respiratory and contact isolation if aplastic crisis is suspected.

Infection control measures for human parvovirus B19 in the hospital setting

A human parvovirus was first discovered serendipitously in blood from asymptomatic donors in 1975' and designated B19 because of the location of the original positive serum in a test panel. Subsequently, the newly discovered virus was determined to be the etiologic agent of most cases of transient aplastic crisis in the setting of chronic hemolytic anemia and of the childhood exanthem erythema infectiosum, or fifth disease. While erythema infectiosum with its classic “slapped-cheek” rash is a childhood illness, “fifth disease” in the adult should not be overlooked. At least 40% of adults lack serological evidence of past human parvovirus B19 infection and are at risk. Adults tend to have a more subtle rash, often lacking the “slapped cheeks,” and tend to have a more severe constitutional, flu-like illness with prominent joint symptoms. While the arthralgia and arthritis of adult “fifth disease” are often self-limiting, they may become chronic and lead to an arthropathy that meets American College of Kheumatology criteria for a diagnosis of rheumatoid arthritis. The arthropathy has been reported to persist up to five years, the longest follow-up now available (A. Wolf; MD, personal communication, August 27, 1987).

Detection of parvovirus B19 DNA in fetal tissues by in situ hybridisation and polymerase chain reaction

Attempts were made to detect human parvovirus B19-DNA by in situ hybridisation and the polymerase chain reaction in placental and fetal tissues from a case of intrauterine fetal death. In the in situ hybridisation experiments radioactive and non-radioactive (labelled with 2-acetyl-aminofluorene, AAF) DNA probes were used. B19-DNA was detectable in paraffin wax embedded fetal tissue from the liver, heart, lung, brain and thymus. The resolution with the AAF-labelled probes was higher than with the radiolabelled DNA. Parvovirus B19 DNA sequences were also detected in these tissues by an enzymatic in vitro amplification technique--the polymerase chain reaction. Amplification of a B19-DNA sequence before detection increases the rapidity and sensitivity of detection. The rapid, specific, and sensitive analysis of parvovirus B19 in normal and diseased tissues using these techniques may contribute considerably to determining the role of this virus as a risk factor in the outcome of pregnancy.

Human parvovirus (HPV/B19) infection with purpura

A 33-year-old man complained of purpura (petechial hemorrhage) in chelidons, poples, axillae, and bilateral chest in addition to other symptoms such as lumbago, arthralgia, muscular pain, and fever. On the next day of the onset, human parvovirus (HPV/B19) antigen and HPV/B19 DNA were detected in his serum, and twelve days later IgM antibody to HPV/B19 became detectable. This case supports the relationship between purpura and HPV/B19 infection.

Embryonic malformations in a case of intrauterine parvovirus B19 infection

An incomplete embryo of 9 weeks development from a woman infected by human parvovirus B19 during early pregnancy was histologically examined. B19-DNA was detected in both embryonic and placental tissue by dot-blot hybridization. Focal vascular endothelial damage was found throughout the entire embryo and placenta together with mononuclear infiltrations around the vessels. In the placenta these mononuclear cells belonged for the greater part to the cytotoxic and/or suppressor T-cell group. One eye showed lens abnormalities and retinal folds. The other eye was microphthalmic and aphakic and showed dysplasia of the sclera, anterior segment, and retina. The skeletal muscle cells displayed a general eosinophilic degeneration. Focally, similar changes were found in heart muscle and smooth muscle tissue. In several tissues pathologic effects at a cellular level were noted, as intranuclear vacuole-like inclusions and nuclear ballooning. On the basis of this study it is concluded that human parvovirus B19 may affect several fetal tissues and may even have teratological effects on a developing human embryo.

The presentation, management and prophylaxis of sickle cell disease

Sickle cell disease (SCD) is encountered in all parts of the world where plasmodium falciparum has been endemic and has spread by migration to the temperate countries of the world resulting in a heavy caseload in Northern Europe and the United States. These patients in the temperate climates manifest most of the clinical problems associated with SCD in Tropical Africa and the West Indies. There are, however, differences between the groups in both the frequency and presentations of the clinical syndromes. The clinical management of SCD is discussed with particular reference to the potentially fatal sequestration syndromes: splenic, hepatic, 'the girdle syndrome' and 'the chest syndrome'. In all clinical situations encountered in SCD blood transfusions should be by isovolaemic exchange unless there is a marked fall in haematocrit (less than 5 g/dl) as may occur with sequestration and aplasia. The criteria for exchange transfusion in the chest syndrome are a pAO2 of less than 60 mm Hg while breathing air or a rapidly deteriorating clinical picture. Analgesia for vaso-occlusive sickle pain should be adequate and freely available which often requires the parental administration of opiates. We have delineated a small sub-group (6%) of SCD patients, 'the non-copers', who manifest a high demand for analgesia. The prospects for cure, and the techniques and issues for antenatal diagnosis are reviewed demonstrating the importance of education and counselling. The significant reduction in mortality and morbidity of children with SCD taking penicillin prophylaxis is emphasised with the need for its early institution.

A new peptide for human parvovirus B19 antibody detection

A serological assay for human parvovirus B19 was developed. Linear overlapping synthetic peptides were synthesised according to parts of open reading frames 1 and 2. A region at the N-terminus of viral protein VP2 detected serological reactivity in indirect enzyme-linked immunosorbent assays for IgG and IgM with known seropositive human sera. A cyclized peptide taken from this region, amino acids 284-307, gave the best selective reactivity with seropositive and seronegative sera. The peptide assay appears suitable for further studies of B19 infections and their complications.

Viruses and bone marrow failure

Some generalizations can be drawn from a review of virus-associated bone marrow failure. The story of B19 parvovirus illustrates that viral infection may be an occult cause of marrow failure. Although the epidemiology of transient aplastic crisis suggested a viral aetiology, the implication of a single virus was surprising; the sporadic appearance of chronic bone marrow failure in immunosuppressed persons has had none of the features of a viral illness. The incrimination of parvovirus in these cases required development of specific immunological and molecular assays. Human and animal retrovirus studies have shown that small changes in the virus genome can have dramatic effects on the biology of the infectious agent and its pathogenicity in infected hosts. In Epstein-Barr virus infection, the host's immune response may play a more important role in mediating disease than virus cytotoxicity. Finally, the association of aplastic anaemia with hepatitis may be underestimated because of the inability to diagnose virus infection without obvious liver disease. The true spectrum of bone marrow disease due to virus infection is not known.

Severe erythroblastopenia and hemolytic anemia during a hepatitis A infection

A 41-year-old woman had acute hepatitis A infection complicated with severe anemia due to selective erythroblastopenia and hemolysis. A mechanism involving a cellular immune reaction is suggested. The hematological complications resolved during steroid treatment. She later developed a transient seropositive arthritis.

Parvovirus infections. From benign to life-threatening

Erythema infectiosum, aplastic crisis, intrauterine fetal demise, and an acute polyarthralgia syndrome can all be caused by human parvovirus B19. The major pathophysiologic effect of infection seems to be cessation of erythropoiesis as a result of cytolytic infection of red cell precursors. Erythema infectiosum is a benign disease that usually occurs in childhood. The acute polyarthralgia syndrome is likewise benign, and patients in whom parvovirus infection has been confirmed by serologic testing can be reassured that their joint symptoms are likely to be self-limited. Parvovirus-induced aplastic crisis in a patient with chronic hemolytic anemia is life-threatening but can be reversed with blood transfusions if recognized promptly. Parvovirus infection during pregnancy clearly increases the risk of fetal demise, and parental anxiety is understandably high. An organized approach using a combination of tests to monitor mother and fetus can provide optimal care in these cases.

Human parvovirus B19-induced transient pancytopenia in a child with hereditary spherocytosis

We report a child with hereditary spherocytosis who developed human parvovirus B19 (HPV B19)-induced transient pancytopenia. Symptoms of acute-phase illness subsided promptly after infusion of gammaglobulin containing HPV B19 antibody. The HPV B19-containing serum on admission inhibited not only erythroid colony growth but also myeloid and megakaryocyte colony growths. The inhibitory effect was abrogated by convalescent-phase serum or gammaglobulin solution containing HPV B19 antibody. These findings suggest that HPV B19-induced inhibition of haematopoiesis may be pathogenetic for transient bone marrow failure of the patient. The passive immunization may be effective in shortening the duration of acute-phase illness of HPV B19 infection.

Replication of B19 parvovirus in highly enriched hematopoietic progenitor cells from normal human bone marrow

The target cell specificity of the B19 parvovirus infection was examined by isolating highly enriched hematopoietic progenitor and stem cells from normal human bone marrow. The efficiency of the B19 parvovirus replication in enriched erythroid progenitor cells was approximately 100-fold greater than that in unseparated bone marrow cells. The more-primitive progenitor cells identical to or closely related to the human pluripotent hematopoietic stem cells, on the other hand, did not support viral replication. The B19 progeny virus produced by the enriched erythroid progenitor cells was infectious and strongly suppressed erythropoiesis in vitro. The susceptibility of both the more-primitive erythroid progenitors (burst-forming units-erythroid) and the more-mature erythroid progenitors (CFU-erythroid) to the cytolytic response of the virus and the lack of effect on the myeloid progenitors (CFU-granulocyte-macrophage) further give evidence to the remarkable tropism of the B19 parvovirus for human hematopoietic cells of erythroid lineage.

Aplastic crisis in sickle cell disorders: bone marrow necrosis and human parvovirus infection

Aplastic crisis in patients with sickle cell disease who develop a parvovirus infection may be associated with extensive bone marrow necrosis as well as acute selective erythroblastopenia. This illness may be manifested by pyrexia, lymphadenopathy, bone tenderness and significant hypoxemia with minimal roentgenographic findings in the lungs. It is uncertain whether the hypoxemia is caused by the effects of the viral infection on the lungs or is secondary to sickling of red blood cells in the pulmonary vasculature or both. The hypoxia may be sufficiently severe to require treatment with both oxygen and transfusion. The physical damage to the bone marrow associated with bone marrow necrosis may be more important than selective acute erythroblastopenia in inducing aplastic crisis in patients with sickle cell disorders. Studies of bone marrow biopsy specimens collected during parvovirus-associated aplastic crisis in patients with nonsickle cell hemolytic disorders would be helpful in determining the pathophysiology of parvovirus-associated disorders.

Detection of parvovirus DNA in human serum using biotinylated RNA hybridisation probes

Methods were established for the detection of parvovirus DNA in human serum using single-stranded RNA probes. The sensitivity of detection of virus using 32P-radiolabelled RNA versus non-radiolabelled biotinylated RNA probes using a streptavidin-polyalkaline phosphatase detection system was compared. Virus was detected using 32P-labelled and biotinylated RNA probes at serum dilutions of 10(-3), equivalent to approx. 3 pg of viral DNA. Using biotinylated RNA probes and a dot-blot system, diagnosis of numerous serum samples could be performed within 8 h of receipt of samples, using an RNA probe which was synthesised and stored at -20 degrees C for up to 12 months without loss of sensitivity. Our work demonstrates the potential of biotinylated RNA probes in the routine analysis of viral sequences in serum.

Intrauterine infection with human parvovirus B19: a light and electron microscopy study

Recent reports have documented human parvovirus B19 infection in pregnancy, which may lead to spontaneous abortion, stillbirth or hydrops fetalis. Transplacental infection in a case of hydrops fetalis is demonstrated by light and electron microscopy observation of virus inclusions in all tissues examined. Parvovirus particles measuring approximately 20 nm were observed within the nuclei of erythropoietic cells. The parvovirus virions were observed most commonly as randomly distributed particles and rarely in crystalline assays. Thus definitive evidence of fetal infection confined to red cell precursors is documented.

Temporal clustering of transient erythroblastopenia (cytopenia) of childhood

A temporal cluster of four cases of transient childhood erythroblastopenia is described. In all cases there was an associated transient neutropenia and in one case a transient mild thrombocytopenia. In all cases reticulo-endothelial iron overload was a prominent feature but there was no evidence of a pre-existing chronic haemolytic state. All children made a full recovery with only supportive treatment, although in three cases blood transfusion was necessary.

Human parvovirus infections

Discovered by chance in 1974, the human serum parvovirus B19 is at present the only recognized, autonomous, pathogenic human parvovirus. For some years following its discovery, B19 was not associated with any defined clinical syndrome; although a high titre viraemia was often noted in infected individuals they were largely asymptomatic. In 1980 the causal association between B19 infection and aplastic crisis in chronic haemolytic anaemia began to emerge with the discovery of B19 as the agent responsible for aplastic crisis in sickle cell anaemia. This fulfilled the expectation of a disease of tissue comprising a large proportion of dividing cells, namely the erythropoietic elements of the bone marrow, anticipated in autonomous parvovirus infection where viral replication is confined to dividing cells. More recently, erythema infectiosum, an illness sharing many of the clinical features of rubella, has been found to be the common result of B19 infection, although a spectrum of disease is now emerging. Much effort is currently directed toward the elucidation of the effects of maternal B19 infection on the developing fetus.

An outbreak of 'slapped cheek' parvovirus infection (erythema infectiosum) in a Scottish street

One adult and six children living in a small Scottish street developed erythema infectiosum (fifth disease) during the summer of 1985. The rash was attributed to infection with the human parvovirus. Leg pain and arthralgia occurred in five of the children.

Variation of erythroid and myeloid precursors in the marrow and peripheral blood of volunteer subjects infected with human parvovirus (B19)

Infection of normal individuals with human parvovirus (B19) results in a mild disease (erythema infectiosum) but gives rise to aplastic crises in patients with chronic hemolytic anemias. The effects of this disease on hemopoiesis were investigated following intranasal inoculation of the virus into three volunteers. A typical disease ensued with a viremia peaking at 9 d. Marrow morphology 6 d after inoculation appeared normal but at 10 d there was a severe loss of erythroid precursors followed by a 1-2-g drop in hemoglobin, and an increase in serum immunoreactive erythropoietin. Erythroid burst-forming units (BFU-E) from the peripheral blood were considerably reduced, starting at the time of viremia and persisting for 4-8 d depending on the individual. Granulocyte-macrophage colony-forming units (CFU-GM) were also affected but the loss started 2 d later. Both CFU-GM and BFU-E showed a sharp overshoot at recovery. In the marrow, BFU-E and CFU-E were reduced at 6 and 10 d in the individual having the longest period of peripheral progenitor loss. In contrast, there was an increase in BFU-E and CFU-E in the subject with least change in peripheral progenitors. In the third subject, with an intermediate picture, there was a loss at 6 d but an increase at 10 d of erythroid progenitors. It is suggested that the architecture of the marrow might partially isolate progenitors from high titers of virus in the serum and individual variation in this respect might give the results observed.

Serological study of rubella-like illnesses

We investigated 627 patients who within a period of 2 1/2 years had had a rubelliform rash and/or symptoms of arthritis and arthralgia. Sera from these patients were investigated for evidence of rubella, human parvovirus B19 (HPV), and measles infection with methods to detect specific IgM and IgG antibodies. Complement fixation tests were used to screen for a wide range of other infectious agents. We detected 229 cases of rubella, 43 cases of HPV infection, 7 cases of measles, and 9 cases of infection by various other aetiological agents. This left a large proportion of rubelliform rashes, 54% (339 cases), whose aetiology was unknown. This study confirmed that the diagnosis of rubella on clinical grounds alone is unreliable. Many (6.8%) of the rashes in the study were due to HPV infection, and the seasonal incidence was the same as for rubella. There was considerable overlap between the features of rubella and HPV infections, although in adults arthralgia occurred more frequently in HPV infections than in rubella. In all cases HPV infection was self-limiting, although, as in rubella, symptoms can be prolonged and one adult's disease lasted almost 9 months. Purpura was noted in only one patient with HPV infection. In this study three patients had HPV infection during pregnancy. Two patients spontaneously aborted one month later. The third patient progressed to full term and delivered a healthy baby.