Parvovirus B19 for the hematologist

Rheumatic manifestations and sequela of acute parvovirus B19 infection in hospitalized adult population

BACKGROUND

Parvovirus B19 infection has been associated with various clinical entities including musculoskeletal manifestations and the development of different autoimmune diseases. The aim of our study is to examine the musculoskeletal manifestations associated with acute parvovirus B19 infection and the possible development of chronic autoimmune rheumatic diseases.

PATIENTS AND METHODS

Retrospective cohort study that included adult hospitalized patients diagnosed with an acute parvovirus B19 infection between 1 January 2021 and 1 February 2024. Subjects were followed-up for 6-12 months after hospitalization aiming to identify patients who developed chronic autoimmune rheumatic diseases.

RESULTS

The study included 23 patients diagnosed with acute parvovirus B19 infection. Patients were predominantly females (16, 69.6%) with mean age at diagnosis of 39.3 ± 13.11 years. Most patients were Jewish (15, 65.2%). The two most common acute symptoms were fever (82.6%) and myalgia (56.5%). Polyarthritis was present only in three patients (13%) and all of them had wrists involvement. Anti-nuclear antibodies and rheumatoid factor were the most common autoantibodies present with equal prevalence each (13%). Five patients were treated with prednisone during the acute phase (21%), two (8.7%) of them needed drug escalation and were subsequently treated with hydroxychloroquine and methotrexate. One patient developed systemic lupus erythematosus during the first 6 months of follow-up.

CONCLUSION

Musculoskeletal manifestations developing during acute parvovirus B19 are usually self-limited with only a small minority of patients developing chronic autoimmune diseases. It is crucial to differentiate self-limited manifestations related to acute parvovirus B19 from idiopathic autoimmune diseases aiming to avoid unnecessary immunosuppressive therapy.

Transient aplastic crisis triggered by parvovirus B19 in a family with hereditary spherocytosis

Acute parvovirus B19 infection may lead to erythroblastopenia crisis in patients with underlying red blood cells disorders. We report herein an uncommon concomitant transient aplastic crisis in a mother and her daughter, both affected by hereditary spherocytosis. The diagnosis was confirmed by the detection of a very high parvovirus B19 DNA load in both the mother’s and daughter’s sera, associated with the presence of parvovirus B19 specific immunoglobulin-M antibodies. This rapid etiologic diagnosis allowed to save bone marrow sampling, although blood transfusion was required regarding the severe anemia associated with pancytopenia. Our observation illustrates first line parvovirus B19 hypothesis in the context of transient aplastic crisis and that contagiousness in household contacts should be considered in family with a medical history of red blood cell pathology.

A dutch family with Hb Debrousse: severe anemia after parvovirus B19 infection

Hb Debrousse [beta96(FG3)Leu-->Pro] is an unstable hemoglobin (Hb) variant with high oxygen affinity. We describe a case of chronic compensated hemolysis in a 39-year-old woman in whom the variant was found. Soon after the diagnosis was made, she and her son were admitted to the hospital with severe anemia due to Parvovirus B19 infection. The son also appeared to have the Hb Debrousse variant. Parvovirus B19 infection is a life-threatening disease in patients with (compensated) hemolysis.

Clinical aspects of parvovirus B19 infection

Parvovirus B19 is a significant human pathogen that causes a wide spectrum of clinical complications ranging from mild, self-limiting erythema infectiosum in immunocompetent children to lethal cytopenias in immunocompromised patients and intrauterine foetal death in primary infected pregnant women. The infection may also be persistent and can mimic or trigger autoimmune inflammatory disorders. Another important clinical aspect to consider is the risk of infection through B19-contaminated blood products. Recent advances in diagnosis and pathogenesis, new insights in the cellular immune response and newly discovered genotypes of human parvoviruses form a platform for the development of modern therapeutic and prophylactic alternatives.

Parvovirus B19 and the pathogenesis of anaemia

Human parvovirus B19 (B19) infection causes human bone marrow failure, by affecting erythroid-lineage cells which are well-known target cells for B19. The anaemia induced by B19 infection is of minor clinical significance in healthy children and adults, however, it becomes critical in those afflicted with haemolytic diseases. This condition is called transient aplastic crisis, and the pathogenesis is explained by the short life-span of red blood cells. Similarly, fetuses are thought to be severely affected by B19-intrauterine infection in the first and second trimester, as the half-life of red blood cells is apparently shorter than RBC at the bone marrow haematopoietic stage. On the other hand, B19 is also the causative agent of persistent anaemia in immunocompromised patients, transplant recipients and infants. The deficiencies of appropriate immune responses to B19 impair viral elimination in vivo, which results in enlargement of B19-infected erythroid-lineage cells. The B19-associated damage of erythroid lineage cells is due to cytotoxicity mediated by viral proteins. B19-infected erythroid-lineage cells show apoptotic features, which are thought to be induced by the non-structural protein, NS1, of B19. In addition, B19 infection induces cell cycle arrests at the G(1) and G(2) phases. The G(1) arrest is induced by NS1 expression prior to apoptosis induction in B19-infected cells, while the G(2) arrest is induced not only by infectious B19 but also by UV-inactivated B19, which lacks the ability to express NS1. In this review, we address the clinical manifestations and molecular mechanisms for B19-induced anaemia in humans and a mouse model, and of B19-induced cell cycle arrests in erythroid cells.

Pure red cell aplasia in a patient with trisomy X chromosome abnormality and reactivated Epstein-Barr virus infection

We describe a woman with a congenital chromosome anomaly, 47,XXX, who developed chronic pure red cell aplasia (PRCA). The patient had serologic reactivity consistent with that of reactivated Epstein-Barr virus (EBV) infection, as judged by high titers for anti-EBV viral capsid antigen (VCA) immunoglobulin G (IgG) and anti-early antigen (EA) IgG. Detection of EBV genome in peripheral blood cells and cell-free serum also supported the diagnosis. Although EBV infection has been implicated in the pathogenesis of acute PRCA, the viral infection rarely results in a chronic disease state. So far, only 1 case of EBV-associated chronic PRCA has been reported, to the best of our knowledge. Chronic PRCA also is known to occur on an autoimmune basis. Individuals carrying an extra X chromosome, such as XXY and XXX, are prone to development of immune abnormalities. Our patient had an anti-DNA autoantibody and a positive result of the direct Coombs test. The pathogenesis of PRCA in this case seemed to involve multiple factors. In addition to the infectious agent, host factors may have played a role. Although the etiologic link between chronic PRCA and trisomy X remains to be elucidated, our findings suggest the importance of karyotype analysis as well as search for infectious agents in patients with chronic PRCA.

Parvovirus B19 in the acute arthropathies and juvenile rheumatoid arthritis

OBJECTIVE

To evaluate the prevalence of recent parvovirus B19 infection in a cohort of children presenting with acute arthropathy and to determine the prevalence of a subsequent diagnosis of juvenile rheumatoid arthritis in this cohort.

METHOD

In this prospective study, parvovirus B19 IgM antibody was investigated in 75 patients who were referred to our clinic with acute joint complaints and also in 75 healthy controls. One patient in each group was excluded due to neuroblastoma and acute lymphoblastic leukaemia. The characteristics of parvovirus B19 IgM positive patients who were accepted as parvovirus B19 arthropathy were further evaluated. All the patients were followed up for at least 6 weeks and the patients with chronic progression of joint complaints were followed for at least 6 months to determine their progress. The cases of juvenile rheumatoid arthritis in this chronic group were identified.

RESULTS

Parvovirus B19 IgM was detected in 16 of 74 patients (21.6%) with acute arthropathy compared with 3 of 74 (4.1%) in the healthy control group (chi(2) = 8.67; P = 0.003). The parvovirus B19 positive patients with arthropathy were more likely to become chronic (P = 3.7 x 10(-7)) and to be diagnosed as juvenile rheumatoid arthritis (P = 0.03) than the parvovirus B19 IgM negative group with arthropathy. Additional joint destruction developed in one case who was parvovirus B19 IgM positive in whom juvenile rheumatoid arthritis was diagnosed during follow up.

CONCLUSION

These data support the hypothesis that parvovirus B19 infection may be associated with the onset of juvenile rheumatoid arthritis in a proportion of patients.

Human parvovirus B19

Parvovirus B19 (B19) was discovered in 1974 and is the only member of the family Parvoviridae known to be pathogenic in humans. Despite the inability to propagate the virus in cell cultures, much has been learned about the pathophysiology of this virus, including the identification of the cellular receptor (P antigen), and the control of the virus by the immune system. B19 is widespread, and manifestations of infection vary with the immunologic and hematologic status of the host. In healthy immunocompetent individuals B19 is the cause of erythema infectiosum and, particularly in adults, acute symmetric polyarthropathy. Due to the tropism of B19 to erythroid progenitor cells, infection in individuals with an underlying hemolytic disorder causes transient aplastic crisis. In the immunocompromised host persistent B19 infection is manifested as pure red cell aplasia and chronic anemia. Likewise, the immature immune response of the fetus may render it susceptible to infection, leading to fetal death in utero, hydrops fetalis, or development of congenital anemia. B19 has also been suggested as the causative agent in a variety of clinical syndromes, but given the common nature, causality is often difficult to infer. Diagnosis is primarily based on detection of specific antibodies by enzyme-linked immunosorbent assay or detection of viral DNA by dot blot hybridization or PCR. Treatment of persistent infection with immunoglobulin reduces the viral load and results in a marked resolution of anemia. Vaccine phase I trials show promising results.

Pure red cell aplasia due to parvovirus B19 in a patient treated with rituximab

Rituximab is a chimeric monoclonal antibody directed against CD20 and used in the treatment of B-cell non-Hodgkin's lymphoma. Due to its ability to deplete B lymphocytes, rituximab can interfere with humoral immunity, causing it to be suppressed for several months after treatment. The reported case depicts a serious consequence of this effect of rituximab therapy: pure red cell aplasia resulting from chronic parvovirus B19 infection. The point of interest in this case is not only the association between rituximab therapy and pure red cell aplasia, but the diagnostic and therapeutic utility of the knowledge of parvovirus B19 as the likely etiologic link between the two. Given the known efficacy of intravenous immunoglobulin (IVIg) in the treatment of chronic parvovirus B19 infection, this therapy can cure some of these patients and successfully render most others transfusion-independent until recovery of their own humoral immune system.

Pure red cell aplasia due to parvovirus B19 in a patient treated with rituximab

Rituximab is a chimeric monoclonal antibody directed against CD20 and used in the treatment of B-cell non-Hodgkin's lymphoma. Due to its ability to deplete B lymphocytes, rituximab can interfere with humoral immunity, causing it to be suppressed for several months after treatment. The reported case depicts a serious consequence of this effect of rituximab therapy: pure red cell aplasia resulting from chronic parvovirus B19 infection. The point of interest in this case is not only the association between rituximab therapy and pure red cell aplasia, but the diagnostic and therapeutic utility of the knowledge of parvovirus B19 as the likely etiologic link between the two. Given the known efficacy of intravenous immunoglobulin (IVIg) in the treatment of chronic parvovirus B19 infection, this therapy can cure some of these patients and successfully render most others transfusion-independent until recovery of their own humoral immune system.

Severe leukopenia and dysregulated erythropoiesis in SCID mice persistently infected with the parvovirus minute virus of mice

Parvovirus minute virus of mice strain i (MVMi) infects committed granulocyte-macrophage CFU and erythroid burst-forming unit (CFU-GM and BFU-E, respectively) and pluripotent (CFU-S) mouse hematopoietic progenitors in vitro. To study the effects of MVMi infection on mouse hemopoiesis in the absence of a specific immune response, adult SCID mice were inoculated by the natural intranasal route of infection and monitored for hematopoietic and viral multiplication parameters. Infected animals developed a very severe viral-dose-dependent leukopenia by 30 days postinfection (d.p.i.) that led to death within 100 days, even though the number of circulating platelets and erythrocytes remained unaltered throughout the disease. In the bone marrow of every lethally inoculated mouse, a deep suppression of CFU-GM and BFU-E clonogenic progenitors occurring during the 20- to 35-d.p.i. interval corresponded with the maximal MVMi production, as determined by the accumulation of virus DNA replicative intermediates and the yield of infectious virus. Viral productive infection was limited to a small subset of primitive cells expressing the major replicative viral antigen (NS-1 protein), the numbers of which declined with the disease. However, the infection induced a sharp and lasting unbalance of the marrow hemopoiesis, denoted by a marked depletion of granulomacrophagic cells (GR-1(+) and MAC-1(+)) concomitant with a twofold absolute increase in erythroid cells (TER-119(+)). A stimulated definitive erythropoiesis in the infected mice was further evidenced by a 12-fold increase per femur of recognizable proerythroblasts, a quantitative apoptosis confined to uninfected TER-119(+) cells, as well as by a 4-fold elevation in the number of circulating reticulocytes. Therefore, MVMi targets and suppresses primitive hemopoietic progenitors leading to a very severe leukopenia, but compensatory mechanisms are mounted specifically by the erythroid lineage that maintain an effective erythropoiesis. The results show that infection of SCID mice with the parvovirus MVMi causes a novel dysregulation of murine hemopoiesis in vivo.

Novel cytomorphology of the giant proerythroblasts of parvovirus B19 infection

The morphology of the giant proerythroblasts (GPE) in air-dried and Wright-Giemsa-stained smears of bone marrow in 16 patients with pure red cell aplasia (PRCA) caused by parvovirus B19 infection is described. B19 infection was diagnosed by the presence of the virus or viral DNA and/or IgM antibodies. Twelve patients had chronic hemolytic anemia and aplastic crisis and 4 patients had AIDS with chronic PRCA. In patients with chronic hemolytic anemia and aplastic crisis, GPE were not detectable in bone marrow biopsies that showed any degree of recovery of erythropoiesis. The GPE morphology was quite variable. The early (basophilic) GPE measured 25 to 35 microm in diameter, had a narrow rim of intensely blue and often vacuolated cytoplasm with pseudopodia, round nuclei with compact uncondensed chromatin, and an indistinct and inclusion-like purple-colored tinctorial change. The "intermediate" and "late" GPE measured 25 to 45 microm in diameter and showed cytoplasmic swelling, gradual loss of cytoplasmic basophilia, and fraying of the cytoplasm with focal rupture; the nuclei showed an increase in volume, a highly uncondensed and coarse sieve-like chromatin, and 1 to 3 prominent, pale to moderate purple inclusion-like nucleoli or inclusions. Bare nuclei similar in size and chromatin pattern to those of the GPE were present in proximity to the GPE and may have arisen from the GPE by dissolution of the cytoplasm. The glassy intranuclear inclusions with central clearing, the so-called lantern cells described in formalin-fixed tissues of patients with B19 infection, were absent in all cases. These findings suggest that direct toxic cell injury rather than apoptosis may be involved in the pathogenesis of erythroid aplasia in B19 infection.

Typing of European strains of parvovirus B19 by restriction endonuclease analyses and sequencing: identification of evolutionary lineages and evidence of recombination of markers from different lineages

European isolates of parvovirus B19 were analyzed by restriction enzyme analysis of PCR products of the VP1/2 coding region and sequencing of the same amplified region, five cloned fragments from each PCR product. Two main groupings were found based on three perfectly linked point deviations. On the assumption that identical point deviations causing the various restriction patterns regardless of time and origin of virus isolation were unlikely to emerge independently in different evolutionary lineages, traits of evolutionary lineages were identified, suggesting a clonal population structure of global circulating B19 strains. However, combinations of markers from different evolutionary lineages were also found, particularly in a strain derived from an individual chronically infected with B19 for more than 7 years. As chronically infected individuals might be subject to superinfections due to contacts or possibly due to blood transfusions or the administration of gamma-globulin, it is suggested that coexistence of, and recombination between variants of B19 of different phylogenetic origin incidentally occur in such individuals.

Higher prevalence of parvovirus B19 in Belgian as compared to Tunisian blood donors: differential implications for prevention of transfusional transmission

Serious anaemia can be induced by human parvovirus B19 (HPV) infection in immuno-compromised patients or subjects with an haemolytic disorder. Routine inactivation procedures are insufficient to neutralize the virus, but screening for HPV is an effective means to avoid transmission by transfusion of blood components. In the present study, we have compared for the first time the IgG and IgM seroprevalence in a North African (Tunisian) and Western European (Belgian) population of blood donors. The prevalence of HPV-specific IgM was less than 2% in both populations, pointing to the absence of an epidemic. The prevalence HPV IgG was significantly (p < 0.01) higher in Belgium (74%) than in Tunisia (65%), without any relationship with age or sex. This finding may suggest a south-north gradient of this infectious disease. Since the presence or absence of HPV-specific antibodies does not preclude transfusional transmission, screening for the virus itself should be done to avoid iatrogenic infection in HPV-naive subjects at risk. In view of the different transfusion policies in Belgium and Tunisia, a strategy for each of both countries is proposed.

Human parvovirus B19 infection associated with idiopathic thrombocytopenic purpura in a child following liver transplantation

BACKGROUND/AIMS

Idiopathic (autoimmune) thrombocytopenic purpura has been previously reported as a rare complication in children following parvovirus B19 infection. In the immunocompromised host who is unable to produce neutralizing antibody, an infection with parvovirus B19 can persist and cause chronic bone marrow failure.

METHODS

We describe a child who had undergone liver transplantation and who had idiopathic thrombocytopenic purpura, whose history and laboratory findings suggested parvovirus B19 infection. The infection disappeared without persistent viremia, and the thrombocytopenia responded completely to the administration of gamma globulin while the patient was undergoing chronic immunosuppression therapy.

RESULTS/CONCLUSION

Transplant physicians need to be aware of this complication, and parvovirus B19 infection should be included in the differential diagnosis of liver recipients presenting with severe thrombocytopenia.

Acquired pure red cell aplasia in Japan

We reviewed the clinical features of 150 patients with acquired pure red cell aplasia (PRCA) in Japan. There were 35 patients with acute type and 115 with chronic type PRCA. Of the acute PRCA patients, 17 had human parvovirus B19 infection. Drug-induced PRCA was demonstrated in 7 patients. Of the 115 patients with chronic PRCA, 51 patients were classified as primary and 64 cases were associated with miscellaneous diseases such as thymoma, a variety of hematological disorders and collagen diseases. Among the hematological disorders, PRCA was most frequently seen in granular lymphocyte proliferative disorders (GLPD). The erythroid colony growth patterns from bone marrow were variable. The serum erythropoietin level was high in most patients. Various kinds of treatment were tried for the chronic PRCA cases. Cyclosporin A (CyA) was the most effective form of treatment and the response rate was 82% (31/38). Twenty-three of 37 patients (62%) responded to bolus methylprednisolone therapy. The largest number of patients were treated with oral prednisolone, and the therapy was effective in 27 of the 55 (49%). The response rate to cyclophosphamide was only 29% (5/17), but in combination with prednisolone, half of the patients (7/14) responded to the therapy. CyA is recommended as the first-line therapy for acquired chronic PRCA.

Pure red cell aplasia associated with hepatitis C infection

We report the case of a 34-year-old woman with recurrent pure red cell aplasia and evidence of hepatitis B and C infection. Review of the English literature identified 19 prior cases in which pure red cell aplasia was associated with hepatitis. This case is the first in which serologic evidence of hepatitis C infection was documented. This patient also had porphyria cutanea tarda and marked hepatic siderosis but no active hepatitis or cirrhosis. Treatment with cyclophosphamide and prednisone produced complete remission of the pure red cell aplasia. Erythroid colony formation (colony-forming unit-erythroid and erythroid burst-forming unit) was reduced in cultures of bone marrow obtained during relapse but was normal in remission marrow. However, addition of the patient serum, whether collected during relapse or remission, inhibited erythroid colony formation by her bone marrow. These observations, and the known extrahepatic immunologic manifestations of hepatitis C infection, suggest that the pure red cell aplasia occurred because of autoimmune mechanism provoked by the infection.

Human parvovirus B19 and blood products

BACKGROUND AND OBJECTIVES

Human B19 parvovirus (B19), identified in 1975, was only recognised as the causative agent of fifth disease in 1983. The incidence of viraemia is low, around 1 in 1,000, but is sufficient to ensure that most plasma pools for fractionation contain some virus. While infection usually occurs in childhood and is benign, chronic infection sometimes occurs and may be of concern in certain patient groups.

MATERIALS AND METHODS

This review is based on a meeting held in March 1995, and addresses recent concerns regarding the potential transmission of B19 infection by pooled plasma products.

RESULTS

Recent data on the pathophysiology and assay of this virus are summarised along with possible approaches to donor screening, product screening, and virus removal. Only five cases of symptomatic infection have been reported in persons with haemophilia, but no technology for virus removal is established, and infection may be of concern in pregnant women, and in patients with enhanced red cell turnover or who are immunosuppressed, including those infected with human immunodeficiency virus, but only rarely in immunocompetent patients.

CONCLUSIONS

For the future, well-validated assays relevant to virus infectivity are required if blood donations, plasma pools, or plasma products are to be screened, and an in-process virus inactivation step for B19 would be highly desirable. In the interim, non-plasma or recombinant products or a selective transfusion policy might be used in patient groups in which B19 infection is of particular concern. Further clinical data on the prognosis and impact of B19 infection are needed to justify both such policies and the future adoption of new technologies designed to reduce any excess B19 infectivity arising from transfused products.

Severe Shwachman-Diamond syndrome and invasive parvovirus B19 infection

Parvovirus B19 (PVB19) is the causative agent of infectious erythema. In healthy children the virus causes transient erythroid aplasia, whereas in children with chronic hemolytic anemias it can cause severe aplastic crises, and in immunodeficient individuals it can produce chronic red cell aplasia. If contracted during pregnancy, the infection may induce serious damage to the fetus (abortion or hydrops fetalis). Shwachman-Diamond (S-D) syndrome, a rare autosomal recessive condition, consists of exocrine pancreatic insufficiency plus neutropenia; many patients develop either anemia or thrombocytopenia or both. We describe a newborn baby with severe congenital bone marrow failure who was diagnosed with S-D syndrome and persistence of PVB19 virus contracted by the mother in the third trimester of pregnancy.

Acute transient hemolytic anemia with a positive Donath-Landsteiner test following parvovirus B19 infection

PURPOSE

A case of childhood acute hemolytic anemia following parvovirus infection provided an hypothesis for the high frequency of Donath-Landsteiner antibodies and inappropriately low reticulocyte counts in this disease.

PATIENTS AND METHODS

A 3-year-old boy with hematuria and jaundice was found to have autoimmune hemolytic anemia due to a biphasic IgG Donath-Landsteiner antibody. Despite profound anemia (hematocrit 14.5%), the reticulocyte count was low (1.0%) and examination of his normocellular bone marrow showed erythroid hypoplasia.

RESULTS

A clinical diagnosis 2 weeks earlier of acute parvovirus B19 was serologically confirmed as the associated antecedent infection. Hemolytic anemia resolved with packed red cell transfusion, and intravenous immune globulin and steroid treatment.

CONCLUSIONS

The high-frequency red cell P antigen is both the unusual specificity of Donath-Landsteiner antibody and the viral receptor for parvovirus infection of red cell precursors. We speculate that interaction of the virus with its receptor may change antigenicity such that anti-P autoantibody forms. Parvovirus B19 may be a primary cause of reticulocytopenic postinfectious hemolytic anemia in children.

Hemoglobin Debrousse (beta 96[FG3]Leu-->Pro): a new unstable hemoglobin with twofold increased oxygen affinity

Hemoglobin Debrousse (beta 96[FG3]Leu-->Pro) is a new unstable variant, with high oxygen affinity responsible, in the steady state, for an apparently well-compensated chronic hemolytic anemia. The functional properties of this variant are due to the replacement of a leucine residue which is involved in the hydrophobic environment of the proximal side of the heme. This electrophoretically neutral hemoglobin was found as a de novo case in a 6-year-old girl suffering from severe anemia with hemolysis and transient aplastic crisis, following infection by parvovirus B19.

[Severe parvovirus B19 infection in an immunocompetent child with hemophilia A]

BACKGROUND

B19 parvovirus is a widespread virus whose typical manifestations in immunocompetent children are erythema infectiosum, acute erythroblastopenia and fetal anemia.

CASE REPORT

An 11 year-old immunocompetent patient with hemophilia A was referred for an hemorrhagic syndrome. Forty days after a pasteurized coagulation factor concentrates treatment, and after 12 days of treatment with solvent/detergent factor VIII concentrates, he developed fever, consciousness disorders, pancytopenia, liver cytolysis and probably minor haemophagocytic syndrome, associated with human parvovirus B19 infection. His clinical state returned to normal within 15 days. A retrospective study revealed that the patient had received every day for 12 days, one parvovirus B19 polymerase chain reaction positive batch before the occurrence of symptoms.

CONCLUSION

This case highlights the possibility of severe parvovirus B19 infection transmitted by clotting factors prepared from large pools of plasma. The use of recombinant factors would allow to reduce human virus contamination, even if immune risk has to be more accurately assessed.

Infectious causes of hydrops fetalis

A variety of infectious agents have been associated with nonimmune hydrops fetalis, most notably parvovirus B19, cytomegalovirus, herpes simplex virus, Toxoplasma gondii, and Treponema pallidum. These agents produce hydrops through effects on fetal bone marrow, myocardium, or vascular endothelium. Knowledge of the epidemiology and clinical characteristics of maternal and fetal infection can be used to select a diagnostic approach. Etiologic diagnosis will guide prognosis and the selection of specific chemotherapy.

[Human parvovirus B19 infection. Update]

Pathogenicity of parvovirus B19 has been demonstrated. The spectrum of clinical manifestations varies according to the age and immune status of affected patients. Parvovirus B19 is the aetiologic agent of erythema infectiosum in children. In normal adults, it is responsible for acute, bilateral and symmetrical arthritis, although chronic arthritis can develop. Parvovirus B19 has a particular tropism for erythroid precursors: in patients with underlying hemolysis, it induces transient aplastic crisis; in immunosuppressed patients the virus can lead to chronic pure red cell aplasia. Hydrops fetalis is one of the most severe manifestation of the infection. Diagnosis of recent parvovirus B19 infection is based upon serology and PCR, especially in immunosuppressed patients in whom polyvalent intravenous immunoglobulins must be started. The link between parvovirus B19 and systemic vasculitis is questioned.

Acquired pure red cell aplasia: a study of six cases

Persistent infection by parvovirus B19 associated with pure red cell aplasia (PRCA) has been documented in immunocompromised patients. Bone marrow failure is associated with conditions in which immune surveillance is impaired, and in these instances occult parvovirus infection may be suspected. In this study we have assessed by serological and molecular methods whether parvovirus B19 infection may be a more frequent cause of PRCA than hitherto suspected and whether it may be present in the absence of a typical bone marrow picture. Six patients with PRCA--two with isolated PRCA and no apparent underlying disease, two with a lymphoproliferative disease, one with thymoma, and one with chronic myelomonocytic leukemia--have been studied. Four of the six patients had overt PCRA and were clearly immunocompromised. Parvovirus B19 was not detected in any of the six patients by PCR analysis and serology investigating the presence of IgM or IgG antibodies. Although parvovirus B19 infection needs to be ruled out in PRCA it represents only one, and probably not the most frequent, etiological factor of PRCA.

Management of persistent B19 parvovirus infection in AIDS

An HIV+ 26-year-old white man with a CD4 count of 0.06 x 10(9)/l was found to have red blood cell aplasia secondary to B19 parvovirus infection. Regular infusions of intravenous immunoglobulin (IVIG) were begun and resulted in marked reticulocytosis and correction of anaemia. The patient has been followed for over 4 years and has become anaemic and reticulocytopenic whenever IVIG was interrupted. Serial dot blot analysis of the patient's sera for B19 parvovirus DNA showed absence of DNA immediately following IVIG treatments but reappearance within 3-6 weeks. Regular IVIG was effective in controlling but not eradicating B19 parvovirus infection in this HIV+ patient.

Myeloid depression follows infection of susceptible newborn mice with the parvovirus minute virus of mice (strain i)

The in vivo myelosuppressive capacity of strain i of the parovirus minute virus of mice (MVMi) was investigated in newborn BALB/c mice inoculated with a lethal intranasal dose. MVMi infection reached maximum levels of DNA synthesis and infectious titers in lymphohemopoietic organs at 4 to 6 days postinoculation and was restricted by an early neutralizing humoral immune response. After viral control (by 10 days postinoculation), a significant decrease in femoral and splenic cellularity, as well as in granulocyte-macrophage colony-forming unit and erythroid burst-forming unit hemopoietic progenitors, was observed in most inoculated animals. This delayed myeloid depression, although it may be not a major cause of the lethality of the infection, implies indirect pathogenic mechanisms induced by MVMi infection in a susceptible host.

Parvovirus: the expanding spectrum of disease

Treatment of parvovirus infections among immunocompromised hosts using immunoglobulin has provided the clinician with a useful therapeutic tool but has also highlighted the problems concerning chronic disease states. The discovery of the human parvovirus B19 in 1975 and subsequent studies of its effects in humans have identified this virus as the causative agent of a broad spectrum of diseases. Recent improvements regarding the development of sensitive PCR techniques and methods for cultivation have provided new insight into its pathogenic role, its virology and immunology, and the varied clinical manifestations. The current state of knowledge concerning parvovirus enabled us to divide the long list of diseases caused by this virus into three main categories: (1) disease found among normal hosts (asymptomatic disease, erythema infectiosum, arthropathy, hydrops fetalis), (2) hematologic diseases (aplastic crisis, chronic anemia, idiopathic thrombocytopenic purpura, transient erythroblastopenia of childhood, Diamond-Blackfan anemia) and, finally, (3) a heterogeneous group of diseases, in which the etiologic role of parvovirus is less clear and sometimes putative (neurologic disease, rheumatologic disease, vasculitic and myocarditic syndromes). In particular, arthropathy, hydrops fetalis and the hematologic disorders may be of pediatric concern. Consequently, it is of paramount importance that in all of these cases the clinician includes parvovirus as a differential diagnosis.

Combined immunocytochemistry and non-isotopic in situ hybridization for the ultrastructural investigation of human parvovirus B19 infection

Parvovirus B19 is a single-stranded DNA virus with a specific tropism for human erythroid precursor cells. The virus codes for two overlapping structural (capsid) proteins and one non-structural protein which is thought to perform essential functions in viral replication, transcription and packaging. The ultrastructural localization of these proteins was achieved in cultured haemopoietic cells derived from fetal liver which had been infected in vitro and subsequently embedded in LR White acrylic resin. Postembedding immunogold detection of B19 structural and non-structural proteins was combined with localization of viral nucleic acid by in situ hybridization using a digoxigenin-labelled probe and different sized gold labels. The majority of the B19 capsid protein and DNA present in cells harvested 48 hours post-infection co-localized within the centri-nuclear region of erythroid cells demonstrating characteristic chromatin margination. Relatively little DNA hybridization signal was present over paracrystalline inclusions strongly labelled with anti-capsid protein monoclonal antibody R92F6. Viral DNA and capsid protein were co-localized in apparent egress from the nucleus through nuclear pores. B19 non-structural protein was detected in association with both nuclear and cytoplasmic arrays of capsids, supporting the view that this protein plays an important role in viral packaging and remains associated with the complete viral particle until its release from the cell. Co-localization of viral nucleic acid and proteins at the ultrastructural level is a flexible, rapid and highly specific tool for examination of viral life-cycles within cells.

Parvovirus infection causing red cell aplasia and leukopenia in rheumatoid arthritis

A case of acute parvovirus B19 infection causing fever, anaemia, leukopenia, and red cell aplasia, in a patient with chronic rheumatoid arthritis is described. The patient had received low doses of corticosteroids for several years, and a small dose of methotrexate recently. There was no evidence of haemolytic anaemia, iron deficiency or drug toxicity. Recovery was associated with the development of antibodies against parvovirus B19, and clearance of viraemia as detected by the polymerase chain reaction. Possible mechanisms for the development of leukopenia are discussed, but there was no evidence for haemophagocytosis.

Parvovirus B19 induced red cell aplasia in myelofibrosis

A 38-year-old female presented with moderate anaemia and a leucoerythroblastic blood film. Subsequent investigation showed myelofibrosis in cellular phase. Her haemoglobin quickly and spontaneously recovered with concurrent serological evidence of recent parvovirus B19 infection. This is the first report in the literature of parvovirus causing red cell aplasia in myelofibrosis.

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.

Intracellular localization of parvovirus B19 nucleic acid at the ultrastructural level by in situ hybridization with digoxigenin-labelled probes

Conditions suitable for immunogold detection of digoxigenin-labelled DNA probes hybridized to parvovirus B19-infected erythroid cells embedded in Lowicryl K4M and LR White acrylic resins were established at the electron microscope level. The protocol was initially optimized using a positive control probe for whole human DNA which produced signal over the heterochromatin of all nucleated cells. In cultures harvested 2 days postinfection, B19 nucleic acid was detected mainly within the centrinuclear region of erythroid cells exhibiting characteristic margination of the chromatin. The B19 hybridization signal was largely unaffected by denaturation and was resistant to RNase digestion but sensitive to DNase digestion, indicating that it was mainly single-stranded B19 DNA. Relatively few gold particles were found over crystalline arrays of viral capsids, consistent with the observation that they are composed of mainly 'empty' capsids. B19 nucleic acid was detected in apparent transit from nucleus to cytoplasm through pores in the nuclear membrane. While the sensitivity of this system is limited by the fact that hybridization occurs only at the surface of the section, it is a rapid and specific means of localizing viral nucleic acids with a high degree of resolution.

Ultrastructural features of fetal erythroid precursors infected with parvovirus B19 in vitro: evidence of cell death by apoptosis

Human parvovirus B19 cannot be cultured in standard cell lines and relatively little is known about the intracellular life-cycle of the virus. In this study, ultrastructural features of B19 infection were examined using haemopoietic cell suspension cultures derived from human fetal liver. Erythroblasts from infected cultures frequently contained crystalline arrays of both full and empty virus-like particles. The number and size of these arrays increased with the duration of culture, and their location changed from exclusively nuclear at 24 h post-infection to both nuclear and cytoplasmic at 3 days post-infection. Arrays were occasionally found in cytoplasmic protuberances which appeared to be pinching off from the cell. The location of the arrays corresponded to the distribution of viral capsid protein determined by immunolabelling at the light microscope level. Cells containing viral crystalline arrays also exhibited nucleolar degeneration, extreme margination of the nuclear heterochromatin, and cytoplasmic vacuolation. These features are typical of cells undergoing individual programmed cell death or 'apoptosis'. The triggering of apoptosis in erythroid precursors by parvovirus B19 may help to explain the apparent lack of a strong inflammatory response to fetal B19 infection and may have implications for understanding the mechanisms of viral spread throughout the host.

Detection of parvovirus B19 in donated blood: a model system for screening by polymerase chain reaction

A highly sensitive and rapid method for routinely screening large numbers of donated blood units for parvovirus B19 by the polymerase chain reaction (PCR) was developed. Over a 3-month trial period in Edinburgh, B19 DNA was detected in 6 of 20,000 consecutive units of blood (0.03%), in concentrations ranging from 2.4 x 10(4) to 5 x 10(10) copies of viral DNA per ml. Seroconversion for B19-specific immunoglobulin M and immunoglobulin G and disappearance of circulating B19 DNA occurred in the interval between donation and recall in four of the five implicated donors who could be recalled. B19 DNA was detected in 18 of 27 separate batches of non-heat-treated factor VIII and IX concentrate manufactured from donated plasma unscreened for B19 DNA. Dry-heat treatment at 80 degrees C for 72 h reduced but did not always eliminate detectable B19 from factor VIII concentrates, consistent with recent observations that current methods for virus inactivation during blood product manufacture are insufficient to entirely eliminate B19 infectivity. The methods developed in this study for PCR screening could be applied routinely to prevent transfusion of B19 in blood and blood products and could play an important role in the prevention of iatrogenic transmission of infection. PCR screening could also be used for detection and exclusion of a range of other transmission-associated viruses for which current serological detection methods are only partially effective.