Human parvovirus infection in homozygous sickle cell disease

Exagamglogene Autotemcel for Severe Sickle Cell Disease

BACKGROUND

Exagamglogene autotemcel (exa-cel) is a nonviral cell therapy designed to reactivate fetal hemoglobin synthesis by means of ex vivo clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing of autologous CD34+ hematopoietic stem and progenitor cells (HSPCs) at the erythroid-specific enhancer region of BCL11A.

METHODS

We conducted a phase 3, single-group, open-label study of exa-cel in patients 12 to 35 years of age with sickle cell disease who had had at least two severe vaso-occlusive crises in each of the 2 years before screening. CD34+ HSPCs were edited with the use of CRISPR-Cas9. Before the exa-cel infusion, patients underwent myeloablative conditioning with pharmacokinetically dose-adjusted busulfan. The primary end point was freedom from severe vaso-occlusive crises for at least 12 consecutive months. A key secondary end point was freedom from inpatient hospitalization for severe vaso-occlusive crises for at least 12 consecutive months. The safety of exa-cel was also assessed.

RESULTS

A total of 44 patients received exa-cel, and the median follow-up was 19.3 months (range, 0.8 to 48.1). Neutrophils and platelets engrafted in each patient. Of the 30 patients who had sufficient follow-up to be evaluated, 29 (97%; 95% confidence interval [CI], 83 to 100) were free from vaso-occlusive crises for at least 12 consecutive months, and all 30 (100%; 95% CI, 88 to 100) were free from hospitalizations for vaso-occlusive crises for at least 12 consecutive months (P<0.001 for both comparisons against the null hypothesis of a 50% response). The safety profile of exa-cel was generally consistent with that of myeloablative busulfan conditioning and autologous HSPC transplantation. No cancers occurred.

CONCLUSIONS

Treatment with exa-cel eliminated vaso-occlusive crises in 97% of patients with sickle cell disease for a period of 12 months or more. (CLIMB SCD-121; ClinicalTrials.gov number, NCT03745287.).

An Outbreak of Parvovirus B19 in Israel

Human parvovirus B19 (B19V) has a wide clinical spectrum, ranging from an asymptomatic infection to a life threatening one. During pregnancy, it can lead to fetal loss and hydrops fetalis. This retrospective study examined the incidence rates of B19V in Israel, analyzing anonymized electronic medical records of 2.7 million individuals between January 2015 and September 2023. A generalized linear model with a Poisson distribution was fit to the data, adjusting for potential confounders. A marked increase in B19V was observed in 2023, with an adjusted incidence rate ratio (IRR) of 6.6 (95% CI 6.33-6.89) when comparing 2023 to previous years. When specifically comparing 2023 to COVID-19 years (2020-2022), adjusted IRR climbs to 9.21 (8.66-9.80). Moreover, in 2023, previously existing seasonality has largely disappeared. High SES characterized most infected individuals with a marked discrepancy in social sectors; the Arab population was significantly less likely to be found B19V positive, even when adjusting for SES. Most infections occurred in school-aged children (6-11 years old). Pregnant women experienced the most significant rise in B19V, with an adjusted IRR of 11.47 (9.44-13.97) in 2023 compared to previous years; most cases were diagnosed in the first trimester. This study demonstrates that Israel is currently experiencing the largest and longest reported outbreak of B19V to date. Policymakers should consider setting screening policies in place, at least for populations at risk, while specifically studying and potentially targeting low socioeconomic populations and specific social sectors to avoid health inequalities.

[Parvovirus B19 infections in adults]

Acute Parvovirus B19 (PVB19) infection is responsible for erythema infectiosum in children and non-specific polyarthralgias in immunocompetent adults associated with skin lesions and rarer manifestations (hepatic, neurological, cardiac or nephrological). In immunocompromised patients, cytopenias are more frequent and in some cases, viremia persists and is responsible for PVB19 chronic infection. PVB19 is responsible for pure red cell aplasia during chronic hemolytic diseases. Acute PVB19 infection is a differential diagnosis of some autoimmune diseases and has been suspected to be a trigger for some autoimmune diseases because of its ability to promote the emergence of autoimmune markers. Mechanisms of molecular mimicry, induction of apoptosis and activation of enzymes have been demonstrated, explaining in part the production of autoantibodies during infection. However, the demonstration of a causal relationship in the triggering of autoimmune disease remains to be done. This review provides a synthesis of the PVB19 infection clinical data in adults with a particular focus on these links with autoimmunity.

A Meta-Analysis on the Seroprevalence of Parvovirus B19 among Patients with Sickle Cell Disease

Background

Parvovirus B19 (B19 V) infection had been reported to be more frequent with serious clinical outcomes in patients with sickle cell disease (SCD) than in the general population. There is a wide variation in data among the existing literature regarding the seroprevalence of B19 V in patients with SCD. These data require further summary and analyses for better accuracy. This systematic review and meta-analysis was done to estimate the seroprevalence of B19 V in patients with SCD.

Methods

This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The databases of MEDLINE/PubMed, Virtual Health Library (VHL), ScienceDirect, Google Scholar, and OpenGrey were used for the systematic search. The random-effects model was used to estimate the pooled prevalence with the corresponding 95% confidence interval (CI) using OpenMeta Analyst software. Publication bias was estimated based on Begg's test, Egger's test, and examination of the funnel plot. Subgroup analyses and metaregression were used to explore the moderators of heterogeneity between studies.

Results

A total of 18 studies including 2890 patients were analyzed. The overall IgG seroprevalence of B19 V infection among patients with SCD was found to be 48.8% (95% CI 39.5%-58.0%). Evidence of publication bias was not detected. Evidence of acute viral infection detected by positive IgM antibodies among the screened SCD patients was found in 8.30% (95% CI 5.20%-11.4%) of them. There was a statistically significant association between seroprevalence of B19 V and geographical areas.

Conclusion

There was a high prevalence of B19 V in patients with SCD. Healthcare providers need to be aware of the magnitude of B19 V infection in patients with SCD to ensure effective management. This review could provide a comprehensive view of B19 V prevalence in this susceptible population.

Prevalence and Factors Associated with Human Parvovirus B19 Infection in Sickle Cell Patients Hospitalized in Tanzania

Background

The distribution of human parvovirus B19 (HPV B19) infection is ubiquitous and occurs worldwide. The virus has high tropism to red blood cells progenitor’s cells leading to temporary infection of bone marrow and transient arrest of erythropoiesis. People with frequent episodes of hemolytic anemia including sickle cell disease (SCD) and thalassemia are at increased risk of infection. This study aimed at assessing prevalence and factors associated with HPV B19 infections among hospitalized SCD patients.

Methodology

This was a cross-sectional hospital-based study among SCD patients hospitalized at Muhimbili National Hospital. HPV B19 was detected using RT-PCR. Hematological and Chemistry tests were done using Sysmex XT2000i and Chemistry analyzer respectively.

Results

A total of 329 SCD patients, median age 15 years (interquartile range 7–22 years) were tested for HPV B19. The prevalence of HPV B19 was 29%. In multivariate logistic regression model, HPV B19 infection was associated with pain (OR=4.28, 95%CI: 1.20–15.19; p=0.025), low neutrophil counts (OR=0.57, 95%CI: 0.35–0.92, p=0.022) and MCH (OR=0.92, 95%CI: 0.85–0.99; p=0.033). Individuals infected with HPV B19 had slightly higher prevalence of severe anaemia (30.4% vs. 20.3%, p=0.054) and HIV infection (6.0% vs. 2.1%, p=0.083) in the univariate analysis. Considering the effect of HPV B19 virus on spleen, aplastic anemia and platelet counts in SCD patients, our study did not find any association with these parameters (p=0.244; p= 0.205 and p=0.567 respectively).

Conclusion

The prevalence of HPV B19 among hospitalized SCD patients at MNH was high. SCD patients with HPV B19 were more likely to present with pain, low neutrophils levels, and MCH. HIV infection might be associated with a high risk of HPV infection in SCD patients; however, this requires further investigation.

Kidney biopsy findings in children with sickle cell disease: a Midwest Pediatric Nephrology Consortium study

BACKGROUND

Renal damage is a progressive complication of sickle cell disease (SCD). Microalbuminuria is common in children with SCD, while a smaller number of children have more severe renal manifestations necessitating kidney biopsy. There is limited information on renal biopsy findings in children with SCD and subsequent management and outcome.

METHODS

This is a multicenter retrospective analysis of renal biopsy findings and clinical outcomes in children and adolescents with SCD. We included children and adolescents (age ≤ 20 years) with SCD who had a kidney biopsy performed at a pediatric nephrology unit. The clinical indication for biopsy, biopsy findings, subsequent treatments, and outcomes were analyzed.

RESULTS

Thirty-six SCD patients (ages 4-19 years) were identified from 14 centers with a median follow-up of 2.6 years (0.4-10.4 years). The indications for biopsy were proteinuria (92%) and elevated creatinine (30%). All biopsies had abnormal findings, including mesangial hypercellularity (75%), focal segmental glomerulosclerosis (30%), membranoproliferative glomerulonephritis (16%), and thrombotic microangiopathy (2%). There was increased use of hydroxyurea, angiotensin-converting-enzyme inhibitors, and angiotensin receptor blockers following renal biopsy. At last follow-up, 3 patients were deceased, 2 developed insulin-dependent diabetes mellitus, 6 initiated chronic hemodialysis, 1 received a bone marrow transplant, and 1 received a kidney transplant.

CONCLUSIONS

Renal biopsies, while not commonly performed in children with SCD, were universally abnormal. Outcomes were poor in this cohort of patients despite a variety of post-biopsy interventions. Effective early intervention to prevent chronic kidney disease (CKD) is needed to reduce morbidity and mortality in children with SCD.

A Differential Approach to an Uncommon Case of Acute Anemia in a Child With Sickle Cell Disease

Introduction: Hyperhemolytic crisis is a rare and dangerous complication of sickle cell disease where the hemoglobin level drops rapidly. This can quickly lead to organ failure and death. In the literature, most cases of hyperhemolysis in sickle cell patients followed a red cell transfusion. Case Summary: In this article, we report a case of a 6-year-old African American boy with sickle cell disease who presented with fever, increased work of breathing, and consolidation in the left lower lobe of the lung on chest X-ray. He initially improved with oxygen, fluids, and antibiotics but his hemoglobin acutely dropped from 7.6 to 6 g/dL the next day of admission. He was not previously transfused, and his reticulocyte count remained high. Subsequent transfusion recovered his hemoglobin. Conclusion: This case demonstrates that in the background of the chronic hemolysis of sickle cell disease, an acute anemia should warrant exploration of aplastic crisis (parvovirus infection), immune hemolytic anemia, hepatic sequestration crisis, splenic sequestration crisis, and hyperhemolytic crisis as possible etiologies. Ongoing reticulocytosis and a source of infection may direct suspicion especially toward hyperhemolytic crisis even without preceding red cell transfusion. We propose that the optimum management should include full supportive care (including transfusions if necessary) and treatment of the underlying cause of hemolysis (such as infections or drug exposure).

Kidney Diseases Associated With Parvovirus B19, Hanta, Ebola, and Dengue Virus Infection: A Brief Review

Viral infection-associated kidney diseases are an emerging public health issue in both developing and developed countries. Many new viruses have emerged with new paradigms of kidney injury, either directly through their cytopathic effect or indirectly through immune-mediated glomerulopathy, tubulointerstitial disease, and acute kidney injury as part of multiorgan failure. Herein, we will discuss Parvovirus, which causes glomerulopathy, and Hanta, Ebola, and Dengue viruses, which cause viral hemorrhagic fever and acute kidney injury. Clinical manifestations also depend on extrarenal organ systems involved. Diagnosis of these viral infections is mainly based on a high index of suspicion, serologic testing, and isolation of viral DNA/RNA. Management is largely conservative, as specific antiviral agents are unavailable.

Evolving locally appropriate models of care for indian sickle cell disease

The sickle cell gene in India represents a separate occurrence of the HbS mutations from those in Africa. Sickle cell disease in India occurs against different genetic and environmental backgrounds from those seen in African patients and there is evidence of clinical differences between the populations. Knowledge of the clinical features of African disease was drawn from the Jamaican Cohort Study, based on prospective follow up of all cases of sickle cell disease detected by the screening of 100,000 consecutive newborns in Kingston, Jamaica, and supplemented by observations from the Cooperative Study of Sickle Cell Disease in the US. Defining the principal causes of early morbidity in African sickle cell disease led to successful interventions including pneumococcal prophylaxis, parental education in the early diagnosis of acute splenic sequestration, and the early detection by trans-cranial Doppler of cerebral vessel stenosis predictive of stroke but their success depended on early diagnosis, ideally at birth. Although reducing mortality among patients with African forms of SS disease, the question remains whether these interventions are appropriate or justified in Indian patients. This dilemma is approached by comparing the available data in African and Indian forms of SS disease seeking to highlight the similarities and differences and to identify the deficiencies in knowledge of Indian disease. These deficiencies could be most readily addressed by cohort studies based on newborn screening and since much of the morbidity of African disease occurs in the first five years of life, these need not be a daunting prospect for Indian health care personnel. Newborn screening programmes for sickle cell disease are already underway in India and appropriate protocols and therapeutic trials could quickly answer many of these questions. Without this knowledge, Indian physicians may continue to use possibly unnecessary and expensive models of care.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Original Research: Parvovirus B19 infection in children with sickle cell disease in the hydroxyurea era

Parvovirus B19 infection causes transient aplastic crisis in sickle cell disease (SCD) due to a temporary interruption in the red blood cell production. Toxicity from hydroxyurea includes anemia and reticulocytopenia, both of which also occur during a transient aplastic crisis event. Hydroxyurea inhibits proliferation of hematopoietic cells and may be immunosuppressive. We postulated that hydroxyurea could exacerbate parvovirus B19-induced aplastic crisis and inhibit the development of specific immune responses in children with SCD. We conducted a retrospective review of parvovirus B19 infection in 330 children with SCD. Altogether there were 120 known cases of aplastic crisis attributed to parvovirus B19 infection, and 12% of children were on hydroxyurea treatment during the episode. We evaluated hematological and immune responses. Children with HbSS or HbSβ(0)-thalassemia treated with hydroxyurea, when compared with untreated children, required fewer transfusions and had higher Hb concentration nadir during transient aplastic crisis. Duration of hospital stays was no different between hydroxyurea-treated and untreated groups. Children tested within a week following aplastic crisis were positive for parvovirus-specific IgG. Immune responses lasted for the duration of the observation period, up to 13 years after transient aplastic crisis, and there were no repeat aplastic crisis episodes. The frequencies of parvovirus-specific antibodies in all children with SCD increased with age, as expected due to the increased likelihood of a parvovirus exposure, and were comparable to frequencies reported for healthy children. Approximately one-third of children had a positive parvovirus B19-specific IgG test without a documented history of transient aplastic crisis, and 64% of them were treated with hydroxyurea. Hydroxyurea may reduce requirements for blood transfusions and may attenuate symptoms during transient aplastic crisis episodes caused by parvovirus B19 infections. Children with SCD, whether treated or untreated with hydroxyurea, generate sustained and protective parvovirus B19-specific immune responses.

How we prevent and manage infection in sickle cell disease

Sickle cell disease (SCD) affects approximately 100,000 people in the US, 12,500 in the UK, and millions worldwide. SCD is typified by painful vaso-occlusive episodes, haemolytic anaemia and organ damage. A secondary complication is infection, which can be bacterial, fungal or viral. Universal newborn screening, routine use of penicillin prophylaxis, availability of conjugated vaccines against S. pneumoniae and comprehensive care programmes instituted during the past few decades in industrialized countries have dramatically reduced childhood mortality and improved life expectancy. Yet patients with SCD remain at increased risk of infection. Unfortunately, the treatment of most bacterial infections that are common in SCD is not based on the results of randomized controlled clinical trials. In their absence, treatment decisions are based on consensus guidelines, clinical experience or adapting treatment applied in other diseases. This leads to wide variation in treatment among institutions and even between treating physicians in a single institution. Prevention of infection, when possible, is most important and we focus on prevention through targeted prophylaxis and vaccination. We will share our management strategies for managing the more common infections in SCD and provide the rationale for our recommendations.

Human parvovirus B19-induced aplastic crisis in an adult patient with hereditary spherocytosis: a case report and review of the literature

BACKGROUND

Although there are several case reports of human parvovirus B19 infection in patients with hereditary spherocytosis, no systematic reviews of adult patients with hereditary spherocytosis with human parvovirus B19 infection have been published as clinical case reports. In this study, we report a case of aplastic crisis due to human parvovirus B19 infection in an adult patient with hereditary spherocytosis.

CASE PRESENTATION

A 33-year-old woman with hereditary spherocytosis and gallstones was admitted because of rapid progress in marked anemia and fever. Although empiric antibiotic therapy was prescribed, her clinical symptoms and liver function test worsened. Because the anti-human parvovirus B19 antibody and deoxyribonucleic acid levels assessed by polymerase chain reaction were positive, the patient was diagnosed with aplastic crisis due to the human parvovirus B19 infection.

CONCLUSION

We collected and reviewed several case reports of patients with hereditary spherocytosis aged > 18 years with human parvovirus B19 infection between 1984 and 2010. A total of 19 reports with 22 cases [median age, 28 years (range, 18-43 range); male: female ratio, 6:16], including the present case were identified. The male-to-female ratio of 6:16 implied that younger females were predominantly affected. Although fever and abdominal symptoms were common initial symptoms, liver dysfunction or skin eruptions were less commonly documented. Anti-human parvovirus B19 antibody or deoxyribonucleic acid levels assessed by polymerase chain reaction was commonly used to diagnose human parvovirus B19 infection and may be useful to distinguish human parvovirus B19 infection from other abdominal infection in patients with hereditary spherocytosis.

Sickle cell disease: new opportunities and challenges in Africa

Sickle cell disease (SCD) is one of the most common genetic causes of illness and death in the world. This is a review of SCD in Africa, which bears the highest burden of disease. The first section provides an introduction to the molecular basis of SCD and the pathophysiological mechanism of selected clinical events. The second section discusses the epidemiology of the disease (prevalence, morbidity, and mortality), at global level and within Africa. The third section discusses the laboratory diagnosis and management of SCD, emphasizing strategies that been have proven to be effective in areas with limited resources. Throughout the review, specific activities that require evidence to guide healthcare in Africa, as well as strategic areas for further research, will be highlighted.

Concise review: Anemia caused by viruses

Most of the viruses known to be associated with anemia in human tend to persistently infect their host and are noncytopathic or poorly cytopathic for blood cell progenitors. Infections with Epstein-Barr virus, cytomegalovirus, varicella-zoster virus, human herpes virus 6 (HHV-6), B19 parvovirus, human immunodeficiency virus, hepatitis A and C viruses and the putative viral agent associated with non-A-G post-hepatitis aplastic anemia have been reported in association with anemia. Nevertheless, a direct cytotoxic effect on erythroid progenitors has been clearly demonstrated only for human parvovirus B19 and evocated for HHV-6. A major role for destructive immunity is strongly suspected in the pathogenesis of anemia associated with the other viral infections. Host genes play a role in the occurrence of virus-induced anemia in animal models, and there are some evidences that genetic background could also influence the occurrence of virus-associated anemia in human.

Safety and immunogenicity of a candidate parvovirus B19 vaccine

Parvovirus B19 is an important human pathogen causing erythema infectiosum, transient aplastic crisis in individuals with underlying hemolytic disorders and hydropsfetalis. We therefore evaluated a parvovirus B19 virus like particle (VLP) vaccine. The safety and immunogenicity of a 25 μg dose of parvovirus B19 recombinant capsid; 2.5 and 25 μg doses of the recombinant capsid given with MF59; and saline placebo were assessed in healthy adults. Because of 3 unexplained cutaneous events the study was halted after enrollment of 43 subjects and before any subject received their third scheduled dose. The rashes developed 5-9 days after the first or second injection and were seen in one placebo recipient (without an injection site lesion) and two vaccine recipients (with injection site reactions). No clear cause was established. Other safety evaluations revealed mostly injection site reactions that were mild to moderate with an increase in pain in subjects receiving vaccine and MF59. After dose 2 the majority of vaccine recipients developed ELISA and neutralizing antibody to parvovirus B19. Given the possible severe consequences of parvovirus B19 infection, further development of a safe and effective vaccine continues to be important.

[Human parvovirus B19 infection in sickle cell anemia patient in Mali: a case-control study]

Human parvovirus B19 (HP-19) is the only Parvoviridae known to be pathogenic in human. Studies of HP-19 infection and its associated life-threatening complications in sickle cell anemia patients have been reported in Europe and the US. These results justify the development of HP-B19 prevention and strategies to reduce the incidence of severe and life-threatening complications associated with the infection in patients with sickle cell anemia, particularly in sub-Saharan Africa where the sickle cell anemia burden is high. In light of these considerations, we conducted a case-control study including 163 patients with sickle cell anemia and 163 controls. HP-B19 diagnosis was based on the detection of IgG and IgM antibodies specific for HP-B19 using commercially available enzyme immunoassays. Anti-human parvovirus B19 IgG antibodies were found in 105 of 193 (64.8%) patients vs 79 of 193 controls (48.4%). IgM antibodies were found at a higher frequency in sickle cell anemia patients than in controls. This higher frequency was found to be age-dependent. However, the reticulocyte count showed no significant decrease in Malian patients with sickle cell anemia. Further studies are needed to better characterize the implication of HP-B19 infection in sickle cell anemia mortality and morbidity and to develop preventive strategies and efficient management of the resulting complications.

[Parvovirus B19 infection after kidney transplantation]

Prevalence for human parvovirus B19 infection is estimated to be between 2% and 30% in renal transplant recipients. In post-transplant settings, parvovirus B19 infection may occur either as a primary infection or a reactivation. Parvovirus transmission most commonly occurs through respiratory tract but may also result from graft or blood packs contamination. Co-infections with HHV-6 and CMV viruses are frequent. The hallmark symptom is anemia, more rarely pancytopenia and hemophagocytic syndrome. In respect to renal involvement, parvovirus B19 infection has been associated with graft dysfunction in 10% of cases. Both thrombotic microangiopathies and collapsing glomerulopathies have been reported concomitantly with parvovirus B19 infection but the causal link remains unclear. Other complications are seldomly reported, including hepatitis, encephalitis, and myocarditis. Diagnosis is based on pre and post-transplant serological status. In addition, the management of parvovirus B19 infection in immunocompromised patients requires quantitative assessment of blood viral load by PCR. The treatment relies primarily on reduction of immunosuppression combined with intravenous immunoglobulin infusions. Relapses occur in 30% of cases.

How I treat acute chest syndrome in children with sickle cell disease

Acute chest syndrome describes new respiratory symptoms and findings, often severe and progressive, in a child with sickle cell disease and a new pulmonary infiltrate. It may be community-acquired or arise in children hospitalized for pain or other complications. Recognized etiologies include infection, most commonly with atypical bacteria, and pulmonary fat embolism (PFE); the cause is often obscure and may be multifactorial. Initiation of therapy should be based on clinical findings. Management includes macrolide antibiotics, supplemental oxygen, modest hydration and often simple transfusion. Partial exchange transfusion should be reserved for children with only mild anemia (Hb > 9 g/dL) but deteriorating respiratory status. Therapy with corticosteroids may be of value; safety, efficacy and optimal dosing strategy need prospective appraisal in a clinical trial. On recovery, treatment with hydroxyurea should be discussed to reduce the likelihood of recurrent episodes.

Generation of multifunctional murine monoclonal antibodies specifically directed to the VP1unique region protein of human parvovirus B19

Little is known about the VP1unique region (VP1u), a part of one major capsid protein of human parvovirus B19 (B19), concerning its involvement in viral replication and infection cycle. Showing a phospholipase A2 (PLA2)-like activity, which is discussed to be necessary for viral release from host cell, its precise function remains unclear. The purpose of this study was to generate multifunctional monoclonal antibodies (mabs) for different applications that may be useful in investigating VP1u's relevance. To establish antiVP1u antibodies, spleen cells from Balb/c mice immunized with purified recombinant viral protein were used for generating antibody-producing hybridoma cell lines. Usability of the antibodies was tested in enzyme-linked immunosorbent assay (ELISA), Western-blot analysis, immunofluorescence and an inhibition assay of enzymatic activity of PLA2. Three hybridoma cell lines secreting mab's specifically directed against the VP1u protein of B19 could be generated and functioned in every screening method used in this study. These antibodies are helpful tools for investigations in B19 research and diagnosis. Furthermore, the antibodies could help in gaining a deeper understanding of VP1u's role in viral replication and infection especially in the importance of its constitutive PLA2-like activity.

Parvovirus B19 infection in Tunisian patients with sickle-cell anemia and acute erythroblastopenia

BACKGROUND

Human parvovirus B19 is the etiologic agent of erythema infectiosum in children. It is also associated with other clinical manifestations in different target groups. Patients with chronic hemolytic anemia are at high risk of developing acute erythroblastopenia following infection by the virus. They usually become highly viremic and pose an increased risk of virus transmission. Close monitoring of such high risk groups is required for epidemiologic surveillance and disease prevention activities. Here we report a molecular epidemiological study on B19 virus infection in Tunisian patients with chronic hemolytic anemia.

METHODS

This study was conducted on 92 young chronic hemolytic anemia patients who attended the same ward at the National Bone Marrow Transplantation Center of Tunis and 46 controls from a different hospital. Screening for IgM and IgG anti-B19 antibodies was performed using commercially available enzyme immunoassays and B19 DNA was detected by nested PCR in the overlapping VP1/VP2 region. DNA was sequenced using dideoxy-terminator cycle sequencing technology.

RESULTS

Anti-parvovirus B19 IgG antibodies were detected in 26 of 46 sickle-cell anemia patients, 18 of 46 beta-thalassemia and 7 of 46 controls. Anti-parvovirus B19 IgM antibodies were detected only in 4 of the sickle-cell anemia patients: two siblings and two unrelated who presented with acute erythroblastopenia at the time of blood collection for this study and had no history of past transfusion. B19 DNA was detected only in sera of these four patients and the corresponding 288 bp nested DNA amplicons were sequenced. The sequences obtained were all identical and phylogenetic analysis showed that they belonged to a new B19 virus strain of Genotype1.

CONCLUSION

A new parvovirus B19 strain of genotype1 was detected in four Tunisian patients with sickle-cell anemia. Virus transmission appeared to be nosocomial and resulted in acute erythroblastopenia in the four patients. The possibility of independent transmission of this B19 variant to the patients is unlikely in light of the present epidemiological data. However this possibility cannot be ruled out because of the low genetic variability of the virus.

Parvovirus-B19-associated complications in renal transplant recipients

Parvovirus B19 is a common human pathogen, causing erythema infectiosum in children, hydrops fetalis in pregnant women, and transient aplastic crisis in patients with chronic hemolytic anemia. Immunosuppressed patients can fail to mount an effective immune response to B19, resulting in prolonged or persistent viremia. Renal transplant recipients can develop symptomatic B19 infections as a result of primary infection acquired via the usual respiratory route or via the transplanted organ, or because of reactivation of latent or persistent viral infection. The most common manifestations of B19 infection in immunosuppressed patients are pure red cell aplasia and other cytopenias. Thus, this diagnosis should be considered in transplant recipients with unexplained anemia and reticulocytopenia or pancytopenia. Collapsing glomerulopathy and thrombotic microangiopathy have been reported in association with B19 infection in renal transplant recipients, but a causal relationship has not been definitively established. Prompt diagnosis of B19 infection in the renal transplant recipient requires a high index of suspicion and careful selection of diagnostic tests, which include serologies and polymerase chain reaction. Most patients benefit from intravenous immunoglobulin therapy and/or alteration or reduction of immunosuppressive therapy. Conservative therapy might be sufficient in some cases.

Parvovirus B19 and the kidney

Infection with parvovirus B19 causes several clinical syndromes (fifth disease, transient aplastic crisis, pure red cell aplasia, and hydrops fetalis) and may contribute to other illnesses. B19 has been linked to renal disease in three settings: As a cause of acute glomerulopathy and as a cause of anemia in ESRD and kidney transplantation. Case reports implicate parvovirus in the pathogenesis of proliferative glomerulonephritis and collapsing glomerulopathy, but a causal relationship has not been established. A proposed role for B19 infection is based on the temporal association of renal findings with viral infection, positive serology, and identification of the viral genome in the glomerulus. Mechanisms may include cytopathic effects on glomerular epithelial cells and/or endothelial cells and glomerular deposition of immune complexes. Patients who require dialysis may have increased susceptibility to acute and chronic anemia after parvoviral infection. Factors that predispose this population to complications of B19 infection include impaired immune response, deficient erythropoietin production, and possibly decreased erythrocyte survival. The clinical burden of parvovirus B19 infection in renal transplant recipients may be underestimated; these individuals may develop persistent viremia as a result of a dysfunctional immune response. Chronic anemia and pure red blood cell aplasia are the most common complications of parvovirus infection in this population; the diagnosis should be considered in transplant recipients with unexplained anemia or pancytopenia. Allograft rejection and dysfunction have been reported in association with infection, but a cause-effect relationship has not been proved. Further investigation of the relationship between B19 and kidney disease is warranted.

Sickle cell disease in Africa: burden and research priorities

Sickle cell disease (SCD) has recently been recognised as a problem of major public-health significance by the World Health Organization. Despite the fact that >70% of sufferers live in Africa, expenditure on the related care and research in the continent is negligible, and most advances in the understanding and management of this condition have been based on research conducted in the North. In order to target limited resources, African countries need to focus research and interventions on areas that will lead to the maximum impact. This review details the epidemiological and clinical background of SCD, with an emphasis on Africa, before identifying the research priorities that will provide the necessary evidence base for improving the management of African patients. Malaria, bacterial and viral infections and cerebrovascular accidents are areas in which further research may lead to a significant improvement in SCD-related morbidity and mortality. As patients with high concentrations of foetal haemoglobin (HbF) appear to be protected from all but mild SCD, the various factors and pharmacological agents that might increase HbF levels need to be assessed in Africa, as options for interventions that would improve quality of life and reduce mortality.

Classic transient erythroblastopenia of childhood with human parvovirus B19 genome detection in the blood and bone marrow

The etiology of transient erythroblastopenia of childhood (TEC) remains unknown, although an association with viral infections has been proposed. The authors describe a 3.5-year-old girl with classic TEC concomitantly with human parvovirus B19 (HPV) infection. The infection was evident by detection of HPV genome in the blood and the bone marrow by polymerase chain reaction. Viral genome was no longer detected when the TEC resolved clinically. The patient was immunocompetent and the anemia has not recurred. To the authors' knowledge, this is one of the few documented cases of classic TEC attributable to HPV infection.

Sickle-cell disease

With the global scope of sickle-cell disease, knowledge of the countless clinical presentations and treatment of this disorder need to be familiar to generalists, haematologists, internists, and paediatricians alike. Additionally, an underlying grasp of sickle-cell pathophysiology, which has rapidly accrued new knowledge in areas related to erythrocyte and extra-erythrocyte events, is crucial to an understanding of the complexity of this molecular disease with protean manifestations. We highlight studies from past decades related to such translational research as the use of hydroxyurea in treatment, as well as the therapeutic promise of red-cell ion-channel blockers, and antiadhesion and anti-inflammatory therapy. The novel role of nitric oxide in sickle-cell pathophysiology and the range of its potential use in treatment are also reviewed. Understanding of disease as the result of a continuing interaction between basic scientists and clinical researchers is best exemplified by this entity.

Manifestations systémiques des infections à Parvovirus B19

PURPOSE

Parvovirus B19 (B19) causes many clinical disorders, of which the most common are erythema infectiosum, aplastic crisis complicating chronic hemolytic anemia, and hydrops fetalis. In young adults, the skin eruption caused by B19 is accompanied by polyarthritis and polyarthralgia in 60% of the cases. Rheumatoid factors and other antibodies including antinuclear antibodies, anti-ADN, and antiphospholipids can be produced in the wake of B19 infection.

CURRENT KNOWLEDGE AND KEY POINTS

These features may simulate systemic diseases as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) (lupus-like eruption over the cheeks, cytopenia, etc.) or vasculitis (purpura, renal involvement). In addition, there have been a few reports of SLE, vasculitis and other connective tissue diseases developing shortly after a B19 infection associated with virus clearance suggesting that B19 can act as a trigger of systemic disease. However, studies in large series indicate that in fact B19 is probably an extremely rare cause of RA, SLE or vasculitis.

FUTURE PROSPECTS AND PROJECTS

In fundamental studies B19 interacts with inflammatory cells by regulation of cytokines. More recently, two studies suggest that viral infection due to B19 may affect the course of SLE, leading to specific biological subsets. These preliminary findings require confirmation to elucidate the significance of the presence of B19 in systemic disease.

Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and beta-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

Viremic blood donor found by a rapid screening method in a season of high human parvovirus B19 activity in Niterói, Rio de Janeiro, Brazil

Erythrovirus B19 infection is usually benign but may have serious consequences in patients with hemolytic anemia (transient aplastic crisis), immunodeficiency (in whom persistent infection can lead to chronic bone marrow failure with anemia), or who are in the first or second trimester of gestation (spontaneous abortion, hydrops fetalis, and fetal death). Being non-enveloped, B19 resists most inactivation methods and can be transmitted by transfusion. B19 is difficult to cultivate and native virus is usually obtained from viremic blood. As specific antibodies may be absent, and there is no reliable immunological method for antigen detection, hybridization or polymerase chain reaction are needed for detecting viremia. A rapid method, gel hemagglutination (Diamed ID-Parvovirus B19 Antigen Test), can disclose highly viremic donations, whose elimination lessens the viral burden in pooled blood products and may even render them non-infectious. In order to obtain native antigen and to determine the frequency of viremic donors, we applied this test to blood donors in a period of high viral activity in our community. Positive or indeterminate results were re-tested by dot-blot hybridization. We tested 472 donors in 1998 and 831 ones in 1999. One viremic donor was found in 1999. We suggest that in periods of high community viral activity the gel hemagglutination test may be useful in avoiding highly viremic blood being added to plasma pools or directly transfused to patients under risk.

Epidemiology of human parvovirus B19 in children with sickle cell disease

Human parvovirus (HPV) B19 causes significant morbidity and mortality in children with sickle cell disease (SCD), but little data are published about the epidemiology of HPV B19 infection and its associated complications in this patient population. In this study, prevalence and incidence rates of HPV B19 were determined in 633 patients with SCD followed at The Children's Hospital of Philadelphia between November 1996 and December 2001. Thirty percent (30%) were HPV B19 immunoglobulin G (IgG) positive at first testing, and the 70% without evidence of past HPV B19 infection were tested annually. One hundred ten patients developed evidence of HPV B19 infection for an incidence rate of 11.3 per 100 patient years. Sixty-eight episodes of HPV B19-induced transient red cell aplasia occurred with the following clinical events: fever (89.7%), pain (61.8%), acute splenic sequestration (19.1%), and acute chest syndrome (11.8%). Pain, fever, and acute splenic sequestration were more frequent events with acute HPV B19 infections compared with acute events in uninfected patients. The results of this epidemiologic study, the largest and most comprehensive to date, justify the development of HPV B19 prevention strategies to diminish the frequent and often severe complications associated with HPV B19 infections in patients with SCD.

Ex vivo cytokine responses against parvovirus B19 antigens in previously infected pregnant women

Parvovirus B19 infection is a significant cause of fetal death. The aim of this study was to investigate the role of maternal immune status in modulating susceptibility to fetal B19 infection. Peripheral blood was obtained from pregnant women (n = 199) with no clinical evidence of recent B19 infection. Evaluation of ex vivo T cell responses from 149/199 individuals showed significantly higher interferon-gamma levels for seropositive individuals following VP1 (268 +/- 36 versus 103 +/- 19 pg/ml; P = 0.003) and VP2 (242 +/- 42 versus 91 +/- 16 pg/ml; P = 0.01) antigen stimulation. Significantly higher levels of interleukin-2 were also observed in seropositive individuals following both VP1 (P = 0.0003) and VP2 (P = 0.0005) stimulation. The observed Th1 cellular response is lower than that documented previously for non-pregnant individuals and strongly suggests that diminution of the maternal anti-viral immune response may increase susceptibility to fetal B19 infection.

Papular-purpuric "gloves and socks" syndrome in a mother and daughter

The papular-purpuric "gloves and socks" syndrome (PPGSS) is a unique exanthem characterized by petechiae with painful edema of the hands and feet extending proximally with less severity. Constitutional symptoms of fever, lethargy, and arthralgia have also been described. Human parvovirus B19 has been implicated in most cases as the causative agent. We describe a mother and her daughter presenting with the characteristic findings of PPGSS and demonstrating the seroconversion of human parvovirus B19 a few days after the onset of their illness. Additional clinical findings of cutaneous vesicles, bullae, and conjunctivitis are reported in the mother's case. To our knowledge, these are the first 2 cases of PPGSS in a household setting.

Subclinical parvovirus B19 infection in children with sickle cell anemia

PURPOSE

To investigate the prevalence and clinical consequences of previous parvovirus B19 exposure in a large cohort of pediatric patients with sickle cell anemia (SCA).

METHODS

Prospective serologic testing for previous parvovirus B19 exposure was performed in steady-state pediatric patients with SCA, either prior to starting hydroxyurea therapy or in preparation for transition to the adult service. A retrospective chart review was performed to ascertain whether patients had a documented history of a transient aplastic crisis.

RESULTS

The prevalence of serologic evidence of previous parvovirus infection increased with age. The overall prevalence in 102 children with SCA was 53%, ranging from 44% between 5 and 9 years of age to 71% between 17 and 21 years of age. Only 27% of patients had a previous clinically recognized transient aplastic crisis.

CONCLUSIONS

By the teenage years, most pediatric patients with SCA have serologic evidence of previous parvovirus B19 exposure. However, subclinical parvovirus infection appears to be common in children with SCA, since most patients have no documented previous transient aplastic crisis.

Sickle cell disease

Sickle cell disease is a serious and life threatening disease that affects approximately 1 in 600 African-Americans. Since its first description in 1910 by Herrick, our understanding and treatment of this disease has grown tremendously. Most pediatricians will encounter one or more children with sickle cell disease and should have a thorough understanding of the disease, its complications, and treatment. This article summarizes present day knowledge about the complications and potential treatments for patients with sickle cell disease.