Feasibility of Domain Segmentation of B19V VP1u Using Intein Technology for Structural Studies

INTRODUCTION

Parvovirus B19 (B19V) is a human pathogen, and the minor capsid protein of B19V possesses a unique N terminus called VP1u that plays a crucial role in the life cycle of the virus.

OBJECTIVE

The objective of this study was to develop a method for domain segmentation of B19 VP1u using intein technology, particularly its receptor binding domain (RBD) and phospholipase A2 (PLA2 ) domain.

METHODS

RBD and PLA2 domains of VP1u were each fused to the DnaE split inteins derived from the Nostoc punctiforme. Each of these precursor proteins was expressed in E. coli. Combining the purified precursors in equal molar ratios resulted in the formation of full-length VP1u. Furthermore, Circular Dichroism (CD) spectroscopy and PLA2 assays were used to probe the structure and activity of the newly formed protein.

RESULTS

The CD spectrum of the full length VP1u confirmed the secondary structure of protein, while the PLA2 assay indicated minimal disruption in enzymatic activity.

CONCLUSION

This method would allow for the selective incorporation of NMR-active isotopes into either of the VP1u domains, which can reduce signal overlap in NMR structural determination studies.

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.

Identification and Genomic Characterization of Parvovirus B19V Genotype 3 Viruses from Cases of Meningoencephalitis in West Bengal, India

Brain infections are a major public health problem in India and other parts of the world, causing both mortality and lifelong disability. Even after a thorough investigation, many cases remain without an etiological diagnosis. Primate erythroparvovirus 1 (B19V) has been identified as a pathogen associated with undiagnosed meningoencephalitis in other settings, including the United Kingdom, France, and Latvia. Here, we reported 13/403 (3.2%) B19V PCR positive cases of meningoencephalitis in West Bengal, India. The positive samples were mostly from children (10/13, 76.92%) and presented as a spectrum consisting of acute encephalitis (7/13), acute meningoencephalitis (3/13), and meningitis (3/13). Of the 13 cases, 8/13 (61.5%) had no known etiology and 5/13 (38.5%) had a previous etiological diagnosis. The cases did not cluster in time or by location, suggesting sporadic occurrence rather than outbreaks. We were able to retrieve the complete B19V genomes from cerebrospinal fluid (CSF) in 12/13 cases. The sequences clustered into genotype 3b with complete genomes from Brazil, Ghana, and France, and partial genomes from India and Kyrgyzstan. This is the first report of B19V in cases of neurological infections from India. It highlights the need to evaluate the causal relationship between B19V with meningoencephalitis in the country. These were also the first complete genomes of genotype 3b from CSF and will be critical in the evaluation of the relationship between genotypes and disease. IMPORTANCE Cases of meningoencephalitis with no known etiology remain a major challenge to clinical management of brain infections across the world. In this study, we detected and characterized the whole-genome of primate erythroparvovirus 1 (B19V) in cases of meningoencephalitis in India. Our work highlighted the association between B19V and brain infections which has been reported in other countries. Our work also emphasized the need to examine the role of B19V in meningoencephalitis, specifically whether it caused or contributed to the disease together with other pathogens in India. Our study provided the first 12 genomes of B19V from cerebrospinal fluid. These genomes will contribute to an understanding of how the virus is changing across different locations and over time.

Ancient viral genomes reveal introduction of human pathogenic viruses into Mexico during the transatlantic slave trade

After the European colonization of the Americas, there was a dramatic population collapse of the Indigenous inhabitants caused in part by the introduction of new pathogens. Although there is much speculation on the etiology of the Colonial epidemics, direct evidence for the presence of specific viruses during the Colonial era is lacking. To uncover the diversity of viral pathogens during this period, we designed an enrichment assay targeting ancient DNA (aDNA) from viruses of clinical importance and applied it to DNA extracts from individuals found in a Colonial hospital and a Colonial chapel (16th-18th century) where records suggest that victims of epidemics were buried during important outbreaks in Mexico City. This allowed us to reconstruct three ancient human parvovirus B19 genomes and one ancient human hepatitis B virus genome from distinct individuals. The viral genomes are similar to African strains, consistent with the inferred morphological and genetic African ancestry of the hosts as well as with the isotopic analysis of the human remains, suggesting an origin on the African continent. This study provides direct molecular evidence of ancient viruses being transported to the Americas during the transatlantic slave trade and their subsequent introduction to New Spain. Altogether, our observations enrich the discussion about the etiology of infectious diseases during the Colonial period in Mexico.

Prevalence and Phylogenetic Analysis of Parvovirus (B19V) among Blood Donors with Different Nationalities Residing in Qatar

Human parvovirus (B19V) is the causative agent of erythema infectiosum in children and is linked to a wide range of clinical manifestations. Studies related to B19V prevalence in the Middle East and North Africa (MENA) region and other parts of Asia are very scarce. The objectives of this study were to estimate the seroprevalence (anti-B19V IgM and IgG), the viremia rate (B19V DNA), and the circulating genotypes of B19V among blood donors in Qatar. Methods: Donors’ blood samples (n = 5026) from different nationalities, mainly from the MENA region and South East Asia, were collected from 2014–2016. Samples were tested for the B19V DNA using RT-PCR. Furthermore, 1000 selected samples were tested to determine the seroprevalence of B19V antibodies using enzyme-linked immunosorbent assay (ELISA). Genotyping was performed on 65 DNA positive samples by sequencing of nested PCR fragments (NS1-VP1u region, 927 nt). Results: Only 1.4% (70/5026) of the samples had detectible B19V DNA in their blood. B19V DNA prevalence statistically decreased with age (p = 0.03). Anti-B19V IgG was detected in 60.3% (561/930) of the tested samples, while only 2.1% (20/930) were IgM-positive and 1.2% (11/930) were both IgM- and IgG-positive. B19V genotyping showed a predominance of Genotype 1 (100%). Sequence analysis of the NS1-VP1u region revealed 139 mutation sites, some of which were amino acid substitutions. Conclusion: Our results indicated a relatively high seroprevalence of B19V in Qatar. Most importantly, B19 DNA was detected among Qatari and non-Qatari blood donors. Therefore, blood banks in Qatar might need to consider screening for B19V, especially when transfusion is intended for high-risk populations, including immunocompromised patients.

The VP1u of Human Parvovirus B19: A Multifunctional Capsid Protein with Biotechnological Applications

The viral protein 1 unique region (VP1u) of human parvovirus B19 (B19V) is a multifunctional capsid protein with essential roles in virus tropism, uptake, and subcellular trafficking. These functions reside on hidden protein domains, which become accessible upon interaction with cell membrane receptors. A receptor-binding domain (RBD) in VP1u is responsible for the specific targeting and uptake of the virus exclusively into cells of the erythroid lineage in the bone marrow. A phospholipase A₂ domain promotes the endosomal escape of the incoming virus. The VP1u is also the immunodominant region of the capsid as it is the target of neutralizing antibodies. For all these reasons, the VP1u has raised great interest in antiviral research and vaccinology. Besides the essential functions in B19V infection, the remarkable erythroid specificity of the VP1u makes it a unique erythroid cell surface biomarker. Moreover, the demonstrated capacity of the VP1u to deliver diverse cargo specifically to cells around the proerythroblast differentiation stage, including erythroleukemic cells, offers novel therapeutic opportunities for erythroid-specific drug delivery. In this review, we focus on the multifunctional role of the VP1u in B19V infection and explore its potential in diagnostics and erythroid-specific therapeutics.

Parvovirus B19V Nonstructural Protein NS1 Induces Double-Stranded Deoxyribonucleic Acid Autoantibodies and End-Organ Damage in Nonautoimmune Mice

Background

Viral infection is implicated in development of autoimmunity. Parvovirus B19 (B19V) nonstructural protein, NS1, a helicase, covalently modifies self double-stranded deoxyribonucleic acid (dsDNA) and induces apoptosis. This study tested whether resulting apoptotic bodies (ApoBods) containing virally modified dsDNA could induce autoimmunity in an animal model.

Methods

BALB/c mice were inoculated with (1) pristane-induced, (2) B19V NS1-induced, or (3) staurosporine-induced ApoBods. Serum was tested for dsDNA autoantibodies by Crithidia luciliae staining and enzyme-linked immunosorbent assay. Brain, heart, liver, and kidney pathology was examined. Deposition of self-antigens in glomeruli was examined by staining with antibodies to dsDNA, histones H1 and H4, and TATA-binding protein.

Results

The B19V NS1-induced ApoBod inoculation induced dsDNA autoantibodies in a dose-dependent fashion. Histopathological features of immune-mediated organ damage were evident in pristane-induced and NS1-induced ApoBod groups; severity scores were higher in these groups than in staurosporine-treated groups. Tissue damage was dependent on NS1-induced ApoBod dose. Nucleosomal antigens were deposited in target tissue from pristane-induced and NS1-induced ApoBod inoculated groups, but not in the staurosporine-induced ApoBod inoculated group.

Conclusions

This study demonstrated proof of principle in an animal model that virally modified dsDNA in apoptotic bodies could break tolerance to self dsDNA and induce dsDNA autoantibodies and end-organ damage.

Presence of B19V in Patients with Thyroid Gland Disorders

Background and Objectives: Viral infections are frequently cited as a major environmental factor implicated in thyroid gland diseases. This work aimed to estimate the presence of B19V infection in patients with thyroid gland disorders. Materials and Methods: Thyroid gland tissue and blood samples of 50 patients with autoimmune thyroid gland diseases (AITDs), 76 patients with non-autoimmune thyroid gland diseases (non-AITDs), and 35 deceased subjects whose histories did not show any autoimmune or thyroid diseases (control group) were enrolled in the study. Virus-specific IgM and IgG were detected using ELISA, and the presence and viral load of B19V in the tissue and blood were detected using PCRs. Results: B19V IgG antibodies were detected in 35/50 AITDs patients and in 51/76 non-AITDs patients, and B19V IgM antibodies were detected in 1/50 patients with AITDs and in none of the 76 patients with non-AITDs. The B19V NS sequence was found in the tissue DNA of 10/50 patients with AITDs, in 30/76 with non-AITDs, and in 1/35 control group individuals. The median B19V load in the tissue of patients with AITDs and non-AITDs was 423.00 copies/µg DNA (IQR: 22.50-756.8) and 43.00 copies/µg DNA (IQR: 11.50-826.5), respectively. The viral load in one of the 35 nPCR B19V-positive thyroid tissue samples from the deceased subjects was 13.82 copies/µg DNA. The viral load in the tissue of patients with AITDs was higher than in whole blood, which possibly indicates B19V persistency in thyrocytes (p = 0.0076). Conclusion: The fact that the genoprevalence of B19V NS was significantly higher in patients with non-AITDs compared to the control group and in the thyroid gland tissue of patients with AITDs, and that the non-AITDs viral load was higher than in tissue derived from the control group individuals, suggest the possibility that B19V infection could be involved in the development of thyroid gland diseases.

Systematic Review of PCR Proof of Parvovirus B19 Genomes in Endomyocardial Biopsies of Patients Presenting with Myocarditis or Dilated Cardiomyopathy

Background: Diverse viral infections have been associated with myocarditis (MC) and dilated cardiomyopathy (DCM). In this meta-analysis, we summarize the published results on the association of parvovirus B19 (B19V) genomes with human MC/DCM versus controls. Methods: n = 197 publications referring to B19V and MC or DCM were retrieved using multiple PubMed search modes. Out of these, n = 29 publications met the inclusion criteria with data from prospective analyses on >10 unselected patients presenting with MC or DCM (dataset: MA01). Data retrieved simultaneously from both controls and MC/DCM patients were available from n = 8 from these publications (dataset: MA02). Results: In the dataset MA01 B19V genomes were detected in 42.6% of the endomyocardial biopsies (EMB) in this cohort by PCR. In the dataset MA02 comprising n = 638 subjects, there was no statistically significant different rate of B19V positivity in myocardial tissues comparing controls (mean: 38.8 + 24.1%) versus the MC/DCM-patients (45.5 + 24.3%; p = 0.58). There was also no statistical difference between the positivity rate of B19V genomes in myocardial tissues of MA01 (46.0 + 19.5%) and the two patient groups of MA02 (p > 0.05). Conclusions: This systematic review reveals that the mean rate of PCR detected B19V genomes in patients presenting with MC/DCM does not differ significantly from the findings in control myocardial tissues. These data imply pathogenetically insignificant latency of B19V genomes in a proportion of myocardial tissues, both in MC-/DCM-patients and in controls. More information (i.e., replicative status, viral protein expression) is pertinent to achieve a comprehensive workup of myocardial B19V infection.

Parvovirus B19 Uncoating Occurs in the Cytoplasm without Capsid Disassembly and It Is Facilitated by Depletion of Capsid-Associated Divalent Cations

Human parvovirus B19 (B19V) traffics to the cell nucleus where it delivers the genome for replication. The intracellular compartment where uncoating takes place, the required capsid structural rearrangements and the cellular factors involved remain unknown. We explored conditions that trigger uncoating in vitro and found that prolonged exposure of capsids to chelating agents or to buffers with chelating properties induced a structural rearrangement at 4 °C resulting in capsids with lower density. These lighter particles remained intact but were unstable and short exposure to 37 °C or to a freeze-thaw cycle was sufficient to trigger DNA externalization without capsid disassembly. The rearrangement was not observed in the absence of chelating activity or in the presence of MgCl₂ or CaCl₂, suggesting that depletion of capsid-associated divalent cations facilitates uncoating. The presence of assembled capsids with externalized DNA was also detected during B19V entry in UT7/Epo cells. Following endosomal escape and prior to nuclear entry, a significant proportion of the incoming capsids rearranged and externalized the viral genome without capsid disassembly. The incoming capsids with accessible genomes accumulated in the nuclear fraction, a process that was prevented when endosomal escape or dynein function was disrupted. In their uncoated conformation, capsids immunoprecipitated from cytoplasmic or from nuclear fractions supported in vitro complementary-strand synthesis at 37 °C. This study reveals an uncoating strategy of B19V based on a limited capsid rearrangement prior to nuclear entry, a process that can be mimicked in vitro by depletion of divalent cations.

Secondary structure of DNA released from purified capsids of human parvovirus B19 under moderate denaturing conditions

Parvovirus B19 (B19V) possesses a linear single-stranded DNA genome of either positive or negative polarity. Due to intramolecular sequence homologies, either strand may theoretically be folded in several alternative ways. Viral DNA, when extracted from virions by several procedures, presents as linear single-stranded and/or linear double-stranded molecules, except when one particular commercial kit is used. This protocol yields DNA with an aberrant electrophoretic mobility in addition to linear double-stranded molecules, but never any single-stranded molecules. This peculiar kind of DNA was found in all plasma or serum samples tested and so we decided to analyse its secondary structure. In line with our results for one- and two-dimensional electrophoresis, mobility shift assays, DNA preparation by an in-house extraction method with moderate denaturing conditions, density gradient ultracentrifugation, DNA digestion experiments and competition hybridization assays, we conclude that (i) the unique internal portions of this distinctive single-stranded molecules are folded into tight tangles and (ii) the two terminal redundant regions are associated with each other, yielding non-covalently closed pseudo-circular molecules stabilized by a short (18 nucleotides) intramolecular stem, whereas the extreme 3'- and 5'-ends are folded back on themselves, forming a structure resembling a twin hairpin. The question arises as to whether this fairly unstable structure represents the encapsidated genome structure. The answer to this question remains quite relevant in terms of comprehending the initiation and end of B19V genome replication.

Telbivudine Reduces Parvovirus B19-Induced Apoptosis in Circulating Angiogenic Cells

Aims: Human parvovirus B19 (B19V) infection directly induces apoptosis and modulates CXCR4 expression of infected marrow-derived circulating angiogenic cells (CACs). This leads to dysfunctional endogenous vascular repair. Treatment for B19V-associated disease is restricted to symptomatic treatment. Telbivudine, a thymidine analogue, established in antiviral treatment for chronic hepatitis B, modulates pathways that might influence induction of apoptosis. Therefore, we tested the hypothesis of whether telbivudine influences B19V-induced apoptosis of CAC. Methods and Results: Pretreatment of two CAC-lines, early outgrowth endothelial progenitor cells (eo-EPC) and endothelial colony-forming cells (ECFC) with telbivudine before in vitro infection with B19V significantly reduced active caspase-3 protein expression (−39% and −40%, both p < 0.005). Expression of Baculoviral Inhibitor of apoptosis Repeat-Containing protein 3 (BIRC3) was significantly downregulated by in vitro B19V infection in ECFC measured by qRT-PCR. BIRC3 downregulation was abrogated with telbivudine pretreatment (p < 0.001). This was confirmed by single gene PCR (p = 0.017) and Western blot analysis. In contrast, the missing effect of B19V on angiogenic gene expression postulates a post-transcriptional modulation of CXCR4. Conclusions: We for the first time show a treatment approach to reduce B19V-induced apoptosis. Telbivudine reverses B19V-induced dysregulation of BIRC3, thus, intervening in the apoptosis pathway and protecting susceptible cells from cell death. This approach could lead to an effective B19V treatment to reduce B19V-related disease.

Genotypes of erythrovirus B19, their geographical distribution & circulation in cases with various clinical manifestations

Erythrovirus B19 (B19V) is one of the erythroviruses known to be pathogenic in humans. B19V is classified into three distinct genotypes; 1, 2 and 3, differing from each other by 2-13 per cent. Genotype 1 consists of the prototype B19V isolates, genotype 2 comprises the A6, LaLi and their related isolates while genotype 3 includes the V9- and V9-related isolates. The classification of genotype 1 into two subtypes (1A and 1B) and genotype 3 into two subtypes (3a and 3b) with an estimated nucleotide difference of about 5 per cent has been done. Predominance of genotype 1 across all the continents is seen followed by genotypes 2 and 3. There are no disease-specific genotypes. All the three genotypes have been found in symptomatic as well as asymptomatic individuals and have been reported from several countries across the world. The prevalence of genotype 2 in older populations and its absence from current circulation in Northern Europe has also been reported. The present review focuses on geographic distribution and association of genotypes of B19V with different clinical manifestations.

Parvovirus B19: What Is the Relevance in Transfusion Medicine?

Parvovirus B19 (B19V) has been discovered in 1975. The association with a disease was unclear in the first time after the discovery of B19V, but meanwhile, the usually droplet transmitted B19V is known as the infectious agent of the “fifth disease,” a rather harmless children’s illness. But B19V infects erythrocyte progenitor cells and thus, acute B19V infection in patients with a high erythrocyte turnover may lead to a life-threatening aplastic crisis, and acutely infected pregnant women can transmit B19V to their unborn child, resulting in a hydrops fetalis and fetal death. However, in many adults, B19V infection goes unnoticed and thus many blood donors donate blood despite the infection. The B19V infection does not impair the blood cell counts in healthy blood donors, but after the acute infection with extremely high DNA concentrations exceeding 10¹⁰ IU B19V DNA/ml plasma is resolved, B19V DNA persists in the plasma of blood donors at low levels for several years. That way, many consecutive donations that contain B19V DNA can be taken from a single donor, but the majority of blood products from donors with detectable B19V DNA seem not to be infectious for the recipients from several reasons: first, many recipients had undergone a B19V infection in the past and have formed protective antibodies. Second, B19V DNA concentration in the blood product is often too low to infect the recipient. Third, after the acute infection, the presence of B19V DNA in the donor is accompanied by presumably neutralizing antibodies which are protective also for the recipient of his blood products. Thus, transfusion-transmitted (TT-) B19V infections are very rarely reported. Moreover, in most blood donors, B19V DNA concentration is below 1,000 IU/ml plasma, and no TT-B19V infections have been found by such low-viremic donations. Cutoff for an assay for B19V DNA blood donor screening should, therefore, be approximately 1,000 IU/ml plasma, if a general screening of blood donors for single donation blood components is considered at all: for the overwhelming majority of transfusion recipients, B19V infection is not relevant as well as for the blood donors. B19V DNA screening of vulnerable patients after transfusion seems to be a more reasonable approach than general blood donor screening.

The Chemokine CXCL-10 Is a Marker of Infection Stage in Individuals With DNAemia Due to Parvovirus B19

Background

Accurate diagnosis of parvovirus B19 (B19V) infection requires the differentiation between acute and past infection, which is especially important when DNAemia due to B19V (hereafter, "B19V DNAemia") is detected in pregnancy. Here, we explored whether the level of the chemokine CXCL-10, in combination with findings of molecular and serological assays, can discriminate between acute and past B19V infection.

Methods

B19V DNA-positive serum samples from 222 immunocompetent individuals were analyzed for (1) viral DNA loads, (2) anti-B19V immunoglobulin M (IgM) and immunoglobulin G (IgG), (3) anti-VP1 IgG avidity, (4) anti-VP-2 epitope type specificity (ETS), and (5) CXCL-10 serum levels.

Results

Anti-B19V IgM and IgG, avidity, and ETS assays were used to categorize individuals with B19V DNAemia as having acute or past B19V infection. Acute B19V infection caused a significant increase in the serum concentration of CXCL-10, compared with the concentration at baseline, before infection. Higher CXCL-10 serum levels were furthermore detected in acute B19V infection as compared to past infection. As a marker, CXCL-10 serum levels could discriminate between acute and past B19V infection, with an excellent discriminatory capacity when CXCL-10 and B19V DNA levels were used as combined parameters.

Conclusion

Acute B19V infection is associated with increased CXCL-10 production, and measurement of CXCL-10 serum levels thus allows for the staging of B19V infection in individuals with B19V DNAemia.

The formation and modification of chromatin-like structure of human parvovirus B19 regulate viral genome replication and RNA processing

B19 virus (B19V) is a single stranded virus in the genus of Erythroparvovirus in the family of Parvoviridae. One of the limiting steps of B19V infection is the replication of viral genome which affected the alternative processing of its RNA. Minute virus of mice (MVM) and adeno-associated virus (AAV) has been reported to form chromatin-like structure within hours after infection of cells. However, the role of chromatin-like structure is unclear. In the present study, we found that B19V formed chromatin-like structure after 12h when B19V infectious clone was co-transfected with pHelper plasmid to HEK293T cells. Interestingly, the inhibitor of DNA methyl-transferase (5-Aza-2'-deoxycytidine, DAC) inhibited not only the formation of chromatin-like structure, but also the replication of the viral genomic DNA. More importantly, the splicing of the second intron at splice acceptor sites (A2-1, and A2-2) were reduced and polyadenylation at (pA)p increased when transfected HEK293T cells were treated with DAC. Our results showed that the formation and modification of chromatin-like structure are a new layer to regulate B19V gene expression and RNA processing.

The prevalence of hepatitis A virus and parvovirus B19 in source-plasma donors and whole blood donors in China

AIMS

To compare the prevalence of hepatitis A virus (HAV) and human parvovirus B19 (B19V) between source-plasma (SP) donors and whole blood (WB) donors.

BACKGROUND

In China, source plasma is in severe shortage while plasma recovered from WB is in surplus. Thus, the government is considering transferring the recovered plasma (RP) to produce plasma derivatives. HAV and B19V are two pathogens threatening the safety of plasma-based derivatives. However, there is no data about if transferring of the RP to produce plasma derivatives will increase the risk of HAV and B19V infection. Thus, we compared the prevalence of HAV and B19V between SP donors and WB donors in this study.

METHODS

A total of 5030 samples from SP donors and 5040 samples from WB donors were collected. All the samples were tested for HAV RNA and B19V DNA and tested for HAV IgM by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The prevalence of B19V DNA was 0.06% (95% confidence interval (CI), 0-0.09%) in WB donors and 0.079% (95% CI, 0-0.12%) in SP donors, respectively. No significant difference was found in the prevalence of B19V DNA between SP donors and WB donors. The prevalence of anti-HAV IgM in SP donors was 0.079% whereas no WB donor sample was found anti-HAV IgM reactive.

CONCLUSIONS

The transfer of RP to producing plasma derivatives will not increase the risk of transmission of HAV and B19 through plasma products.

Prevalence and Viral Load of Human Parvovirus B19 (B19V) Among Blood Donors in South-East Brazil

The infection of human parvovirus B19 (B19V) is a common event in the general population, including volunteer blood donors. In some cases it can be asymptomatic and can remain persistent for a long period of time. The objective of this study was to examine the B19V DNA prevalence and viral load in first-time volunteer blood donors. Blood samples were collected from 91 primary blood donors at the Regional Blood Center of Ribeirão Preto, Southeast Brazil. Viral detection and quantitation was performed by an in-house TaqMan(®) real-time PCR with high sensitivity. B19V DNA was detected in one male blood donor (1.0 %) and was characterized by a very low viral load (537.36 copies/mL). Our studies demonstrate that B19V DNA at low titer may be present in apparently healthy individuals. Sensitive molecular diagnostic tools can be applied for the screening of fresh blood derived products in order to prevent transfusion-transmitted B19V infection.

Look-back study on recipients of Parvovirus B19 (B19V) DNA-positive blood components

BACKGROUND AND OBJECTIVES

To assess the relevance of Parvovirus B19 (B19V) DNA at low to intermediate concentrations in blood donors for the recipients of their blood components.

MATERIAL AND METHODS

We studied recipients of B19V DNA-positive blood components [red blood cell concentrates (RBCs), pooled platelet concentrates and fresh frozen plasma]. This included archived pretransfusion samples as well as follow-up samples investigated by ELISA or NAT and genome sequence analysis.

RESULTS

In 132 out of 424 recipients, we could detect no anti-B19V IgG before transfusion. In 67 out of 132 sero-negative recipients, a follow-up sample was available. Sixty-five of these received blood components from donors with <10(4) IU B19V DNA/ml plasma and had no evidence of transfusion-transmitted (TT)-B19V infection. Homology in genome sequences in donor and recipient provided evidence for a TT-B19V infection in two recipients. Both patients received RBC containing 3.4 × 10(6) and 1.8 × 10(4) IU B19V DNA/ml plasma, respectively. The anti-B19V IgG titres in the donors were 2 and 76 IU/ml plasma, respectively. The antibodies in the second donor were directed against capsid proteins and are thus considered as potential neutralizing antibodies.

CONCLUSIONS

TT-B19V infections through blood components with low (<10(4) IU/ml plasma) B19V DNA concentrations did not occur in our study. One of the TT-B19V infections occurred from RBC with intermediate B19V DNA concentration despite the presence of potential neutralizing antibodies in the donor, but its clinical significance was low.

Human parvovirus B19: a mechanistic overview of infection and DNA replication

Human parvovirus B19 (B19V) is a human pathogen that belongs to genus Erythroparvovirus of the Parvoviridae family, which is composed of a group of small DNA viruses with a linear single-stranded DNA genome. B19V mainly infects human erythroid progenitor cells and causes mild to severe hematological disorders in patients. However, recent clinical studies indicate that B19V also infects nonerythroid lineage cells, such as myocardial endothelial cells, and may be associated with other disease outcomes. Several cell culture systems, including permissive and semipermissive erythroid lineage cells, nonpermissive human embryonic kidney 293 cells and recently reported myocardial endothelial cells, have been used to study the mechanisms underlying B19V infection and B19V DNA replication. This review aims to summarize recent advances in B19V studies with a focus on the mechanisms of B19V tropism specific to different cell types and the cellular pathways involved in B19V DNA replication including cellular signaling transduction and cell cycle arrest.

Persistence of Parvovirus B19 (B19V) DNA and humoral immune response in B19V-infected blood donors

BACKGROUND AND OBJECTIVES

Parvovirus B19 (B19V) DNA seems to persist in the plasma of B19V-infected blood donors. The relevance of this for recipients of single-donor blood components is yet unclear.

MATERIAL AND METHODS

We studied serial archive and follow-up samples from 75 B19V-infected blood donors to obtain more data about the duration and degree of viraemia and the presence of IgG and IgM anti-B19V. IgG antibodies were further characterized by Western blot analysis in 29 donors.

RESULTS

In 411 B19V DNA-positive samples collected, we found high concentrations (>10(6) IU B19V DNA/ml plasma) in five. B19V DNA persisted for a mean of 21·5 months (range: 2·3-52·4; 95% confidence interval, 19·1-23·9 months) in all donors. Only 15 such samples had either no or low-titre IgG anti-B19V. IgG antibodies were predominantly directed against epitopes on the minor capsid protein VP1, thus probably of neutralizing type with high avidity. IgM anti-B19V was detectable in 9/13 samples with high DNA concentrations.

CONCLUSIONS

The vast majority of single-donor blood components with detectable B19V DNA are probably not infectious for their recipients because DNA is at only low levels and the donors also have potentially neutralizing antibodies with high avidity. Anti-B19V IgM testing does not identify every donation with high B19V DNA concentrations, but, in addition to B19V NAT testing, donors with persistent IgG anti-B19V might be considered 'B19V-safe' for single-donor blood components.