Human Parvoviruses

Comparison of phenotypic and genotypic diagnosis of acute human bocavirus 1 infection in children

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Diagnosis of HBoV1 has been based on detection of DNA or mRNA.

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Rapid HBoV1 antigen detection is beneficial for diagnosing acute HBoV1 infections.

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HBoV1 antigen detection is attractive for point-of-care use.

Background

Diagnosis of human bocavirus 1 (HBoV1) has been based on qualitative PCRs detecting HBoV1 DNA or detection of HBoV1 mRNA.

Objective

This study aims to assess whether a rapid and automated HBoV1 antigen test is suitable for diagnosis of acute HBoV1 infection.

Study design

HBoV1 antigen detection has been compared with quantitative HBoV1 DNA PCR and HBoV1 mRNA RT-PCR.

Results and conclusion

We conclude that HBoV1 antigen detection has higher clinical specificity and positive predictive value than HBoV1 DNA qualitative PCRs, yet a lower sensitivity than HBoV1 mRNA detection. Additionally, HBoV1 antigen detection is beneficial in its rapidity and availability as a point-of-care test.

Severe Human Bocavirus 1 Respiratory Tract Infection in an Immunodeficient Child With Fatal Outcome

We report a case of lower respiratory tract infection with human bocavirus 1 (HboV1) in an immunodeficient 6-month-old boy leading to respiratory failure with fatal outcome. Polymerase chain reaction of serum/tracheal secretions revealed exceptionally high HboV1-DNA levels and immunoassays showed seroconversion indicating an acute primary HboV1 infection. All assays for other pathogens were negative, strongly suggesting that HboV1 was the causative agent in this case.

Advances in the Development of Antiviral Strategies against Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus, responsible for an ample range of clinical manifestations. Infections are usually mild, self-limiting, and controlled by the development of a specific immune response, but in many cases clinical situations can be more complex and require therapy. Presently available treatments are only supportive, symptomatic, or unspecific, such as administration of intravenous immunoglobulins, and often of limited efficacy. The development of antiviral strategies against B19V should be considered of highest relevance for increasing the available options for more specific and effective therapeutic treatments. This field of research has been explored in recent years, registering some achievements as well as interesting future perspectives. In addition to immunoglobulins, some compounds have been shown to possess inhibitory activity against B19V. Hydroxyurea is an antiproliferative drug used in the treatment of sickle-cell disease that also possesses inhibitory activity against B19V. The nucleotide analogues Cidofovir and its lipid conjugate Brincidofovir are broad-range antivirals mostly active against dsDNA viruses, which showed an antiviral activity also against B19V. Newly synthesized coumarin derivatives offer possibilities for the development of molecules with antiviral activity. Identification of some flavonoid molecules, with direct inhibitory activity against the viral non-structural (NS) protein, indicates a possible line of development for direct antiviral agents. Continuing research in the field, leading to better knowledge of the viral lifecycle and a precise understanding of virus–cell interactions, will offer novel opportunities for developing more efficient, targeted antiviral agents, which can be translated into available therapeutic options.

Emerging Human Parvoviruses: The Rocky Road to Fame

Parvoviruses are structurally simple viruses with linear single-stranded DNA genomes and nonenveloped icosahedral capsids. They infect a wide range of animals from insects to humans. Parvovirus B19 is a long-known human pathogen, whereas adeno-associated viruses are nonpathogenic. Since 2005, many parvoviruses have been discovered in human-derived samples: bocaviruses 1-4, parvovirus 4, bufavirus, tusavirus, and cutavirus. Some human parvoviruses have already been shown to cause disease during acute infection, some are associated with chronic diseases, and others still remain to be proven clinically relevant-or harmless commensals, a distinction not as apparent as it might seem. One initially human-labeled parvovirus might not even be a human virus, whereas another was originally overlooked due to inadequate diagnostics. The intention of this review is to follow the rocky road of emerging human parvoviruses from discovery of a DNA sequence to current and future clinical status, highlighting the perils along the way.

Molecular screening of the human parvoviruses B19 and bocavirus 1 in the study of congenital diseases as applied to symptomatic pregnant women and children

Introduction

B19 virus (B19V) and bocavirus 1 (HBoV1) are human pathogenic parvoviruses that are prevalent worldwide and are responsible for a diverse and not yet fully established spectrum of clinical manifestations.

Objective

To screen B19V and HBoV1 in patients with clinical manifestations associated with acquisition of the infection during gestation.

Methods

A retrospective, observational study was performed that included serum samples from patients without a previous known aetiology. B19V and HBoV1 were determined by end-point PCR. Positive samples were genotyped.

Results

A total of 106 serum samples were analysed, 61 from pregnant women and 45 from neonates and paediatric patients. None were positive for HBoV1, while B19V was detected in 37/106 [34.9 %, 95 % confidence interval (CI): 26.5–44.4] of the samples studied. In the group of pregnant women, 28/61 (45.9 %, 95 % CI: 34.0–58.3) were B19V-positive, and 2 of them had foetal anaemia followed by hydrops and foetal death, 3 were associated with a history of recurrent pregnancy loss and there was 1 case of spontaneous abortion. B19V was also detected in cases of maternal febrile exanthema, polyhydramnios, oligohydramnios and foetal ascites. In the group of children, 9/45 (20.0 %, 95 % CI: 10.9–33.8) neonatal patients were B19V-positive, and this was associated with foetal hydrops, TORCH syndrome and cardiac alterations. The nucleotide sequences analysed confirmed the identity of B19V genotype 1.

Conclusions

We found no evidence to indicate the presence of HBoV1 in maternal blood or in the newborns/paediatric patients (hence providing no support for the supposed vertical transmission). On the other hand, the high frequency of B19V in the pathologies studied indicates the importance of molecular diagnosis in both the mother and the child. Future efforts should contribute to early detection and characterization of infections.

Clinical impact & pathogenic mechanisms of human parvovirus B19: A multiorgan disease inflictor incognito

Human parvovirus B19 (B19V) causes myriads of clinical diseases; however, owing to lack of awareness and undetermined clinical impact, it has failed to become a virus pathogen of global concern. Cryptically, B19V causes significant morbidity and mortality. Half of the world population and 60 per cent of Indians are known to be serologically naive and are at risk of acquiring B19V infections. Cumulatively, our data showed 21.3 per cent B19V-infected patients with juvenile chronic arthropathy, recurrent abortions, multi-transfused thalassaemia and leukaemia. In addition, B19V-infected cases that ended fatally included patients with pure red cell aplasia, fulminant hepatitis and haemophagocytic syndrome. Novel clinical associations of B19V observed were amegakaryocytic thrombocytopaenia, myositis and non-occlusive ischaemic gangrene of bowel. B19V possesses multiple receptors which are distributed widely in human tissues. Vascular endothelial cell infection by B19V causes endothelialitis and vasculitic injuries besides antibody-dependent enhancement which empowered B19V to cause multiorgan diseases. Owing to lack of suitable animal model for B19V, true causal role remains to be determined, but numerous reports on B19V infections substantiate a causal role in multiorgan diseases. Hence, B19V infections need to be recognized, investigated and treated besides making efforts on vaccine developments.

The effects of human parvovirus VP1 unique region in a mouse model of allergic asthma

Evidence has indicated that viral infection increases the risk of developing asthma. Although the association of human parvovirus B19 (B19V) or human bocavirus (HBoV) with respiratory diseases has been reported, little is known about the influence of the B19V-VP1u and HBoV-VP1u proteins on the symptoms of asthma. Herein, we investigated the systemic influence of subcutaneously injected B19V-VP1u and HBoV-VP1u recombinant proteins in an OVA-sensitized asthmatic mouse model. A significantly higher Penh ratio and IgE level were detected in the serum, bronchoalveolar lavage fluid (BALF) and the supernatant of a lymphocyte culture from mice treated with HBoV-VP1u or B19V-VP1u than in a lymphocyte culture from OVA-sensitized mice. Significantly higher levels of serum and BALF IgE, total IgG, IgG1, OVA-specific IgE and OVA-specific IgG1 were detected in mice treated with HBoV-VP1u or B19V-VP1u than in OVA-sensitized mice. Conversely, a significantly lower IgG2a level was detected in mice from the HBoV-VP1u or B19V-VP1u groups than in mice from the OVA group. The mice treated with HBoV-VP1u or B19V-VP1u exhibited more significant lung inflammatory indices, including elevated serum and BALF IL-4, IL-5, IL-10 and IL-13 levels; BALF lymphocyte, neutrophil and eosinophil counts, MMP-9 and MMP-2 activity; and the amount of lymphocyte infiltration, relative to those in the control mice or in those sensitized with OVA. These findings demonstrate that the subcutaneous injection of HBoV-VP1u or B19V-VP1u proteins in OVA-sensitized mice result in elevated asthmatic indices and suggest that human parvoviruses may increase the risk of developing airway inflammation in a mouse model of asthma.

Human bocavirus detection and quantification in fecal and serum specimens from recipients of allogeneic hematopoietic stem cell transplantation: A longitudinal study

OBJECTIVES

The aim of this study was to evaluate the occurrence of human bocavirus (HBoV) and to determine viral loads in samples of patients admitted for allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

Fecal and serum samples were collected from 19 patients, during a 24-month period. Samples were screened by quantitative polymerase chain reaction TaqMan assay, with specific probe and primers targeting the NP1 gene of all HBoVs genotypes (HBoV-1 to - 4), and viral loads were determined using serial dilutions of a recombinant plasmid.

RESULTS

HBoV DNA was detected in 42.1% (8 of 19) of the patients in at least one type of sample (feces and/or serum) during the study period, with 75% (6 of 8) of the patients being positive in both types of sample. Viral shedding in feces had a median of 26 days (range, 5 to 121) and viremia was detected in 87.5% (7 of 8) of the patients. The HBoV loads in fecal samples were higher than in sera and, in most cases, HBoV was detected earlier in fecal than in sera samples. In six HBoV-positive patients (6 of 8) diarrhea was observed concomitantly to viral detection in fecal samples.

CONCLUSIONS

A high frequency and loads of HBoV in allo-HSCT recipients was observed, especially in fecal samples. Positivity in fecal samples was an early predictor of HBoV presence.

Human parvovirus B19 in solid organ transplantation: Guidelines from the American society of transplantation infectious diseases community of practice

Clinical manifestations of human parvovirus B19 infection can vary widely and may be atypical in solid organ transplant (SOT) recipients. However, disease is apparent when there is destruction of erythrocyte progenitor cells leading to severe acute or chronic anemia with lack of an appropriate reticulocyte response in the setting of active parvovirus B19 infection. Serology may not reliably establish the diagnosis. High-level viremia is more likely to be associated with symptomatic disease. Conversely, ongoing DNAemia after infection may not be clinically significant, if detected at low levels. Despite lack of robust data, intravenous immunoglobulin (IVIG) is frequently used for the treatment of SOT recipients with symptomatic parvovirus B19 infection. Although the optimal dosage and duration of IVIG is not known, most patients receive a total of 2 g/kg over a period of 2-5 days. A daily dose of 1 g/kg or more seems to be associated with higher incidence of toxicity. Application of standard and droplet isolation precautions remains the cornerstone for preventing human parvovirus B19 transmission. Additional research is needed to assess the efficacy of current and novel therapies and to develop a safe and effective parvovirus B19 vaccine.

Global Distribution of Human Protoparvoviruses

Development of next-generation sequencing and metagenomics has revolutionized detection of novel viruses. Among these viruses are 3 human protoparvoviruses: bufavirus, tusavirus, and cutavirus. These viruses have been detected in feces of children with diarrhea. In addition, cutavirus has been detected in skin biopsy specimens of cutaneous T-cell lymphoma patients in France and in 1 melanoma patient in Denmark. We studied seroprevalences of IgG against bufavirus, tusavirus, and cutavirus in various populations (n = 840), and found a striking geographic difference in prevalence of bufavirus IgG. Although prevalence was low in adult populations in Finland (1.9%) and the United States (3.6%), bufavirus IgG was highly prevalent in populations in Iraq (84.8%), Iran (56.1%), and Kenya (72.3%). Conversely, cutavirus IgG showed evenly low prevalences (0%–5.6%) in all cohorts, and tusavirus IgG was not detected. These results provide new insights on the global distribution and endemic areas of protoparvoviruses.

Human bocaviruses and paediatric infections

Human bocavirus 1 (HBoV1), belonging to the Parvoviridae family, was discovered in 2005, in nasopharyngeal samples from children with respiratory tract infections. Three additional bocaviruses, HBoV2-4, were discovered in 2009-10. These viruses have mainly been found in faecal samples and their role in human diseases is still uncertain. HBoV1 causes a wide spectrum of respiratory diseases in children, including common cold, acute otitis media, pneumonia, bronchiolitis, and asthma exacerbations. HBoV1 DNA can persist in airway secretions for months after an acute infection. Consequently, acute HBoV1 infection cannot be diagnosed with standard DNA PCR; quantitative PCR and serology are better diagnostic approaches. Because of their high clinical specificity, diagnostic developments such as HBoV1 mRNA and antigen detection have shown promising results. This Review summarises the knowledge on human bocaviruses, with a special focus on HBoV1.

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.

Parvovirus B19 seroprevalence, viral load, and genotype characterization in volunteer blood donors from southern Brazil

Usually transmitted via respiratory droplets, parvovirus B19 (B19V) can also be acquired by blood transfusion especially because of viral persistence, resistance to blood treatment procedures, and high viral load during the early infection phase. This is particularly problematic in immunocompromised or anemic patients where the infection can have a severe outcome. As B19V DNA was detected in blood donations from South Brazil during a viral metagenomic survey performed by Next-Generation Sequencing, the objective of this retrospective study was to evaluate the seroprevalence, B19V DNA presence and circulating genotypes in a Hospital Blood Transfusion Service in Santa Maria city in South Brazil (Rio Grande do Sul state). Among 480 volunteer blood donors, 53.9% (n = 258 of 479) were anti-B19V IgG-positive, and 9 (1.9%) plasma samples presented B19V DNA. In almost all cases (n = 7 of 9, 77.8%), B19V DNA load was accompanied by the presence of anti-B19V IgG suggesting a persistent infection. The sequencing of the strains demonstrated that all belong to genotype 1 which is the most prevalent worldwide. The analysis of the recipient information of the positive for B19V DNA units revealed no related posttransfusion adverse effects. Our results demonstrate for the first time, B19V seroprevalence, viral load, and genotypes among blood donors from South Brazil and give a light for the circulation and impact of this B19V in this part of the country.

First identification of a novel parvovirus distantly related to human bufavirus from diarrheal dogs in China

Bufaviruses are small, nonenveloped, single-stranded DNA viruses belonging to the subfamily Parvovirinae. Human bufaviruses were first identified in 2012 in fecal samples from children with diarrhea. A new parvovirus of canines that was first detected in various samples from dogs with enteric and respiratory symptoms in Italy between 2014 and 2018 is closely related to the newly described human bufavirus. To explore the prevalence and genetic diversity of CBuV in Chinese dogs, 540 canine parvovirus (CPV)-positive serum and diarrhea samples were collected in Guangxi Province between 2016 and 2018. Among the samples, 6.25% (5/80) of rectal swabs and 2.5% (5/200) of CPV PCR-positive samples were positive for CBuV. However, the virus was not detected in CPV PCR-negative samples or nasal swabs. Two CBuV isolates were identified from CPV-positive fecal and serum samples by complete sequence analysis, with 99.8%-99.9% NS1 and VP2 protein identity to each another. Sequence analysis indicated that the CBuV GXNN01-2018 isolate VP2 protein shares 99.6% identity with the Italian CBuV ITA/2015/297 isolate and 62.3%-65.5% identity with human bufavirus. Phylogenetic analysis showed that CBuV was significantly distinct from other known bufaviruses and was most closely related to CBuV ITA/2015/297. This is the first report of the existence of CBuV in China, and our findings will strengthen the understanding of the epidemiology of bufaviruses in different animals.

Synthesis of 3-(Imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one Derivatives and Study of Their Antiviral Activity against Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus associated with a wide range of clinical conditions. Currently, there are no recognized antiviral drugs for B19V treatment; therefore, efforts in the search for compounds inhibiting B19V replication are now being pursued. Coumarins (chromen-2-ones) are considered a privileged structure for designing novel orally bioavailable and non-peptidic antiviral agents. To further contribute to the development of new drugs against B19V, our research was focused on the synthesis, characterization and evaluation of antiviral activity of some new 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one derivatives. The effects of the synthesized compounds on cell viability and viral replication were investigated by employing two relevant cellular systems, the myeloblastoid cell line UT7/EpoS1 and primary erythroid progenitor cells (EPCs). Some of the tested compounds showed inhibitory activity both on cell viability and on viral replication, depending on the cellular system. These results suggest that the mechanism involved in biological activity is sensitive to small structural changes and that it is possible to direct the activity of the 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one core.

Endonuclease Activity Inhibition of the NS1 Protein of Parvovirus B19 as a Novel Target for Antiviral Drug Development

Human parvovirus B19 (B19V), a member of the genus Erythroparvovirus of the family Parvoviridae, is a small nonenveloped virus that has a single-stranded DNA (ssDNA) genome of 5.6 kb with two inverted terminal repeats (ITRs). B19V infection often results in severe hematological disorders and fetal death in humans. B19V replication follows a model of rolling hairpin-dependent DNA replication, in which the large nonstructural protein NS1 introduces a site-specific single-strand nick in the viral DNA replication origins, which locate at the ITRs. NS1 executes endonuclease activity through the N-terminal origin-binding domain. Nicking of the viral replication origin is a pivotal step in rolling hairpin-dependent viral DNA replication. Here, we developed a fluorophore-based in vitro nicking assay of the replication origin using the origin-binding domain of NS1 and compared it with the radioactive in vitro nicking assay. We used both assays to screen a set of small-molecule compounds (n = 96) that have potential antinuclease activity. We found that the fluorophore-based in vitro nicking assay demonstrates sensitivity and specificity values as high as those of the radioactive assay. Among the 96 compounds, we identified 8 which have an inhibition of >80% at 10 µM in both the fluorophore-based and radioactive in vitro nicking assays. We further tested 3 compounds that have a flavonoid-like structure and an in vitro 50% inhibitory concentration that fell in the range of 1 to 3 µM. Importantly, they also exhibited inhibition of B19V DNA replication in UT7/Epo-S1 cells and ex vivo-expanded human erythroid progenitor cells.

A Comprehensive RNA-seq Analysis of Human Bocavirus 1 Transcripts in Infected Human Airway Epithelium

Human bocavirus 1 (HBoV1) infects well-differentiated (polarized) human airway epithelium (HAE) cultured at an air-liquid interface (ALI). In the present study, we applied next-generation RNA sequencing to investigate the genome-wide transcription profile of HBoV1, including viral mRNA and small RNA transcripts, in HBoV1-infected HAE cells. We identified novel transcription start and termination sites and confirmed the previously identified splicing events. Importantly, an additional proximal polyadenylation site (pA)p2 and a new distal polyadenylation site (pA)d_REH lying on the right-hand hairpin (REH) of the HBoV1 genome were identified in processing viral pre-mRNA. Of note, all viral nonstructural proteins-encoding mRNA transcripts use both the proximal polyadenylation sites [(pA)p1 and (pA)p2] and distal polyadenylation sites [(pA)d1 and (pA)d_REH] for termination. However, capsid proteins-encoding transcripts only use the distal polyadenylation sites. While the (pA)p1 and (pA)p2 sites were utilized at roughly equal efficiency for proximal polyadenylation of HBoV1 mRNA transcripts, the (pA)d1 site was more preferred for distal polyadenylation. Additionally, small RNA-seq analysis confirmed there is only one viral noncoding RNA (BocaSR) transcribed from nt 5199⁻5340 of the HBoV1 genome. Thus, our study provides a systematic and unbiased transcription profile, including both mRNA and small RNA transcripts, of HBoV1 in HBoV1-infected HAE-ALI cultures.

The 11-Kilodalton Nonstructural Protein of Human Parvovirus B19 Facilitates Viral DNA Replication by Interacting with Grb2 through Its Proline-Rich Motifs

Lytic infection of human parvovirus B19 (B19V) takes place exclusively in human erythroid progenitor cells of bone marrow and fetal liver, which disrupts erythropoiesis. During infection, B19V expresses three nonstructural proteins (NS1, 11-kDa, and 7.5-kDa) and two structural proteins (VP1 and VP2). While NS1 is essential for B19V DNA replication, 11-kDa enhances viral DNA replication significantly. In this study, we confirmed the enhancement role of 11-kDa in viral DNA replication and elucidated the underlying mechanism. We found that 11-kDa specially interacts with cellular growth factor receptor-bound protein 2 (Grb2) during virus infection and in vitro We determined a high affinity interaction between 11-kDa and Grb2 that has an equilibrium dissociation constant (KD ) value of 18.13 nM. In vitro, one proline-rich motif was sufficient for 11-kDa to sustain a strong interaction with Grb2. In consistence, in vivo during infection, one proline-rich motif was enough for 11-kDa to significantly reduce phosphorylation of extracellular signal-regulated kinase (ERK). Mutations of all three proline-rich motifs of 11-kDa abolished its capability to reduce ERK activity and, accordingly, decreased viral DNA replication. Transduction of a lentiviral vector encoding a short hairpin RNA (shRNA) targeting Grb2 decreased the expression of Grb2 as well as the level of ERK phosphorylation, which resulted in an increase of B19V replication. These results, in concert, indicate that the B19V 11-kDa protein interacts with cellular Grb2 to downregulate ERK activity, which upregulates viral DNA replication.IMPORTANCE Human parvovirus B19 (B19V) infection causes hematological disorders and is the leading cause of nonimmunological fetal hydrops during pregnancy. During infection, B19V expresses two structural proteins, VP1 and VP2, and three nonstructural proteins, NS1, 11-kDa, and 7.5-kDa. While NS1 is essential, 11-kDa plays an enhancing role in viral DNA replication. Here, we elucidated a mechanism underlying 11-kDa protein-regulated B19V DNA replication. 11-kDa is tightly associated with cellular growth factor receptor-bound protein 2 (Grb2) during infection. In vitro, 11-kDa interacts with Grb2 with high affinity through three proline-rich motifs, of which at least one is indispensable for the regulation of viral DNA replication. 11-kDa and Grb2 interaction disrupts extracellular signal-regulated kinase (ERK) signaling, which mediates upregulation of B19V replication. Thus, our study reveals a novel mechanism of how a parvoviral small nonstructural protein regulates viral DNA replication by interacting with a host protein that is predominately expressed in the cytoplasm.

Congenital and perinatal infections

Congenital and perinatal infections represent major causes of permanent disability among children worldwide. Linked together by the acronym TORCH, denoting Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes virus, congenital infections can result from only a modest number of human pathogens that cross the placenta and infect the fetus. Although congenital rubella syndrome has been eliminated in the Americas by immunization, several pathogens discussed in this chapter cannot currently be prevented by vaccines or effectively treated with the available antimicrobial drugs. Due to the immaturity of the immune system, newborn infants are at risk for postnatally acquired infections with certain viruses and several bacteria. This chapter summarizes the epidemiology, pathogenesis, clinical manifestations, diagnosis, treatment, and prevention of selected pathogens that can damage the developing nervous system. As emphasized by the persisting challenges of preventing congenital cytomegalovirus infection and the emergence of severe brain damage associated with congenital Zika syndrome, these pathogens remain important causes of cerebral palsy, epilepsy, and intellectual disability.

Modeling the parvovirus B19 blood safety risk in Australia

BACKGROUND

Three probable cases of transfusion-transmitted (TT) parvovirus B19 (B19V) occurred in Australia between 2014 and 2017. This study aimed to determine the B19V DNA prevalence among blood donors, to model the risk to recipients of fresh components, and to assess risk management options.

STUDY DESIGN AND METHODS

Plasma samples from 4232 donors were tested for B19V DNA by polymerase chain reaction. Reactive samples were confirmed and viral load determined. A transmission-risk model was used to estimate recipient risk, and the risk from community exposure was estimated using seroprevalence data.

RESULTS

Two samples (0.0473%, 95% confidence interval [CI] 0.0130-0.172) confirmed positive for B19V DNA had a potentially infectious viral load of 10⁵ IU/mL or higher. The estimated risk of a TT-B19V-associated significant complication was low overall at approximately 1 in 300,000 (95% CI, 1 in 82,000 to 1 in 1 million) fresh components transfused, with 3.1 (95% CI, 0.85-11.3) complications modeled per year. Among vulnerable recipient groups, the risk was higher than 1 in 15,000 patients, but the risk from community exposure far exceeded the transfusion risk for all patient and age groups.

CONCLUSION

In the context of the small contribution of transfusion to the burden of B19V disease, the significant costs that would be incurred by any strategy to reduce the risk, and given the significant uncertainties and likely overestimation of the risk, we conclude TT-B19V is a tolerable risk to blood safety, despite being high for some vulnerable recipient groups.

Seroprevalence of antibodies to primate erythroparvovirus 1 (B19V) in Australia

Backgroud

Primate erythroparvovirus 1 (B19V) is a globally ubiquitous DNA virus. Infection results in a variety of clinical presentations including erythema infectiosum in children and arthralgia in adults. There is limited understanding of the seroprevalence of B19V antibodies in the Australian population and therefore of population-wide immunity. This study aimed to investigate the seroprevalence of B19V antibodies in an Australian blood donor cohort, along with a cohort from a paediatric population.

Methods

Age/sex/geographical location stratified plasma samples (n = 2221) were collected from Australian blood donors. Samples were also sourced from paediatric patients (n = 223) in Queensland. All samples were screened for B19V IgG using an indirect- enzyme-linked immunosorbent assay.

Results

Overall, 57.90% (95% CI: 55.94%–59.85%) of samples tested positive for B19V IgG, with the national age-standardized seroprevalence of B19V exposure in Australians aged 0 to 79 years estimated to be 54.41%. Increasing age (p < 0.001) and state of residence (p < 0.001) were independently associated with B19V exposure in blood donors, with the highest rates in donors from Tasmania (71.88%, 95% CI: 66.95%–76.80%) and donors aged 65–80 years (78.41%, 95% CI: 74.11%–82.71%). A seroprevalence of 52.04% (95% CI: 47.92%–56.15%) was reported in women of child-bearing age (16 to 44 years). Sex was not associated with exposure in blood donors (p = 0.547) or in children (p = 0.261) screened in this study.

Conclusions

This study highlights a clear association between B19V exposure and increasing age, with over half of the Australian population likely to be immune to this virus. Differences in seroprevalence were also observed in donors residing in different states, with a higher prevalence reported in those from the southern states. The finding is consistent with previous studies, with higher rates observed in countries with a higher latitude. This study provides much needed insight into the prevalence of B19V exposure in the Australian population, which has implications for public health as well as transfusion and transplantation safety in Australia.

Changing pattern of prevalence and genetic diversity of rotavirus, norovirus, astrovirus, and bocavirus associated with childhood diarrhea in Asian Russia, 2009-2012

This hospital-based surveillance study was carried out in Novosibirsk, Asian Russia from September 2009 to December 2012. Stool samples from 5486 children with diarrhea and from 339 healthy controls were screened for rotavirus, norovirus, astrovirus, and bocavirus by RT-PCR. At least one enteric virus was found in 2075 (37.8%) cases with diarrhea and 8 (2.4%) controls. In the diarrhea cases, rotavirus was the most commonly detected virus (24.9%), followed by norovirus (13.4%), astrovirus (2.8%) and bocavirus (1.1%). Mixed viral infections were identified in 4.3% cases. The prevalence of enteric viruses varied every season. Rotavirus infection was distributed in a typical seasonal pattern with a significant annual increase from November to May, while infections caused by other viruses showed no apparent seasonality. The most common rotavirus was G4P[8] (56%), followed by G1P[8] (20.1%), G3P[8] (5.5%), G9P[8], G2P[4] (each 1.3%), six unusual (1.2%), and five mixed strains (0.5%). Norovirus GII.3 (66.5%) was predominant, followed by GII.4 (27.3%), GII.6 (3.7%), GII.1 (1.6%), and four rare genotypes (totally, 0.9%). Re-infection with noroviruses of different genotypes was observed in four children. The classic human astrovirus belonged to HAstV-1 (82%), HAstV-5 (8%), HAstV-4 (4.7%), HAstV-3 (4%) and HAstV-2 (1.3%). Consecutive episodes of HAstV-1 and HAstV-4 infections were detected in one child with an 8-month interval. Bocavirus strains were genotyped as HBoV2 (56.5%), HBoV1 (38.7%), HBoV4 (3.2%) and HBoV3 (1.6%). In the controls, norovirus strains belonged to GII.4 (n = 4), GII.1, GII.3, and GII.6, and HBoV2 strain were detected. Most of the detected virus isolates were characterized by a partial sequencing of the genomes. The genotype distribution of most common enteric viruses found in the Asian part of Russia did not differ considerably from their distribution in European Russia in 2009-2012.

Evidence of Human Parvovirus B19 Infection in the Post-Mortem Brain Tissue of the Elderly

After primary exposure, the human parvovirus B19 (B19V) genome may remain in the central nervous system (CNS), establishing a lifelong latency. The structural characteristics and functions of the infected cells are essential for the virus to complete its life cycle. Although B19V has been detected in the brain tissue by sequencing PCR products, little is known about its in vivo cell tropism and pathogenic potential in the CNS. To detect B19V and investigate the distribution of its target cells in the CNS, we studied brain autopsies of elderly subjects using molecular virology, and optical and electron microscopy methods. Our study detected B19V in brain tissue samples from both encephalopathy and control groups, suggesting virus persistence within the CNS throughout the host’s lifetime. It appears that within the CNS, the main target of B19V is oligodendrocytes. The greatest number of B19V-positive oligodendrocytes was found in the white matter of the frontal lobe. The number was significantly lower in the gray matter of the frontal lobe (p = 0.008) and the gray and white matter of the temporal lobes (p < 0.0001). The morphological changes observed in the encephalopathy group, propose a possible B19V involvement in the demyelination process.

A detailed analysis of synonymous codon usage in human bocavirus

Human bocavirus (HBoV) is a recently discovered parvovirus associated with respiratory and gastroenteric infections in children. To date, four distinct subtypes have been identified worldwide. HBoV1 is the most frequently detected bocavirus in clinical samples derived from the respiratory tract. HBoV has a single-stranded DNA genome, which encodes two nonstructural proteins, NS1 and NP1, and two structural proteins, VP1 and VP2. Despite a large number of available HBoV sequences, the molecular evolution of this virus remains enigmatic. Here, we applied bioinformatic methods to measure the codon usage bias in 156 HBoV genomes and analyzed the factors responsible for preferential use of various synonymous codons. The effective number of codons (ENC) indicates a highly conserved, gene-specific codon usage bias in the HBoV genome. The structural genes exhibit a higher degree of codon usage bias than the non-structural genes. Natural selection emerged as dominant factor influencing the codon usage bias in the HBoV genome. Other factors that influence the codon usage include mutational pressure, gene length, protein properties, and the relative abundance of dinucleotides. The results presented in this study provide important insight into the molecular evolution of HBoV and may serve as a primer for HBoV gene expression studies and development of safe and effective vaccines to prevent infection.

Association of the Human Bocavirus With Tonsil Squamous Cell Carcinomas

Background: The human bocavirus (HBoV) is known to persist latently in the infected host cells and seems to replicate its DNA via the DNA damage response system, which is frequently defect in tumors and correlates with microsatellite instability (MSI). Because HBoV is able to persist in the infected tissues, induces pro-fibrotic and pro- cancerogenic cytokines in vivo and in vitro, and is detected in colorectal and lung tumors, the virus may be involved in cancerogenesis at least as a cofactor. Recently it was shown that the adenotonsillar tissue is an important site of HBoV1 persistence and replication. Considering the background that approximately 60% of oropharyngeal cancers were thought to be attributable to a HPV infection, a co-participation of HBoV in terms of a chronic virus infection might play a role in the cancerogenesis of tonsil tumors.

Methods: Formalin-fixed, paraffin-embedded tonsil tumor samples were screened for HBoV and HPV DNA. Positive tissue sections were afterward subjected to fluorescence in situ hybridization (FISH) analysis to identify HBoV and HPV infected cells. By use of an in vitro cell culture model with primary tonsil fibroblasts, keratinocytes, and lymphocytes infected by HBoV we tried to find the target cells of virus replication. MSI testing was based on a previously published protocol using a de-multiplexed PCR followed by fluorescent detection of PCR products in a capillary sequencing device.

Results: In total 62 of 103 (60, 19%) of the tonsil squamous cell carcinomas tested positive for HBoV DNA and 66 of 103 (66%) samples were identified as HPV positive. The FISH analysis revealed both double infection of HPV and HBoV in the same cells as well as single infections of both viruses within the tumor tissue. Twenty-two of 62 HBoV positive tumors tested HPV negative, 40 of 62 tissue sections were HBoV and HPV positive. We analyzed 21 out of the 62 HBoV positive tumors for MSI. Of those four tonsils displayed MSI in at least 1 of 10 microsatellite markers.

Conclusion: Our findings support the hypothesis that human bocavirus infections as a cofactor may have an impact on tumor development in tonsils, although it still remains possible that HBoV solely displays a tumor tropism.

The 5' Untranslated Region of Human Bocavirus Capsid Transcripts Regulates Viral mRNA Biogenesis and Alternative Translation

Alternative translation of HBoV1 capsid mRNAs is vital for the viral life cycle, as capsid proteins perform essential functions in genome packaging, assembly, and antigenicity. The 5′ untranslated regions (UTRs) of capsid mRNAs are generated by alternative splicing, and they contain different exons. Our study shows that the 5′ UTR not only modulates mRNA abundance but also regulates capsid expression. Two upstream ATGs (uATGs) that were upstream of the capsid translation initiation site in the 5′ UTR were found to affect viral capsid mRNA polyadenylation, alternative translation, and progeny virus production. The results reveal that uATGs play an important role in the viral life cycle and represent a new layer to regulate HBoV1 RNA processing, which could be a target for gene therapy.

The capsid mRNA transcripts of human bocavirus 1 (HBoV1) can be generated by alternative splicing from the mRNA precursor transcribed from the P5 promoter. However, the alternative translation regulation mechanism of capsid mRNA transcripts is largely unknown. Here we report that the polycistronic capsid mRNA transcripts encode VP1, VP2, and VP3 in vitro and in vivo. The 5′ untranslated regions (UTRs) of capsid mRNA transcripts, which consist of exons, affected not only the abundance of mRNA but also the translation pattern of capsid proteins. Further study showed that exons 2 and 3 were critical for the abundance of mRNA, while exon 4 regulated capsid translation. Alternative translation of capsid mRNA involved a leaky scan mechanism. Mutating the upstream ATGs (uATGs) located in exon 4 resulted in more mRNA transcripts polyadenylated at the proximal polyadenylation [(pA)p] site, leading to increased capsid mRNA transcripts. Moreover, uATG mutations induced more VP1 expression, while VP3 expression was decreased, which resulted in less progeny virus production. Our data show that the 5′ UTR of HBoV1 plays a critical role in the modulation of mRNA abundance, alternative RNA processing, alternative translation, and progeny virus production.

IMPORTANCE Alternative translation of HBoV1 capsid mRNAs is vital for the viral life cycle, as capsid proteins perform essential functions in genome packaging, assembly, and antigenicity. The 5′ untranslated regions (UTRs) of capsid mRNAs are generated by alternative splicing, and they contain different exons. Our study shows that the 5′ UTR not only modulates mRNA abundance but also regulates capsid expression. Two upstream ATGs (uATGs) that were upstream of the capsid translation initiation site in the 5′ UTR were found to affect viral capsid mRNA polyadenylation, alternative translation, and progeny virus production. The results reveal that uATGs play an important role in the viral life cycle and represent a new layer to regulate HBoV1 RNA processing, which could be a target for gene therapy.

Selective activation of inflammation factors by human parvovirus B19 and human bocavirus VP1 unique region on H9c2 cardiomyocyte

Human parvovirus B19 (B19) and human bocavirus 1 (HBoV) are the only known pathogenic parvoviruses, and are responsible for a variety of diseases in human beings. Mounting evidence indicates a strong association between B19 infection and cardiac disorders including myocarditis, dilated cardiomyopathy and heart failure. However, very limited information about the role of HBoV in cardiac disorders is known. To elucidate the effects of B19 and HBoV on cardiac disorders, we expressed EGFP‑conjugate constructs of B19‑VP1 unique region (VP1u) and HBoV‑VP1u, along with the mutants EGFP‑B19‑VP1uD175A and EGFP‑HBoV‑VP1uV12A, in H9c2 cells by stable transfection. The protein expression levels of EGFP, EGFP‑B19‑VP1u, EGFP‑B19‑VP1uD175A, EGFP‑HBoV‑VP1u and EGFP‑HBoV‑VP1uV12A in H9c2 cells were observed under a fluorescence microscope and confirmed by western blotting. Secreted phospholipase A2 (sPLA2) activity was detected in B19‑VP1u and HBoV‑VP1u but not B19‑VP1uD175A and HBoV‑VP1uV12A recombinant proteins. Significantly higher expression levels of MCP2 and IP‑10 mRNA were detected in H9c2 cells that were transfected with pEGFP‑B19‑VP1u, compared with in those cells transfected with pEGFP‑HBoV‑VP1u, pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. Significantly higher protein levels of IL‑1β and IL‑6 were detected in H9c2 cells transfected with pEGFP‑B19‑VP1u or pEGFP‑HBoV‑VP1u, compared with in those cells transfected with pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. Notably, significantly higher expression of both TNF‑α and NF‑κB was observed only in H9c2 cells transfected with pEGFP‑B19‑VP1u, but not in those cells transfected with pEGFP‑HBoV‑VP1u, pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. These findings, to our knowledge for the first time, reveal the difference between B19‑VP1u and HBoV‑VP1u in H9c2 cells and provide insight into the roles of B19‑VP1u and HBoV‑VP1u in the pathogenesis of cardiac inflammation.

Congenital Viral Infection: Traversing the Uterine-Placental Interface

Why certain viruses cross the physical barrier of the human placenta but others do not is incompletely understood. Over the past 20 years, we have gained deeper knowledge of intrauterine infection and routes of viral transmission. This review focuses on human viruses that replicate in the placenta, infect the fetus, and cause birth defects, including rubella virus, varicella-zoster virus, parvovirus B19, human cytomegalovirus (CMV), Zika virus (ZIKV), and hepatitis E virus type 1. Detailed discussions include ( a) the architecture of the uterine-placental interface, ( b) studies of placental explants ex vivo that provide insights into the infection and spread of CMV and ZIKV to the fetal compartment and how these viruses undermine early development, and ( c) novel treatments and vaccines that limit viral replication and have the potential to reduce dissemination, vertical transmission and the occurrence of congenital disease.

Epidemiology of HBoV1 infection and relationship with meteorological conditions in hospitalized pediatric patients with acute respiratory illness: a 7-year study in a subtropical region

BACKGROUND

Human bocavirus 1 (HBoV1) is an important cause of acute respiratory illness (ARI), yet the epidemiology and effect of meteorological conditions on infection is not fully understood. To investigate the distribution of HBoV1 and determine the effect of meteorological conditions, hospitalized pediatric patients were studied in a subtropical region of China.

METHODS

Samples from 11,399 hospitalized pediatric patients (≤14 years old), with ARI were tested for HBoV1 and other common respiratory pathogens using real-time PCR, between July 2009 and June 2016. In addition, local meteorological data were collected.

RESULTS

Of the 11,399 patients tested, 5606 (49.2%) were positive for at least one respiratory pathogen. Two hundred forty-eight of 11,399 (2.2%) were positive for HBoV1 infection. Co-infection was common in HBoV1-positive patients (45.2%, 112/248). A significant difference in the prevalence of HBoV1 was found in patients in different age groups (p < 0.001), and the peak prevalence was found in patients aged 7-12 months (4.7%, 56/1203). Two HBoV1 prevalence peaks were found in summer (between June and September) and winter (between November and December). The prevalence of HBoV1 was significantly positively correlated with mean temperature and negatively correlated with mean relative humidity, and the mean temperature in the preceding month had better explanatory power than the current monthly temperature.

CONCLUSIONS

This study provides a better understanding of the characteristics of HBoV1 infection in children in subtropical regions. Data from this study provide useful information for the future control and prevention of HBoV1 infections.

Possible risks posed by single-stranded DNA viruses of pigs associated with xenotransplantation

Routine large-scale xenotransplantation from pigs to humans is getting closer to clinical reality owing to several state-of-the-art technologies, especially the ability to rapidly engineer genetically defined pigs. However, using pig organs in humans poses risks including unwanted cross-species transfer of viruses and adaption of these pig viruses to the human organ recipient. Recent developments in the field of virology, including the advent of metagenomic techniques to characterize entire viromes, have led to the identification of a plethora of viruses in many niches. Single-stranded DNA (ssDNA) viruses are the largest group prevalent in virome studies in mammals. Specifically, the ssDNA viral genomes are characterized by a high rate of nucleotide substitution, which confers a proclivity to adapt to new hosts and cross-species barriers. Pig-associated ssDNA viruses include torque teno sus viruses (TTSuV) in the Anelloviridae family, porcine parvoviruses (PPV), and porcine bocaviruses (PBoV) both in the family of Parvoviridae, and porcine circoviruses (PCV) in the Circoviridae family, some of which have been confirmed to be pathogenic to pigs. The risks of these viruses for the human recipient during xenotransplantation procedures are relatively unknown. Based on the scant knowledge available on the prevalence, predilection, and pathogenicity of pig-associated ssDNA viruses, careful screening and monitoring are required. In the case of positive identification, risk assessments and strategies to eliminate these viruses in xenotransplantation pig stock may be needed.

Recent Advances in Replication and Infection of Human Parvovirus B19

Parvovirus B19 (B19V) is pathogenic to humans and causes bone marrow failure diseases and various other inflammatory disorders. B19V infection exhibits high tropism for human erythroid progenitor cells (EPCs) in the bone marrow and fetal liver. The exclusive restriction of B19V replication to erythroid lineage cells is partly due to the expression of receptor and co-receptor(s) on the cell surface of human EPCs and partly depends on the intracellular factors essential for virus replication. We first summarize the latest developments in the viral entry process and the host cellular factors or pathways critical for B19V replication. We discuss the role of hypoxia, erythropoietin signaling and STAT5 activation in the virus replication. The B19V infection-induced DNA damage response (DDR) and cell cycle arrest at late S-phase are two key events that promote B19V replication. Lately, the virus infection causes G2 arrest, followed by the extensive cell death of EPCs that leads to anemia. We provide the current understanding of how B19V exploits the cellular resources and manipulate pathways for efficient virus replication. B19V encodes a single precursor mRNA (pre-mRNA), which undergoes alternate splicing and alternative polyadenylation to generate at least 12 different species of mRNA transcripts. The post-transcriptional processing of B19V pre-mRNA is tightly regulated through cis-acting elements and trans-acting factors flanking the splice donor or acceptor sites. Overall, in this review, we focus on the recent advances in the molecular virology and pathogenesis of B19V infection.

Identification and characterization of a novel rodent bocavirus from different rodent species in China

Members in the genus Bocaparvovirus are closely related to human health and have a wide host range. The diverse hosts raise the possibility of crossing species barrier, which is a feature of emerging viruses. Among the mammalian hosts, rodents are generally acknowledged to be important reservoirs of emerging viruses. Here, rodent samples collected from six provinces and autonomous regions of China (Liaoning, Inner Mongolia, Tibet, Xinjiang, Guangxi and Yunnan) were used to investigate the prevalence and distribution of bocaparvoviruses. By using next-generation sequencing first, a partial non-structural protein 1 (NS1) gene belonging to a possible novel bocaparvovirus was discovered. Following this, PCR-based screening of NS1 gene was conducted in 485 rodent samples, with 106 positive results found in seven rodent species (Rattus norvegicus, Mus musculus, Apodemus agrarius, Cricetulus barabensis, Rattus flavipectus, Rattus rattus and Rhombomys opimus). Finally, six nearly full-length genomes and three complete CDS were obtained and the newly identified bocaparvovirus was tentatively named rodent bocavirus (RoBoV). RoBoV has three ORFs: NS1, NP1, and VP, which are characteristics of bocaparvoviruses. Phylogenetic analyses revealed that porcine bocavirus isolate PBoV-KU14, a member of Ungulate bocaparvovirus 4, was the most related virus to RoBoV, with 92.1-92.9% amino acid identities in NS1 protein. Alignments of RoBoV-related sequences showed RoBoV isolates could be classified into two clades, demonstrating an inter-host genetic diversity. The results indicate a potential interspecies transmission of RoBoV between rodents and swine and expand our knowledge on bocaparvoviruses in rodent populations.

RNA Binding Protein RBM38 Regulates Expression of the 11-Kilodalton Protein of Parvovirus B19, Which Facilitates Viral DNA Replication

Human parvovirus B19 (B19V) expresses a single precursor mRNA (pre-mRNA), which undergoes alternative splicing and alternative polyadenylation to generate 12 viral mRNA transcripts that encode two structural proteins (VP1 and VP2) and three nonstructural proteins (NS1, 7.5-kDa protein, and 11-kDa protein). Splicing at the second 5' donor site (D2 site) of the B19V pre-mRNA is essential for the expression of VP2 and the 11-kDa protein. We previously identified that cis-acting intronic splicing enhancer 2 (ISE2) that lies immediately after the D2 site facilitates the recognition of the D2 donor for its efficient splicing. In this study, we report that ISE2 is critical for the expression of the 11-kDa viral nonstructural protein. We found that ISE2 harbors a consensus RNA binding motif protein 38 (RBM38) binding sequence, 5'-UGUGUG-3'. RBM38 is expressed during the middle stage of erythropoiesis. We first confirmed that RBM38 binds specifically with the ISE2 element in vitro The knockdown of RBM38 significantly decreases the level of spliced mRNA at D2 that encodes the 11-kDa protein but not that of the D2-spliced mRNA that encodes VP2. Importantly, we found that the 11-kDa protein enhances viral DNA replication and virion release. Accordingly, the knockdown of RBM38 decreases virus replication via downregulating 11-kDa protein expression. Taken together, these results suggest that the 11-kDa protein facilitates B19V DNA replication and that RBM38 is an essential host factor for B19V pre-mRNA splicing and for the expression of the 11-kDa protein.IMPORTANCE B19V is a human pathogen that can cause fifth disease, arthropathy, anemia in immunocompromised patients and sickle cell disease patients, myocarditis, and hydrops fetalis in pregnant women. Human erythroid progenitor cells (EPCs) are most susceptible to B19V infection and fully support viral DNA replication. The exclusive tropism of B19V for erythroid-lineage cells is dependent not only on the expression of viral receptors and coreceptors on the cell surface but also on the intracellular host factors that support B19V replication. Our present study shows that B19V uses a host factor, RNA binding motif protein 38 (RBM38), for the processing of its pre-mRNA during virus replication. Specifically, RBM38 interacts with the intronic splicing enhancer 2 (ISE2) element of B19V pre-mRNA and promotes 11-kDa protein expression, thereby regulating the 11-kDa protein-mediated augmentation of B19V replication. The identification of this novel host-pathogen interaction will provide mechanistic insights into B19V replication and aid in finding new targets for anti-B19V therapeutics.

DNA indicative of human bocaviruses detected in non-human primates in the Democratic Republic of the Congo

Bocaparvoviruses are members of the family Parvovirinae and human bocaviruses have been found to be associated with respiratory and gastrointestinal disease. There are four known human bocaviruses, as well as several distinct ones in great apes. The goal of the presented study was to detect other non-human primate (NHP) bocaviruses in NHP species in the Democratic Republic of the Congo using conventional broad-range PCR. We found bocavirus DNA in blood and tissues samples in 6 out of 620 NHPs, and all isolates showed very high identity (>97 %) with human bocaviruses 2 or 3. These findings suggest cross-species transmission of bocaviruses between humans and NHPs.

Novel Parvoviruses from Wild and Domestic Animals in Brazil Provide New Insights into Parvovirus Distribution and Diversity

Parvoviruses (family Parvoviridae) are small, single-stranded DNA viruses. Many parvoviral pathogens of medical, veterinary and ecological importance have been identified. In this study, we used high-throughput sequencing (HTS) to investigate the diversity of parvoviruses infecting wild and domestic animals in Brazil. We identified 21 parvovirus sequences (including twelve nearly complete genomes and nine partial genomes) in samples derived from rodents, bats, opossums, birds and cattle in Pernambuco, São Paulo, Paraná and Rio Grande do Sul states. These sequences were investigated using phylogenetic and distance-based approaches and were thereby classified into eight parvovirus species (six of which have not been described previously), representing six distinct genera in the subfamily Parvovirinae. Our findings extend the known biogeographic range of previously characterized parvovirus species and the known host range of three parvovirus genera (Dependovirus, Aveparvovirus and Tetraparvovirus). Moreover, our investigation provides a window into the ecological dynamics of parvovirus infections in vertebrates, revealing that many parvovirus genera contain well-defined sub-lineages that circulate widely throughout the world within particular taxonomic groups of hosts.

Selected Viruses Detected on and in our Food

PURPOSE OF REVIEW

The purpose of this review is to provide an update on recent literature and findings concerning selected foodborne viruses. Two groups of viruses were selected: (a) the most important viruses contaminating food, based on numbers of publications in the last 5 years and (b) viruses infecting sources of food that might have an impact on human health.

RECENT FINDINGS

Important foodborne viruses such as norovirus, hepatitis A and rotavirus are usually "only" contaminating food and are detected on the surface of foodstuffs. However, they are threats to human public health and make up for the majority of cases. In contrast, the meaning of viruses born from within the food such as natural animal and plant viruses is still in many cases unknown. An exception is Hepatitis E virus that is endemic in pigs, transmitted via pork meat and is recognised as an emerging zoonosis in industrialised countries.

SUMMARY

Even though the clinical meaning of "new" foodborne viruses, often detected by next generation sequencing, still needs clarification, the method has great potential to enhance surveillance and detection particularly in view of an increasingly globalised food trade.

Detection of Human Bocavirus Species 2 and 3 in Bivalve Shellfish in Italy

Human bocavirus (HBoV) has been shown to be a common cause of respiratory infections and gastroenteritis in children. Recently, HBoVs have been detected in sewage and river waters in Italy and worldwide. However, studies on their presence in other water environments and in bivalve mollusks are not yet available. In this study, 316 bivalve shellfish samples collected in three Italian regions over a 6-year period (2012 to 2017) were analyzed by nested PCR and sequencing using broad-range primer pairs targeting the capsid proteins VP1 and VP2 of HBoV. The virus was detected in 27 samples (8.5% of the total samples), and a statistically significant difference was found within the three regions. A further 13 samples, collected in geographic and temporal proximity to positive samples, were included in the study to assess the spread of HBoV in shellfish production areas at the time of contamination. Twelve of these additional samples were found to be positive for HBoV. All positive samples in this study were characterized as HBoV species 2 (17 samples; 8 different sequences) or species 3 (22 samples; 4 different sequences). This study reports the occurrence of HBoV in bivalve shellfish and shows evidence of considerable spatial spread of the virus throughout shellfish production areas. Further studies are needed to elucidate both the role of HBoV as an agent of gastroenteritis and the risk for foodborne transmission of this virus.IMPORTANCE Human bocavirus is recognized as an important cause of acute respiratory tract infections and has recently been considered an etiological agent of gastroenteritis in the pediatric population. Our findings document that HBoVs are detected in bivalve shellfish with a relevant prevalence and suggest that an assessment of the risk for foodborne transmission of these viruses should be undertaken.

Mahfouz M, Zytouni DM. Detection of human bocavirus in Saudi healthy blood donors

Human bocavirus is associated with respiratory disease worldwide, mainly in children. There are conflicting results, however, regarding the existence of the HBoV in blood donors. Three hundred whole blood samples from non-immunodeficient healthy blood donors were screened for the presence of HBoV by polymerase chain reaction. The HBoV genotype of positive samples was determined using direct gene sequencing. Twenty-one out of the three hundred blood samples were found to be positive for HBoV. Sequence analysis of the positive samples revealed that all the strains were related to the HBoV-1 type with a low rate of variation among the detected sequences. It was concluded that there is a considerable risk of contracting HBoV from a blood transfusion from normal healthy individuals.

Human Parvovirus B19 Utilizes Cellular DNA Replication Machinery for Viral DNA Replication

Human parvovirus B19 (B19V) infection of human erythroid progenitor cells (EPCs) induces a DNA damage response and cell cycle arrest at late S phase, which facilitates viral DNA replication. However, it is not clear exactly which cellular factors are employed by this single-stranded DNA virus. Here, we used microarrays to systematically analyze the dynamic transcriptome of EPCs infected with B19V. We found that DNA metabolism, DNA replication, DNA repair, DNA damage response, cell cycle, and cell cycle arrest pathways were significantly regulated after B19V infection. Confocal microscopy analyses revealed that most cellular DNA replication proteins were recruited to the centers of viral DNA replication, but not the DNA repair DNA polymerases. Our results suggest that DNA replication polymerase δ and polymerase α are responsible for B19V DNA replication by knocking down its expression in EPCs. We further showed that although RPA32 is essential for B19V DNA replication and the phosphorylated forms of RPA32 colocalized with the replicating viral genomes, RPA32 phosphorylation was not necessary for B19V DNA replication. Thus, this report provides evidence that B19V uses the cellular DNA replication machinery for viral DNA replication.IMPORTANCE Human parvovirus B19 (B19V) infection can cause transient aplastic crisis, persistent viremia, and pure red cell aplasia. In fetuses, B19V infection can result in nonimmune hydrops fetalis and fetal death. These clinical manifestations of B19V infection are a direct outcome of the death of human erythroid progenitors that host B19V replication. B19V infection induces a DNA damage response that is important for cell cycle arrest at late S phase. Here, we analyzed dynamic changes in cellular gene expression and found that DNA metabolic processes are tightly regulated during B19V infection. Although genes involved in cellular DNA replication were downregulated overall, the cellular DNA replication machinery was tightly associated with the replicating single-stranded DNA viral genome and played a critical role in viral DNA replication. In contrast, the DNA damage response-induced phosphorylated forms of RPA32 were dispensable for viral DNA replication.

Parvovirus B19 Infection in a Fatal Case of Acute Liver Failure

B19V has been proposed as an etiologic agent for hepatitis, mainly in children, but this is a rare clinical occurrence. In this article, we report a case of non-A-E acute liver failure in an immunocompetent child with B19 infection. The clinical findings of severe anemia and pancytopenia combined with the detection of anti-B19 Immunoglobulin G (IgG), B19 DNA and B19 mRNA in liver indicate a persistent infection and suggest a diagnosis of parvovirus B19-associated acute liver failure.

Human Parvovirus Infection of Human Airway Epithelia Induces Pyroptotic Cell Death by Inhibiting Apoptosis

Human bocavirus 1 (HBoV1) is a human parvovirus that causes acute respiratory tract infections in young children. In this study, we confirmed that, when polarized/well-differentiated human airway epithelia are infected with HBoV1 in vitro, they develop damage characterized by barrier function disruption and cell hypotrophy. Cell death mechanism analyses indicated that the infection induced pyroptotic cell death characterized by caspase-1 activation. Unlike infections with other parvoviruses, HBoV1 infection did not activate the apoptotic or necroptotic cell death pathway. When the NLRP3-ASC-caspase-1 inflammasome-induced pathway was inhibited by short hairpin RNA (shRNA), HBoV1-induced cell death dropped significantly; thus, NLRP3 mediated by ASC appears to be the pattern recognition receptor driving HBoV1 infection-induced pyroptosis. HBoV1 infection induced steady increases in the expression of interleukin 1α (IL-1α) and IL-18. HBoV1 infection was also associated with the marked expression of the antiapoptotic genes BIRC5 and IFI6 When the expression of BIRC5 and/or IFI6 was inhibited by shRNA, the infected cells underwent apoptosis rather than pyroptosis, as indicated by increased cleaved caspase-3 levels and the absence of caspase-1. BIRC5 and/or IFI6 gene inhibition also significantly reduced HBoV1 replication. Thus, HBoV1 infection of human airway epithelial cells activates antiapoptotic proteins that suppress apoptosis and promote pyroptosis. This response may have evolved to confer a replicative advantage, thus allowing HBoV1 to establish a persistent airway epithelial infection. This is the first report of pyroptosis in airway epithelia infected by a respiratory virus.IMPORTANCE Microbial infection of immune cells often induces pyroptosis, which is mediated by a cytosolic protein complex called the inflammasome that senses microbial pathogens and then activates the proinflammatory cytokines IL-1 and IL-18. While virus-infected airway epithelia often activate NLRP3 inflammasomes, studies to date suggest that these viruses kill the airway epithelial cells via the apoptotic or necrotic pathway; involvement of the pyroptosis pathway has not been reported previously. Here, we show for the first time that virus infection of human airway epithelia can also induce pyroptosis. Human bocavirus 1 (HBoV1), a human parvovirus, causes lower respiratory tract infections in young children. This study indicates that HBoV1 kills airway epithelial cells by activating genes that suppress apoptosis and thereby promote pyroptosis. This strategy appears to promote HBoV1 replication and may have evolved to allow HBoV1 to establish persistent infection of human airway epithelia.