Human bocavirus-the first 5 years

B cell immune response to human bocaviruses

BACKGROUND

Human bocaviruses (HBoVs) have been demonstrated in respiratory and gastrointestinal infections; however, the immune response to them has not been studied in detail. In this study, we investigated the B cell immune responses to HBoV1 and HBoV2, representing two different species of bocaviruses in humans.

METHODS

We analyzed the effects of stimulations with HBoV1 and 2 virus-like particles (VLPs) and of co-stimulation with HBoV1-rhinovirus (RV) on cells of the immune system by flow cytometry, transcriptomics, and luminometric immune assays.

RESULTS

Human B cells, and particularly B regulatory cells (Breg cells), showed an increased immune response to HBoV1-VLPs stimulation. These immune responses were also supported by increased IL-1RA and PDL1 expressions in IL-10+ B cells from peripheral blood mononuclear cells (PBMCs) stimulated with HBoV1-VLPs. In addition, increased levels of IL-10 and IL-1RA were determined in the supernatants of PBMCs following HBoV1-VLPs stimulation. HBoV1-VLPs and RV co-stimulation increased the IL-10+ B cell population. Transcriptome analysis by next-generation RNA sequencing showed an increased expression of IL-10 signalling and Breg cell markers in PBMCs stimulated with HBoV1-VLPs. Furthermore, TGF-β and chemoattractants MIP-1α, MIP-1β and IP10 protein levels were high in the supernatants of PBMCs stimulated with HBoV1-VLPs.

CONCLUSIONS

The findings demonstrate that in Breg cells, IL-10 signalling pathways, and anti-inflammatory activity are induced by HBoV1, which can explain the often mild nature of the disease. In addition, the immune regulatory response induced by HBoV1-VLPs may indicate a potential immunomodulatory role of HBoV1 on the immune system and may represent an immune regulatory strategy.

Human Bocavirus in Childhood: A True Respiratory Pathogen or a "Passenger" Virus? A Comprehensive Review

Recently, human bocavirus (HBoV) has appeared as an emerging pathogen, with an increasing number of cases reported worldwide. HBoV is mainly associated with upper and lower respiratory tract infections in adults and children. However, its role as a respiratory pathogen is still not fully understood. It has been reported both as a co-infectious agent (predominantly with respiratory syncytial virus, rhinovirus, parainfluenza viruses, and adenovirus), and as an isolated viral pathogen during respiratory tract infections. It has also been found in asymptomatic subjects. The authors review the available literature on the epidemiology of HBoV, the underlying risk factors associated with infection, the virus's transmission, and its pathogenicity as a single pathogen and in co-infections, as well as the current hypothesis about the host's immune response. An update on different HBoV detection methods is provided, including the use of quantitative single or multiplex molecular methods (screening panels) on nasopharyngeal swabs or respiratory secretions, tissue biopsies, serum tests, and metagenomic next-generations sequencing in serum and respiratory secretions. The clinical features of infection, mainly regarding the respiratory tract but also, though rarely, the gastrointestinal one, are extensively described. Furthermore, a specific focus is dedicated to severe HBoV infections requiring hospitalization, oxygen therapy, and/or intensive care in the pediatric age; rare fatal cases have also been reported. Data on tissue viral persistence, reactivation, and reinfection are evaluated. A comparison of the clinical characteristics of single infection and viral or bacterial co-infections with high or low HBoV rates is carried out to establish the real burden of HBoV disease in the pediatric population.

Comparison of MT-PCR with Quantitative PCR for Human Bocavirus in Respiratory Samples with Multiple Respiratory Viruses Detection

Human bocavirus (HBoV) is an important respiratory pathogen, especially in children, but it is often found in co-detection with other respiratory viruses, which makes the diagnostic approach challenging. We compared multiplex PCR and quantitative PCR for HBoV with multiplex tandem PCR (MT-PCR) in 55 cases of co-detection of HBoV and other respiratory viruses. In addition, we investigated whether there is a connection between the severity of the disease, measured by the localization of the infection, and amount of virus detected in the respiratory secretions. No statistically significant difference was found, but children with large amount of HBoV and other respiratory virus had a longer stay in hospital.

Human bocavirus-1 infections in Australian children aged < 2 years: a birth cohort study

To determine human bocavirus-1 (HBoV1) infection characteristics in young Australian children. Data were from the Observational Research in Childhood Infectious Diseases (ORChID) study, a Brisbane, Australia-based birth cohort of healthy, term, newborns followed prospectively for 2 years. Parents recorded daily symptoms, maintained an illness-burden diary, and collected weekly nasal swabs, which were tested for 17 respiratory viruses, including HBoV1, by real-time polymerase chain reaction (PCR) assays. Main outcomes measured were infection incidence, risk factors, symptoms, and healthcare use. One hundred fifty-eight children in the ORChID cohort provided 11,126 weekly swabs, of which 157 swabs were HBoV1 positive involving 107 incident episodes. Co-detections were observed in 65/157 (41.4%) HBoV1-positive swabs (or 41/107 [38.3%] infection episodes), principally with rhinovirus. Shedding duration was 1 week in 64.5% of episodes. The incidence of HBoV1 infections in the first 2 years of life was 0.58 episodes per child-year (95% confidence interval [CI] 0.47-0.71), including 0.38 episodes per child-year (95% CI 0.30-0.49) associated with respiratory symptoms. Recurrent episodes occurred in 18/87 (20.7%) children following their primary infection. In the first 2 years of life, incidence of HBoV1 episodes increased with age, during winter and with childcare attendance. Overall, 64.2% of HBoV1 episodes were symptomatic, with 26.4% having healthcare contact. Viral load estimates were higher when children were symptomatic than when asymptomatic (mean difference = 3.4; 95% CI 1.0-5.7 PCR cycle threshold units). After age 6 months, HBoV1 is detected frequently in the first 2 years of life, especially during winter. Symptoms are usually mild and associated with higher viral loads.

Epidemiologic and clinical characteristics of human bocavirus infection in children hospitalized for acute respiratory tract infection in Qingdao, China

Persistent infection and prolonged shedding of human bocavirus 1 (HBoV1) in children have been reported, and the role of HBoV1 as a sole causative pathogen in acute respiratory infection (ARI) is yet to be established. While the reported prevalence of HBoV infection varies due to different detection methods and sampling criteria, determining the viral and bacterial etiology of HBoV infection using multiplex real-time PCR is yet to be reported. Herein, we aimed to further explore the pathogenicity of HBoV in patients with ARI by screening the viral and bacterial infections in children with ARI in Qingdao and comparing the epidemiological, clinical characteristics, and etiological results. Human bocavirus was identified in 28.1% of the samples, and further sequencing analysis of the detected HBoV confirmed 96.4% as HBoV1. The rate of HBoV as a single viral infection was 75%, and the rate of coinfection with bacteria was 66.1%, suggesting the need for continued monitoring of HBoV in children with ARIs. Clinical characterization suggested that HBoV infection may affect the function of organs, such as the liver, kidney, and heart, and the blood acid–base balance. Additionally, it is essential to promote awareness about the importance of disinfection and sterilization of the hospital environment and standardizing operations. The interactions between HBoV and other pathogens remain to be investigated in further detail in the future.

Human bocavirus 1 is a genuine pathogen for acute respiratory tract infection in pediatric patients determined by nucleic acid, antigen, and serology tests

Background

Human bocavirus 1 (HBoV1), first discovered in 2005, was positive in symptomatic and healthy children and co-detected with other respiratory viruses. It is a long journey to decisively demonstrate the unique viral pathogenic function of acute respiratory tract infection (ARTI) in pediatric patients.

Methods

Respiratory specimens collected from pediatric patients with ARTI from January 2017 to December 2021 were screened by a capillary electrophoresis-based multiplex PCR (CEMP) assay, then genotyped by PCR and sequencing for HBoV1. For the antigen test, a part of HBoV1 DNA positive nasopharyngeal aspirates (NPAs) was used as an antigen, while a rabbit anti-HBoV1 DR2 specific to HBoV1 was used as an antibody in the indirect-immunofluorescence assay (IFA). Finally, the levels of IgG specific to HBoV1 in acute and convalescent sera selected retrospectively from only HBoV1 DNA-positive patients were evaluated by IFA.

Results

Among 9,899 specimens, 681 were positive for HBoV1 DNA (6.88%, 681/9899), which included 336 positives only for HBoV1 (49.34%, 336/681) and 345 (50.66%, 345/681) positives also for other pathogens. In the antigen test, there were 37 among 47 NPAs determined as HBoV1 antigen-positive (78.72%, 37/47), including 18 (48.65%, 18/37) positives solely for HBoV1 DNA. Among 4 pediatric patients with both acute and convalescent sera, there was one positive for HBoV1 antigen (D8873) and 2 lack the antigen results (D1474 and D10792), which showed seroconversion with a ≥ 4-fold increase in IgG levels.

Conclusions

The combination results of nucleic acid, antigen, and serology tests answered that HBoV1 is a genuine pathogen for ARTI in pediatric patients.

A STUDY OF THE NOVEL WU AND KI POLYOMAVIRUSES, BOCAVIRUS ADENOVIRUS IN CHILDREN WITH UPPER RESPIRATORY TRACT INFECTIONS

OBJECTIVE

The aim: To find out the frequency of WU and KI polyomaviruses, and Human Boca and Adenoviruses infections among children with different types of acute upper respiratory tract infections and to compare the frequency of these viruses among immune-competent and immune compromised patients.

PATIENTS AND METHODS

Materials and methods: A case-control study conducted in children aged 3-18 years with acute upper respiratory tract infections. The samples were taken from: Group 1: 100 immuno competent children with acute upper respiratory tract infections. Group 2: 100 immuno compromised children (Leukemic, cancer, Nephrotic syndrome, chronic renal failure and children with renal transplant) with acute upper respiratory tract infections. Group 3: 100 apparently healthy children without respiratory infections as control group. Nasal swap samples were collected from children and then viral DNA extracted from these samples. Then detection of WU, KI polyomaviruses HBoV and HAdv was done by using real time PCR.

RESULTS

Results: All of 300 samples were negative for WU and KI polyomaviruses. However, human Bocavirus was detected in the three groups (immunocompromised, immunocompetent and control group) and the positivity rates were 61.61%, 37.37% and 18.18%, respectively. While human adenovirus was found only in 2% of immunocompromised patients and 1.1% of immunocompetent patients also there were cases positive for both HBoV and HAdv in 5.5% of immunocompromised patients, and 8.8% of immunocompetent patients.

CONCLUSION

Conclusions: High frequency of HBoV especially in immunocompromised patients while low number of positive cases for HAdv by using nasal swab samples, WU and KI polyomaviruses could not be detected in samples.

The small nonstructural protein NP1 of human bocavirus 1 directly interacts with Ku70 and RPA70 and facilitates viral DNA replication

Human bocavirus 1 (HBoV1), a member of the genus Bocaparvovirus of the family Parvoviridae, causes acute respiratory tract infections in young children. Well-differentiated pseudostratified human airway epithelium cultured at an air-liquid interface (HAE-ALI) is an ideal in vitro culture model to study HBoV1 infection. Unique to other parvoviruses, bocaparvoviruses express a small nonstructured protein NP1 of ~25 kDa from an open reading frame (ORF) in the center of the viral genome. NP1 plays an important role in viral DNA replication and pre-mRNA processing. In this study, we performed an affinity purification assay to identify HBoV1 NP1-inteacting proteins. We identified that Ku70 and RPA70 directly interact with the NP1 at a high binding affinity, characterized with an equilibrium dissociation constant (KD) of 95 nM and 122 nM, respectively. Furthermore, we mapped the key NP1-interacting domains of Ku70 at aa266-439 and of RPA70 at aa181-422. Following a dominant negative strategy, we revealed that the interactions of Ku70 and RPA70 with NP1 play a significant role in HBoV1 DNA replication not only in an in vitro viral DNA replication assay but also in HBoV1-infected HAE-ALI cultures. Collectively, our study revealed a novel mechanism by which HBoV1 NP1 enhances viral DNA replication through its direct interactions with Ku70 and RPA70.

Non-COVID-19 respiratory viral infection

Implemented control measures brought about by the coronavirus disease 2019 (COVID-19) pandemic have changed the prevalence of other respiratory viruses, often relegating them to a secondary plan. However, it must not be forgotten that a diverse group of viruses, including other human coronaviruses, rhinoviruses, respiratory syncytial virus, human metapneumoviruses, parainfluenza and influenza, continue to be responsible for a large burden of disease. In fact, they are among the most common causes of acute upper and lower respiratory tract infections globally. Viral respiratory infections can be categorised in several ways, including by clinical syndrome or aetiological agent. We describe their clinical spectrum. Distinctive imaging features, advances in microbiological diagnosis and treatment of severe forms are also discussed.

Non-COVID-19 respiratory viral infections are a major burden of disease. Emerging molecular-based detection methods and knowledge of viral lower respiratory tract infections’ distinctive features improve diagnosis, treatment and outcome of severe forms.https://bit.ly/3qMqk3T

Prevalence and Clinical Characterization of Bocavirus Infection in a Specialized Children's Hospital in Saudi Arabia

Aim

The aim of this study was to assess the prevalence and clinical characterization of bocavirus infection in patients admitted with respiratory symptoms to a specialized children’s hospital in Riyadh, Saudi Arabia.

Methods

This is a retrospective cross-sectional study that included children aged 0-14 years and was conducted over a two-year period (2017-2019). All data were gathered from an electronic information recording system, which included patients’ demographics, comorbidities, clinical presentation, complication, and duration of hospitalization.

Results

Among all patients (11,709) admitted to King Abdullah Specialized Children’s Hospital with predominant respiratory symptoms during the study period, 193 (1.6%) patients had bocavirus infections. Most of the patients were diagnosed in winter months. Cough was the primary presenting symptom (91.7%) followed by fever (83.4%). Gastrointestinal symptoms were also common (anorexia in 62% and vomiting in 39%). In 80% (n=154/193) of cases, bocavirus co-existed with other viruses, namely, human rhinovirus (45.8%), human adenovirus (31.2%), and respiratory syncytial virus type A (17.5%). Moreover, those who required oxygen supply stayed longer in the hospital (p<0.001) and were more likely to receive multiple medications such as bronchodilators (p<0.001), corticosteroids (p<0.001), and nebulized racemic epinephrine (p>0.05). Children infected with bocavirus and co-existing viruses were less likely to require oxygen supply (p<0.050).

Conclusion

Bocavirus infection is more common during winter months and predominantly affects respiratory and gastrointestinal systems in children. More studies are needed to evaluate the global impact of this recently recognized infection.

Respiratory tract infection of fatal severe human bocavirus 1 in a 13-month-old child: A case report and literature review

Human bocavirus 1 (HBoV1) belongs to the family Parvoviridae and it is acknowledged that HBoV1 is a respiratory pathogen. We report the case of a 13-month-old boy who presented with a cough, shortness of breath, and wheezing, and who eventually died of severe pneumonia and acute respiratory distress syndrome (ARDS). Metagenomics next-generation sequencing (mNGS) showed that HBoV1 was the only detected pathogen. The nasopharyngeal aspirate viral load was 2.08 × 10¹⁰ copies/ml and the serum viral load was 2.37 × 10⁵ copies/ml. The child was still oxygen deficient under mechanical ventilation. Chest imaging suggested diffuse lesions in both lungs, an injury caused by ARDS. In this case, the clinical symptoms and signs of the child, the high viral load, viremia, and the detection of mNGS in the tracheal aspirate all supported that HBoV1 could cause severe acute respiratory tract infection in children without other pathogen infections.

The large nonstructural protein (NS1) of the human bocavirus 1 (HBoV1) directly interacts with Ku70, which plays an important role in virus replication in human airway epithelia

Human bocavirus 1 (HBoV1), an autonomous human parvovirus, causes acute respiratory tract infections in young children. HBoV1 infects well-differentiated (polarized) human airway epithelium cultured at an air-liquid interface (HAE-ALI). HBoV1 expresses a large nonstructural protein, NS1, that is essential for viral DNA replication. HBoV1 infection of polarized human airway epithelial cells induces a DNA damage response (DDR) that is critical to viral DNA replication involving DNA repair with error-free Y-family DNA polymerases. HBoV1 NS1 or the isoform NS1-70 per se induces a DDR. In this study, using the second-generation proximity-dependent biotin identification (BioID2) approach, we identified that Ku70 is associated with the NS1-BioID2 pulldown complex through a direct interaction with NS1. Biolayer interferometry (BLI) assay determined a high binding affinity of NS1 with Ku70, which has an equilibrium dissociation constant (K_D) value of 0.16 μM and processes the strongest interaction at the C-terminal domain. The association of Ku70 with NS1 was also revealed during HBoV1 infection of HAE-ALI. Knockdown of Ku70 and overexpression of the C-terminal domain of Ku70 significantly decreased HBoV1 replication in HAE-ALI. Thus, our study provides, for the first time, a direct interaction of parvovirus large nonstructural protein NS1 with Ku70.

IMPORTANCE Parvovirus infection induces a DNA damage response (DDR) that plays a pivotal role in viral DNA replication. The DDR includes activation of ATM (ataxia telangiectasia mutated), ATR (ATM- and RAD3-related), and DNA-PKcs (DNA-dependent protein kinase catalytic subunit). The large nonstructural protein (NS1) often plays a role in the induction of DDR; however, how the DDR is induced during parvovirus infection or simply by the NS1 is not well studied. Activation of DNA-PKcs has been shown as one of the key DDR pathways in DNA replication of HBoV1. We identified that HBoV1 NS1 directly interacts with Ku70, but not Ku80, of the Ku70/Ku80 heterodimer at high affinity. This interaction is also important for HBoV1 replication in HAE-ALI. We propose that the interaction of NS1 with Ku70 recruits the Ku70/Ku80 complex to the viral DNA replication center, which activates DNA-PKcs and facilitates viral DNA replication.

Prevalence and Genetic Characteristics of Human Bocaviruses Detected in Patients with Acute Respiratory Infections in Bulgaria

Нuman bocaviruses (hBoVs) are often associated with acute respiratory infections (ARIs). Information on the distribution and molecular epidemiology of hBoVs in Bulgaria is currently limited. The objectives of this study were to investigate the prevalence and genetic characteristics of hBoVs detected in patients with ARIs in Bulgaria. From October 2016 to September 2019, nasopharyngeal/oropharyngeal swabs were prospectively collected from 1842 patients of all ages and tested for 12 common respiratory viruses using a real-time RT-PCR. Phylogenetic and amino acid analyses of the hBoV VP1/VP2 gene/protein were performed. HBoV was identified in 98 (5.3%) patients and was the 6^th most prevalent virus after respiratory-syncytial virus (20.4%), influenza A(H1N1)pdm09 (11.1%), A(H3N2) (10.5%), rhinoviruses (9.9%), and adenoviruses (6.8%). Coinfections with other respiratory viruses were detected in 51% of the hBoV-positive patients. Significant differences in the prevalence of hBoVs were found during the different study periods and in patients of different age groups. The detection rate of hBoV was the highest in patients aged 0-4 years (6.9%). In this age group, hBoV was the only identified virus in 9.7%, 5.8%, and 1.1% of the children diagnosed with laryngotracheitis, bronchiolitis, and pneumonia, respectively. Among patients aged ≥5 years, hBoV was detected as a single agent in 2.2% of cases of pneumonia. Phylogenetic analysis showed that all Bulgarian hBoV strains belonged to the hBoV1 genotype. A few amino acid substitutions were identified compared to the St1 prototype strain. This first study amongst an all-age population in Bulgaria showed a significant rate of hBoV detection in some serious respiratory illnesses in early childhood, year-to-year changes in the hBoV prevalence, and low genetic variability in the circulating strains.

Identification and characterization of a novel bocaparvovirus in tufted deer (Elaphodus cephalophus) in China

We used viral metagenomics and next-generation sequencing to identify a novel strain of bocaparvovirus in the intestinal tract of tufted deer (Elaphodus cephalophus), tentatively named "Elaphodus cephalophus bocaparvovirus" (ECBOV). A nearly complete genome sequence of 5,354 nucleotides was obtained, which had the typical genome organization and protein motifs of a bocaparvovirus. Sequence comparisons and phylogenetic analysis revealed that ECBOV may be a new ungulate bocaparvovirus. The identification and characterization of viruses in wildlife will facilitate our understanding of genetic evolution and cross-species transmission and thus further reduce the potential threat to human and animal health.

Epidemiology of Human Bocavirus in the Middle East and North Africa: Systematic Review

The emergence of the COVID-19 pandemic highlighted the importance of studying newly emerging viruses that cause respiratory illnesses. Human bocavirus (HBoV) is one of the relatively newly discovered viruses that has been detected worldwide and causes respiratory and gastrointestinal infections, mainly in pediatric patients. However, little is known about the pathogenicity and evolution of HBoV. This systematic review was initiated to clarify the prevalence and circulating genotypes of HBoV in both respiratory and stool samples from patients of all age groups in the Middle East and North Africa (MENA) from 2005 to February 2021. We performed an electronic search through Science Direct, Scopus, PubMed, Mendeley and Cochrane Library databases. We included all studies reporting the detection rate of HBoV in the MENA region. Data were extracted, and the quality of the included articles was assessed. We included articles containing data on HBoV only or with other respiratory or gastrointestinal viral infections. Review articles, case studies, and animal and environmental studies were excluded. The final number of articles included in this study was 65 articles. The results showed that the HBoV prevalence in children was the lowest in Iran (0%) and the highest in Egypt (56.8%). In adults, the lowest and the highest prevalence were reported in Iran, with values of 0% and 6.6%, respectively. Regarding the respiratory cases, our findings revealed no significant difference between HBoV prevalence among the tested categories (p-value = 0.998). The present study has shown that HBoV is common in children and adults in the MENA region. This systematic review highlights the need for more data on the role of coinfection of HBoV and other viruses, for instance, SARS-CoV-2 in children with acute bronchiolitis.

Epidemiologic and clinical characteristics of human bocavirus infection in infants and young children suffering with community acquired pneumonia in Ningxia, China

Background

Pneumonia has a high incidence rate and is a major cause of mortality in children, mostly community-acquired pneumonia (CAP). Human bocavirus (HBoV), since it first identified in 2005, has been repeatedly associated with respiratory tract infections. Nevertheless, the role and related information of HBoV as a pathogen of CAP has not been fulfilled. Here our study is to assess the epidemiological and clinical features in HBoV-positive children with CAP.

Methods

A total of 878 secretions of lower respiratory samples were obtained, multiplex PCR was used to detect HBoV and other respiratory viruses.

Results

Of all cases, HBoV was detected in 10.0%, with a peak incidence of infection among children < 2 year old, and predominantly noted in autumn and winter. Only 8 patients were HBoV single infection. Co-infection with other respiratory viruses was observed in 86.4%. Moreover, co-infection with bacteria occurred in 27.3% and with Mycoplasma pneumoniae (MP) in 33.0% of HBoV-positive patients. Among all HBoV-positive samples co-infected with bacteria, 87.5% are gram negative bacteria. Compared with HBoV-negative group, age (P = 0.048), wheezing (P = 0.015), tachypnea (P = 0.016), lactate dehydrogenase (P = 0.026) and severe pneumonia (P = 0.023) were statistically significant in HBoV-positive patients. Furthermore, HBoV-positive patients less than 1 year old were more likely to have co-infection with bacteria (P = 0.007).

Conclusions

HBoV can be detected alone in respiratory samples of children with CAP, maybe it is one of the causes of CAP in infants. The high incidence of severe pneumonia was found in HBoV-positive patients compared with HBoV-negative cases may indicate a relationship between severe pneumonia and HBoV.

Human bocavirus 2 detected in Rattus norvegicus feces in China

Bocaviruses are typical zoonotic pathogens with a wide range of hosts. Here, we report the detection of human bocavirus (HBoV) in Rattus norvegicus captured in China and the results of sequencing and phylogenetic analysis based on the partial VP1 region and the entire viral genome. A total of 357 fecal samples from rats were collected in 2015-2017 and analyzed for HBoV using PCR. The detection rate of HBoV was 0.84% (3/357). Phylogenetic analysis revealed that this virus is genetically closely related to HBoV-2. R. norvegicus may be a carrier of HBoV, and its impact on public health merits attention.

Hairpin transfer-independent Parvovirus DNA Replication Produces Infectious Virus

Parvoviruses package a linear single-stranded DNA genome with hairpin structures at both ends. It has been thought that terminal hairpin sequences are indispensable for viral DNA replication. Here, we provide evidence that the hairpin-deleted duplex genomes of human bocavirus 1 (HBoV1) replicate in human embryonic kidney (HEK) 293 cells. We propose an alternative model for HBoV1 DNA replication in which the leading strand can initiate strand-displacement without "hairpin-transfer." The transfection of the HBoV1 duplex genomes that retain a minimal replication origin at the right-end (OriR), but with extensive deletions in the right-end hairpin (REH), generated viruses in HEK293 cells at a level 10-20 times lower than the wild-type (WT) duplex genome. Importantly, these viruses that have a genome with various deletions after the OriR, but not the one retaining only the OriR, replicated in polarized human airway epithelia. We discovered that the 18-nt sequence (nt 5,403-5,420) beyond the OriR was sufficient to confer virus replication in polarized human airway epithelia, although its progeny virus production was ∼5 times lower than that of the WT virus. Thus, our study demonstrates that hairpin transfer-independent productive parvovirus DNA replication can occur. Importance Hairpin transfer-independent parvovirus replication was modeled with human bocavirus 1 (HBoV1) duplex genomes whose 5' hairpin structure was ablated by various deletions. In HEK293 cells, these duplex viral genomes with ablated 5'/hairpin sequence replicated efficiently and generated viruses that productively infected polarized human airway epithelium. Thus, for the first time, we reveal a previously unknown phenomenon that the productive parvovirus DNA replication does not depend on the hairpin sequence at REH to initiate "rolling hairpin" DNA replication. Notably, the intermediates of viral DNA replication, as revealed two-dimensional electrophoresis, from transfections of hairpin sequence-deleted duplex genome and full-length genome in HEK293 cells, as well as from virus infection of polarized human airway epithelia are similar. Thus, the establishment of the hairpin transfer-independent parvoviral DNA replication deepens our understanding in viral DNA replication and may have implications in development of parvovirus-based viral vectors with alternative properties.

Interplay between hypoxia and inflammation contributes to the progression and severity of respiratory viral diseases

History of pandemics is dominated by viral infections and specifically respiratory viral diseases like influenza and COVID-19. Lower respiratory tract infection is the fourth leading cause of death worldwide. Crosstalk between resultant inflammation and hypoxic microenvironment may impair ventilatory response of lungs. This reduces arterial partial pressure of oxygen, termed as hypoxemia, which is observed in a section of patients with respiratory virus infections including SARS-CoV-2 (COVID-19). In this review, we describe the interplay between inflammation and hypoxic microenvironment in respiratory viral infection and its contribution to disease pathogenesis.

Severe Human Bocavirus-Associated Pneumonia in Adults at a Referral Hospital, Seoul, South Korea

We report a case series of severe human bocavirus–associated pneumonia in adults in Seoul, South Korea. The virus accounted for 0.5% of all severe pneumonia cases. Structural lung disease and hematologic malignancy were common underlying diseases. Overall death rate was 54.5%. Higher death rates were associated with co-infection (83.3%) and immunocompromise (80.0%).

Airway tight junctions as targets of viral infections

The apical junctional complexes (AJCs) of airway epithelial cells are a key component of the innate immune system by creating barriers to pathogens, inhaled allergens, and environmental particles. AJCs form between adjacent cells and consist of tight junctions (TJs) and adherens junctions (AJs). Respiratory viruses have been shown to target various components of the AJCs, leading to airway epithelial barrier dysfunction by different mechanisms. Virus-induced epithelial permeability may allow for allergens and bacterial pathogens to subsequently invade. In this review, we discuss the pathophysiologic mechanisms leading to disruption of AJCs and the potential ensuing ramifications. We focus on the following viruses that affect the pulmonary system: respiratory syncytial virus, rhinovirus, influenza viruses, immunodeficiency virus, and other viruses such as coxsackievirus, adenovirus, coronaviruses, measles, parainfluenza virus, bocavirus, and vaccinia virus. Understanding the mechanisms by which viruses target the AJC and impair barrier function may help design therapeutic innovations to treat these infections.

Bocavirus Infection in a Young Pregnant Woman: A Case Report and Literature Review

BACKGROUND Human bocavirus (HBoV) is a parvovirus found primarily in children and was first identified in 2005. It usually causes mild upper- and lower-respiratory tract infections. HBoV infection seems to be rare during adulthood, probably due to high antibody titers resulting from childhood infection and seroconversion. The clinical significance, possible complications, and consequences of an adulthood infection are still unclear. Furthermore, the consequences of HBoV infection during pregnancy are seldom reported in the literature. CASE REPORT We report the case of a 22-year-old pregnant woman in her third trimester who presented with a 1-week history of fever and cough followed by progressive shortness of breath. She was treated initially as a case of severe pneumonia; however, her condition deteriorated rapidly, resulting in hypoxic respiratory failure that required intensive care support. The patient was found to have dilated cardiomyopathy on echocardiography, and her fetal ultrasound showed no fetal heart activity; subsequently, labor induction for stillbirth was performed. An extensive workup for an underlying cause was unrevealing apart from positive respiratory viral PCR assay for human bocavirus, performed twice. A provisional diagnosis of HBoV pneumonia complicated by dilated cardiomyopathy, stillbirth, and multiorgan failure was made. Fortunately, the patient had a good recovery and was discharged home in good clinical condition. CONCLUSIONS In addition to severe pneumonia, HBoV infection may result in other life-threatening complications. Although the infection is rare during adulthood, infection in a pregnant woman should be taken seriously and close monitoring of such patients is advised.

Molecular and epidemiological trends of human bocavirus and adenovirus in children with acute gastroenteritis in Bangladesh during 2015 to 2019

Virus associated diarrhea remains one of the leading causes of children morbidity and mortality in Bangladesh. Human bocavirus (HBoV) has been reported as a potential pathogen of children's diarrhea worldwide. However, due to its frequent association with other gastroenteric pathogens, its role as diarrhea causative agent remains to be defined. This study focuses to detect the incidence of HBoV and adenovirus (AdV) and to determine the molecular and epidemiological characteristics of HBoV and AdV. Between January 2015 to January 2019, 290 fecal specimens were collected from diarrheal children in Bangladesh. All fecal specimens were tested for HBoV and AdV by conventional polymerase chain reaction and sequencing methods. HBoV was detected in 7.24% (21 of 290) of the stool samples, as a sole virus in 71.42% (15 of 21) of the positive samples. AdV was detected in 4.82% (14 of 290) of the samples. The most common clinical symptoms of HBoV infected patients were diarrhea (100%) and vomiting (57%). All of the isolates of HBoV were from HBoV1 and AdV were from AdV41, AdV5, AdV7, and AdV8. To the best of our knowledge, this is the first epidemiological and molecular analysis report of HBoV from clinical specimens in Bangladesh. In the future, more studies are needed to clarify the role of HBoV as diarrheal pathogens.

Human bocavirus and metapneumovirus in acute wheezing in children-Is there a link with atopy?

INTRODUCTION

Viral respiratory tract infections are the leading cause of acute wheezing in children with a significant risk of hospital admission, risk of recurrence and subsequent asthma. Human respiratory syncytial virus (RSV) and human rhinovirus (RV) in childhood wheezing are widely studied; however, accessible PCR assays enabled diagnosis of other pathogens, including bocavirus (hBOV) and metapneumovirus (hMPV).

OBJECTIVES

The aim of the study was to evaluate the prevalence of respiratory viruses in children hospitalized for acute wheezing along with demographic and clinical data.

METHODS

We enrolled 101 children, n = 50 (49.5%) with wheezy bronchitis, n = 34 (33.7%) with acute bronchiolitis and n = 17 (16.8%) with exacerbation of asthma; (median age 1.41 ± 2.84 years). Multiplex real-time PCR assay was used for virus detection.

RESULTS

One or more viruses were detected in 83.2% subjects: RSV in 44.6%, followed by RV (23.8%), hBOV and hMPV (both 11.9%); other viruses were less frequent (<8%). Viral coinfection was found in 38 (37.6%) of children. ANCOVA analysis revealed significantly higher total IgE concentrations in the hMPV-positive subgroup compared to RSV (34 kU/L vs 12.7 kU/L; P = .009) and RV (13.3 kU/L, P = .022). For both hMPV and hBOV an association with atopic dermatitis (AD) was observed: aOR for hMPV and AD was 5.6 (95%CI: 1.4-22.7; P = .016) and 4.7 for hBOV and AD (95%CI: 1.3-18; P = .024).

CONCLUSION

Viral detection ratio in wheezy respiratory tract infections in Polish children is high (83.2%), with both hBOV and hMPV at 11.9% The results also suggest possible relationship of hBOV wheezy infection with nonspecific markers of atopy in children.

Detection and phylogenetic analysis of Human bocavirus in children diagnosed with acute respiratory tract infection

Introduction. Human bocavirus (HBoV) is a recently discovered parvovirus; it has been shown to be a common cause of respiratory infections and gastroenteritis in children. Since its identification, HBoV has been detected worldwide in nasopharyngeal swabs, serum and stool samples particularly those obtained from young children suffering from respiratory or gastrointestinal tract infections.Aim. The aim of this work was to determine HBoV prevalence among children with acute respiratory tract infection in Egypt, to detect the most prevalent HBoV genotype and to compare PCR and ELISA as diagnostic techniques for HBoV infection.Methods. Nasopharyngeal swabs and blood samples were obtained within the first day of admission from 75 children diagnosed with acute respiratory tract infection in El-Shatby University Hospital for Children in Alexandria, Egypt from October 2018 to March 2019. Conventional PCR was used to detect HBoV DNA, ELISA was used to detect HBoV IgM antibodies and sequencing of the VP1/2 genes was used for genotyping.Results. Seven (9.3%) of the 75 nasopharyngeal swabs obtained from patients with acute respiratory tract infection were positive for HBoV by PCR, while 5 (6.7 %) of the 75 serum samples were positive for HBoV IgM antibodies using ELISA. The correlation between PCR and ELISA results showed a highly significant association between PCR and ELISA techniques (X ²=52.041, P<0.01) and a highly significant agreement between the two methods (Kappa=81.9 %, P<0.01). Phylogenetic analysis showed that all positive samples were related to the HBoV-1 genotype.Conclusion. Human bocavirus was detected at 9.3 % prevalence in nasopharyngeal swabs obtained from children with acute respiratory tract infection. The HBoV-1 genotype was the only genotype detected, suggesting that a single genetic lineage of HBoV is circulating in Egypt. PCR and ELISA are two reliable methods for detection and diagnosis of HBoV.

Human Bocavirus in Brazil: Molecular Epidemiology, Viral Load and Co-Infections

Human bocavirus (HBoV) is an emerging virus and has been detected worldwide, especially in pediatric patients with respiratory and gastrointestinal infection. In this study, we describe HBoV prevalence, genotypes circulation and DNA shedding, in stool samples from children up to two years of age in Brazil. During 2016 and 2017, 886 acute gastroenteritis (AGE) stool samples from ten Brazilian states were analyzed by TaqMan^®-based qPCR, to detect and quantify HBoV. Positive samples were genotyped by sequencing the VP1/2 overlap region, followed by phylogenetic analysis and co-infections were accessed by screening other gastroenteric viruses. HBoV was detected in 12.4% (n = 110) of samples, with viral load ranging from 1.6 × 10² to 1.2 × 10⁹ genome copies per gram of stool. From these, co-infections were found in 79.1%, and a statistically lower HBoV viral load was found compared to viral loads of rotavirus, norovirus and adenovirus in double infected patients (p < 0.05). No significant differences were found between HBoV viral load in single or co-infections, age groups or genotypes. Phylogenetic analysis identified the circulation of HBoV-1 in 38%, HBoV-2 in 40% and HBoV-3 in 22%. Continuous HBoV monitoring is needed to clarify its role in diarrhea disease, especially in the absence of classic gastroenteric viruses.

Human bocavirus (HBoV) in Kuwait: molecular epidemiology and clinical outcome of the virus among patients with respiratory diseases

Introduction. Globally, human bocavirus (HBoV) has been detected in respiratory samples from patients suffering from upper and lower respiratory diseases. In Kuwait, little is known about the epidemiological and clinical characterization of the virus and genetic characterization of the virus as a respiratory pathogen is unknown.Aim. This study aims to explore the molecular epidemiology and clinical features of HBoV isolates in patients with respiratory diseases.Methodology. Retrospectively, between 2018 and 2020, 5941 respiratory samples from patients with respiratory diseases were screened for respiratory viruses using multiplex real-time PCR. Samples that were positive for HBoV were then subjected to NP1 and VP1/PV2 phylogenetic analysis.Results. HBoV was detected in 1.9 % of the patients, with a peak incidence of infection among children <1 year old. Co-infection with other respiratory viruses was observed in 56.8 % of HBoV-positive patients. Fever, cough and respiratory distress were the most common clinical features of HBoV infection. Phylogenetic analysis of the Kuwaiti HBoV isolates revealed that all the isolates were of the HBoV-1 genotype, with slight sequence variations among the isolates.Conclusion. This study illustrated the predominance of the HBoV-1 genotype in patients with respiratory diseases in Kuwait with minimal genetic variability. It also highlighted the clinical features of HBoV-1 infection, verifying its role in respiratory diseases.

Human Parvoviruses May Affect the Development and Clinical Course of Meningitis and Meningoencephalitis

Meningitis and meningoencephalitis are neurological inflammatory diseases, and although routine diagnostics include testing of a wide range of pathogens, still in many cases, no causative agent is detected. Human parvovirus B19 (B19V), human bocaviruses 1–4 (HBoV1–4), and human parvovirus 4 (hPARV4) are members of the Parvoviridae family and are associated with a wide range of clinical manifestations including neurological disorders. The main aim of this study was to determine whether human parvoviruses infection markers are present among patients with meningitis/meningoencephalitis in Latvia as well as to clarify the role of these viruses on the clinical course of the mentioned diseases. Our study revealed HBoV1–4 and B19V genomic sequences in 52.38% and 16.67% of patients, respectively. Furthermore, symptoms such as the presence of a headache and its severity, fatigue, disorientation, and difficulties to concentrate were significantly frequently present in patients with active parvovirus infection in comparison with parvoviruses negative patients, therefore we suggest that HBoV1–4 and B19V infection should be included in the diagnostics to reduce the number of meningitis/meningoencephalitis with unknown/unexplained etiology.

Human Bocavirus infection and respiratory tract disease identified in a UK patient cohort

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Human Bocavirus 1 (HBoV1) was commonly detected in a survey of circa 13,000 UK respiratory samples between 2015 and 2019.

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Co-infection with other viruses was observed in approximately three quarters of samples.

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However, mono-infection was also prevalent, and associated with clinically relevant disease.

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Intensive care was required in 31% of HBoV1 mono-infections and ventilation in 17%.

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Fatal multi-organ failure was observed in an apparently HBoV1 mono-infected and otherwise healthy child.

Background

Since its first isolation in 2005, Human Bocavirus (HBoV) has been repeatedly associated with acute respiratory tract infections, although its role in pathogenicity remains unclear due to high co-infection rates.

Objectives

To assess HBoV prevalence and associated disease in a cohort of respiratory patients in the East Midlands, UK between 2015 and 2019.

Study design

We initially investigated the undiagnosed burden of HBoV in a retrospective paediatric cohort sampled between 2015 and 2017 using an in-house PCR assay. HBoV was subsequently incorporated into the standard respiratory diagnostic pathway and we audited a calendar year of HBoV positive results between 2018 and 2019.

Results

Our retrospective PCR screening of previously routine diagnostic-negative samples from juvenile patients identified a 9% (n = 30) prevalence of HBoV type 1. These apparent HBoV1 mono-infections were frequently associated with respiratory tract symptoms, often severe requiring ventilation, oxygen and steroid intervention with 31% (n = 9) of individuals requiring intensive care. When HBoV screening was subsequently adopted into the routine respiratory diagnostic pathway, year-round infections were observed in both children and adults peaking in February. 185 of 9098 (2.03%) individuals were found to be HBoV positive with children aged 12–24 months the principally infected group. However, HBoV infection was also observed in patients aged over 60, predominantly as a mono-infection. 23% of the 185 unique patients were HBoV monoinfected and persistent low-level DNA positivity was observed in 15 individuals up to 6-months after initial presentation.

Conclusion

HBoV1 is a prevalent respiratory infection in the UK capable of causing serious monoinfections.

Identification of a novel bocaparvovirus in a wild squirrel in Kunming, Yunnan Province, China

In December 2017, a squirrel (Callosciurus phayrei) died 2 days after capture in Kunming, and its intestinal tract, heart, liver, spleen, lung, and kidney were subjected to metagenomics analysis. Reassembly and verification by reverse transcription PCR of contigs generated by next-generation sequencing yielded a 5176-nt sequence, which was designated "squirrel bocaparvovirus" (SQBOV). Phylogenetic trees based on the aa sequences of NS1, NP1, and VP1 showed that SQBOV formed an independent branch in the bocaparvovirus phylogenetic tree. The amino acid sequence identity of the NS1 of SQBOV to those of other bocaparvoviruses was below the threshold of 85% that is used to demarcate species within the genus, indicating that it should be considered a member of a new bocaparvovirus species. To our knowledge, this is the first report of a bocaparvovirus in squirrels. Our findings will enable further studies of viral diversity in rodents and of the genetic diversity and host range of bocaparvoviruses.

Virome of a Feline Outbreak of Diarrhea and Vomiting Includes Bocaviruses and a Novel Chapparvovirus

An unexplained outbreak of feline diarrhea and vomiting, negative for common enteric viral and bacterial pathogens, was subjected to viral metagenomics and PCR. We characterized from fecal samples the genome of a novel chapparvovirus we named fechavirus that was shed by 8/17 affected cats and identified three different feline bocaviruses shed by 9/17 cats. Also detected were nucleic acids from attenuated vaccine viruses, members of the normal feline virome, viruses found in only one or two cases, and viruses likely derived from ingested food products. Epidemiological investigation of disease signs, time of onset, and transfers of affected cats between three facilities support a possible role for this new chapparvovirus in a highly contagious feline diarrhea and vomiting disease.

Keeping all secondary structures of the non-coding region in the circular genome of human bocavirus 2 is important for DNA replication and virus assembly, as revealed by three hetero-recombinant genomic clones

The episomal structures of all human bocavirus (HBoV) genotypes have been deciphered, including the circular genome of HBoV2 (HBoV2-C1). To discern the role of the circular HBoV2 genome, three distinct linearized HBoV2-C1 genomes were cloned into pBlueScript SKII(+) to obtain pBlueScript HBoV2 5043–5042 (retaining all secondary structures), pBlueScript-HBoV2 5075–5074 (retaining hairpin number 2 and the 5′ terminal structure), and pBlueScript-HBoV2 5220–5219 (retaining only the 5′ terminal structure at the 5′ -genome end). The recombinant plasmids were separately transfected HEK293 cells, revealing that more HBoV2 DNA had accumulated in the pBlueScript HBoV2 5043–5042-transfected HEK293 cells at 72 h post-transfection, as determined by real-time PCR. However, more mRNA was transcribed by pBlueScript-HBoV2 5075–5074 than by the other constructs, as determined by dot-blot hybridization and RNAscope. No significant differences in NS1-70 protein expression were observed among the three HBoV2 genomic clones. However, electron microscopy showed that HBoV2 virus particles were only present in the pBlueScript HBoV2 5043–5042-transfected HEK293 cells. By using three hetero-recombinant HBoV2 genomic clones in HEK293 transfected cells, only the genome with intact secondary structures produced virus particles, suggesting that retaining these structures in a circular genome is important for HBoV2 DNA replication and virus assembly.

Detection, genetic, and codon usage bias analyses of the VP2 gene of mink bocavirus

Mink bocavirus 1 (MiBoV1), a novel virus detected from the feces of domestic minks in China in 2016, may be related to gastrointestinal diseases. However, its prevalence and genetic characteristics are poorly described. In this study, we examined 192 samples collected from minks in the major mink industry province from northern China. PCR results showed that 10 samples (5.2%) were positive for MiBoV1, and 60% of MiBoV1-positive samples were co-infected with Aleutian mink disease virus or mink circovirus. MiBoV1 was detected in six serum samples. Sequence analysis demonstrated that the VP2 gene of MiBoV1 was highly conserved and had low viral diversity over the VP2 region and unique nucleotide mutations. Phylogenetic analysis of the VP2 sequence demonstrated that MiBoV1 strains formed two clades and were grouped with California sea lion bocavirus, Canine bocavirus, and Feline bocavirus. Codon usage analysis revealed that most of the preferentially used codons in MiBoV1 were A- or U-ended codons, and no evident codon usage bias was found. This study provides evidence that MiBoV1 has a low prevalence in Jilin and Hebei provinces in China. Moreover, it contributes information regarding the expansion of the limited mink bocavirus sequence and determines the codon usage bias of the VP2 gene for the first time. Epidemiological surveillance is necessary to understand the importance and evolution of MiBoV1.

Fatal Primary Human Bocavirus Pneumonia in an Immunocompetent Adult

A 70-year-old woman was admitted to our hospital for dyspnea and a fever of 2 weeks duration. Chest imaging showed bilateral infiltration, and a rapid diagnostic test for influenza virus, Mycoplasma pneumoniae, Streptococcus pneumoniae, and Legionella spp. was negative. She was intubated and mechanically ventilated and underwent bronchoalveolar lavage. Bronchoalveolar lavage fluid yielded no significant pathogens, and the multiplex polymerase chain reaction test was positive only for human bocavirus. Specific antibodies against significant pathogens were not increased in paired sera, so we diagnosed her with primary human bocavirus pneumonia.

iTRAQ-based high-throughput proteomics analysis reveals alterations of plasma proteins in patients infected with human bocavirus

Human bocavirus (HBoV) is a member of the genus Bocavirus, family Parvoviridae, and subfamily Parvovirus and was first identified in nasopharyngeal aspirates of Swedish children with acute respiratory tract infection (ARTI) in 2005. It is the causative agent of nasopharyngeal aspirate disease and death in children. The HboV genomic structure is a linear single-stranded DNA (ssDNA). Its clinical pathogenic characteristics have been extensively studied, however, at present the molecular mechanism underlying the pathogenesis of HBoV infection is not completely clear. In this study, a total of 293 differentially expressed proteins (DEPs) between ARTI cases and healthy plasma samples were characterized using isobaric tags for relative and absolute quantitation (iTRAQ)-coupled bioinformatics analysis, among which 148 were up-regulated and 135 were down-regulated. Gene Ontology (GO) and Cluster of Orthologous Groups of proteins (COG) annotated an enrichment of DEPs in complement activation and biological processes like immunity, inflammation, signal transduction, substance synthesis, and metabolism. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis enriched DEPs mainly in the Wnt signaling pathway (ko04310), PPAR signaling pathway (ko03320), intestinal immune network for IgA production (ko04672), complement and coagulation cascades (ko04610), Toll-like receptor signaling pathway (ko04620) and B cell receptor signaling pathway (ko04662). Further, expression levels of three candidate proteins (upregulated PPP2R1A and CUL1, and downregulated CETP) were validated using western blotting. Our investigation is the first analysis of the proteomic profile of HBoV-infected ARTI cases using the iTRAQ approach, providing a foundation for a better molecular understanding of the pathogenesis of ARTI in children.

Are Community Acquired Respiratory Viral Infections an Underestimated Burden in Hematology Patients?

Despite a plethora of studies demonstrating significant morbidity and mortality due to community-acquired respiratory viral (CRV) infections in intensively treated hematology patients, and despite the availability of evidence-based guidelines for the diagnosis and management of respiratory viral infections in this setting, there is no uniform inclusion of respiratory viral infection management in the clinical hematology routine. Nevertheless, timely diagnosis and systematic management of CRV infections in intensively treated hematology patients has a demonstrated potential to significantly improve outcome. We have briefly summarized the recently published data on CRV infection epidemiology, as well as guidelines on the diagnosis and management of CRV infections in patients intensively treated for hematological malignancies. We have also assessed available treatment options, as well as mentioned novel agents currently in development.

Novel Primate Bocaparvovirus Species 3 Identified in Wild Macaca Mulatta in China

Primate bocaparvovirus (BOV) is a possible cause of respiratory disorders and gastroenteritis in humans. However, the diversity and evolution of these viruses remain largely unknown, despite the identification of a growing number of BOVs in non-human primates (NHPs). Here, we report the identification of a novel BOV (provisionally named Macaca mulatta bocaparvovirus [MmBOV]) in the feces of wild Macaca mulatta in China by viral metagenomic analysis. Seven of 400 fecal samples from Macaca mulatta were positive for MmBOV. An almost complete genome sequence of 4,831 nucleotides was obtained, which had genomic organization and protein motifs similar to human bocaviruses (HOBVs), and shared characteristically low G/C content and weak codon usage bias. Sequence analyses of NS1, NP1, and VP1 revealed that MmBOV was most closely related to HBOV4 of Primate bocaparvovirus 2 (approximately 68.4%/70.6%, 73.3%/67.6%, and 70.4%/73.1% nucleotide/amino acid identities, respectively). Additionally, phylogenetic analysis revealed that MmBOV formed an independent peripheral branch, but clustered closely with those of the Primate bocaparvovirus species in the BOV genus (particularly HBOV4). These data strongly suggest that HBOV4 originated from NHP bocaparvoviruses around 200-300 years ago, and that NHPs may act as HBOV reservoirs. Following the International Committee of Taxonomy for Viruses guidelines, we propose MmBOV as a new species (tentatively named Primate bocaparvovirus 3) in the genus Bocaparvovirus, which is the first report of a novel species of primate BOV. Our data facilitate future research on the genetic diversity and evolution of primate bocaparvoviruses and highlight the importance of bocaparvovirus surveys in wild NHPs.

Human bocavirus infections and co-infections with respiratory syncytial virus and Rotavirus in children with acute respiratory or gastrointestinal disease

The objective of this study was to determine the frequency and seasonal distributions of HBoV detections among Iranian children presenting with acute respiratory or gastrointestinal symptoms and to compare infections among children with concomitant respiratory syncytial virus (RSV) and rotavirus (RV) infections. A cross-sectional study at Mofid Children's Hospital in Tehran, Iran, enrolled children < 3 years old presenting with either acute respiratory or gastrointestinal symptoms during the period of 2017-2018. Respiratory or stool specimens collected from each group were initially tested by RT-PCR assays for RSV and RV, respectively, and all specimens were tested for HBoV by PCR assay. Clinical and demographic data were collected and statistically compared. Five hundred respiratory and stool specimens each were tested and 67 (13.4%) and 72 (14.4%) were PCR positive for HBoV, respectively. Of 128 (25.6%) respiratory specimens positive for RSV, 65% were also positive for HBoV (p = 0.019); of 169 (33.8%) stool specimens positive for RV, 62.5% were also positive for HBoV (p = 0.023). Peak circulation of all viruses was during late winter and early spring months (Jan-Mar) in gastrointestinal infections and during winter (Feb-Jan) in respiratory infections. HBoV is commonly detected among Iranian children presenting with acute respiratory or gastrointestinal symptoms and is often present as co-infections with RSV and RV, respectively.

Acute human bocavirus 1 infection in child with life-threatening bilateral bronchiolitis and right-sided pneumonia: a case report

Background

Human bocavirus 1 is a commonly detected human parvovirus. Many studies have shown human bocavirus 1 as a pathogen in association with acute respiratory tract infections in children. However, because human bocavirus 1 persists in the upper airways for extensive time periods after acute infection, the definition and diagnostics of acute human bocavirus 1 infection is challenging. Until now, detection of human bocavirus 1 exclusively, high viral load in respiratory samples, and viremia have been associated with a clinical picture of acute respiratory illness. There are no studies showing detection of human bocavirus 1 messenger ribonucleic acid in the peripheral blood mononuclear cells as a diagnostic marker for acute lower respiratory tract infection.

Case presentation

We report the case of a 17-month-old Latvian boy who presented in intensive care unit with acute bilateral bronchiolitis, with a history of rhinorrhea and cough for 6 days and fever for the last 2 days prior to admission, followed by severe respiratory distress and tracheal intubation. Human bocavirus 1 was the only respiratory virus detected by a qualitative multiplex polymerase chain reaction panel. For the diagnosis of acute human bocavirus 1 infection, both molecular and serological approaches were used. Human bocavirus 1 deoxyribonucleic acid (DNA) was detected simultaneously in nasopharyngeal aspirate, stool, and blood, as well as in the corresponding cell-free blood plasma by qualitative and quantitative polymerase chain reaction, revealing high DNA-copy numbers in nasopharyngeal aspirate and stool. Despite a low-load viremia, human bocavirus 1 messenger ribonucleic acid was found in the peripheral blood mononuclear cells. For detection of human bocavirus 1-specific antibodies, non-competitive immunoglobulin M and competitive immunoglobulin G enzyme immunoassays were used. The plasma was positive for both human bocavirus 1-specific immunoglobulin M and immunoglobulin G antibodies.

Conclusions

The presence of human bocavirus 1 genomic DNA in blood plasma and human bocavirus 1 messenger ribonucleic acid in peripheral blood mononuclear cells together with human bocavirus 1-specific immunoglobulin M are markers of acute human bocavirus 1 infection that may cause life-threatening acute bronchiolitis.

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.

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.

Phylogenetic analysis of human bocavirus in children with acute respiratory infections in Iran

Human bocavirus (HBoV) was first characterized in nasopharyngeal aspirates from young children with acute respiratory infections. It is prevalent among children with acute wheezing. This study was carried out in order to analyze the infection frequency and coinfection rates of HBoV with respiratory syncytial virus (RSV) and to perform phylogenetic analysis of HBoV in samples of children with acute respiratory infection in Isfahan, Iran. During the time period 2016-2017, altogether 75 respiratory samples from children hospitalized with acute respiratory infection were collected. The samples were first screened for RSV by direct immunofluorescence method and then subjected to detect HBoV DNA by PCR. Genotyping of HBoV-positive samples was conducted by direct sequencing of PCR products using NP and VP1/VP2 genes. Out of 75 respiratory samples, 20 (26.7%) and 10 (13.3%) were positive for RSV and HBoV, respectively. The coinfection rate was 40% (p = 0.048). Considering the seasonal distribution, winter has the highest extent outbreak (p = 0.036). Sequence analysis of positive samples exhibits that all of the isolated HBoV were related to genotype 1 (HBoV-1) with minimal sequence variations. Increasing frequency of HBoV suggests that the virus is related to acute respiratory infection in children. A single genetic lineage of HBoV1 seems to be the major genotype in Iran.

Beyond Respiratory Syncytial Virus and Rhinovirus in the Pathogenesis and Exacerbation of Asthma: The Role of Metapneumovirus, Bocavirus and Influenza Virus

Respiratory viruses other than rhinovirus or respiratory syncytial virus, including human metapneumovirus, influenza virus, and human bocavirus, are important pathogens in acute wheezing illness and asthma exacerbations in young children. Whether infection with these viruses in early life is associated with recurrent wheezing and/or asthma is not fully investigated, although there are data to suggest children with human metapneumovirus lower respiratory tract infection may have a higher likelihood of subsequent and recurrent wheezing several years after initial infection.

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 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.

Establishment of a High-Yield Recombinant Adeno-Associated Virus/Human Bocavirus Vector Production System Independent of Bocavirus Nonstructural Proteins

The genome of recombinant adeno-associated virus 2 (rAAV2) remains a promising candidate for gene therapy for cystic fibrosis (CF) lung disease, but due to limitations in the packaging capacity and the tropism of this virus with respect to the airways, strategies have evolved for packaging an rAAV2 genome (up to 5.8 kb) into the capsid of human bocavirus 1 (HBoV1) to produce a chimeric rAAV2/HBoV1 vector. Although a replication-incompetent HBoV1 genome has been established as a trans helper for capsid complementation, this system remains suboptimal with respect to virion yield. Here, a streamlined production system is described based on knowledge of the involvement of HBoV1 nonstructural (NS) proteins NS1, NS2, NS3, NS4, and NP1 in the process of virion production. The analyses reveal that NS1 and NS2 negatively impact virion production, NP1 is required to prevent premature termination of transcription of the cap mRNA from the native genome, and silent mutations within the polyadenylation sites of the cap coding sequence can eliminate this requirement for NP1. It is further shown that preventing the expression of all NS proteins significantly increases virion yield. Whereas the expression of capsid proteins VP1, VP2, and VP3 from a codon-optimized cap mRNA was highly efficient, optimal virion assembly, and thus potency, required enhanced VP1 expression, entailing a separate VP1 expression cassette. The final NS protein-free production system uses three-plasmid co-transfection of HEK293 cells, with one trans helper plasmid encoding VP1 and the AAV2 Rep proteins, and another encoding VP2-3 and components from adenovirus. This system yielded >16-fold more virions than the prototypic system, without reducing transduction potency. This increase in virion production is expected to facilitate greatly both research on the biology of rAAV2/HBoV1 and preclinical studies testing the effectiveness of this vector for gene therapy of CF lung disease in large animal models.

Novel Chimeric Gene Therapy Vectors Based on Adeno-Associated Virus and Four Different Mammalian Bocaviruses

Parvoviruses are highly attractive templates for the engineering of safe, efficient, and specific gene therapy vectors, as best exemplified by adeno-associated virus (AAV). Another candidate that currently garners increasing attention is human bocavirus 1 (HBoV1). Notably, HBoV1 capsids can cross-package recombinant (r)AAV2 genomes, yielding rAAV2/HBoV1 chimeras that specifically transduce polarized human airway epithelia (pHAEs). Here, we largely expanded the repertoire of rAAV/BoV chimeras, by assembling packaging plasmids encoding the capsid genes of four additional primate bocaviruses, HBoV2–4 and GBoV (Gorilla BoV). Capsid protein expression and efficient rAAV cross-packaging were validated by immunoblotting and qPCR, respectively. Interestingly, not only HBoV1 but also HBoV4 and GBoV transduced pHAEs as well as primary human lung organoids. Flow cytometry analysis of pHAEs revealed distinct cellular specificities between the BoV isolates, with HBoV1 targeting ciliated, club, and KRT5+ basal cells, whereas HBoV4 showed a preference for KRT5+ basal cells. Surprisingly, primary human hepatocytes, skeletal muscle cells, and T cells were also highly amenable to rAAV/BoV transduction. Finally, we adapted our pipeline for AAV capsid gene shuffling to all five BoV isolates. Collectively, our chimeric rAAV/BoV vectors and bocaviral capsid library represent valuable new resources to dissect BoV biology and to breed unique gene therapy vectors.