Human bocavirus

Human bocavirus NP1 inhibits IFN-β production by blocking association of IFN regulatory factor 3 with IFNB promoter

Human bocavirus (HBoV) mainly infects young children. Although many infected children suffer from respiratory or gastroenteric tract diseases, an association between HBoV and these diseases is not definite. Because modulation of type I IFN is crucial for viruses to establish efficient replication, in this study, we tested whether HBoV modulates type I IFN production. We observed that a nearly full-length HBoV clone significantly reduced both Sendai virus (SeV)- and poly(deoxyadenylic-thymidylic) acid-induced IFN-β production. Further study showed that NP1 blocked IFN-β activation in response to SeV, poly(deoxyadenylic-thymidylic) acid, and IFN-β pathway inducers, including retinoic acid-inducible protein I, mitochondrial antiviral signaling protein, inhibitor of κB kinase ε, and TANK-binding kinase 1. In addition, NP1 interfered with IRF-3-responsive PRD(III-I) promoter activated by SeV and a constitutively active mutant of IRF-3 (IRF-3/5D). Although NP1 suppressed the IRF-3 pathway, it did not affect IRF-3 activation processes, including phosphorylation, dimerization, and nuclear translocation. Coimmunoprecipitation assays confirmed the interaction between NP1 and IRF-3. Additional deletion mutagenesis and coimmunoprecipitation assays revealed that NP1 bound to the DNA-binding domain of IRF-3, resulting in the interruption of an association between IRF-3 and IFNB promoter. Altogether, our results indicate that HBoV NP1 blocks IFN production through a unique mechanism. To our knowledge, this is the first study to investigate the modulation of innate immunity by HBoV. Our findings suggest a potential immune-evasion mechanism used by HBoV and provide a basis for better understanding HBoV pathogenesis.

Differential seroprevalence of human bocavirus species 1-4 in Beijing, China

Background

Four species of human bocaviruses (HBoV1-4) have been identified based on phylogenetic analysis since its first report in 2005. HBoV1 has been associated with respiratory disease, whereas HBoV2-4 are mainly detected in enteric infections. Although the prevalence of HBoVs in humans has been studied in some regions, it has not been well addressed globally.

Methodology/Principal Findings

Cross-reactivity of anti-VP2 antibodies was detected between HBoV1, 2, 3, and 4 in mouse and human serum. The prevalence of specific anti-VP2 IgG antibodies against HBoV1-4 was determined in different age groups of healthy individuals aged 0-70 years old in Beijing, China, using a competition ELISA assay based on virus-like particles of HBoV1-4. The seroprevalence of HBoV1-4 was 50%, 36.9%, 28.7%, and 0.8%, respectively, in children aged 0-14 years (n = 244); whereas the seroprevalence of HBoV1-4 was 66.9%, 49.3%, 38.7% and 1.4%, respectively, in healthy adults (≥15 years old; n = 142). The seropositive rate of HBoV1 was higher than that of HBoV2, HBoV3, and HBoV4 in individuals older than 0.5 years. Furthermore, IgG seroconversion of HBoV1 (10/31, 32.3%), HBoV2 (8/31, 25.8%), and HBoV3 (2/31, 6.5%) was found in paired sera collected from children with respiratory tract infections who were positive for HBoV1 according to PCR analysis.

Conclusions/Significance

Our data indicate that HBoV1 is more prevalent than HBoV2, HBoV3, and HBoV4 in the population we sampled in Beijing, China, suggesting that HBoV species may play differential roles in disease.

Parvoviruses: structure and infection

Parvoviruses package a ssDNA genome. Both nonpathogenic and pathogenic members exist, including those that cause fetal infections, encompassing the entire spectrum of virus phenotypes. Their small genomes and simple coding strategy has enabled functional annotation of many steps in the infectious life cycle. They assemble a multifunctional capsid responsible for cell recognition and the transport of the packaged genome to the nucleus for replication and progeny virus production. It is also the target of the host immune response. Understanding how the capsid structure relates to the function of parvoviruses provides a platform for recombinant engineering of viral gene delivery vectors for the treatment of clinical diseases, and is fundamental for dissecting the viral determinants of pathogenicity. This review focuses on our current understanding of parvovirus capsid structure and function with respect to the infectious life cycle.

Internal polyadenylation of parvoviral precursor mRNA limits progeny virus production

Aleutian Mink Disease Virus (AMDV) is the only virus in the genus Amdovirus of family Parvoviridae. In adult mink, AMDV causes a persistent infection associated with severe dysfunction of the immune system. Cleavage of AMDV capsid proteins has been previously shown to play a role in regulating progeny virus production (Fang Cheng et al., J. Virol. 84:2687-2696, 2010). The present study shows that AMDV has evolved a second strategy to limit expression of capsid proteins by preventing processing of the full-length capsid protein-encoding mRNA transcripts. Characterization of the cis-elements of the proximal polyadenylation site [(pA)p] in the infectious clone of AMDV revealed that polyadenylation at the (pA)p site is controlled by an upstream element (USE) of 200 nts in length, the AAUAAA signal, and a downstream element (DSE) of 40 nts. A decrease in polyadenylation at the (pA)p site, either by mutating the AAUAAA signal or the DSE, which does not affect the encoding of amino acids in the infectious clone, increased the expression of capsid protein VP1/VP2 and thereby increased progeny virus production approximately 2-3-fold. This increase was accompanied by enhanced replication of the AMDV genome. Thus, this study reveals correlations among internal polyadenylation, capsid production, viral DNA replication and progeny virus production of AMDV, indicating that internal polyadenylation is a limiting step for parvovirus replication and progeny virus production.

Circulating of human bocavirus 1, 2, 3, and 4 in pediatric patients with acute gastroenteritis in Thailand

Human bocavirus (HBoV) is a newly identified human parvovirus that associated with respiratory and gastrointestinal diseases. Epidemiological surveillance of HBoV was conducted on fecal specimens collected from hospitalized children with diarrhea in Chiang Mai, Thailand in 2011. Among a total of 222 fecal specimens tested, 17 (7.7%) were positive for HBoV by PCR. Of the 17 HBoV positive samples, double- or triple-infections together with other enteric viruses were found in 10 (58.8%) pediatric patients, while monoinfection with HBoV alone was detected in seven (41.2%) cases. Mixed infection among HBoV with norovirus GII was frequently observed in this population. The partial VP1 nucleotide sequences of all 17 HBoV strains demonstrated that all four species of HBoV were found in the specimens tested. Eleven strains were HBoV1. Other three strains showed the sequence identity with HBoV2, which were most closely related to the HBoV2A. In addition, other two HBoV strains showed the highest level of nucleotide sequence identity with the HBoV3. It was surprisingly to observe that one Thai HBoV strain showed a unique characteristic similar to the HBoV4, a rare species of HBoV found in acute gastroenteritis patients. In summary, this study presents the genetic background information of HBoV circulated in acute gastroenteritis children in Chiang Mai, Thailand and it was clearly demonstrated that HBoVs circulated in this area were genetically diverse as all four species of HBoVs (HBoV1-4) were detected in the fecal specimens collected from pediatric patients admitted to the hospitals in this area.

Respiratory viruses involved in influenza-like illness in a Greek pediatric population during the winter period of the years 2005-2008

Viruses are the major cause of pediatric respiratory tract infection and yet many suspected cases of illness remain uncharacterized. This study aimed to determine the distribution of several respiratory viruses in children diagnosed as having influenza‐like illness, over the winter period of 2005–2008. Molecular assays including conventional and real time PCR protocols, were employed to screen respiratory specimens, collected by clinicians of the Influenza sentinel system and of outpatient pediatric clinics, for identification of several respiratory viruses. Of 1,272 specimens tested, 814 (64%) were positive for at least one virus and included 387 influenza viruses, 160 rhinoviruses, 155 respiratory syncytial viruses, 95 adenoviruses, 81 bocaviruses, 47 parainfluenza viruses, 44 metapneumoviruses, and 30 coronaviruses. Simultaneous presence of two or three viruses was observed in 173 of the above positive cases, 21% of which included influenza virus and rhinovirus. The majority of positive cases occurred during January and February. Influenza virus predominated in children older than 1 year old, with type B being the dominant type for the first season and subtypes A/H3N2 and A/H1N1 the following two winter seasons, respectively. Respiratory syncytial virus prevailed in children younger than 2 years old, with subtypes A and B alternating from year to year. This is the most comprehensive study of the epidemiology of respiratory viruses in Greece, indicating influenza, rhinovirus and respiratory syncytial virus as major contributors to influenza‐like illness in children. J. Med. Virol. 83:1841–1848, 2011. © 2011 Wiley‐Liss, Inc.

Human bocavirus in the nasopharynx of otitis-prone children

OBJECTIVES

Human bocavirus (HBoV) is frequently identified in children with respiratory tract infections, and its role in acute otitis media (AOM) has been suggested. The disease associations for the closely related bocaviruses HBoV2-4 remain unknown. Increasing evidence shows that probiotics may reduce the risk of AOM of viral origin. Objectives of the study was to examine the prevalence and persistence of bocaviruses in consecutive nasopharyngeal samples (NPS) of otitis-prone children, and whether an association exists between HBoV and the child's characteristics, respiratory symptoms, and AOM pathogens, and whether probiotics reduce the occurrence of HBoV.

METHODS

In a double-blind, placebo-controlled, randomized, 6-month intervention study, 269 otitis-prone children (aged 9 months to 5.6 years), consumed daily either one capsule of probiotics (Lactobacillus rhamnosus GG, L. rhamnosus Lc705, Bifidobacterium breve 99 and Propionibacterium freudenreichii JS) or placebo. After a clinical examination and NPS collected at three-time points, the presence and persistence of HBoV1-4 DNA in NPS was determined by RT-qPCR at the baseline, after 3, and 6 months.

RESULTS

A high load (>10,000 copies/ml) of HBoV DNA was detected in 26 (17.1%) of 152 children, and 16 (10.5%) showed a prolonged presence of HBoV for at least 3 months. None had DNA of HBoV2-4. Higher number of siblings associated with increased HBoV prevalence (p=0.029). Prevalence or persistence of HBoV was not significantly associated with other characteristics, respiratory symptoms, or AOM pathogens. Probiotic intervention significantly reduced the number of HBoV DNA-positive samples (probiotic vs. placebo: 6.4% vs. 19.0%, OR=0.25, CI 95%=0.07-0.94, p=0.039).

CONCLUSIONS

HBoV, but not HBoV2-4, DNA occurs often in the nasopharynx of otitis-prone children, and may persist for 3-6 months. Probiotic treatment possibly reduced the presence of HBoV.

Infection, eosinophilia and childhood asthma

There is a growing list of viruses and bacteria associated with wheezing illness and asthma. It is well known that a few of these pathogens are strongly associated with wheezing illness and asthma exacerbations. What is not known is if early childhood infections with these pathogens cause asthma, and, if so, exactly what are the pathophysiologic mechanisms behind its development. The current consensus is respiratory infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between respiratory infection and asthma may be the eosinophil, a cell that plays prominently in asthma and allergy, but can also be found in the body in response to infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can also be used for diagnosis, treatment and monitoring. The optimal care of a patient must take into consideration not only symptoms, but also the underlying disease mechanisms.

High prevelance of human parvovirus infection in patients with malignant tumors

It is well known that the immunity of patients with malignant tumors decreases significantly. An increased parvovirus B19 (B19) infection rate has been observed in immunocompromised hosts. However, only a small amount of literature regarding the risk of human parvovirus infection in patients with malignant tumors is available. To evaluate the correlation of human parvovirus infection with malignant tumors, 288 serum samples from patients with malignant tumors were screened for B19 DNA by nested-PCR. The serum samples, 156 of which were from known clinicopathological cancer patients, were subjected to analysis of the seropositive rate of human bocavirus (HBoV), hepatitis B virus (HBV) and transfusion transmitted virus (TTV) by PCR. A total of 800 normal population sera and 941 aspirate samples from children with respiratory tract infections were used as controls for the detection of B19 and HBoV, respectively. Pairwise comparison between cancerous serum and control samples, and the correlation between parvovirus infection and clinicopathological variables, including gender and cancer type, were evaluated using the χ2 test, Fisher's exact test or the t-test. P<0.05 was considered to indicate a statistically significant difference. The overall prevalence of B19 DNA in cancer patients was 50.69% (146/288), which was significantly higher than that of the healthy controls with 4.5% (36/800) (χ2 test, P<0.0001). Similar results were obtained for HBoV with a 39.74% (62/156) prevalence in cancer patients. However, the infection prevalence of HBV and TTV in the cancer patients was 5.13 (8/156) and 6.41% (10/156), respectively (P<0.0001), which was much less than that of B19 and HBoV. These results revealed that a high risk of B19 and HBoV infection occurred in cancer patients, and a potential correlation exists between parvovirus infection and occurrence of malignant tumors.

Genomic features of the human bocaviruses

The human bocavirus (HBoV) was initially discovered in 2005 as the second pathogenic member of the parvovirus family, next to the human parvovirus B19. HBoV has since been shown to be extremely common worldwide and to cause a systemic infection in small children often resulting in respiratory disease. Three more, presumably enteric, human bocaviruses (HBoV2-4) have been identified in stool samples. Parvoviruses are assumed to replicate via their genomic terminal hairpin-like structures in a so-called 'rolling-hairpin model'. These terminal sequences have recently been partially identified in head-to-tail HBoV-PCR amplicons from clinical samples, and are most likely hybrid relics of HBoV's predecessors, namely bovine parvovirus 1 on the left-hand side and minute virus of canines on the right, shown for the first time in this article. Thereby, the replication model postulated for HBoV remains questionable as the occurrence of head-to-tail sequences is not a typical feature of the rolling-hairpin replication model. However, such episomes can also be persistent storage forms of the genome.

High frequency of human bocavirus 1 DNA in infants and adults with lower acute respiratory infection

Human bocavirus (HBoV) is a parvovirus with a possible aetiological role in respiratory disease that is currently under investigation. We detected HBoV1 in children and adults hospitalized with acute disease of the lower respiratory tract. HBoV genome was detected by PCR in nasopharyngeal swabs collected from 75 patients aged 0-89 years during 2010. HBoV was found in 17/75 (22.7 %) patients, 64.7 % of them infants younger than 1 year old and 29.4 % adults older than 30 years [the bimodal age distribution among HBoV-positive (HBoV(+)) patients was statistically significant, P<0.001]. Of all HBoV(+) cases, 35.3 % were co-infected; all co-infections occurred in children (≤13 years old) and 83.3 % of them were HBoV-respiratory syncytial virus (RSV) co-infections. Among infants younger than 1 year, 50 % HBoV(+) specimens were co-infected, all of them with RSV. The rate of co-infection in infants was significantly higher compared to the frequency of co-infection in the whole cohort (P = 0.003). The results suggest that HBoV1 is involved in acute respiratory disease. Interplay between HBoV1 and RSV cannot be discarded as a cause of elevated percentages of co-detections in infants.

The fecal virome of pigs on a high-density farm

Swine are an important source of proteins worldwide but are subject to frequent viral outbreaks and numerous infections capable of infecting humans. Modern farming conditions may also increase viral transmission and potential zoonotic spread. We describe here the metagenomics-derived virome in the feces of 24 healthy and 12 diarrheic piglets on a high-density farm. An average of 4.2 different mammalian viruses were shed by healthy piglets, reflecting a high level of asymptomatic infections. Diarrheic pigs shed an average of 5.4 different mammalian viruses. Ninety-nine percent of the viral sequences were related to the RNA virus families Picornaviridae, Astroviridae, Coronaviridae, and Caliciviridae, while 1% were related to the small DNA virus families Circoviridae, and Parvoviridae. Porcine RNA viruses identified, in order of decreasing number of sequence reads, consisted of kobuviruses, astroviruses, enteroviruses, sapoviruses, sapeloviruses, coronaviruses, bocaviruses, and teschoviruses. The near-full genomes of multiple novel species of porcine astroviruses and bocaviruses were generated and phylogenetically analyzed. Multiple small circular DNA genomes encoding replicase proteins plus two highly divergent members of the Picornavirales order were also characterized. The possible origin of these viral genomes from pig-infecting protozoans and nematodes, based on closest sequence similarities, is discussed. In summary, an unbiased survey of viruses in the feces of intensely farmed animals revealed frequent coinfections with a highly diverse set of viruses providing favorable conditions for viral recombination. Viral surveys of animals can readily document the circulation of known and new viruses, facilitating the detection of emerging viruses and prospective evaluation of their pathogenic and zoonotic potentials.

Human bocavirus and other respiratory viral infections in a 2-year cohort of hospitalized children

Human bocavirus (HBoV) infection is reported worldwide and may cause severe respiratory tract infections. The aim of the present study was to assess the prevalence of HBoV, and other respiratory viral pathogens, in a 2‐year retrospective study of children admitted to hospital, and to investigate whether viral loads of HBoV DNA were associated with severity of infection. Between April 2007 and March 2009, 891 respiratory samples from 760 children admitted to hospital with acute respiratory tract infection were tested for the presence of respiratory viruses by real‐time PCR or direct immunofluorescence testing. HBoV DNA was detected by using internally controlled real‐time quantitative PCR assay and 25 samples selected at random were sequenced. The virus detected most frequently was rhinovirus, followed by respiratory syncytial virus, HBoV, and human metapneumovirus. HBoV DNA was detected in 18.4% of children admitted to hospital. HBoV was the only viral pathogen detected in 66/164 (40.2%) of HBoV DNA‐positive children and in 7.4% of all 891 samples. Ninety‐seven percent (64/66) of children with an HBoV single infection were diagnosed as having lower respiratory tract infection. Median HBoV DNA viral load was significantly higher in children when HBoV was detected as a single pathogen. Higher HBoV DNA viral loads were associated with prematurity and age. HBoV seems to be an important and frequent pathogen in respiratory tract infections in children, and it is likely that the severity of illness is comparable to the severity of RSV illness. J. Med. Virol. 84:99–108, 2011. © 2011 Wiley Periodicals, Inc.

Seroepidemiology of human bocaviruses 1-4

BACKGROUND

Recently, 3 new members of the genus Bocavirus, human bocavirus 2 (HBoV2), human bocavirus 3 (HBoV3), and human bocavirus 4 (HBoV4), were discovered. HBoV2-4 occur mainly in the gastrointestinal tract but rarely in the respiratory tract, contrary to human bocavirus 1 (HBoV1).

METHODS

To investigate HBoV1-4 seroepidemiology among 195 adults and 252 wheezing children, we conducted immunoglobulin G (IgG) and immunoglobulin M (IgM) enzyme immunoassays with recombinant viruslike particles (VLPs). The children's sera were also tested for HBoV1-4 DNA by quantitative polymerase chain reaction (qPCR).

RESULTS

Both rabbit and human antibodies to HBoV1-4 VP2 VLPs were found to be cross-reactive. After depletion of HBoV1-reactive antibodies, the HBoV2-4 approximate seroprevalences in adults were 34%, 15%, and 2% and in children aged 1-2 years 25%, 10%, and 5%, respectively. After depletion of HBoV2-4-reactive antibodies, the HBoV1 seroprevalence among adults decreased from 96% to 59%. No cross-reactivity of human anti-HBoV IgG was observed with bovine parvovirus1, parvovirus B19 or PARV4. No child was HBoV2-4 viremic.

CONCLUSIONS

HBoV2-4 infect humans less commonly and elicit weaker B-cell responses than HBoV1. In our study HBoV2-4 did not seem to have a major etiological role in wheezing. Cross-reactivity with HBoV2-4 IgG partially accounts for the high HBoV1 seroprevalences previously reported. Correction for cross-reactivity is a prerequisite for VLP-based HBoV seroepidemiology.

Bocavirus episome in infected human tissue contains non-identical termini

Human bocaviruses (HBoV) are highly prevalent human infections whose pathogenic potential remains unknown. Recent identification of the first non-human primate bocavirus [1] in captive gorillas raised the possibility of the persistent nature of bocavirus infection. To characterize bocavirus infection in humans, we tested intestinal biopsies from 22 children with gastrointestinal disease for the presence of HBoV DNA. Four HBoV-positive tissue samples were analyzed to determine whether viral DNA was present in the linear genomic, the episomal closed circular or the host genome-integrated form. Whereas one tissue sample positive for HBoV3 contained the episomal form (HBoV3-E1), none had the genome-integrated form. The complete genome sequence of HBoV3-E1 contains 5319 nucleotides of which 513 represent the non-coding terminal sequence. The secondary structure of HBoV3-E1 termini suggests several conserved and variable features among human and animal bocaviruses. Our observation that HBoV genome exists as head-to-tail monomer in infected tissue either reflects the likely evolution of alternative replication mechanism in primate bocaviruses or a mechanism of viral persistence in their host. Moreover, we identified the HBoV genomic terminal sequences that will be helpful in developing reverse genetic systems for these widely prevalent parvoviruses.

Significance

HBoV have been found in healthy human controls as well as individuals with respiratory or gastrointestinal disease. Our findings suggest that HBoV DNA can exist as episomes in infected human tissues and therefore can likely establish persistent infection in the host. Previous efforts to grow HBoV in cell culture and to develop reverse genetic systems have been unsuccessful. Complete genomic sequence of the HBoV3 episome and its genomic termini will improve our understanding of HBoV replication mechanism and its pathogenesis.

Viral infections of the lower respiratory tract: old viruses, new viruses, and the role of diagnosis

Viral infections of the lower respiratory tract cause an enormous disease burden in children, and the role of respiratory viruses in serious lower respiratory tract infections (LRTIs) in older adults is increasingly appreciated. Although viruses are responsible for a large proportion LRTIs, antibiotics are often prescribed. New diagnostic platforms have the potential to detect a wider range of established and newly discovered viruses with greater sensitivity. This will create additional challenges. Although it is clear that influenza, parainfluenza, respiratory syncytial virus, human metapneumovirus, and adenovirus are important causes of pneumonia, the role of rhinoviruses and some of the newly described viruses, including human coronaviruses and bocavirus, is harder to determine. Better diagnostic tests that establish the cause of LRTIs in children have the potential to both reduce overall antibiotic use and to improve the targeted use of antibiotics. In addition, rapid identification of viral infections can help control nosocomial transmission.

Genomic characterization and high prevalence of bocaviruses in swine

Using random PCR amplification followed by plasmid subcloning and DNA sequencing, we detected bocavirus related sequences in 9 out of 17 porcine stool samples. Using primer walking, we sequenced the nearly complete genomes of two highly divergent bocaviruses we provisionally named porcine bocavirus 1 isolate H18 (PBoV1-H18) and porcine bocavirus 2 isolate A6 (PBoV2-A6) which differed by 51.8% in their NS1 protein. Phylogenetic analysis indicated that PBoV1-H18 was very closely related to a ∼2 Kb central region of a porcine bocavirus-like virus (PBo-LikeV) from Sweden described in 2009. PBoV2-A6 was very closely related to the porcine bocavirus genomes PBoV-1 and PBoV2 from China described in 2010. Among 340 fecal samples collected from different age, asymptomatic swine in five Chinese provinces, the prevalence of PBoV1-H18 and PBoV2-A6 related viruses were 45-75% and 55-70% respectively, with 30-47% of pigs co-infected. PBoV1-A6 related strains were highly conserved, while PBoV2-H18 related strains were more diverse, grouping into two genotypes corresponding to the previously described PBoV1 and PBoV2. Together with the recently described partial bocavirus genomes labeled V6 and V7, a total of three major porcine bocavirus clades have therefore been described to date. Further studies will be required to elucidate the possible pathogenic impact of these diverse bocaviruses either alone or in combination with other porcine viruses.

Molecular diagnostic assays for detection of viral respiratory pathogens in institutional outbreaks

Outbreaks of viral respiratory disease in institutions may be associated with high morbidity and mortality, depending upon the viral etiology and the age and immune status of the affected patients. Control of outbreaks may include isolation and/or cohorting, and prohylaxis or treatment with specific antiviral agents may be indicated, all dependent upon the specific cause of the outbreak. Conventional methods of viral diagnosis detect only a limited number of the viruses that are known to cause outbreaks. The availability of sensitive and specific molecular assays has facilitated rapid diagnosis of a wider range of viruses from respiratory outbreaks. Molecular methods have distinct advantages over conventional methods, including the ability to rapidly develop assays for emerging viruses and new variants of existing viruses. In addition, molecular testing allows rapid detection of resistance to antiviral agents or mutations leading to increased virulence. However, high-throughput molecular testing requires batch processes that may compromise the ability to respond quickly to urgent testing demands.

Kawasaki disease and human bocavirus--potential association?

Kawasaki disease (KD) is an acute febrile multisystem vasculitic syndrome of unknown etiology, occurring mostly in infants and children younger than 5 years of age. We present a 13-month-old male with KD from whom was found human bocavirus DNA in nasopharyngeal secretions. Human bocavirus DNA in a patient with KD raised question about the coincidental or possible etiological association.

Hospital-acquired human bocavirus in infants

Human bocavirus (HBoV) is a respiratory pathogen that affects young children. We screened 511 nasopharyngeal aspirates for hospital-acquired HBoV from infants hospitalised with respiratory infection from January to December 2008. Among 55 children with HBoV infection, 10 cases were hospital-acquired. Compared with the community-acquired cases, coinfection with other respiratory viruses in these patients was uncommon. HBoV should be considered for inclusion in screening protocols for nosocomial childhood respiratory infections, especially in intensive care units.

Respiratory viruses, eosinophilia and their roles in childhood asthma

With the advent of highly sensitive and specific screening of respiratory specimens for viruses, new viruses are discovered, adding to the growing list of those associated with wheezing illness and asthma exacerbations. It is not known whether early childhood infections with these viruses cause asthma, and, if so, what exactly are the pathophysiologic mechanisms behind its development. The current consensus is that respiratory viral infection works together with allergy to produce the immune and physiologic conditions necessary for asthma diasthesis. One link between viruses and asthma may be the eosinophil, a cell that plays a prominent role in asthma and allergy, but can also be found in the body in response to viral infection. In turn, the eosinophil and its associated products may be novel therapeutic targets, or at the very least, used to elucidate the complex pathophysiologic pathways of asthma and other respiratory illnesses. Together or separately, they can be used for diagnosis, treatment and monitoring. Not only symptoms, but also the underlying disease mechanisms must be taken into consideration for the optimal care of a patient.

Molecular monitoring of causative viruses in child acute respiratory infection in endemo-epidemic situations in Shanghai

BACKGROUND

Numerous viruses are responsible for respiratory infections; however, both their distribution and genetic diversity, in a limited area and a population subgroup, have been studied only rarely during a sustained period of time.

METHODS

A 2-year surveillance program of children presenting with acute respiratory infections (ARIs) was carried out to characterize the viral etiology and to assess whether using gene amplification and sequencing could be a reliable approach to monitor virus introduction and spread in a population subgroup.

RESULTS

Using multiplex RT-PCR, 15 different respiratory viruses were detected within the 486 nasopharyngeal positive samples collected among 817 children aged <9-year old who presented with ARI during October 2006 to September 2008. A single virus was detected in 373 patients (45.7%), and two to four viruses in 113 patients (13.8%). The most frequent causative viruses were respiratory syncytial virus (RSV) (24.7%), human bocavirus (24.5%), and human rhinovirus (HRV) (15%). RSV was more prevalent in winter and among young infants. Cases of seasonal influenza A and B viruses were reported mainly in January and August. An increase in adenovirus infection was observed during the spring of the second year of the study. Sequence analyses showed multiple introductions of different virus subtypes and identified a high prevalence of the newly defined HRV-C species. A higher viral incidence was observed during the winter of 2008, which was unusually cold.

CONCLUSIONS

This study supports the usefulness of multiplex RT-PCR for virus detection and co-infection, and for implementation of a molecular monitoring system for endemic and epidemic viral respiratory infections.

Frequency of human bocavirus (HBoV) infection among children with febrile respiratory symptoms in Argentina, Nicaragua and Peru

BACKGROUND

Globally, respiratory infections are the primary cause of illness in developing countries, specifically among children; however, an etiological agent for many of these illnesses is rarely identified.

OBJECTIVES

Our study aimed to estimate the frequency of human bocavirus (HBoV) infection among pediatric populations in Argentina, Nicaragua and Peru.

METHODS

We conducted a cross-sectional study using stored samples of an influenza-like illness surveillance program. Irrespective of previous diagnosis, nasopharyngeal or nasal swab specimens were randomly selected and tested using real-time PCR from three sites during 2007 from patients younger than 6 years old.

RESULTS

A total of 568 specimens from Argentina (185), Nicaragua (192) and Peru (191) were tested. The prevalence of HBoV was 10·8% (95% CI: 6·3; 15·3) in Argentina, 33·3% in Nicaragua (95% CI: 26·6; 40·1) and 25·1% in Peru (95% CI: 18·9; 31·3).

CONCLUSIONS

These findings demonstrate circulation of HBoV in Argentina, Nicaragua and Peru among children with influenza-like symptoms enrolled in a sentinel surveillance program.

A novel RT-multiplex PCR for detection of Aichi virus, human parechovirus, enteroviruses, and human bocavirus among infants and children with acute gastroenteritis

A novel reverse transcription-multiplex polymerase chain reaction assay was developed to detect Aichi virus, human parechovirus, enteroviruses, and human bocavirus. A mixture of four pairs of published specific primers, 6261 and 6779, ev22(+) and ev22(-), F1 and R1, 188F and 542R, was used to amplify the viral genomes and specifically generate four different amplicon sizes of 519, 270, 440, and 354 bp for Aichi virus, human parechovirus, enteroviruses, and human bocavirus, respectively. A total of 247 fecal specimens previously screened for rotavirus, adenovirus, norovirus, sapovirus, and astrovirus-negative, collected from infants and children with acute gastroenteritis in Japan from July 2007 to June 2008, were tested further for the presence of the four viruses, Aichi virus, human parechovirus, enteroviruses, and human bocavirus, by RT-multiplex PCR. The total detection rate of these viruses was 26.7% (66 out of 247 samples). Of these, HPeV, EVs, and HBoV were identified in 20, 41, and 5 specimens. No Aichi virus was found among these subjects. The sensitivity and specificity of RT-multiplex PCR were assessed and demonstrated a strong validation against RT-monoplex PCR. This is the first report of detecting these types of viruses in fecal samples from infants and children with acute gastroenteritis by RT-multiplex PCR.

Widespread infection with homologues of human parvoviruses B19, PARV4, and human bocavirus of chimpanzees and gorillas in the wild

Infections with human parvoviruses B19 and recently discovered human bocaviruses (HBoVs) are widespread, while PARV4 infections are transmitted parenterally and prevalent specifically in injecting drug users and hemophiliacs. To investigate the exposure and circulation of parvoviruses related to B19 virus, PARV4, and HBoV in nonhuman primates, plasma samples collected from 73 Cameroonian wild-caught chimpanzees and gorillas and 91 Old World monkey (OWM) species were screened for antibodies to recombinant B19 virus, PARV4, and HBoV VP2 antigens by enzyme-linked immunosorbent assay (ELISA). Moderate to high frequencies of seroreactivity to PARV4 (63% and 18% in chimpanzees and gorillas, respectively), HBoV (73% and 36%), and B19 virus (8% and 27%) were recorded for apes, while OWMs were uniformly negative (for PARV4 and B19 virus) or infrequently reactive (3% for HBoV). For genetic characterization, plasma samples and 54 fecal samples from chimpanzees and gorillas collected from Cameroonian forest floors were screened by PCR with primers conserved within Erythrovirus, Bocavirus, and PARV4 genera. Two plasma samples (chimpanzee and baboon) were positive for PARV4, while four fecal samples were positive for HBoV-like viruses. The chimpanzee PARV4 variant showed 18% and 15% nucleotide sequence divergence in NS and VP1/2, respectively, from human variants (9% and 7% amino acid, respectively), while the baboon variant was substantially more divergent, mirroring host phylogeny. Ape HBoV variants showed complex sequence relationships with human viruses, comprising separate divergent homologues of HBoV1 and the recombinant HBoV3 species in chimpanzees and a novel recombinant species in gorillas. This study provides the first evidence for widespread circulation of parvoviruses in primates and enables future investigations of their epidemiology, host specificity, and (co)evolutionary histories.

Identification and characterization of a new bocavirus species in gorillas

A novel parvovirus, provisionally named Gorilla Bocavirus species 1 (GBoV1), was identified in four stool samples from Western gorillas (Gorilla gorilla) with acute enteritis. The complete genomic sequence of the new parvovirus revealed three open reading frames (ORFs) with an organization similar to that of known bocaviruses. Phylogenetic analysis using complete capsid and non structural (NS) gene sequence suggested that the new parvovirus is most closely related to human bocaviruses (HBoV). However, the NS ORF is more similar in length to the NS ORF found in canine minute virus and bovine parvovirus than in HBoV. Comparative genetic analysis using GBoV and HBoV genomes enabled characterization of unique splice donor and acceptor sites that appear to be highly conserved among all four HBoV species, and provided evidence for expression of two different NS proteins in all primate bocaviruses. GBoV is the first non-human primate bocavirus identified and provides new insights into the genetic diversity and evolution of this highly prevalent and recently discovered group of parvoviruses.

High prevalence of antibodies against polyomavirus WU, polyomavirus KI, and human bocavirus in German blood donors

Background

DNA of the polyomaviruses WU (WUPyV) and KI (KIPyV) and of human bocavirus (HBoV) has been detected with varying frequency in respiratory tract samples of children. However, only little is known about the humoral immune response against these viruses. Our aim was to establish virus-specific serological assays and to determine the prevalence of immunoglobulin G (IgG) against these three viruses in the general population.

Methods

The capsid proteins VP1 of WUPyV and KIPyV and VP2 of HBoV were cloned into baculovirus vectors and expressed in Sf9 insect cells. IgG antibodies against WUPyV VP1, KIPyV VP1, and HBoV VP2 were determined by immunofluorescence assays in 100 plasma samples of blood donors.

Results

The median age of the blood donors was 31 years (range 20 - 66 yrs), 52% were male. 89% of the samples were positive for WUPyV IgG (median age 31 yrs, 49.4% male), 67% were positive for KIPyV IgG (median age 32 yrs, 46.3% male), and 76% were positive for HBoV IgG (median age 32 yrs, 51.3% male). For WUPyV and HBoV, there were no significant differences of the seropositivity rates with respect to age groups or gender. For KIPyV, the seropositivity rate increased significantly from 59% in the age group 20 - 29 years to 100% in the age group > 50 years.

Conclusions

High prevalences of antibodies against WUPyV, KIPyV, and HBoV were found in plasma samples of healthy adults. The results indicate that primary infection with these viruses occurs during childhood or youth. For KIPyV, the seropositivity appears to increase further during adulthood.

High prevalence of a novel porcine bocavirus in weanling piglets with respiratory tract symptoms in China

This study presents the first evidence of infection by a novel porcine bocavirus (PBoV) in Chinese swine herds. The PCR detection results showed that PBoV was significantly more prevalent in weanling piglets (69.7%, 69/99) with respiratory tract symptoms than that in other samples (0-13.6%) (P < 0.01). Sequence analysis showed that the partial VP1/2 genes were highly conserved (99-100% identity), and only five frequent nucleotide mutation positions existed in Chinese PBoV strains. These data indicate that PBoV might be an emerging virus for swine respiratory tract diseases. This study could help us to better understand the epidemiology of PBoV.

Human bocaviruses are highly diverse, dispersed, recombination prone, and prevalent in enteric infections

A new species of parvovirus, tentatively named human bocavirus 4 (HBoV4), was genetically characterized. Among 641 feces samples obtained from children and adults, the most commonly detected bocavirus species were, in descending order, HBoV2, HBoV3, HBoV4, and HBoV1, with an HBoV2 prevalence of 21% and 26% in Nigerian and Tunisian children, respectively. HBoV3 or HBoV4 species were found in 12 of 192 patients with non-polio acute flaccid paralysis in Tunisia and Nigeria and 0 of 96 healthy Tunisian contacts (P= .01). Evidence of extensive recombination at the NP1 and VP1 gene boundary between and within bocavirus species was found. The high degree of genetic diversity seen among the human bocaviruses found in feces specimens, relative to the highly homogeneous HBoV1, suggest that this worldwide-distributed respiratory pathogen may have recently evolved from an enteric bocavirus after acquiring an expanded tropism favoring the respiratory tract. Elucidating the possible role of the newly identified enteric bocaviruses in human diseases, including acute flaccid paralysis and diarrhea, will require further epidemiological studies.

Correlation between bocavirus infection and humoral response, and co-infection with other respiratory viruses in children with acute respiratory infection

BACKGROUND

Human bocavirus (HBoV), a recently discovered virus, is prevalent among children with respiratory tract infection throughout the world. Co-infection was frequently found in HBoV-positive patients. Thus, whether HBoV is responsible for the respiratory disease is still arguable.

OBJECTIVES

A comprehensive study was carried out to integrate clinical and virological prevalence in HBoV-positive outpatient children, and to determine genetic and serologic characteristics of HBoV in Shanghai, China.

STUDY DESIGN

Nasal/throat swabs and sera were obtained over a 2-year period from 817 children with respiratory tract infection to examine the presence of HBoV and its co-infection. The seroepidemiology of HBoV was studied by ELISA and Western blot against the capsid protein VP2-based fragment. Persistence of HBoV was also analyzed in 12 pairs of return-visit cases.

RESULTS

HBoV was identified in 96 samples (11.8%). The co-infection rate with other respiratory viruses was 51%. IgM was detected in 55.7% of HBoV RT-PCR-positive patients, and in 72.7% of those who had high viral genome load. In addition, persistent viral DNA positivity was detected in 10 of 12 HBoV-positive cases tested, an average of 14 days later, and one child was still HBoV-positive after 31 days.

CONCLUSION

HBoV was found frequently in children with respiratory tract symptoms associated with other respiratory viruses, and persisted in the respiratory tract and in serum and urine. The presence of IgM was significantly more prevalent in viremic patients and those diagnosed with high load of HBoV DNA in nasal/throat swabs.

Human bocavirus in very young infants hospitalized with acute respiratory infection in northeast Brazil

A cross-sectional study was carried out over a period of 12 months to investigate the occurrence of human bocavirus (HBoV) infection in infants hospitalized for respiratory infections in a teaching hospital in Salvador, Brazil, and to describe the clinical manifestations of this infection. Nasopharyngeal aspirates were collected from the children and immunofluorescence and polymerase chain reaction were performed to investigate the presence of respiratory viruses. HBoV was detected in 4 out of 66 patients. Two of the HBoV-positive infants were co-infected with other viruses. The principal clinical findings in HBoV-positive children were: nasal obstruction, catarrh, cough, fever and dyspnea. This study revealed HBoV infection in children aged <2 months, suggesting that the infection may occur at a very early age.

Bocavirus infection induces mitochondrion-mediated apoptosis and cell cycle arrest at G2/M phase

Bocavirus is a newly classified genus of the family Parvovirinae. Infection with Bocavirus minute virus of canines (MVC) produces a strong cytopathic effect in permissive Walter Reed/3873D (WRD) canine cells. We have systematically characterized the MVC infection-produced cytopathic effect in WRD cells, namely, the cell death and cell cycle arrest, and carefully examined how MVC infection induces the cytopathic effect. We found that MVC infection induces an apoptotic cell death characterized by Bax translocalization to the mitochondrial outer membrane, disruption of the mitochondrial outer membrane potential, and caspase activation. Moreover, we observed that the activation of caspases occurred only when the MVC genome was replicating, suggesting that replication of the MVC genome induces apoptosis. MVC infection also induced a gradual cell cycle arrest from the S phase in early infection to the G(2)/M phase at a later stage, which was confirmed by the upregulation of cyclin B1 and phosphorylation of cdc2. Cell cycle arrest at the G(2)/M phase was reproduced by transfection of a nonreplicative NS1 knockout mutant of the MVC infectious clone, as well as by inoculation of UV-irradiated MVC. In contrast with other parvoviruses, only expression of the MVC proteins by transfection did not induce apoptosis or cell cycle arrest. Taken together, our results demonstrate that MVC infection induces a mitochondrion-mediated apoptosis that is dependent on the replication of the viral genome, and the MVC genome per se is able to arrest the cell cycle at the G(2)/M phase. Our results may shed light on the molecular pathogenesis of Bocavirus infection in general.

Hematopoietic cell transplantation and emerging viral infections

Viral infections remain important causes of morbidity and mortality in hematopoietic cell transplant recipients. More recent developments in preparative regimens and graft manipulations, as well as the control of well-recognized post-transplant infections by the introduction of prophylaxis and preemptive strategies, have influenced the timing and the epidemiology of infections. As new pathogens, such as human metapneumovirus (HMPV), human bocavirus, human coronaviruses HCoV-NL63 and HCoV-HKU1, human herpesviruses HHV-6 and HHV-7, and polyomaviruses, have emerged, it is fundamental to determine the significance of the newly discovered viruses and their role in the transplantation field. This article summarizes recent data on epidemiology and laboratory diagnosis of new pathogens, as well as clinical features and management of the associated infectious complications. J. Med. Virol. 82:528-538, 2010. (c) 2010 Wiley-Liss, Inc.

Human bocavirus infections in hospitalized Greek children

INTRODUCTION

The epidemiology of human bocavirus (HBoV) infections has not been described in Greece, a south-eastern European country. To define the epidemiological profile and the clinical characteristics associated with HBoV infection in a population of children hospitalized with respiratory tract infection.

MATERIAL AND METHODS

During a one-year period throat swab samples were collected from 370 previously healthy children, aged 14 days to 13 years, admitted to two different paediatric wards because of respiratory tract infection. Samples were tested for HBoV by PCR amplifying a part of the NS1 gene.

RESULTS

Human bocavirus was detected in 12 children (3.2%). Four of the 12 cases were co-infections, 3 of them with influenza A and 1 with coronavirus OC43. Cases were observed only during the cold months. The mean age of children was 1.8 years (range 2 months to 4 years). The most common symptoms were fever, cough and various degrees of respiratory distress. All children were clinically diagnosed as having lower respiratory tract infections, mainly pneumonia and acute laryngotracheobronchitis, and recovered uneventfully.

CONCLUSIONS

HBoV infections occur in Greece mostly among very young children. They accounted for 3.2% of children hospitalized with acute respiratory disease. Cases were observed only in late autumn to early spring.

Serologically verified human bocavirus pneumonia in children

WORKING HYPOTHESIS

Human bocavirus (HBoV) is a newly identified parvovirus frequently found in children suffering from acute respiratory and intestinal infections. The aim of the present study was to evaluate, by using a newly developed antibody assay, the role of HBoV in pediatric community-acquired pneumonia (CAP) and the seropositivity rate to HBoV in a prospective study in North-Italian children.

MATERIALS/PATIENTS AND METHODS

During a 15-month study period, 124 children were admitted due to presumptive pneumonia, and in 101 of them, pneumonia was radiologically confirmed. The etiology of CAP was studied by antibody assays to 16 microbes, including the newly developed enzyme immunoassay for HBoV.

RESULTS

Serological evidence of acute HBoV infection was found in 12 (12%) children, being single in 7 and mixed in 5 cases (4 with other viruses and 3 with bacteria). IgM was positive in 11 cases. A diagnostic rise in IgG antibodies between paired sera was observed in six cases. HBoV was the second most common virus next to respiratory syncytial virus (17%). The seropositivity rate to HBoV increased with age, reaching nearly 100% before school age.

CONCLUSIONS

The present results show that HBoV is able to induce significant antibody responses and suggest that HBoV may be a fairly common cause of pneumonia in children. Seroconversion to HBoV in most children takes place in early childhood.

The detection of parvoviruses

Parvovirus B19 is a single-stranded DNA virus which causes severe disease in immunocompromised patients and foetal loss in pregnant women. It is classified as an Erythrovirus and this genus also comprises two related viral genotypes (so-called LaLi/A6 (genotype 2) and V9 (genotype 3)) which appear to be immunologically indistinguishable from Parvovirus B19. Serological and nucleic acid test (NAT) systems to detect Parvovirus B19-mediated infection are commercially available; however, some NAT systems are genotype-specific. International standard preparations of Parvovirus B19 IgG and DNA have been produced for assay standardisation purposes, and to ensure consistency of assay manufacture and performance. Immunological assays, such as B-cell ELISpot, T-cell stimulation, and cytokine detection can also be used to confirm exposure to Parvovirus B19. Immunohistochemical techniques, employing commercially available monoclonal antibodies, are used to localise the virus in infected tissue and Parvovirus B19 viral antigen can also be detected in serum and plasma using antigen-specific ELISA. NAT systems have also been described to detect newly identified parvoviruses such as human bocavirus (HBoV), PARV4, and PARV5, although absolute confirmation of clinical diseases associated with these agents is required. This chapter describes the current status of detection systems for all the aforementioned parvoviruses, with particular emphasis on Erythrovirus detection by serological, NAT, and immunological approaches.

Management of bacterial infections in children with asthma

Respiratory viruses are the single most common causes of asthma exacerbations in children. Rhinovirus-induced wheezing is a risk factor for chronic asthma, but its mechanism has remained unknown. Human bocavirus is a common finding in wheezing children, but its role as a respiratory pathogen is still unclear. Mycoplasma pneumoniae may, like viruses, induce wheezing and asthma exacerbation. Chlamydia pneumoniae and, in recent studies, Chlamydia trachomatis, may not only induce asthma exacerbations but may also be involved in the pathogenesis of chronic asthma. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis are often involved in respiratory infections associated with wheezing, but there is no evidence for their active role in asthma pathogenesis or exacerbation. This review summarizes current knowledge on the association between respiratory infections and asthma in children, with a special focus on the role of antibiotics in incipient asthma, asthma exacerbation and chronic stable asthma.

Rapid molecular evolution of human bocavirus revealed by Bayesian coalescent inference

Human bocavirus (HBoV) is a linear single-stranded DNA virus belonging to the Parvoviridae family that has recently been isolated from the upper respiratory tract of children with acute respiratory infection. All of the strains observed so far segregate into two genotypes (1 and 2) with a low level of polymorphism. Given the recent description of the infection and the lack of epidemiological and molecular data, we estimated the virus's rates of molecular evolution and population dynamics. A dataset of forty-nine dated VP2 sequences, including also eight new isolates obtained from pharyngeal swabs of Italian patients with acute respiratory tract infections, was submitted to phylogenetic analysis. The model parameters, evolutionary rates and population dynamics were co-estimated using a Bayesian Markov Chain Monte Carlo approach, and site-specific positive and negative selection was also investigated. Recombination was investigated by seven different methods and one suspected recombinant strain was excluded from further analysis. The estimated mean evolutionary rate of HBoV was 8.6x10(-4)subs/site/year, and that of the 1st+2nd codon positions was more than 15 times less than that of the 3rd codon position. Viral population dynamics analysis revealed that the two known genotypes diverged recently (mean tMRCA: 24 years), and that the epidemic due to HBoV genotype 2 grew exponentially at a rate of 1.01year(-1). Selection analysis of the partial VP2 showed that 8.5% of sites were under significant negative pressure and the absence of positive selection. Our results show that, like other parvoviruses, HBoV is characterised by a rapid evolution. The low level of polymorphism is probably due to a relatively recent divergence between the circulating genotypes and strong purifying selection acting on viral antigens.