Human bocavirus in Iranian children with acute respiratory infections

Seroepidemiology of human bocavirus defined using recombinant virus-like particles

BACKGROUND

Human bocavirus (HBoV) is a newly identified human parvovirus for which seroepidemiology and antigenic properties remain undefined.

METHODS

The HBoV VP2 gene, expressed from a baculovirus vector, produced virus-like particles (VLPs), which were used to raise rabbit anti-HBoV antisera and to develop an enzyme-linked immunosorbent assay (ELISA). The VLP-based ELISA was used to screen for HBoV-specific immunoglobulin G antibodies in a convenience sample of 270 serum specimens, mostly from children, obtained at Yale-New Haven Hospital; 208 specimens were also screened for erythrovirus B19-specific antibodies by a B19 VLP-based ELISA.

RESULTS

Immunofluorescence and ELISA showed that human parvoviruses HBoV and B19 are antigenically distinct. By the HBoV VLP-based ELISA, 91.8% and 63.6% of serum specimens from infants in the first and second months of life, respectively, were found to be seropositive, as were 45.4% from 3-month-old infants and 25.0% from 4-month-old infants. The percentages of HBoV-seropositive children increased to 40.7%-60.0% for children 5-47 months of age and to >85% for individuals >or=48 months old. However, the overall percentage of B19-seropositive individuals was <40.5% for all age groups screened.

CONCLUSIONS

HBoV infection is common during childhood, but a minority of children and young adults screened have evidence of B19 infection.

Emerging respiratory agents: new viruses for old diseases?

The recent advances in molecular technology have enabled the detection of several new viral agents in specimens collected from the human respiratory tract. Human metapneumovirus was first described in 2001, and is a significant respiratory pathogen, particularly of children. Following the identification of severe acute respiratory syndrome (SARS) associated coronavirus, two other newly detected coronaviruses, NL63 and HKU1, have been linked to respiratory disease in humans. However, identifying a new virus as the causative agent of a specific disease is difficult, and ideally would involve satisfying Koch's postulates. The recently described human bocavirus and polyomaviruses KI and WU have been detected in samples collected from humans with acute respiratory infection, but as yet, have not been conclusively proven to be agents of human disease. We review the new viral agents that have been detected in respiratory samples since 2001, and examine their contribution as agents of human disease.

Human bocavirus--a novel parvovirus to infect humans

For almost three decades parvovirus B19 has been described as the only member of the Parvoviridae to infect and cause illness in humans. This statement was correct until 2005 when a group of Swedish scientists identified a previously uncharacterized virus in pools of human nasopharyngeal aspirates obtained from individuals suffering from diseases of the respiratory tract. Comprehensive sequence and phylogenetic analysis allowed the identification of the new virus as a member of the Parvoviridae. Based on its close relation to the minute virus of canines and the bovine parvovirus, it was named human bocavirus (HBoV). Since the identification of HBoV, viral genomes have been frequently detected worldwide in nasopharyngeal swabs, serum and fecal samples almost exclusively derived from young children with various symptoms of the respiratory or the gastrointestinal tract. The detection of HBoV genomes tends to be associated with elevated rates of coinfections with further respiratory viruses, e.g. respiratory syncytial virus or metapneumovirus. First studies on virus-specific immune responses have described the presence of ubiquitous humoral and cellular immune reactions against HBoV in adults and adolescents, indicating a high seroprevalence of this new virus in humans.

Human bocavirus: passenger or pathogen in acute respiratory tract infections?

Human bocavirus (HBoV) is a newly identified virus tentatively assigned to the family Parvoviridae, subfamily Parvovirinae, genus Bocavirus. HBoV was first described in 2005 and has since been detected in respiratory tract secretions worldwide. Herein we review the literature on HBoV and discuss the biology and potential clinical impact of this virus. Most studies have been PCR based and performed on patients with acute respiratory symptoms, from whom HBoV was detected in 2 to 19% of the samples. HBoV-positive samples have been derived mainly from infants and young children. HBoV DNA has also been detected in the blood of patients with respiratory tract infection and in fecal samples of patients with diarrhea with or without concomitant respiratory symptoms. A characteristic feature of HBoV studies is the high frequency of coinciding detections, or codetections, with other viruses. Available data nevertheless indicate a statistical association between HBoV and acute respiratory tract disease. We present a model incorporating these somewhat contradictory findings and suggest that primary HBoV infection causes respiratory tract symptoms which can be followed by prolonged low-level virus shedding in the respiratory tract. Detection of the virus in this phase will be facilitated by other infections, either simply via increased sample cell count or via reactivation of HBoV, leading to an increased detection frequency of HBoV during other virus infections. We conclude that the majority of available HBoV studies are limited by the sole use of PCR diagnostics on respiratory tract secretions, addressing virus prevalence but not disease association. The ability to detect primary infection through the development of improved diagnostic methods will be of great importance for future studies seeking to assign a role for HBoV in causing respiratory illnesses.

Presence of the newly discovered human polyomaviruses KI and WU in Australian patients with acute respiratory tract infection

Background

Currently, the role of the novel human polyomaviruses, KI (KIV) and WU (WUV) as agents of human disease remains uncertain.

Objectives

We sought to determine the prevalence of these viruses and their rate of co-detection with other viral respiratory pathogens, in an Australian population.

Study design

Polymerase chain reaction assays previously described were used to examine the presence of KIV and WUV in 2866 respiratory specimens collected from January to December 2003 from Australian patients with acute respiratory infections.

Results

KIV and WUV were present in our population with an annual prevalence of 2.6% and 4.5%, respectively. There was no apparent seasonal variation for KIV, but a predominance of infection was detected during late winter to early summer for WUV. The level of co-infection of KIV or WUV with other respiratory viruses was 74.7% and 79.7%, respectively. Both viruses were absent from urine and blood specimens collected from a variety of patient sources.

Conclusions

KIV and WUV circulate annually in the Australian population. Although there is a strong association with the respiratory tract, more comprehensive studies are required to prove these viruses are agents causing respiratory disease.

Impact of human bocavirus on children and their families

This study was planned to investigate the prevalence and clinical features of the illnesses associated with human bocavirus (hBoV) in children with acute disease. We prospectively enrolled all subjects aged less than 15 years attending an emergency room in Milan, Italy, on Wednesdays and Sundays between 1 November 2004 and 31 March 2005 for any acute medical reason, excluding surgical diseases and trauma. Nasopharyngeal swabs were collected at admission to detect hBoV; influenza A and B viruses; respiratory syncytial virus; human metapneumovirus; parainfluenza viruses 1, 2, 3, and 4; rhinovirus; adenovirus; and coronaviruses 229E, OC43, NL63, and HKU1 by real-time PCR. Among the 1,332 enrolled children, hBoV was the fifth most frequently detected virus (7.4%). The rate of hBoV coinfections with other viruses was significantly higher than for the other viruses (50.5% versus 27.5%; P < 0.0001). Eighty-nine of the 99 hBoV-positive children (89.9%) had a respiratory tract infection, and 10 (10.1%) had gastroenteritis. hBoV coinfections had a significantly greater clinical and socioeconomic impact on the infected children and their households than hBoV infection alone. In conclusion, these findings show that the role of hBoV infection alone seems marginal in children attending an emergency room for acute disease; its clinical and socioeconomic importance becomes relevant only when it is associated with other viruses.

Human bocavirus: clinical significance and implications

PURPOSE OF REVIEW

Human bocavirus (HBoV), a parvovirus, was discovered in 2005 with the use of nonspecific genome amplification techniques. Since its discovery, HBoV has been identified worldwide. This review will focus on the epidemiology and clinical features associated with HBoV infection.

RECENT FINDINGS

Initial studies demonstrated the presence of HBoV DNA in respiratory specimens of individuals with respiratory tract disease. Data from some studies suggest that HBoV may be the etiological agent responsible for respiratory tract disease, particularly in young children. HBoV, however, is frequently detected in the presence of other common respiratory viruses. HBoV is not confined to the respiratory tract as evidence of the virus has been detected in serum and stool, the significance of which remains unclear. Presence of the virus in respiratory secretions, serum and stool suggests that this virus may cause systemic illness.

SUMMARY

HBoV is an emerging human parvovirus. The full spectrum of disease associated with HBoV remains to be defined.

Human bocavirus (HBoV) in Thailand: clinical manifestations in a hospitalized pediatric patient and molecular virus characterization

Objective

Human bocavirus (HBoV), a novel virus, which based on molecular analysis has been associated with respiratory tract diseases in infants and children have recently been studied worldwide. To determine prevalence, clinical features and perform phylogenetic analysis in HBoV infected Thai pediatric patients.

Methods

HBoV was detected from 302 nasopharyngeal (NP) suctions of pediatric patients with acute lower respiratory tract illness and sequenced applying molecular techniques.

Results

The incidence of HBoV infection in pediatric patients amounted to 6.62% with 40% co-infected with other respiratory viruses. There were no clinical specific manifestations for HBoV; however, fever and productive cough were commonly found. Generalized rales and wheezing were detected in most of the patients as well as perihilar infiltrates. The alignment and phylogenetic analysis of partial VP1 genes showed minor variations.

Conclusion

Our results indicated that HBoV can be detected in nasopharyngeal aspirate specimens from infants and children with acute lower respiratory tract illness.

Human bocavirus

Human bocavirus (HBoV) was first described in 2005 in nasopharyngeal aspirates of children with respiratory tract infection. Multiple studies have confirmed the presence of HBoV in respiratory tract samples of children world-wide. HBoV has recently also been detected in blood and fecal samples. Most studies so far have studied virus prevalence, and only a few reports provide data regarding the linkage of HBoV to disease. These reports indicate that HBoV infection is indeed associated with acute respiratory tract symptoms, but also that HBoV may persist in the respiratory tract for a longer time than other respiratory agents, resulting in frequent detection of low load HBoV carriage. This phenomenon has complicated the use of PCR diagnostics, which has been the only available diagnostic method. Development of alternative diagnostic strategies such as serology will be important for future studies of HBoV and its association with disease.

High rate of human bocavirus and adenovirus coinfection in hospitalized Israeli children

We investigated coinfection of human bocavirus (HBoV) and other respiratory viruses in hospitalized children by real-time PCR. A high rate (69.2%) of adenovirus infection was found among children infected with HBoV. Such high rates of HboV-adenovirus coinfection have not been previously reported, underscoring the need to investigate the contribution of HBoV in patient clinical presentations.

Seroepidemiology of human bocavirus in Hokkaido prefecture, Japan

A new human virus, provisionally named human bocavirus (HBoV), was discovered by Swedish researchers in 2005. A new immunofluorescence assay using Trichoplusia ni insect cells infected with a recombinant baculovirus expressing the VP1 protein of HBoV was developed, and the levels of immunoglobulin G antibody to the VP1 protein of HBoV in serum samples were measured. The overall seroprevalence rate of antibodies against the VP1 protein of HBoV in a Japanese population aged from 0 months to 41 years was 71.1% (145 of 204). The seropositive rate was lowest in the age group of 6 to 8 months and gradually increased with age. All of the children had been exposed to HBoV by the age of 6 years. A rise in titers of antibody against the VP1 protein of HBoV during the convalescent phase was observed for four patients with lower respiratory tract infections, and HBoV DNA was detected in nasopharyngeal swab and serum samples from all four patients. These results suggest that HBoV is a ubiquitous virus acquired early in life and that HBoV might play a role in the course of lower respiratory tract infections.