Human bocavirus - insights into a newly identified respiratory virus

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.

Educational aims

To summarise the knowledge on the spectrum of disease that respiratory viral infections can cause and recognise how often they overlap.To learn the most common causes of respiratory viral infections and acknowledge other less frequent agents that may target certain key populations (e.g. immunocompromised patients).To improve awareness of the recent advances in diagnostic methods, including molecular assays and helpful features in imaging techniques.To identify supportive care strategies pivotal in the management of severe respiratory viral infections.

Case Report: Bocavirus Infection Radiologically Resembling a Congestive Heart Failure in a Patient with Metastatic Castration-Resistant Prostate Cancer Case-Report

Background: Human bocavirus (HBoV) is a viral pathogen from the genus Bocaparvovirus (family Parvoviridae, subfamily Parvovirinae) discovered in 2005. Most of available literature is about HBoV in children and adults with hematological malignancies and in otherwise healthy children with respiratory infections. Information regarding infection in the adult population with solid tumors is scarce. Case Report: We report the case of a 51-year-old male with metastatic castration resistant prostate cancer undergoing chemotherapy treatment who presented with fever, dyspnea, dry cough, and pleuritic pain. Imaging techniques showed signs of congestive heart failure. Symptoms, laboratory tests and echocardiography revealed a more probable infectious etiology. Antibiotic therapy was started. A polymerase chain reaction (PCR) test of nasopharyngeal exudate for respiratory viruses was positive for HBoV. The rest of the microbiological tests were negative. Bronchoalveolar lavage (BAL) was performed. Bacterial culture of BAL was negative while respiratory virus PCR confirmed positivity for HBoV. Antibiotic therapy was discontinued. The patient gradually recovered. Conclusions: Emerging infectious diseases are a notorious threat for immunocompromised populations such as solid tumor patients. This case is unique because to our knowledge this is the first case report article of HBoV in a solid tumor patient and because imaging techniques exhibited signs of congestive heart failure that did not correlate with the rest of the tests. It shows that unusual pathogens should be considered when managing serious clinical complications with uncommon presentations in cancer patients. Notable diagnostic efforts should be made to reach a diagnosis in these cases.

Case Report: Bocavirus Infection Radiologically Resembling a Congestive Heart Failure in a Patient with Metastatic Castration-Resistant Prostate Cancer

Background: Human bocavirus (HBoV) is a viral pathogen from the genus Bocaparvovirus (family Parvoviridae, subfamily Parvovirinae) discovered in 2005. Most of available literature is about HBoV in children and adults with hematological malignancies and in otherwise healthy children with respiratory infections. Information regarding infection in the adult population with solid tumors is scarce. Case Report: We report the case of a 51-year-old male with metastatic castration resistant prostate cancer undergoing chemotherapy treatment who presented with fever, dyspnea, dry cough, and pleuritic pain. Imaging techniques showed signs of congestive heart failure. Symptoms, laboratory tests and echocardiography revealed a more probable infectious etiology. Antibiotic therapy was started. A polymerase chain reaction (PCR) test of nasopharyngeal exudate for respiratory viruses was positive for HBoV. The rest of the microbiological tests were negative. Bronchoalveolar lavage (BAL) was performed. Bacterial culture of BAL was negative while respiratory virus PCR confirmed positivity for HBoV. Antibiotic therapy was discontinued. The patient gradually recovered. Conclusions: Emerging infectious diseases are a notorious threat for immunocompromised populations such as solid tumor patients. This case is unique because to our knowledge this is the first case report article of HBoV in a solid tumor patient and because imaging techniques exhibited signs of congestive heart failure that did not correlate with the rest of the tests. It shows that unusual pathogens should be considered when managing serious clinical complications with uncommon presentations in cancer patients. Notable diagnostic efforts should be made to reach a diagnosis in these cases.

Evolutionary and genetic analysis of human bocavirus genotype-1 strains reveals an evidence of intragenomic recombination

PURPOSE

Human bocavirus (HBoV) exsits in four genotypes: 1 to 4, with HBoV-1 being the most prevalent genotype. The aim of the current study was to genetically analyze the full-length genome of the HBoV-1 of recently detected Egyptian strains.

METHODOLOGY

Seven overlapping sets of primers were developed to amplify an almost complete HBoV-1 genome from the clinical samples. The primer sets were tested on three recently identified Egyptian HBoV-1 strains with viral loads ≥105 ml-1. Sequencing was conducted using the same sets of primers. HBoV-1 virus strains were genetically analyzed based on the sequences of their complete genomes and the individual ORFs.

RESULTS

The new sets of primers successfully amplified the three tested strains. Sequence analysis of the full-length genome of the HBoV-1 revealed a considerable level of genetic heterogenicity between different strains. Based on the full genome and VP1 ORF, HBoV-1 viruses were clustered into three main lineages, A to C, and lineage A was further subdivided into three sublineages, A1-A3. The Egyptian strains were clustered within two sublineages, A1 and A2. New amino acid substitutions were detected in NS1 and VP1/VP2 proteins. Both inter- and intragenomic recombination events were detected among the Egyptian strains.

CONCLUSION

The existence of both intragenomic recombination event and multiple amino acid substitutions in the examined Egyptian HBoV-1 strains elucidates considerable level of genetic alterations among bocaviruses. Their possible effects on the virus virulence and multiplication efficiency need to be investigated.

Human bocavirus: Current knowledge and future challenges

Human bocavirus (HBoV) is a parvovirus isolated about a decade ago and found worldwide in both respiratory samples, mainly from early life and children of 6-24 mo of age with acute respiratory infection, and in stool samples, from patients with gastroenteritis. Since then, other viruses related to the first HBoV isolate (HBoV1), namely HBoV2, HBoV3 and HBoV4, have been detected principally in human faeces. HBoVs are small non-enveloped single-stranded DNA viruses of about 5300 nucleotides, consisting of three open reading frames encoding the first two the non-structural protein 1 (NS1) and nuclear phosphoprotein (NP1) and the third the viral capsid proteins 1 and 2 (VP1 and VP2). HBoV pathogenicity remains to be fully clarified mainly due to the lack of animal models for the difficulties in replicating the virus in in vitro cell cultures, and the fact that HBoV infection is frequently accompanied by at least another viral and/or bacterial respiratory and/or gastroenteric pathogen infection. Current diagnostic methods to support HBoV detection include polymerase chain reaction, real-time PCR, enzyme-linked immunosorbent assay and enzyme immunoassay using recombinant VP2 or virus-like particle capsid proteins, although sequence-independent amplification techniques combined with next-generation sequencing platforms promise rapid and simultaneous detection of the pathogens in the future. This review presents the current knowledge on HBoV genotypes with emphasis on taxonomy, phylogenetic relationship and genomic analysis, biology, epidemiology, pathogenesis and diagnostic methods. The emerging discussion on HBoVs as true pathogen or innocent bystander is also emphasized.

A novel primer set for improved direct gene sequencing of human bocavirus genotype-1 from clinical samples

Human bocavirus genotype (HBoV-1) is a parvovirus associated with respiratory tract infections in children with different degrees of severity. The current study intended to improve the direct gene sequencing of the HBoV-1 using a newly developed primer set. Screening the presence of human bocavirus infection among in-patients children suffering from lower respiratory tract infections was another aim of the current study. Nasopharyngeal swab samples from in-patients children suffering from lower respiratory tract infections were examined. The real-time polymerase chain reaction was used for the initial screening as a highly sensitive method to detect the HBoV. Genotyping of real-time positive samples was attempted by direct sequencing of PCR amplicons using NP, VP1/2 and the newly developed VP/NC primers. HBoV-1 was present in 56.8% of the examined children. The newly developed primer set successfully amplified all real-time PCR positive samples, however, the other primer pairs did not reliably detect real-time PCR positive samples. The gene sequences of the detected HBoV-1 showed conserved sequences to each other with a low rate of discrepancies. The high rate of infection and the similarity between the detected strains strongly suggest nosocomial infections.

Human bocaviruses: Possible etiologic role in respiratory infection

Four species of human bocaviruses (HBoV) are currently included in the Bocavirus genus. There is satisfactory evidence demonstrating an association between HBoV1 and respiratory disease in children, and there is evidence that HBoV2 (and possibly the HBoV3 and HBoV4 species) are associated with gastroenteritis. In particular, HBoV1 has been associated with a prolonged period of persistence in the mucosa of the respiratory tract. Virus persistence does play a role in the high frequency of co-infections with proper pathogens of the upper and lower respiratory tracts. The high detection rate of multiple respiratory viruses in up to 83% of respiratory specimens and the presence of asymptomatic HBoV1 infections complicate the elucidation of the pathogenic role of the agent. Overall, a large amount of data are available concerning HBoV1, whereas little information is available about other bocavirus species. High viral loads are often associated with symptoms, and viremia may be associated with systemic manifestations such as encephalopathy. The effects and mechanisms of latency, persistence, reactivation, and reinfection are poorly understood. Thus, particularly in co-infections, the pathogenic contribution of the detected bocavirus species cannot be accurately stated. This review summarizes the current knowledge of HBoV species and provides perspectives for future clinical studies.

Detection of respiratory viruses by real-time polymerase chain reaction in outpatients with acute respiratory infection

Viruses are the major contributors to the morbidity and mortality of upper and lower acute respiratory infections (ARIs) for all age groups. The aim of this study was to determine the frequencies for a large range of respiratory viruses using a sensitive molecular detection technique in specimens from outpatients of all ages with ARIs. Nasopharyngeal aspirates were obtained from 162 individuals between August 2007-August 2009. Twenty-three pathogenic respiratory agents, 18 respiratory viruses and five bacteria were investigated using multiplex real-time reverse transcriptase polymerase chain reaction (RT-PCR) and indirect immunofluorescence assay (IIF). Through IIF, 33 (20.4%) specimens with respiratory virus were recognised, with influenza virus representing over half of the positive samples. Through a multiplex real-time RT-PCR assay, 88 (54.3%) positive samples were detected; the most prevalent respiratory viral pathogens were influenza, human rhinovirus and respiratory syncytial virus (RSV). Six cases of viral co-detection were observed, mainly involving RSV. The use of multiplex real-time RT-PCR increased the viral detection by 33.9% and revealed a larger number of respiratory viruses implicated in ARI cases, including the most recently described respiratory viruses [human bocavirus, human metapneumovirus, influenza A (H1N1) pdm09 virus, human coronavirus (HCoV) NL63 and HCoV HKU1].

Pan-human coronavirus and human bocavirus SYBR Green and TaqMan PCR assays; use in studying influenza A viruses co-infection and risk of hospitalization

Purpose

Influenza A viruses, human coronaviruses (hCoV) and human bocavirus (hBoV) are emerging respiratory viruses. This study investigated the association between influenza A viruses co-infection with hBoV and hCoV and severity and the sensitivity of a real-time polymerase chain reaction (RT-PCR) assay for identification of 15 coronaviruses.

Methodology

Published sequences for the 15 human coronaviruses were used to design a consensus PCR targeting the replicase open reading frame 1b. A previously published  PCR targeting the NS1 Gene of all known human bocavirus strains was also utilized. A series of 217  samples from patients aged 37.7 (SD ± 30.4)] with seasonal influenza A viruses (SeasFluA) identified between 06/2011 and 06/2012 in NW England were tested for hCoV and hBoV using RT-PCR. Association between co-infection and disease outcome was assessed using logistic regression.

Results

The limit of detection of hCoV RT-PCR assay was 2 copies/µl of human coronavirus RNA template, a sensitivity comparable to a previously published SYBR green assay for human coronaviruses. A total of 12 hCoV and 17 hBoV were identified in the 217 influenza A positive samples. A higher proportion (61.5 %; 8/13) of SeasFluA/hBoV co-infections were identified in patients that were admitted either to a general ward or the intensive care unit compared to 44.3 % (66/149) of single SeasFlu A virus infections (OR 2.5 95 % CI 0.67–9.34, p = 0.17). In a stratified analysis, there was a trend towards higher association between FluA, hCoV and hBoV with increasing age (especially in patients aged 24–45 years and >65 year old).

Conclusion

Our hCoV RT-PCR protocol appeared to be of adequate analytical sensitivity for diagnosis. More and larger studies are needed to confirm the role of hCoV, hBoV in causing severe disease when they co-infect with influenza A viruses.

Detection of human bocaviruses 1, 2 and 3 in Irish children presenting with gastroenteritis

Human bocavirus has been increasingly detected worldwide in patients suffering from gastroenteritis, with the highest incidence reported in children aged between 6 and 24 months. A total of 155 non-bacterial gastroenteritis samples consisting of rotavirus-, adenovirus- and norovirus-positive specimens were collected from patients in the Munster region of Ireland from 2006-2008. Of these 155, a total of 12 were positive for the presence of human bocavirus. Three types of human bocavirus were identified: HBoV1, 2 and 3. In addition, recombinant strains (n=4) were also isolated. This is the first report of all three types of HBoV being detected in southern Ireland.