Human parvovirus 4 as potential cause of encephalitis in children, India

Parvovirus B19 and Parvovirus 4 infections among healthy blood donors; A prevalence report from Iran

Background

Parvoviruses, characterized by their tropism for blood cells, can manifest as asymptomatic infections. With their ability to persist in blood, assessing the prevalence of Parvovirus B19 (B19V) and Parvovirus 4 (PARV4) among healthy blood donors is essential for evaluating the potential transmission risks through blood transfusions, emphasizing the need for comprehensive screening protocols.

Methods

Four hundred blood donors participated in the study, with their blood specimens subjected to Real-Time PCR analysis for B19V and PARV4 nucleic acids after obtaining informed consent. Additionally, Complete Blood Count (CBC) assessments and determination of anti-B19 V-IgM and anti-B19 V-IgG antibody titers were performed using Enzyme-Linked Immunosorbent Assay (ELISA) for all collected samples.

Results

The results reveal that 12 out of 400 individuals (3 %) exhibited positive results for B19V DNA, while 6 out of 400 individuals (1.5 %) tested positive for PARV4 DNA. Additionally, 8 out of 400 individuals (2 %) displayed positive results for anti-B19V IgM, and 306 out of 400 individuals (76.5 %) exhibited positive results for anti-B19 IgG. Notably, one donation from a donor presenting anti-IgM antibodies was subsequently confirmed as B19V DNA-positive through Real-Time PCR. In the analysis of CBC, a significant disparity in platelet levels was observed between B19V-positive donors, PARV4-positive donors, and B19V-negative donors.

Conclusions

The study suggests that individuals at high risk, lacking detectable B19V antibodies, should undergo systematic screening and exclusion. This precaution is intended to minimize potential contamination risks within the studied cohort, despite the undefined pathogenesis and clinical implications of PARV4.

First detection of Tetraparvovirus ungulate 1 in diseased cattle (Chinese Simmental) from Hunan province, China

Tetraparvovirus is an emerging parvovirus infecting a variety of mammals and humans, and associated with human diseases including severe acute respiratory infection and acute encephalitis syndrome. In the present study, a Tetraparvovirus ungulate 1 (formerly known as bovine hokovirus) strain HNU-CBY-2023 was identified and characterized from diseased Chinese Simmental from Hunan province, China. The nearly complete genome of HNU-CBY-2023 is 5346 nt in size and showed genomic identities of 85-95.5% to the known Tetraparvovirus ungulate 1 strains from GenBank, indicating a rather genetic variation. Phylogenetic and genetic divergence analyses indicated that Tetraparvovirus ungulate 1 could be divided into two genotypes (I and II), and HNU-CBY-2023 was clustered into genotype II. This study, for the first time, identified Tetraparvovirus ungulate 1 from domestic cattle from mainland China, which will be helpful to understand the prevalence and genetic diversity of Tetraparvovirus ungulate 1.

Study on genotyping and coinfection rate of human parvovirus 4 among the HTLV-I/II infected blood donors in Khorasan Razavi, Iran

Human Parvovirus 4 (PARV4) is an emerging virus infecting individuals with other blood-borne diseases. This study aimed to determine the prevalence of PARV4 in confirmed HTLVI/II positive samples from blood donors, assessing PARV4 viral load (DNA) and genotyping.

METHODS

A novel qReal-Time PCR, based on a plasmid construct, was developed to simultaneously detect all three PARV4 genotypes using in-house primers and probes. Positive qPCR samples were subjected to nested PCR amplification and subsequent sequencing. Phylogenetic trees were constructed using the Neighbor-joining (N.J.) method.

RESULTS

The coinfection rate of PARV4-DNA in HTLVI/II confirmed infected donors, who were previously deferred, was 14.4 % (13 out of 90), with no observed association with donation status (p = 1.0). Phylogenetic analysis indicated that PARV4-positive samples closely resembled genotype 2 in Iran.qPCR quantification demonstrated significant PARV4 viral loads in positive samples, ranging between 104 and 106 DNA copies/mL of serum.

CONCLUSION

This study presents the first evaluation of HTLVI/II and PARV4coinfection rates among blood donors. Notably, elevated PARV4-DNA titers were detected in HTLVI/II-positive donors. Given PARV's resistance to standard plasma refinery inactivation methods and the absence of its targeted inactivation, its potential impact remains a concern.

Etiological Profile and Clinico Epidemiological Patterns of Acute Encephalitis Syndrome in Tamil Nadu, India

Introduction

Establishing the etiological cause of acute encephalitis syndrome (AES) is challenging due to the distinct distribution of various etiological agents. This study aims to determine the etiological profiles of both viruses and bacteria and their associated clinico-epidemiological features among the AES suspected cases in Tamil Nadu, India.

Methods

Samples of 5136 suspected AES cases from January 2016 to December 2020 (5 years) were subjected to the detection of etiological agents for AES through serological and molecular diagnosis methods. Further, the clinical profile, age- and gender-wise susceptibility of cases, co-infection with other AES etiological agents, and seasonality pattern with respect to various etiological agents were examined.

Results

AES positivity was established in 1480 cases (28.82%) among the 5136 suspected cases and the positivity for male and female groups were 57.77% and 42.23%, respectively. The pediatric group was found to be more susceptible than others. Among the etiological agents tested, the Japanese encephalitis virus (JEV) was the predominant followed by Cytomegalovirus, Herpes Simplex virus, Epstein-Barr virus, Varicella Zoster virus, and others. Co-infection with other AES etiological agents was observed in 3.5% of AES-positive cases. Seasonality was observed only for vector-borne diseases such as JEV, dengue virus, and West Nile virus infections in this study.

Conclusion

AES was found to be a significant burden for Tamil Nadu with a diverse etiological spectrum including both sporadic and outbreak forms. Overlapping clinical manifestations of AES agents necessitate the development of region-specific diagnostic algorithm with distinct etiological profiles for early detection and effective case management.

Capsid Structure of Aleutian Mink Disease Virus and Human Parvovirus 4: New Faces in the Parvovirus Family Portrait

Parvoviruses are small, single-stranded DNA viruses with non-enveloped capsids. Determining the capsid structures provides a framework for annotating regions important to the viral life cycle. Aleutian mink disease virus (AMDV), a pathogen in minks, and human parvovirus 4 (PARV4), infecting humans, are parvoviruses belonging to the genera Amdoparvovirus and Tetraparvovirus, respectively. While Aleutian mink disease caused by AMDV is a major threat to mink farming, no clear clinical manifestations have been established following infection with PARV4 in humans. Here, the capsid structures of AMDV and PARV4 were determined via cryo-electron microscopy at 2.37 and 3.12 Å resolutions, respectively. Despite low amino acid sequence identities (10-30%) both viruses share the icosahedral nature of parvovirus capsids, with 60 viral proteins (VPs) assembling the capsid via two-, three-, and five-fold symmetry VP-related interactions, but display major structural variabilities in the surface loops when the capsid structures are superposed onto other parvoviruses. The capsid structures of AMDV and PARV4 will add to current knowledge of the structural platform for parvoviruses and permit future functional annotation of these viruses, which will help in understanding their infection mechanisms at a molecular level for the development of diagnostics and therapeutics.

Parvovirus 4 in Individuals with Severe Hemophilia A and Matched Control Group

Background: Hemophilia is a well-known bleeding disorder with worldwide distribution. Replacement therapy, using plasma-derived or recombinant coagulation factors, comprises a gold standard regimen for the treatment. Regardless of the advancements made in viral inactivation methods in the production of plasma-derived coagulation factors, the possibility of transmission of new viral infections remained as a noticeable concern yet. The aim of the current study was to investigate the status of parvovirus 4 (PARV4) in severe hemophilia A, von Willebrand disease (vWD), and healthy control. Materials and Methods: In the current case-control study, 76 patients with hemophilia and vWD and 60 individuals from their family members entered the study. Nested PCR used to determine the presence of PARV4 in study subjects (76 cases). To characterize the PARV4 genotype, positive samples subjected to sequencing and phylogenetic analysis. Results: PARV4 genome detected in 11 (14.47%) patients with bleeding disorders. Among whom, nine patients (14.75%) were with severe hemophilia A and two (13.33%) patients with vWD. Only five healthy controls (8.33%) were positive for PARV4. All PARV4 sequences were found to be genotype 1. Conclusion: PARV4 infection in patients with hemophilia and vWD was higher than the control group. While detection of PARV4 DNA in patients with bleeding disorders may not necessarily reflect a clinical urgency, future investigations are needed to define the clinical significance of PARV4. It seems the detection of the virus immune signature of PARV4 infection, particularly in the context of acute and persistent infections, needs to focus on cellular and tissue targets.

Neurotropic Astroviruses in Animals

Astrovirus infections are among the main causes of diarrhea in children, but their significance for animal health has remained underestimated and largely unknown. This is changing due to the increasing amount of newly identified neurotropic astroviruses in cases of nonsuppurative encephalitis and neurological disease in humans, pigs, ruminant species and minks. Neurological cases in ruminants and humans usually occur sporadically and as isolated cases. This contrasts with the situation in pigs and minks, in which diseases associated with neurotropic astroviruses are endemic and occur on the herd level. Affected animals show neurological signs such as mild ataxia to tetraplegia, loss of orientation or trembling, and the outcome is often fatal. Non-suppurative inflammation with perivascular cuffing, gliosis and neuronal necrosis are typical histological lesions of astrovirus encephalitis. Since astroviruses primarily target the gastrointestinal tract, it is assumed that they infect the brain through the circulatory system or retrograde following the nerves. The phylogenetic analysis of neurotropic astroviruses has revealed that they are genetically closely related, suggesting the presence of viral determinants for tissue tropism and neuroinvasion. In this review, we summarize the current knowledge on neurotropic astrovirus infections in animals and propose future research activities.

Identification of human parvovirus 4 genotypes 1 and 2 in Chinese source plasma pools

Human parvovirus B19 (B19V) and human parvovirus 4 (PARV4) are known to infect humans and transmit through contaminated blood and blood products. Globally, three genotypes of B19V, as well as PARV4, have been identified, respectively. The existence of different B19V genotypes in Chinese plasma donors has been investigated, however, the data regarding PARV4 were not available. The main objective of this study is to identify the genotypes of PARV4 circulating in Chinese plasma donors. By using a duplex quantitative polymerase chain reaction assay adapted for all genotypes of B19V and PARV4, 78 source plasma pools for fractionation were screened and quantified. Results showed that positive rates of B19V and PARV4 DNA in plasma pool samples were 25.64% and 14.10%, respectively. PARV4 sequences in two positive samples were next genotyped, and these two sequences belonged to PARV4 genotypes 1 and 2, respectively. In conclusion, the data present demonstrate the existence of PARV4 genotypes 1 and 2 in Chinese plasma donors for the first time and also show the relatively lower prevalence and level of PARV4 DNA in Chinese plasma donors in comparison with that of B19V DNA.

At least two PARV4 genotypes, 1 and 2, were currently present in China.

The prevalence and level of PARV4 DNA in Chinese plasma donors were relatively lower in comparison with that of B19V DNA.

The rate of B19V and PARV4 coinfection in Chinese source plasma pools was low.

Enhanced Detection of DNA Viruses in the Cerebrospinal Fluid of Encephalitis Patients Using Metagenomic Next-Generation Sequencing

The long and expanding list of viral pathogens associated with causing encephalitis confounds current diagnostic procedures, and in up to 50% of cases, the etiology remains undetermined. Sequence-agnostic metagenomic next-generation sequencing (mNGS) obviates the need to specify targets in advance and thus has great potential in encephalitis diagnostics. However, the low relative abundance of viral nucleic acids in clinical specimens poses a significant challenge. Our protocol employs two novel techniques to selectively remove human material at two stages, significantly increasing the representation of viral material. Our bioinformatic workflow using open source protein- and nucleotide sequence-matching software balances sensitivity and specificity in diagnosing and characterizing any DNA viruses present. A panel of 12 cerebrospinal fluid (CSFs) from encephalitis cases was retrospectively interrogated by mNGS, with concordant results in seven of nine samples with a definitive DNA virus diagnosis, and a different herpesvirus was identified in the other two. In two samples with an inconclusive diagnosis, DNA viruses were detected and in a virus-negative sample, no viruses were detected. This assay has the potential to detect DNA virus infections in cases of encephalitis of unknown etiology and to improve the current screening tests by identifying new and emerging agents.

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.

Mass spectrometry-based proteomic techniques to identify cerebrospinal fluid biomarkers for diagnosing suspected central nervous system infections. A systematic review

OBJECTIVES

Central nervous system (CNS) infections account for considerable death and disability every year. An urgent research priority is scaling up diagnostic capacity, and introduction of point-of-care tests. We set out to assess current evidence for the application of mass spectrometry (MS) peptide sequencing in identification of diagnostic biomarkers for CNS infections.

METHODS

We performed a systematic review (PROSPEROCRD42018104257) using PRISMA guidelines on use of MS to identify cerebrospinal fluid (CSF) biomarkers for diagnosing CNS infections. We searched PubMed, Embase, Web of Science, and Cochrane for articles published from 1 January 2000 to 1 February 2019, and contacted experts. Inclusion criteria involved primary research except case reports, on the diagnosis of infectious diseases except HIV, applying MS to human CSF samples, and English language.

RESULTS

4,620 papers were identified, of which 11 were included, largely confined to pre-clinical biomarker discovery, and eight (73%) published in the last five years. 6 studies performed further work termed verification or validation. In 2 of these studies, it was possible to extract data on sensitivity and specificity of the biomarkers detected by ELISA, ranging from 89-94% and 58-92% respectively.

CONCLUSIONS

The findings demonstrate feasibility and potential of the methods in a variety of infectious diseases, but emphasise the need for strong interdisciplinary collaborations to ensure appropriate study design and biomarker validation.

Human Parvovirus 4: A harmless bystander or a pathogen of severe acute respiratory illness

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Severe Acute Respiratory Infection (SARI) is an important cause of morbidity and mortality worldwide.

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We investigated the association of PARV4 virus with SARI.

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PARV4 was detected in 26.55% of cases and only in one healthy control (0.68%).

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Detection of PARV4 is seen in a significantly large number of SARI cases.

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PARV4 genotype 2 was the only genotype detected from cases as well as controls.

Introduction

Severe Acute Respiratory Infection (SARI) is an important cause of morbidity and mortality worldwide, caused by a large number of viral and bacterial agents. PARV4 is a recently identified virus detected in human blood and variety of tissues, but its disease association with SARI could not be established.

Objective

In the present case control study, we aim to investigate the association of PARV4 with SARI.

Methods

The Nasal and Throat swab (NS/TS) samples of 241 cases and 146 healthy controls were tested for most common respiratory viruses and PARV4 by real-time PCR.

Results

PARV4 was detected in 64(26.55%) SARI cases and only one healthy control (0.68%). PARV4 was the most common viral agent detected in SARI cases. A strong association of PARV4 is seen with severe respiratory illness.

Conclusion

Detection of PARV4 in a significantly higher number of SARI cases, in comparison with controls, suggests association of PARV4 with SARI. PARV4 genotype 2 is the only circulating strain detected in our study.

Detection of human parvovirus 4 DNA in the patients with acute encephalitis syndrome during seasonal outbreaks of the disease in Gorakhpur, India

Seasonal outbreaks of acute encephalitis syndrome (AES) at Gorakhpur, India have been recognized since 2006. So far, the causative agent has not been identified. Use of next generation sequencing identified human parvovirus 4 (HPARV4) sequences in a CSF/plasma pool. These sequences showed highest identity with sequences earlier identified in similar patients from south India. Real-time PCR detected HPARV4 DNA in 20/78 (25.6%) CSF and 6/31 (19.3%) plasma of AES patients. Phylogenetic analysis classified three almost complete genomes and 24 partial NS1 sequences as genotype 2A. The observed association of HPARV4 with AES needs further evaluation. ELISAs for the detection of IgM and IgG antibodies against scrub typhus (Orientia tsutsugamushi, OT) showed ∼70% IgM/IgG positivity suggestive of etiologic association. Prospective, comprehensive studies are needed to confirm association of these agents, singly or in combination with AES in Gorakhpur region.

Emerging/re-emerging viral diseases & new viruses on the Indian horizon

Infectious diseases remain as the major causes of human and animal morbidity and mortality leading to significant healthcare expenditure in India. The country has experienced the outbreaks and epidemics of many infectious diseases. However, enormous successes have been obtained against the control of major epidemic diseases, such as malaria, plague, leprosy and cholera, in the past. The country's vast terrains of extreme geo-climatic differences and uneven population distribution present unique patterns of distribution of viral diseases. Dynamic interplays of biological, socio-cultural and ecological factors, together with novel aspects of human-animal interphase, pose additional challenges with respect to the emergence of infectious diseases. The important challenges faced in the control and prevention of emerging and re-emerging infectious diseases range from understanding the impact of factors that are necessary for the emergence, to development of strengthened surveillance systems that can mitigate human suffering and death. In this article, the major emerging and re-emerging viral infections of public health importance have been reviewed that have already been included in the Integrated Disease Surveillance Programme.

Viral metagenomics revealed novel betatorquevirus species in pediatric inpatients with encephalitis/meningoencephalitis from Ghana

The cause of acute encephalitis/meningoencephalitis in pediatric patients remains often unexplained despite extensive investigations for large panel of pathogens. To explore a possible viral implication, we investigated the virome of cerebrospinal fluid specimens of 70 febrile pediatric inpatients with clinical compatible encephalitis/meningoencephalitis. Using viral metagenomics, we detected and genetically characterized three novel human Torque teno mini virus (TTMV) species (TTMV-G1-3). Phylogenetically, TTMV-G1-3 clustered in three novel monophyletic lineages within genus Betatorquevirus of the Anelloviridae family. TTMV-G1-3 were highly prevalent in diseased children, but absent in the healthy cohort which may indicate an association of TTMV species with febrile illness. With 2/3 detected malaria co-infection, it remains unclear if these novel anellovirus species are causative agents or increase disease severity by interaction with malaria parasites. The presence of the viruses 28 days after initiating antimalarial and/or antibiotic treatment suggests a still active viral infection likely as effect of parasitic and/or bacterial co-infection that may have initiated a modulated immune system environment for viral replication or a defective virus clearance. This study increases the current knowledge on the genetic diversity of TTMV and strengthens that human anelloviruses can be considered as biomarkers for strong perturbations of the immune system in certain pathological conditions.

High-throughput sequencing for the aetiologic identification of viral encephalitis, meningoencephalitis, and meningitis. A narrative review and clinical appraisal

Background

Viral aetiologies are the most common cause of central nervous system (CNS) infections. Approximately one-half of CNS infections remain of undetermined origin. High-throughput sequencing (HTS) brought new perspectives to CNS infection investigations, allowing investigation of viral aetiologies with an unbiased approach. HTS use is still limited to specific clinical situations.

Objectives

The aim of this review was to evaluate the contribution and pitfalls of HTS for the aetiologic identification of viral encephalitis, meningoencephalitis, and meningitis in CNS patient samples.

Sources

PubMed was searched from 1 January 2008 to 2 August 2018 to retrieve available studies on the topic. Additional publications were included from a review of full-text sources.

Content

Among 366 studies retrieved, 29 used HTS as a diagnostic technique. HTS was performed in cerebrospinal fluid and brain biopsy samples of 307 patients, including immunocompromised, immunocompetent paediatric, and adult cases. HTS was performed retrospectively in 18 studies and prospectively in 11. HTS led to the identification of a potential causal virus in 41 patients, with 11 viruses known and ten not expected to cause CNS infections. Various HTS protocols were used.

Implications

The additional value of HTS is difficult to quantify because of various biases. Nevertheless, HTS led to the identification of a viral cause in 13% of encephalitis, meningoencephalitis, and meningitis cases in which various assays failed to identify the cause. HTS should be considered early in clinical management as a complement to routine assays. Standardized strategies and systematic studies are needed for the integration of HTS in clinical management.

Encephalitis diagnosis using metagenomics: application of next generation sequencing for undiagnosed cases

BACKGROUND

Current estimates suggest that even in the most resourced settings, the aetiology of encephalitis is identified in less than half of clinical cases. It is acknowledged that filling this gap needs a combination of rigorous sampling and improved diagnostic technologies. Next generation sequencing (NGS) methods are powerful tools with the potential for comprehensive and unbiased detection of pathogens in clinical samples. We reviewed the use of this new technology for the diagnosis of suspected infectious encephalitis, and discuss the feasibility for introduction of NGS methods as a frontline diagnostic test.

METHODS

A systematic literature review was performed, using MESH and text word searches for variants of "sequencing" and "encephalitis" in Medline and EMbase, and searching bibliographies and citations using the Web of Science database. Two authors independently reviewed, extracted and summarised data.

FINDINGS

The review identified 25 articles reporting 44 case reports of patients with suspected encephalitis for whom NGS was used as a diagnostic tool. We present the data and highlight themes arising from these cases. There are no randomly controlled trials to assess the utility of NGS as a diagnostic tool.

INTERPRETATION

There is increasing evidence of a role for NGS in the work-up of undiagnosed encephalitis. Lower costs and increasing accessibility of these technologies will facilitate larger studies of these patients. We recommend NGS should be considered as a front-line diagnostic test in chronic and recurring presentations and, given current sample-to-result turn-around times, as second-line in acute cases of encephalitis.

Human parvovirus B19 and parvovirus 4 among Iranian patients with hemophilia

Background

Human parvovirus B19 (B19V) is one of the smallest DNA viruses and shows great resistance to most disinfectants. Therefore, it is one of the common contaminant pathogens present in blood and plasma products. Parvovirus 4 (PARV4) is a newly identified parvovirus, which is also prevalent in parenteral transmission. In this study, we aimed to evaluate the prevalence of B19V and PARV4 DNA among patients with hemophilia in Birjand County in eastern Iran.

Methods

This was a cross-sectional epidemiological study comprising nearly all people with hemophilia in this region. Whole blood samples were taken after patient registration and sent for plasma isolation. After nucleic acid extraction, B19V was detected with real-time polymerase chain reaction, PARV4 DNA was then detected using sensitive semi-nested PCR.

Results

In total, there were 86 patients with hemophilia, with mean age 28.5±1.5 years. Of these, 90.7% were men and 9.3% women; 84.9% had hemophilia A and 7.0% had hemophilia B. We found 11 patients (12.8%) were positive for B19V DNA and 8 were positive (9.3%) for PARV4 DNA. The prevalence of B19V was higher in middle-aged groups rather than younger people, whereas PARV4 infection was more common in younger patients (P <0.05).

Conclusion

There was a high prevalence of B19V and PARV4 infection in this high-risk group of patients with hemophilia. Due to the clinical significance of the B19 virus, imposing more precautionary measures for serum and blood products is recommended.

Viral Encephalitis of Unknown Cause: Current Perspective and Recent Advances

Viral encephalitis causes acute inflammation of the brain parenchyma and is a significant cause of human morbidity and mortality. Although Herpes Simplex encephalitis is the most frequent known cause of fatal sporadic encephalitis in humans, an increasingly wide range of viruses and other microbial pathogens are implicated. Up to 60% of cases of presumed viral encephalitis remain unexplained due to the failure of conventional laboratory techniques to detect an infectious agent. High-throughput DNA sequencing technologies have the potential to detect any microbial nucleic acid present in a biological specimen without any prior knowledge of the target sequence. While there remain challenges intrinsic to these technologies, they have great promise in virus discovery in unexplained encephalitis.

Human parvovirus 4 'PARV4' remains elusive despite a decade of study

Human parvovirus 4 ('PARV4') is a small DNA tetraparvovirus, first reported in 2005. In some populations, PARV4 infection is uncommon, and evidence of exposure is found only in individuals with risk factors for parenteral infection who are infected with other blood-borne viruses. In other settings, seroprevalence studies suggest an endemic, age-associated transmission pattern, independent of any specific risk factors. The clinical impact of PARV4 infection remains uncertain, but reported disease associations include an influenza-like syndrome, encephalitis, acceleration of HIV disease, and foetal hydrops. In this review, we set out to report progress updates from the recent literature, focusing on the investigation of cohorts in different geographical settings, now including insights from Asia, the Middle East, and South America, and discussing whether attributes of viral or host populations underpin the striking differences in epidemiology. We review progress in understanding viral phylogeny and biology, approaches to diagnostics, and insights that might be gained from studies of closely related animal pathogens. Crucial questions about pathogenicity remain unanswered, but we highlight new evidence supporting a possible link between PARV4 and an encephalitis syndrome. The unequivocal evidence that PARV4 is endemic in certain populations should drive ongoing research efforts to understand risk factors and routes of transmission and to gain new insights into the impact of this virus on human health.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Identification of Viruses in Cases of Pediatric Acute Encephalitis and Encephalopathy Using Next-Generation Sequencing

Acute encephalitis/encephalopathy is a severe neurological syndrome that is occasionally associated with viral infection. Comprehensive virus detection assays are desirable because viral pathogens have not been identified in many cases. We evaluated the utility of next-generation sequencing (NGS) for detecting viruses in clinical samples of encephalitis/encephalopathy patients. We first determined the sensitivity and quantitative performance of NGS by comparing the NGS-determined number of sequences of human herpesvirus-6 (HHV-6) in clinical serum samples with the HHV-6 load measured using real-time PCR. HHV-6 was measured as it occasionally causes neurologic disorders in children. The sensitivity of NGS for detection of HHV-6 sequences was equivalent to that of real-time PCR, and the number of HHV-6 reads was significantly correlated with HHV-6 load. Next, we investigated the ability of NGS to detect viral sequences in 18 pediatric patients with acute encephalitis/encephalopathy of unknown etiology. A large number of Coxsackievirus A9 and mumps viral sequences were detected in the cerebrospinal fluid of 2 and 1 patients, respectively. In addition, Torque teno virus and Pepper mild mottle viral sequences were detected in the sera of one patient each. These data indicate that NGS is useful for detection of causative viruses in patients with pediatric encephalitis/encephalopathy.

Evidence for Vertical Transmission of Novel Duck-Origin Goose Parvovirus-Related Parvovirus

In 2015, novel duck-origin goose parvovirus-related parvovirus (N-GPV) infection progressively appeared in commercial Cherry Valley duck flocks in North China. Diseased ducks were observed to have beak atrophy and dwarfism syndrome (BADS). A previous study showed that a high seropositive rate for N-GPV indicated a latent infection in most breeder duck flocks. To investigate this possibility in hatching eggs collected from N-GPV-infected breeder ducks, 120 eggs were collected at various stages of embryonic development for viral DNA detection and an N-GPV-specific antibody test. N-GPV DNA was present in nine hatching eggs, eleven duck embryo and eight newly hatched ducklings. Of the newly hatched ducklings, 58.33% (21/36) were seropositive. Further, two isolates were obtained from a 12-day-old duck embryo and a newly hatched duckling. N-GPV infection did not reduce the fertilization rate and hatchability. These results indicate possible vertical transmission of N-GPV and suggest that it may be transmitted from breeder ducks to ducklings in ovo.

Characteristic Cytokine and Chemokine Profiles in Encephalitis of Infectious, Immune-Mediated, and Unknown Aetiology

Background

Encephalitis is parenchymal brain inflammation due to infectious or immune-mediated processes. However, in 15–60% the cause remains unknown. This study aimed to determine if the cytokine/chemokine-mediated host response can distinguish infectious from immune-mediated cases, and whether this may give a clue to aetiology in those of unknown cause.

Methods

We measured 38 mediators in serum and cerebrospinal fluid (CSF) of patients from the Health Protection Agency Encephalitis Study. Of serum from 78 patients, 38 had infectious, 20 immune-mediated, and 20 unknown aetiology. Of CSF from 37 patients, 20 had infectious, nine immune-mediated and eight unknown aetiology.

Results

Heat-map analysis of CSF mediator interactions was different for infectious and immune-mediated cases, and that of the unknown aetiology group was similar to the infectious pattern. Higher myeloperoxidase (MPO) concentrations were found in infectious than immune-mediated cases, in serum and CSF (p = 0.01 and p = 0.006). Serum MPO was also higher in unknown than immune-mediated cases (p = 0.03). Multivariate analysis selected serum MPO; classifying 31 (91%) as infectious (p = 0.008) and 17 (85%) as unknown (p = 0.009) as opposed to immune-mediated. CSF data also selected MPO classifying 11 (85%) as infectious as opposed to immune-mediated (p = 0.036). CSF neutrophils were detected in eight (62%) infective and one (14%) immune-mediated cases (p = 0.004); CSF MPO correlated with neutrophils (p<0.0001).

Conclusions

Mediator profiles of infectious aetiology differed from immune-mediated encephalitis; and those of unknown cause were similar to infectious cases, raising the hypothesis of a possible undiagnosed infectious cause. Particularly, neutrophils and MPO merit further investigation.

Exploring the virome of diseased horses

Metagenomics was used to characterize viral genomes in clinical specimens of horses with various organ-specific diseases of unknown aetiology. A novel parvovirus as well as a previously described hepacivirus closely related to human hepatitis C virus and equid herpesvirus 2 were identified in the cerebrospinal fluid of horses with neurological signs. Four co-infecting picobirnaviruses, including an unusual genome with fused RNA segments, and a divergent anellovirus were found in the plasma of two febrile horses. A novel cyclovirus genome was characterized from the nasal secretion of another febrile animal. Lastly, a small circular DNA genome with a Rep gene, from a virus we called kirkovirus, was identified in the liver and spleen of a horse with fatal idiopathic hepatopathy. This study expands the number of viruses found in horses, and characterizes their genomes to assist future epidemiological studies of their transmission and potential association with various equine diseases.

Complete genome sequences of two isolates of human parvovirus 4 from patients with acute encephalitis syndrome

Human parvovirus 4 (Parv4) is a relatively new virus. Association of this virus with any human disease is yet to be established. We detected human parvovirus 4 in the cerebrospinal fluid (CSF) of two patients presenting with acute encephalitis syndrome in northern India. This is the first report of the Parv4 genome sequence from northern India.

Identification of novel viruses using VirusHunter--an automated data analysis pipeline

Quick and accurate identification of microbial pathogens is essential for both diagnosis and response to emerging infectious diseases. The advent of next-generation sequencing technology offers an unprecedented platform for rapid sequencing-based identification of novel viruses. We have developed a customized bioinformatics data analysis pipeline, VirusHunter, for the analysis of Roche/454 and other long read Next generation sequencing platform data. To illustrate the utility of VirusHunter, we performed Roche/454 GS FLX titanium sequencing on two unclassified virus isolates from the World Reference Center for Emerging Viruses and Arboviruses (WRCEVA). VirusHunter identified sequences derived from a novel bunyavirus and a novel reovirus in the two samples respectively. Further sequence analysis demonstrated that the viruses were novel members of the Phlebovirus and Orbivirus genera. Both Phlebovirus and Orbivirus genera include many economic important viruses or serious human pathogens.

Human parvovirus 4 in nasal and fecal specimens from children, Ghana

Nonparenteral transmission might contribute to human parvovirus 4 (PARV4) infections in sub-Saharan Africa. PARV4 DNA was detected in 8 (0.83%) of 961 nasal samples and 5 (0.53%) of 943 fecal samples from 1,904 children in Ghana. Virus concentrations ≤6–7 log₁₀ copies/mL suggest respiratory or fecal–oral modes of PARV4 transmission.

HIV infection and stroke: current perspectives and future directions

HIV infection can result in stroke via several mechanisms, including opportunistic infection, vasculopathy, cardioembolism, and coagulopathy. However, the occurrence of stroke and HIV infection might often be coincidental. HIV-associated vasculopathy describes various cerebrovascular changes, including stenosis and aneurysm formation, vasculitis, and accelerated atherosclerosis, and might be caused directly or indirectly by HIV infection, although the mechanisms are controversial. HIV and associated infections contribute to chronic inflammation. Combination antiretroviral therapies (cART) are clearly beneficial, but can be atherogenic and could increase stroke risk. cART can prolong life, increasing the size of the ageing population at risk of stroke. Stroke management and prevention should include identification and treatment of the specific cause of stroke and stroke risk factors, and judicious adjustment of the cART regimen. Epidemiological, clinical, biological, and autopsy studies of risk, the pathogenesis of HIV-associated vasculopathy (particularly of arterial endothelial damage), the long-term effects of cART, and ideal stroke treatment in patients with HIV are needed, as are antiretrovirals that are without vascular risk.

Acute diarrhea in West African children: diverse enteric viruses and a novel parvovirus genus

Parvoviruses cause a variety of mild to severe symptoms or asymptomatic infections in humans and animals. During a viral metagenomic analysis of feces from children with acute diarrhea in Burkina Faso, we identified in decreasing prevalence nucleic acids from anelloviruses, dependoviruses, sapoviruses, enteroviruses, bocaviruses, noroviruses, adenoviruses, parechoviruses, rotaviruses, cosavirus, astroviruses, and hepatitis B virus. Sequences from a highly divergent parvovirus, provisionally called bufavirus, were also detected whose NS1 and VP1 proteins showed <39% and <31% identities to those of previously known parvoviruses. Four percent of the fecal samples were PCR positive for this new parvovirus, including a related bufavirus species showing only 72% identity in VP1. The high degree of genetic divergence of these related genomes from those of other parvoviruses indicates the presence of a proposed new Parvoviridae genus containing at least two species. Studies of the tropism and pathogenicity of these novel parvoviruses will be facilitated by the availability of their genome sequences.

Human parvovirus 4 infection, Cameroon

In a post hoc analysis of samples collected in 2009, we determined seroprevalence of parvovirus 4 (PARV4) among elderly Cameroonians. PARV4 seropositivity was associated with receipt of intravenous antimalarial drugs, intramuscular streptomycin, or an intramuscular contraceptive, but not hepatitis C virus seropositivity. Findings suggest parenteral acquisition of some PARV4 infections.

Parvovirus 4 infection and clinical outcome in high-risk populations

Parvovirus 4 (PARV4) is a DNA virus frequently associated with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infections, but its clinical significance is unknown. We studied the prevalence of PARV4 antibodies in 2 cohorts of HIV- and HCV-infected individuals (n = 469) and the correlations with disease status. We found that PARV4 infection frequently occurred in individuals exposed to bloodborne viruses (95% in HCV-HIV coinfected intravenous drug users [IDUs]). There were no correlations between PARV4 serostatus and HCV outcomes. There was, however, a significant association with early HIV-related symptoms, although because this was tightly linked to both HCV status and clinical group (IDU), the specific role of PARV4 is not yet clear.

Molecular characterization of the newly identified human parvovirus 4 in the family Parvoviridae

Human parvovirus 4 (PARV4) is an emerging human virus, and little is known about the molecular aspects of PARV4 apart from its incomplete genome sequence, which lacks information of the termini. We analyzed the gene expression profile of PARV4 using a nearly full-length HPV4 genome in a replication competent system in 293 cells. We found that PARV4 utilizes two promoters to transcribe non-structural protein- and structural protein-encoding mRNAs, respectively, which were polyadenylated at the right end of the genome. Three major proteins, including the large non-structural protein NS1a, whose mRNA is spliced, and capsid proteins VP1 and VP2, were detected. Additional functional analysis of the NS1a revealed its capability to induce cell cycle arrest at G2/M phase in ex vivo-generated human hematopoietic stem cells. Taken together, our characterization of the molecular features of PARV4 suggests that PARV4 represents a new genus in the family Parvoviridae.