Parvovirus 4-like virus in blood products

Seroprevalence and Risk Factors Investigations of Parvovirus Disease in Tibetan Pigs: First Report from Tibet

Porcine parvovirus (PPV) disease is a worldwide spread animal disease with high infection rate and serious impact on meat economy causing significant losses in livestock production. The purpose of this paper is to investigate and analyze the regional seroprevalence of PPV in Tibetan pigs in Tibet and evaluate risk factors related to the disease. A total of 356 serum samples of Tibetan pigs were collected from four counties and districts in Tibet, and anti-PPV antibodies were detected by using a commercial competitive ELISA. Our results show a seroprevalence of 91.01% (324 serum samples were found to be positive for anti-PPV antibodies). The positive rate among different district was 100%, 96.55%, 93.68% and 72.83%, respectively in the Mainling County, in Bayi district, Nang County and Bomê County. We found significant differences between different age and gender groups; particularly female animals show a seroprevalence of 96.03% while the males only 83.46%. From the perspective of the growth stage, our results indicate that subadults show a seroprevalence significative higher than other age groups (100%). This study describes for the first time the PPV seroprevalence among Tibetan pigs characterizing risk factors involved in its transmission and providing information to be taken into account for eventual surveillance or eradication plans.

Antigenicity study of the yeast-generated human parvovirus 4 (PARV4) virus-like particles

Human parvovirus 4 (PARV4) is a novel tetraparvovirus that was isolated from intravenous drug users in 2005. Recombinant PARV4 capsid protein VP2 can form stable virus-like particles (VLPs) in yeast. These VLPs could act as antigen carriers during vaccine development. Therefore, the information about PARV4 VP2 VLP antigenic sites could advance further research in this area. In this work, human parvovirus 4 VLPs obtained from yeast were used to generate monoclonal antibodies (mAbs) in mice. Epitope mapping of the obtained mAbs showed at least three distinct antigenic sites of the VP2 protein. On top of that, molecular cloning was used to replace PARV4 VP2 antigenic sites with heterologous peptides. The chimeric PARV4 VLPs bearing polyhistidine inserts obtained from yeast were observed using electron microscopy while polyhistidine-specific antibodies detected heterologous peptides of the chimeric VP2 proteins.

Detection and molecular characterization of porcine parvovirus in fetal tissues from sows without reproductive failure in Argentina

Porcine parvovirus (PPV) is one of many pathogens responsible for reproductive failure in pregnant sows. Several studies have reported the appearance of new PPV strains that differ from previous isolates both genetically and antigenically. Thus, the protective effects of commercially inactivated vaccines could not be complete. In South America, the information about PPV is limited. Thus, the aim of the present study was to detect and characterize the PPV strains present in 131 mummies or stillbirths from normal deliveries in sows from a commercial swine farm of Argentina that uses the commercial vaccine. PCR results showed that 17/131 were positive to PPV. Ten of these viruses were isolated and sequenced. All viruses were related to the PPV1 sequence (NADL-2), maintaining the amino acid differences in positions 436 (S–P) and 565 (R–K). This study is the first to report the isolation of PPV in Argentina and the results suggest that PPV can cross the placenta even in vaccinated sows, thus affecting some of the fetuses and being able to cause fetal death in sows without reproductive failure. The results also suggest that vaccination only reduces clinical signs and reproductive disorders and may thus not be a perfect tool to manage PPV infection. This study provides information that needs to be studied in depth to improve strategies to prevent and control PPV infection in swine farms.

Detection Patterns of Porcine Parvovirus (PPV) and Novel Porcine Parvoviruses 2 through 6 (PPV2-PPV6) in Polish Swine Farms

Porcine parvovirus (PPV) is a major causative agent in reproductive failure, but in the last two decades many novel porcine parvoviruses were described and designated as porcine parvovirus 2 through 6 (PPV2–PPV6). However, their role for pig health is largely unknown. The aim of this study was to better understand the on-farm prevalence of PPVs in different age groups of pigs, and to assess the diagnostic applicability of testing different diagnostic materials. In total, 271 oral fluids, 1244 serum samples, and 1238 fecal samples were collected from 3–21-week-old pigs from 19 farms, and after pooling by 4–6, tested by real-time PCR. The results showed that PPVs are widely spread in Poland and that the highest detection rates were obtained for oral fluids (ranging from 10.7% (PPV1) to 48.7% (PPV2)). Fattening pigs were the age group with the most frequent detection of PPVs (ranging from 8.6% (PPV1) to 49.1% (PPV2)). Porcine parvoviruses were detected mostly in growing-finishing pigs and the infection persisted until the late fattening period, which may suggest the chronic character of the infection (especially for PPV2, which was found to commonly infect animals of all ages). Particularly low Ct values detected for PPV2, PPV3, PPV5, and PPV6 in serum pools from some farms suggested that these viruses may cause high levels of viremia in one or more individuals included in these pools. Further studies are needed to quantify the levels of PPVs viremia and to assess the impact in co-infections with other, often endemic pig viruses, such as porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV).

Simultaneous detection and differentiation of human parvovirus B19 and human parvovirus 4 by an internally controlled multiplex quantitative real-time PCR

Human parvovirus B19 (B19V) and human parvovirus 4 (PARV4) are two parvoviruses known to infect humans and transmit through blood and plasma derived medicinal products (PDMPs). Inactivation of the two parvoviruses has proven to be difficult and nucleic acid testing (NAT) would be an efficient means to exclude viruses. In this study, an internally controlled multiplex quantitative real-time PCR (qPCR) assay for B19V and PARV4 simultaneous detection and quantification was established and evaluated. The optimized multiplex qPCR assay allowed for simultaneous detection of all of the genotypes (1-3) of B19V and PARV4, with equal limit of quantification (LOQ) of 5 copies/μL, rather than other blood-borne viruses. It had a wide dynamic range of reliable amplification linearity of at least 8 orders of magnitude. Low standard deviations (SD) of quantification cycle (Cq) values and low coefficients of variation (CV) of copy numbers for both B19V and PARV4 suggested a high level of repeatability and reproducibility for the multiplex qPCR assay. This multiplex qPCR assay can be served as a readily applicable approach to screen plasma units intended for further manufacturing into PDMPs to reduce the risk of parvoviruses infection by such products and may also be useful for the detection of B19V/PARV4 co-infection or co-existence.

Prevalence and genomic characterization of porcine parvoviruses detected in Chiangmai area of Thailand in 2011

Porcine parvovirus (PPV) causes reproductive failure in sows and has spread worldwide. Several new types of porcine parvoviruses have recently been identified in pig herds. The prevalence of five porcine parvoviruses in the Chiangmai area of Thailand was studied. The prevalence in 80 pigs was 53% for PPV (PPV-Kr or -NADL2 being the new abbreviations), 83% for PPV2 (CnP-PARV4), 73% for PPV3 (P-PARV4), 44% for PPV4 (PPV4), and 18% for PBo-likeV (PBoV7). Over 60% of the pigs carried more than three of the five porcine parvoviruses and occurrence together of the two pairs of viral genes, PPV1/PPV3 and PPV2/PBo-likeV were observed. Phylogenetic analyses for PPV2 and PPV3 indicated the existence of only two major clades of PPV2 and one major clade of PPV3.

First detection of ungulate tetraparvovirus 1 (bovine hokovirus 1) in domestic yaks in northwestern China

We describe the discovery and phylogenetic analysis of ungulate tetraparvovirus 1 (also referred to as bovine hokovirus 1, B-PARV4, or partetravirus) in domestic yaks (Bos grunniens) in northwestern China. The yak B-PARV4 genome was detected in yak blood samples by PCR, using B-PARV4 primers corresponding to conserved regions. Twenty-two of 370 samples were positive for a B-PARV4-related genome sequence, indicating an overall prevalence of 5.95 %. The prevalence in Qinghai Province (13/195, 6.67 %) and Gansu Province (9/175, 5.14 %) was similar, but it varied significantly between yaks ≤ 1 year old (15/177, 8.47 %) and yaks > 1 year old (7/193, 3.6 %) (p < 0.05). An alignment of the nearly full-length genome sequences of all 22 strains identified six different genomic sequences. A phylogenetic analysis revealed 99.0-99.7 % sequence identity between these six genomes and all known B-PARV4 genomes, excluding JF504698 (only 88.6 % identity), which represents another genotype. This is the first discovery of B-PARV4-related viruses in domestic yaks.

CHARACTERIZATION OF PORCINE PARVOVIRUS TYPE 3 AND PORCINE CIRCOVIRUS TYPE 2 IN WILD BOARS (SUS SCROFA) IN SLOVAKIA

As the number of free-living wild boars (Sus scrofa L.) continues to rise in Slovakia, the probability of pathogen transmission between susceptible species increases. We investigated the distribution and genetic characterization of porcine parvovirus type 3 (PPV3), porcine circovirus type 2 (PCV2), and their coinfection in wild boars. Among 194 animals tested, 19.1% were positive for PPV3 and 43.8% for PCV2. Similar rates of coinfection with both viruses reaching 11.0% and 11.8% were observed in juvenile and mature wild boars, respectively. Phylogenetic analysis of PPV3 sequences from VP1 and NS1 genomic regions revealed a close genetic relationship among isolates from Slovakia and those sampled worldwide. Prevalence of PCV2 in wild boars was lower than that reported in domestic pigs in Slovakia. The PCV2 variants originating from sylvatic and domestic hosts in Slovakia were grouped in the same clusters, namely PCV2b-1A/1B and PCV2a-2D.

Identification of recently described porcine parvoviruses in archived North American samples from 1996 and association with porcine circovirus associated disease

The association of porcine circovirus (PCV) type 2 and porcine parvovirus (PPV) type 1 as a cause of porcine circovirus associated disease (PCVAD) is well established. The objective of this study was to investigate the prevalence rates of classical PPV1 and recently recognized PPV2-5 in serum and lung samples from pigs and farms with known PCV2 status. A total of 586 serum samples and 164 lung homogenates collected from 1996 to 2013 in the USA and Canada were utilized. All samples were tested for PPV1-5 and PCV2. PCV2 was detected in 27.7% (162/586) and PPV in 48.8% (286/586) of the serum samples, whereas 78.7% (129/164) of the lung tissues were positive for PCV2 and 56.7% (93/164) were positive for PPV. Overall, PPV2 had the highest prevalence rates in sera (35.2%) and tissues (42.7%). Concurrent infection of PCV2 and PPV occurred in 14.3% (84/586) of the serum samples and in 49.4% (81/164) of the tissue samples. Moreover, the prevalence of PPV1 or PPV2 DNA was significantly higher in tissues containing high amounts of PCV2 DNA compared to non-PCVAD cases. The frequency of concurrent PPV/PCV2 infection was higher for PCVAD herds compared to negative or subclinically infected herds. PPV2, PPV3 and PPV4 were all identified in samples collected in 1998 and PPV5 was first identified in 2006. The obtained findings indicate that similar to PCV2, PPVs are widespread in North American pigs. Nevertheless, diagnostic investigations into PCVAD cases should give more consideration to the role of PPV1 and PPV2 as contributing cofactors.

Porcine circovirus (PCV) removal by Q sepharose fast flow chromatography

The recently discovered contamination of oral rotavirus vaccines led to exposure of millions of infants to porcine circovirus (PCV). PCV was not detected by conventional virus screening tests. Regulatory agencies expect exclusion of adventitious viruses from biological products. Therefore, methods for inactivation/removal of viruses have to be implemented as an additional safety barrier whenever feasible. However, inactivation or removal of PCV is difficult. PCV is highly resistant to widely used physicochemical inactivation procedures. Circoviruses such as PCV are the smallest viruses known and are not expected to be effectively removed by currently-used virus filters due to the small size of the circovirus particles. Anion exchange chromatography such as Q Sepharose(®) Fast Flow (QSFF) has been shown to effectively remove a range of viruses including parvoviruses. In this study, we investigated PCV1 removal by virus filtration and by QSFF chromatography. As expected, PCV1 could not be effectively removed by virus filtration. However, PCV1 could be effectively removed by QSFF as used during the purification of monoclonal antibodies (mAbs) and a log10 reduction value (LRV) of 4.12 was obtained.

Emerging novel porcine parvoviruses in Europe: origin, evolution, phylodynamics and phylogeography

To elucidate the spatiotemporal phylodynamics, dispersion and evolutionary processes underlying the emergence of novel porcine parvovirus 2 (PPV2), PPV3 and PPV4 species, we analysed all available complete capsid genes, together with ours, obtained in Europe. Bayesian phylogeography indicates that Romania (PPV2 and PPV4) and Croatia (PPV3) are the most likely ancestral areas from which PPVs have subsequently spread to other European countries and regions. The timescale of our reconstruction supported a relatively recent history of the currently circulating novel PPV species (1920s to 1980s) in the domestic or sylvatic host. While PPV2 strains exhibited a large genetic exchange characterized by significant recombination and gene flow between distinct regions and hosts, PPV3 and PPV4 showed a diversification reflected by the accumulation of geographically structured polymorphisms. The RNA-like evolutionary rates detected inter- and intrahost recombination and the positive selection sites provided evidence that the PPV2-4 capsid gene plays a prominent role in host adaptation.

Development of a loop-mediated isothermal amplification assay for the detection of porcine hokovirus

Hokoviruses have recently been detected as pathogens belonging to the family Parvoviridae, which comprises porcine hokovirus (PHoV) and bovine hokovirus (BHoV). In this study, we developed a loop-mediated isothermal amplification (LAMP) assay for the rapid, specific and sensitive detection of PHoV. A set of four primers specific for six regions within the PHoV VP1/2 genes was designed using online software. The reaction temperature and time were optimized at 65°C and 60 min, respectively. LAMP products were detected by agarose gel electrophoresis or by visual inspection of a color change caused by a fluorescent dye. The method was highly specific for PHoV, and no cross-reaction was observed with porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine bocavirus (PBoV), pseudorabies virus (PRV), porcine reproductive and respiratory syndrome virus (PRRSV), classic swine fever virus (CSFV), or Japanese encephalitis virus (JEV). The detection limit was approximately 10 copies per reaction, which was 10 times more sensitive than conventional PCR. Furthermore, the efficiency of detection of PHoV in clinical samples was comparable to that of PCR and sequencing. These results show that the LAMP assay is a simple, rapid, sensitive and specific method for detecting PHoV. It does not require specialized equipment and can be used to detect PHoV both in the laboratory and in the field.

Prevalence of porcine hokovirus and its co-infection with porcine circovirus 2 in China

Here, we report the frequency of porcine hokovirus (PHoV) infection and its co-infection with porcine circovirus 2 (PCV2) in China. A total of 485 domestic pig samples were tested for both PHoV and PCV2, and NS1 gene sequences from 11 PHoV strains were used for phylogenetic analysis. The prevalence of PHoV and PCV2 was 51.3 % and 36.3 %, respectively, and co-infection occurred in 20.2 %. PHoVs from the Chinese mainland showed a close relationship to those isolated in Hong Kong. Co-infection with both viruses was prevalent, and PHoV may contribute to the induction of postweaning multisystemic wasting syndrome (PMWS).

Parvovirus transmission by blood products - a cause for concern?

The introduction of dual viral inactivation of clotting factor concentrates has practically eliminated infections by viruses associated with significant pathogenicity over the last 20 years. Despite this, theoretical concerns about transmission of infection have remained, as it is known that currently available viral inactivation methods are unable to eliminate parvovirus B19 or prions from these products. Recently, concern has been raised following the identification of the new parvoviruses, human parvovirus 4 (PARV4) and new genotypes of parvovirus B19, in blood products. Parvoviruses do not cause chronic pathogenicity similar to human immunodeficiency virus or hepatitis C virus, but nevertheless may cause clinical manifestations, especially in immunosuppressed patients. Manufacturers should institute measures, such as minipool polymerase chain reaction testing, to ensure that their products contain no known viruses. So far, human bocavirus, another new genus of parvovirus, has not been detected in fractionated blood products, and unless their presence can be demonstrated, routine testing during manufacture is not essential. Continued surveillance of the patients and of the safety of blood products remains an important ongoing issue.

No evidence of presence of parvovirus 4 in a Swedish cohort of severely immunocompromised children and adults

The recently discovered human parvovirus 4 (PARV4) has been associated with seropositivity for human immunodeficiency virus, hepatitis B virus and hepatitis C virus. High prevalence is seen especially in intravenous drug users. The virus has been detected in blood products and persons who have been repeatedly transfused have shown to be a risk-group. Furthermore, reports from different parts of the world suggesting a prevalence ranging from zero to one third of the healthy population and the virus is thought to cause a latent or persistent infection. We investigated the presence of PARV4 DNA and parvovirus B19 (B19) DNA in serum from 231 severely immunocompromised cancer patients that have been exposed for blood products. Compared to B19, which was found in 3.9% of the patients, we found no evidence of PARV4. Our results may indicate a very low prevalence of the virus in Sweden, and it would be useful to measure the real PARV4 exposure of the healthy population as well as individuals with known risk factors by serology.

Increasing porcine PARV4 prevalence with pig age in the U.S. pig population

A novel parvovirus in pigs currently known as porcine PARV4 was recently discovered in pigs in Asia and Europe. The objective of this study was to investigate if porcine PARV4 is present in the U.S. pig population using a newly developed quantitative real-time PCR assay. Lung tissues obtained from 483 pigs across five different age groups with varying disease manifestations (reproductive failure/abortion, enteritis, respiratory disease, systemic/central nervous disease) were tested. While porcine PARV4 DNA was not detected in fetuses (0/28) or suckling pigs (0/15), it was detected in pigs from 10 of 16 states with increasing prevalence rates in the older pigs. Specifically, porcine PARV4 DNA was detected in 5.6% (10/178) of the nursery pigs, 18.7% (44/235) of the grow-finish pigs and 22.2% (6/27) of the mature pigs tested. Genome sequence comparison and phylogenetic analysis of U.S. porcine PARV4s confirmed that they have similar genomic characteristics and 97.6-99.1% sequence identities to available porcine PARV4 sequences from China, Romania, and the U.K. Porcine PARV4 was identified in 14.4% of respiratory cases and in 11.6% of cases with a history of systemic/central nervous system disease. As strict non-diseased controls were not included in this study, a possible role of porcine PARV4 in these disease manifestations remains inconclusive. To the authors' knowledge, this is the first description of porcine PARV4 in the U.S. pig population.

Genome sequence of a highly prevalent porcine partetravirus in Mainland China

Partetravirus is a novel defined genus of animal parvoviruses. Here, we first report the genome sequence of porcine partetravirus strain JSNJ62, which is highly prevalent in mainland China. It will help in understanding the epidemiology and molecular characteristics of the porcine partetravirus.

Two novel parvoviruses in frugivorous New and Old World bats

Bats, a globally distributed group of mammals with high ecological importance, are increasingly recognized as natural reservoir hosts for viral agents of significance to human and animal health. In the present study, we evaluated pools of blood samples obtained from two phylogenetically distant bat families, in particular from flying foxes (Pteropodidae), Eidolon helvum in West Africa, and from two species of New World leaf-nosed fruit bats (Phyllostomidae), Artibeus jamaicensis and Artibeus lituratus in Central America. A sequence-independent virus discovery technique (VIDISCA) was used in combination with high throughput sequencing to detect two novel parvoviruses: a PARV4-like virus named Eh-BtPV-1 in Eidolon helvum from Ghana and the first member of a putative new genus in Artibeus jamaicensis from Panama (Aj-BtPV-1). Those viruses were circulating in the corresponding bat colony at rates of 7–8%. Aj-BtPV-1 was also found in Artibeus lituratus (5.5%). Both viruses were detected in the blood of infected animals at high concentrations: up to 10E8 and to 10E10 copies/ml for Aj-BtPV-1 and Eh-BtPV-1 respectively. Eh-BtPV-1 was additionally detected in all organs collected from bats (brain, lungs, liver, spleen, kidneys and intestine) and spleen and kidneys were identified as the most likely sites where viral replication takes place. Our study shows that bat parvoviruses share common ancestors with known parvoviruses of humans and livestock. We also provide evidence that a variety of Parvovirinae are able to cause active infection in bats and that they are widely distributed in these animals with different geographic origin, ecologies and climatic ranges.

Distribution and genetic diversity of porcine hokovirus in wild boars

Porcine hokovirus (PHoV), a newly discovered member of the family Parvoviridae and the proposed genus Hokovirus, is considered phylogenetically distinct from other parvoviruses. Here, we report a comprehensive spatio-temporal study of PHoV infection in Romanian wild boars. The prevalence of PHoV differed significantly in samples from 2006/2007 (22.76%) and 2010/2011 (50.54%), and also increased with age. Sequence analysis of PHoVs from 2006/2007 showed a close relationship to PHoVs from pigs from England and wild boars from Germany, while the PHoVs from 2010/2011 were mostly similar to isolates from Hong Kong. The most variable regions were detected in the NS1 gene and proved to be suitable for analysis of the genetic diversity of the virus. It was observed that PHoVs from older wild boar samples differed from those collected recently. These results suggested that porcine hokovirus could be a newly emerging virus of both domestic and wild pigs with yet unknown implications.

Discovery and genomic characterization of a novel ovine partetravirus and a new genotype of bovine partetravirus

Partetravirus is a recently described group of animal parvoviruses which include the human partetravirus, bovine partetravirus and porcine partetravirus (previously known as human parvovirus 4, bovine hokovirus and porcine hokovirus respectively). In this report, we describe the discovery and genomic characterization of partetraviruses in bovine and ovine samples from China. These partetraviruses were detected by PCR in 1.8% of bovine liver samples, 66.7% of ovine liver samples and 71.4% of ovine spleen samples. One of the bovine partetraviruses detected in the present samples is phylogenetically distinct from previously reported bovine partetraviruses and likely represents a novel genotype. The ovine partetravirus is a novel partetravirus and phylogenetically most related to the bovine partetraviruses. The genome organization is conserved amongst these viruses, including the presence of a putative transmembrane protein encoded by an overlapping reading frame in ORF2. Results from the present study provide further support to the classification of partetraviruses as a separate genus in Parvovirinae.

Microbial safety in xenotransplantation

PURPOSE OF REVIEW

As clinical trials are in progress involving porcine islet cell transplantation, microbial safety remains a key issue. Therefore, in the context of pig-to-human xenotransplantation, we provide an overview of the recent progress in the studies of relevant viruses including well known problematic viruses, such as herpesviruses and porcine endogenous retroviruses (PERV) in addition to some emerging issues regarding other pathogens.

RECENT FINDINGS

The ability of herpesvirus to infect across species barriers is probably underestimated and requires monitoring and control of both xenograft donors and recipients for latent infection. Exclusion from donors and recipient monitoring for other exogenous pathogens including newly identified Parvovirus-4 are warranted. The availability of the swine whole genome sequence may help to characterize and select donor animals with less PERV infectivity. Rigorous PERV monitoring in both clinical and preclinical xenotransplantation experiments must be included in clinical protocols.

SUMMARY

A wide range of pathogens, both viruses and bacteria, pose potential safety problems in xenotransplantation, highlighting the importance of prescreening of the donor animals, and careful monitoring and follow-up of the patients.

Detection of a novel porcine parvovirus, PPV4, in Chinese swine herds

To determine whether the novel porcine parvovirus type 4 (PPV4) recently reported in America is prevalent in China, a set of specific primers was designed and used for molecular survey of PPV4 among the clinical samples collected from various provinces of China between 2006 and 2010. The results showed that PPV4 is present in Chinese swine herds at a rate of 2.09% (12/573) among the clinical samples examined and 0.76% (1/132) among the samples taken from healthy animals. We also noted that PPV4 was not detected in samples taken prior to 2009. Analysis of the coding sequences showed that the Chinese and American PPV4 genome sequences are closely related with greater than 99% nucleotide sequence identity. Similar to a previous study, viral genomes in head-to-tail configuration of various lengths of the non-coding region were detected. Our findings confirmed that PPV4 is a unique recently discovered virus in pigs. Phylogenetically, PPV4 is most closely related to bovine parvovirus 2 (BPV2, which is not a Bocavirus and is not assigned to any Parvovirinae genus) and shares limited ORF1 (33.6%) and ORF2 (24.5%) amino acid identity. With respect to genome structure and organization, PPV4 encodes an ORF3 in the middle of the viral genome that resembles the Bocavirus genus. However, the PPV4 ORF3 encoded protein shares minimal amino acid identity with the ORF3 encoded proteins of the Bocavirus genus.