First molecular detection and complete sequence analysis of porcine circovirus type 3 (PCV3) in Peninsular Malaysia

Porcine circovirus type 3 (PCV3) is a newly emerging virus in the swine industry, first reported recently in 2016. PCV3 assembles into a 2000 bp circular genome; slightly larger than PCV1 (1758-1760 bp), PCV2 (1766-1769 bp) and PCV4 (1770 bp). Apart from being associated with porcine dermatitis and nephropathy syndrome (PDNS), PCV3 has been isolated from pigs with clinical signs of reproductive failures, myocarditis, porcine respiratory disease complex (PRDC) and neurologic disease. Given that PCV3 is increasingly reported in countries including Thailand and U.S. with whom Malaysia shares trade and geographical relationship; and that PCV3 is associated with several clinical presentations that affect productivity, there is a need to study the presence and molecular characteristics of PCV3 in Malaysian swine farms. Twenty-four commercial swine farms, three abattoirs and retail shops in Peninsular Malaysia were sampled using convenience sampling method. A total of 281 samples from 141 pigs, including 49 lung archive samples were tested for PCV3 by conventional PCR. Twenty-eight lung samples from wild boar population in Peninsular Malaysia were also included. Nucleotide sequences were analyzed for maximum likelihood phylogeny relationship and pairwise distances. Results revealed that PCV3 is present in Peninsular Malaysia at a molecular prevalence of 17.02%, with inguinal lymph nodes and lungs showing the highest molecular detection rates of 81.82% and 71.43% respectively. Despite wide reports of PCV3 in healthy animals and wild boars, no positive samples were detected in clinically healthy finishers and wild boar population of this study. PCV3 strain A1 and A2 were present in Malaysia, and Malaysian PCV3 strains were found to be phylogenetically related to Spanish, U.S. and Mexico strains.

Beak and feather disease virus (BFDV) prevalence, load and excretion in seven species of wild caught common Australian parrots

Pathogens pose a major risk to wild host populations, especially in the face of ongoing biodiversity declines. Beak and feather disease virus (BFDV) can affect most if not all members of one of the largest and most threatened bird orders world-wide, the Psittaciformes. Signs of disease can be severe and mortality rates high. Its broad host range makes it a risk to threatened species in particular, because infection can occur via spill-over from abundant hosts. Despite these risks, surveillance of BFDV in locally abundant wild host species has been lacking. We used qPCR and haemagglutination assays to investigate BFDV prevalence, load and shedding in seven abundant host species in the wild in south-east Australia: Crimson Rosellas (Platycercus elegans), Eastern Rosellas (Platycercus eximius), Galahs (Eolophus roseicapillus), Sulphur-crested Cockatoos (Cacatua galerita), Blue-winged Parrots (Neophema chrysostoma), Rainbow Lorikeets (Trichoglossus moluccanus) and Red-rumped Parrots (Psephotus haematonotus). We found BFDV infection in clinically normal birds in six of the seven species sampled. We focused our analysis on the four most commonly caught species, namely Crimson Rosellas (BFDV prevalence in blood samples: 41.8%), Sulphur-crested Cockatoos (20.0%), Blue-winged Parrots (11.8%) and Galahs (8.8%). Species, but not sex, was a significant predictor for BFDV prevalence and load. 56.1% of BFDV positive individuals were excreting BFDV antigen into their feathers, indicative of active viral replication with shedding. Being BFDV positive in blood samples predicted shedding in Crimson Rosellas. Our study confirms that BFDV is endemic in our study region, and can inform targeted disease management by providing comparative data on interspecies variation in virus prevalence, load and shedding.

Simultaneous detection of classical swine fever virus and porcine circovirus 3 by SYBR green I-based duplex real-time fluorescence quantitative PCR

In the present study, the SYBR green I-based duplex quantitative polymerase chain reaction (qPCR) was developed for simultaneous detection of classical swine fever virus (CSFV) and porcine circovirus 3 (PCV3). The assay was used to detect both CSFV and PCV3 in one sample by their distinct melting temperatures (melting peaks at 87°C for CSFV and 81.5 °C for PCV3), and no specific fluorescence signals were detected for other non-targeted porcine pathogens. The assay had a high degree of linearity (R² > 0.998) with the detection limits of 23 copies/μL for CSFV and 36 copies/μL for PCV3, and exhibited high repeatability and reproducibility with a low coefficient of variation below 2.0% in both intra- and inter-assay. In this study, 130 clinical samples collected from sick pigs in the field were tested by this assay with the positive rates of 9.23% (12/130) for CSFV and 21.54% (28/130) for PCV3 respectively, and the positive rate of CSFV and PCV3 co-infection was 6.92% (9/130). Our results showed that the developed method was a reliable diagnostic tool to monitor and survey CSFV, PCV3 and CSFV/PCV3 co-infection in the field.

ITRAQ-based quantitative proteomics reveals the first proteome profiles of piglets infected with porcine circovirus type 3

Porcine circovirus type 3 (PCV3) infection induces porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammatory lesions in piglets and sows. To better understand the host responses to PCV3 infection, isobaric tags for relative and absolute quantification (iTRAQ) labeling combined with LC-MS/MS analysis was used for quantitative determination of differentially regulated cellular proteins in the lungs of specific-pathogen-free piglets after 4 weeks of PCV3 infection. Totally, 3429 proteins were detected in three independent mass spectrometry analyses, of which 242 differential cellular proteins were significantly regulated, consisting of 100 upregulated proteins and 142 downregulated proteins in PCV3-infected group relative to control group. Bioinformatics analysis revealed that these higher or lower abundant proteins involved primarily metabolic processes, innate immune response, MHC-I and MHC-II components, and phagosome pathways. Ten genes encoding differentially regulated proteins were selected for investigation via real-time RT-PCR. The expression levels of six representative proteins, OAS1, Mx1, ISG15, IFIT3, SOD2, and HSP60, were further confirmed by Western blotting and immunohistochemistry. This study attempted for the first time to investigate the protein profile of PCV3-infected piglets using iTRAQ technology; our findings provide valuable information to better understand the mechanisms underlying the host responses to PCV3 infection in piglets. SIGNIFICANCE: Our study identified differentially abundant proteins related to a variety of potential signaling pathways in the lungs of PCV3-infected piglets. These findings provide valuable information to better understand the mechanisms of host responses to PCV3 infection.

Identification of a Novel Adélie Penguin Circovirus at Cape Crozier (Ross Island, Antarctica)

Understanding the causes of disease in Antarctic wildlife is crucial, as many of these species are already threatened by environmental changes brought about by climate change. In recent years, Antarctic penguins have been showing signs of an unknown pathology: a feather disorder characterised by missing feathers, resulting in exposed skin. During the 2018-2019 austral summer breeding season at Cape Crozier colony on Ross Island, Antarctica, we observed for the first time an Adélie penguin chick missing down over most of its body. A guano sample was collected from the nest of the featherless chick, and using high-throughput sequencing, we identified a novel circovirus. Using abutting primers, we amplified the full genome, which we cloned and Sanger-sequenced to determine the complete genome of the circovirus. The Adélie penguin guano-associated circovirus genome shares <67% genome-wide nucleotide identity with other circoviruses, representing a new species of circovirus; therefore, we named it penguin circovirus (PenCV). Using the same primer pair, we screened 25 previously collected cloacal swabs taken at Cape Crozier from known-age adult Adélie penguins during the 2014-2015 season, displaying no clinical signs of feather-loss disorder. Three of the 25 samples (12%) were positive for a PenCV, whose genome shared >99% pairwise identity with the one identified in 2018-2019. This is the first report of a circovirus associated with a penguin species. This circovirus could be an etiological agent of the feather-loss disorder in Antarctic penguins.

Design and Development of Photonic Biosensors for Swine Viral Diseases Detection

In this paper we introduce a field diagnostic device based on the combination of advanced bio-sensing and photonics technologies, to tackle emerging and endemic viruses causing swine epidemics, and consequently significant economic damage in farms. The device is based on the use of microring resonators fabricated in silicon nitride with CMOS compatible techniques. In the paper, the designed and fabricated photonic integrated circuit (PIC) sensors are presented and characterized, showing an optimized performance in terms of optical losses (30 dB per ring) and extinction ration for ring resonances (15 dB). Furthermore, the results of an experiment for porcine circovirus 2 (PCV2) detection by using the developed biosensors are presented. Positive detection for different virus concentrations has been obtained. The device is currently under development in the framework of the EU Commission co-funded project SWINOSTICS.

Evolution and Genetic Diversity of Porcine Circovirus 3 in China

The identification of a new circovirus (Porcine Circovirus 3, PCV3) has raised concern because its impact on swine health is not fully known. In Fujian Province in eastern China, even its circulating status and genetic characteristics are unclear. Here, we tested 127 tissue samples from swine from Fujian Province that presented respiratory symptoms. All of the PCV3 positive samples were negative for many other pathogens involved in respiratory diseases like PCV2, PRRSV, and CSFV, suggesting that PCV3 is potentially pathogenic. From phylogenetic analysis, PCV3 strains are divided into two main clades and five sub-clades; PCV3a-1, PCV3a-2, PCV3a-3, PCV3b-1, and PCV3b-2. Our identified strains belong to genotypes PCV3a-1, PCV3a-2, PCV3a-3, and PCV3b-2, indicating a high degree of genetic diversity of PCV3 in Fujian province until 2019. Interestingly, we found the time of the most recent common ancestor (tMRCA) of PCV3 was dated to the 1950s, and PCV3 has a similar evolutionary rate as PCV2 (the main epidemic genotypes PCV2b and PCV2d). In addition, positive selection sites N56D/S and S77T/N on the capsid gene are located on the PCV3 antigen epitope, indicating that PCV3 is gradually adaptive in swine. In summary, our results provide important insights into the epidemiology of PCV3.

An epidemiological investigation of porcine circovirus 3 infection in dogs in the Guangxi Province from 2015 to 2017, China

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This study was the first seroprevalence and genetic investigation of PCV3 in dogs in the Guangxi province, China.

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This work is the first in the world to obtain the complete genome of dog PCV3.

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These PCV3 strains from the Guangxi province help to determine that PCV3 from dog origin and pig origin are from different branches.

Porcine circovirus type 3 (PCV3) is an emerging circovirus species associated with several diseases. The study aimed to investigate the frequency of porcine circovirus 3 (PCV3) and its coinfection with canine parvovirus type 2 (CPV-2) in dogs in the Guangxi province from 2015 to 2017, China, and to examine the genome diversity of PCV3. Using polymerase chain reaction (PCR) amplification and sequencing, 96 of 406 (23.6%)samples were positive for PCV3, 38 out of 406 (9.4%) samples were coinfected with both PCV3 and CPV-2. The CPV-positive rate was significantly higher in the PCV3-positive samples than in the non-PCV3 samples, and the difference was extremely significant (P < 0.01). The complete genome (n=4) and ten capsid genes (n=10) of PCV3 were sequenced. Multiple sequence alignment results showed that these sequences shared 98.5–100% nucleotide similarity with the reference genome sequence and 97.5–100% nucleotide similarity with the reference capsid gene sequence. PCV3 was classified into two different genotypes, according to phylogenetic analysis based on the whole genome. These strains were clustered in PCV3a, showing a close relationship with PCV3-US/SD2016. Surprisingly, we separately analyzed these PCV3 strains from the Guangxi province and found that the dog and pig PCV3 are from different branches. In summary, this was the first seroprevalence and genetic investigation of PCV3 in dogs in the Guangxi province, China, and the first complete genome PCV3 from dogs obtained in the world. The results provide insights into the epidemiology and pathogenesis of this important virus.

Sequence and phylogenetic analysis of novel porcine parvovirus 7 isolates from pigs in Guangxi, China

Parvoviruses are a diverse group of viruses that infect a wide range of animals and humans. In recent years, advances in molecular techniques have resulted in the identification of several novel parvoviruses in swine. In this study, porcine parvovirus 7 (PPV7) isolates from clinical samples collected in Guangxi, China, were examined to understand their molecular epidemiology and co-infection with porcine circovirus type 2 (PCV2). In this study, among the 385 pig serum samples, 105 were positive for PPV7, representing a 27.3% positive detection rate. The co-infection rate of PPV7 and PCV2 was 17.4% (67/385). Compared with the reference strains, we noted 93.9%-97.9% similarity in the NS1 gene and 87.4%-95.0% similarity in the cap gene. Interestingly, compared with the reference strains, sixteen of the PPV7 strains in this study contained an additional 3 to 15 nucleotides in the middle of the cap gene. Therefore, the Cap protein of fourteen strains encoded 474 amino acids, and the Cap protein of the other two strains encoded 470 amino acids. However, the Cap protein of the reference strain PPV7 isolate 42 encodes 469 amino acids. This is the first report of sequence variation within the cap gene, confirming an increase in the number of amino acids in the Cap protein of PPV7. Our findings provide new insight into the prevalence of PPV7 in swine in Guangxi, China, as well as sequence data and phylogenetic analysis of these novel PPV7 isolates.

The prevalence and genetic diversity of porcine circovirus types 2 and 3 in Northeast China from 2015 to 2018

A total of 472 samples from domestic pigs collected in China from 2015 to 2018 were tested for the presence of porcine circovirus types 2 and 3 (PCV2 and PCV3, respectively) by conventional polymerase chain reaction analysis. The prevalence of PCV2, PCV3, and PCV2/3 co-infection was 50.0%, 13.3%, and 6.78%, respectively. The complete genomic sequences of 66 PCV2 isolates and four PCV3 isolates were determined. Based phylogenetic analysis, the PCV2 isolates were assigned to three genotypes, PCV2a, PCV2b, and PCV2d, representing 13.6% (9/66), 25.8% (17/66), and 60.6% (40/66) of the total, respectively. All four PCV3 isolates shared a high degree of similarity in their complete nucleotide sequences (98.8-99.8% identity) and ORF2 amino acid sequences (98.6-99.5% identity). These results indicate that all three PCV2 genotypes (PCV2a, PCV2b, and PCV2d) are present on pig farms and that PCV2d has become the predominant genotype. The predicted amino acid sequences of the four PCV3 isolates indicated that PCV3-CN-JL53/PCV3-CN-LN56, PCV3-CN-HLJ3, and PCV3-CN-0710, belonged to the genotypes PCV3a, PCV3b, and PCV3a-IM, respectively. In view of the great harm that PCV2 causes to the pig industry, the epidemic trend of PCV3 should continue to be closely monitored. This study provides information about the prevalence, genetic diversity, and molecular epidemiology of PCV2 and PCV3 in China from 2015 to 2018.

Porcine circovirus type 3 detection in a Hungarian pig farm experiencing reproductive failures

Porcine circovirus 3 (PCV3) infection has been reported in piglets and sows with porcine dermatitis and nephropathy syndrome, reproductive failure, and cardiac and multisystemic inflammation. Few studies linked PCV3 infection to increased incidence of abortion and weak-born piglets. This is the first report of a detection of PCV3 Hungarian strain in several organs of aborted and weak-born piglets, including the thymus, lymph node, placenta, spleen, kidney and the liver. The tissue tropism of PCV3 in affected litters was analysed using real-time quantitative PCR, and the result showed the highest load of viral DNA in the thymus and lymph nodes. The ORF2 of Hungarian PCV3 strains was 524 nucleotides in length, and the sequence identity to GenBank sequences ranged from 98.5 per cent to 99.2 per cent. The results suggest that PCV3 may have a relevant role in reproductive failure in gilts.

Establishment of a sensitive TaqMan-based real-time PCR assay for porcine circovirus type 3 and its application in retrospective quarantine of imported boars to China

Porcine circovirus type 3 (PCV3) is a novel pathogen first identified in the United States in 2016. As there is a high possibility that no clinical signs of infection are observed in the host, an accurate and sensitive method is needed for quarantine on numerous live pigs especially for international pig trade. In this study, a TaqMan-based real-time PCR assay specifically for PCV3 was established without cross-reactions with other non-targeted pig viruses. The sensitivity of the current approach is about 1.5 × 101  copies μL-1 plasmid DNA while the sensitivity of the conventional PCR is about 1.5 × 102  copies μL-1 plasmid DNA. Further, this assay was applied in the retrospective quarantine on serum samples of 601 commercial live boars imported to China from the United States, France and the United Kingdom from 2011 to 2017. The results revealed that PCV3 could be detected positive in the commercial boars imported from the United States and the above-mentioned western European countries and phylogenetic study also revealed that viral isolates were grouped with some isolates from Korea and the United States. Our study suggested that PCV3 may be prevalent globally since 2011.

Retrospective Detection and Genetic Characterization of Porcine circovirus 3 (PCV3) Strains Identified between 2006 and 2007 in Brazil

Porcine circovirus 3 (PCV3) is an emerging virus that was first identified in the United States in 2016. Since its first detection, PCV3 has already been found in America, Asia, and Europe. Although PCV3 has already been described in Brazil, knowledge of its detection and sequence variation before 2016 is limited, as well as its distribution in the main swine producing regions of Brazil. In this study, 67 porcine clinical samples collected from nine states in Brazil between 2006 and 2007 were analyzed for PCV3 infection by PCR. Results showed that 47.8% of the samples were PCV3 positive, across all nine states. Of the PCV3-positive samples, 37.5% were also positive for PCV2. Interestingly, no clinical signs were associated with samples that were detected singularly with PCV3 infection. Moreover, the positive PCV3 rate in healthy pigs was higher (29.8%) than that found in unhealthy pigs (17.9%), suggesting that most pigs could live with PCV3 infection without any clinical sign in the analyzed samples. Nucleotide sequence analysis showed that PCV3 strains obtained in this study shared 94.44% to 99.83% sequence identity at the open reading frame 2 (ORF2) gene level with available strains from different countries. PCV3 Brazilian sequences collected in 2006 and 2007 shared 97.94% to 99.62% identity with the strains obtained in 2016. The results of neutrality and selective pressure tests indicated that the PCV3 Cap protein seems unable to tolerate high levels of variation on its sequence. Phylogenetic analysis grouped the Brazilian strains in PCV3a and PCV3b genotypes clusters, both including strains collected in America, Asia, and Europe. Taking the results together, multiple events of introduction of PCV3 may have occurred in Brazil, and Brazilian PCV3 strains may show genetic stability over the past 10 years.

Breed Differences in PCV2 Uptake and Disintegration in Porcine Monocytes

Porcine circovirus type 2 (PCV2) is associated with various diseases which are designated as PCV2-associated diseases (PCVADs). Their severity varies among breeds. In the diseased pigs, virus is present in monocytes, without replication or full degradation. PCV2 entry and viral outcome in primary porcine monocytes and the role of monocytes in PCV2 genetic susceptibility have not been studied. Here, virus uptake and trafficking were analyzed and compared among purebreds Piétrain, Landrace and Large White and hybrid Piétrain × Topigs20. Viral capsids were rapidly internalized into monocytes, followed by a slow disintegration to a residual level. PCV2 uptake was decreased by chlorpromazine, cytochalasin D and dynasore. The internalized capsids followed the endosomal trafficking pathway, ending up in lysosomes. PCV2 genome was nicked by lysosomal DNase II in vitro, but persisted in monocytes in vivo. Monocytes from purebred Piétrain and the hybrid showed a higher level of PCV2 uptake and disintegration, compared to those from Landrace and Large White. In conclusion, PCV2 entry occurs via clathrin-mediated endocytosis. After entry, viral capsids are partially disintegrated, while viral genomes largely escape from the pathway to avoid degradation. The degree of PCV2 uptake and disintegration differ among pig breeds.

Columbid circoviruses detected in free ranging pigeons from Southern Brazil: insights on PiCV evolution

Pigeon circovirus (PiCV) is taxonomically classified as a member of the Circovirus genus, family Circoviridae. The virus contains a single stranded DNA genome of approximately 2 kb, with minor length variations among different isolates. The occurrence of PiCV infections in pigeons (Columba livia) has been documented worldwide over the past 20 years; however, in Brazil there were still no reports on PiCV detection. This study identifies seven PiCV genomes recovered from domestic pigeons of South Brazil through high-throughput sequencing and shows a high frequency of PiCV infection, through quantitative real-time PCR. Phylogenetic classification was performed by maximum likelihood analysis of the full genomes, ORF V1 (Rep) and ORF C1 (Cap). The results show that either full genome or Cap based analysis allowed PiCV classification into five major clades (groups A to E), where Brazilian sequences were classified as A, C or D. Recombination analyses were carried out with Simplot and RDP4 and the results show that both Rep and Cap ORFs contain several recombination hotspots, pointing to an important role for such events in PiCV evolution.

Detection and genetic characterisation of porcine circovirus 3 from pigs in Sweden

Porcine circovirus 3 (PCV3) is a newly detected circovirus belonging to the family Circoviridae with a circular ssDNA genome of 2000 bp that encodes two proteins-the replicase protein and the capsid protein. PCV3 was discovered for the first time in the US in 2016. After this initial discovery, PCV3 was detected in other parts of the world such as in China, South Korea, Italy and Poland. In this study, 49 tissue samples from Swedish pig herds were screened for PCV3 using PCR and 10 samples were positive and one was uncertain. The entire PCV3 genome and a mini PCV-like virus (MPCLV) were obtained from one of these samples. These two viruses showed a high sequence identity to PCV3 viruses from other countries as well as to MPCLV from the US. However, the sequence identity to PCV1 and 2 was only 31-48% on amino acid level. This is the first detection and complete genetic characterisation of PCV3 in Swedish pigs. It is also interesting to note that one of the positive samples was collected in 1993, showing that PCV3 has been present for a long time.

Reproductive failure associated with coinfection of porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus

An outbreak of reproductive failure in a pig farm in Taiwan was investigated. Coinfection with porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) was diagnosed in a stillborn pig by histopathology, polymerase chain reaction, and immunohistochemistry, and should be considered as a cause of reproductive failure.

High prevalence of Mycobacterium genavense within flocks of pet birds

Mycobacterium genavense is regarded as the primary cause of mycobacteriosis in psittaciform and passeriform birds, which are commonly kept as pets. In humans, Mycobacterium genavense is especially pathogenic for young, old, pregnant and immunocompromised people (YOPIs). In birds, only few studies, mainly case reports, exist and there is still little e information about occurrence and relevance of this zoonotic pathogen. In this first pilot study concerning the prevalence of Mycobacterium genavense within flocks of naturally infected pet birds, real-time PCR examinations of 170 individual passeriform and psittaciform birds, including commonly kept budgerigars, lovebirds and zebra finches as well as gold finches and weaver finches, were conducted to determine the infection rate in six different aviaries. Antemortem examinations of faeces and cloacal swabs were compared with postmortem examinations of tissue samples to evaluate the reliability of antemortem diagnostics. Additional ophthalmologic examinations were performed to evaluate their diagnostic potential. Molecular examinations for viral co-infections, including circovirus, polyomavirus and adenovirus, were conducted to identify potential risk factors. PCR results revealed a detection prevalence of Mycobacterium genavense in the flocks varying from 3% to 91% based on postmortem testing, while antemortem diagnostics of faecal samples and swabs showed 64% discrepant (false negative) results. Ophthalmologic examinations were not useful in identifying infected birds within the flocks. Viral co-infections, especially with polyomavirus, were common. It has to be assumed that Mycobacterium genavense infections are widespread and underdiagnosed in companion birds. Viral infections might be an important risk factor. There is urgent need to improve antemortem diagnostics.

First molecular detection of porcine circovirus type 3 in dogs in China

Porcine circovirus type 3 (PCV3) has recently been isolated from diseased pigs within the USA. The objective was to detect the presence of PCV3 in dogs. Nested polymerase chain reactions (PCR) with PCV3-specific primers for the capsid gene were used to detect PCV3 genomic DNA in serum samples from dogs (n = 44) in China. There was PCV3 DNA detected in 4 of 44 dogs [all were negative for PCV2 and canine circovirus (CanineCV)]. Based on sequence analysis, positive sequences were grouped into PCV3 genotypes. However, these isolates had close evolutionary relationships with FoxCV (KP941114) and CanineCV (JQ821392). Further investigations of the epidemiology, evolutionary biology, and pathobiology of PCV3 to dogs are warranted.

Recombinant expression of beak and feather disease virus capsid protein and assembly of virus-like particles in Nicotiana benthamiana

BACKGROUND

Beak and feather disease virus (BFDV) is an important disease causing agent affecting psittacines. BFDV is highly infectious and can present as acute, chronic or subclinical disease. The virus causes immunodeficiency and is often associated with secondary infections. No commercial vaccine is available and yields of recombinant BFDV capsid protein (CP) expressed in insect cells and bacteria are yet to be seen as commercially viable, although both systems produced BFDV CP that could successfully assemble into virus-like particles (VLPs). Plants as expression systems are increasingly becoming favourable for the production of region-specific and niche market products. The aim of this study was to investigate the formation and potential for purification of BFDV VLPs in Nicotiana benthamiana.

METHODS

The BFDV CP was transiently expressed in N. benthamiana using an Agrobacterium-mediated system and plant expression vectors that included a bean yellow dwarf virus (BeYDV)-based replicating DNA vector. Plant-produced BFDV CP was detected using immunoblotting. VLPs were purified using sucrose cushion and CsCl density gradient centrifugation and visualised using transmission electron microscopy.

RESULTS

In this study we demonstrate that the BFDV CP can be successfully expressed in N. benthamiana, albeit at relatively low yield. Using a purification strategy based on centrifugation we demonstrated that the expressed CP can self-assemble into VLPs that can be detected using electron microscopy. These plant-produced BFDV VLPs resemble those produced in established recombinant expression systems and infectious virions. It is possible that the VLPs are spontaneously incorporating amplicon DNA produced from the replicating BeYDV plant vector.

CONCLUSIONS

This is the first report of plant-made full-length BFDV CP assembling into VLPs. The putative pseudovirions could be used to further the efficacy of vaccines against BFDV.

Development of a TaqMan-based real-time PCR assay for the specific detection of porcine circovirus 3

Porcine circovirus 3 (PCV3) is a novel circovirus that was associated with porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammation. The objective of this study was to develop a rapid, simple, specific and sensitive TaqMan-based real-time PCR assay for PCV3 detection. Specific primers and probe were designed for the cap gene of PCV3 within the conserved region of viral genome. The assay was highly specific for PCV3, without cross-reactions with other non-targeted pig viruses. The detection limit of this assay was 10² copies. The assay had an efficiency of 95.7%, a regression squared value (R²) of 0.994 and showed a linear range of 10²-10⁷ copies PCV3 DNA per reaction. The assay was also very reproducible, with the intra- and inter-assay coefficient of variation less than 2.0%. For the 112 archived clinical samples collected from 2014 to March 2017, the PCV3 positive ratio was 12.5% (14/112) with the real-time PCR. The presence of the PCV3 dated back to at least 2014 in China and samples collected in 2017 had the highest PCV3 positive ratio (46.7%, 7/15). The real-time PCR assay could be used for detection of PCV3 in epidemiological and pathogenesis studies.

Porcine reproductive and respiratory syndrome virus (PRRSV) in pig meat

Porcine reproductive and respiratory syndrome, caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is an economically important disease in the swine industry. Previous studies demonstrated the presence of the virus in pig meat and its transmissibility by oral consumption. This study further analyzed the infectivity of PRRSV in commercial pig meat. Fresh bottom meat pieces (n = 1500) randomly selected over a period of 2 y from a pork ham boning plant located in Quebec, Canada, were tested by reverse transcriptase polymerase chain reaction (RT-PCR). Each trimmed meat was stored in the plant freezer, subsampled weekly for up to 15 wk, and tested with quantitative RT-PCR to determine the viral load. Meat infectivity was evaluated using specific pathogen-free piglets, each fed with approximately 500 g of meat at the end of the storage time. Genotype-specific RT-PCR confirmed the presence of PRRSV mainly during cold weather in 0.73% of the fresh meat pieces. Wild and vaccine strains of genotype 2 were detected. Porcine reproductive and respiratory syndrome virus nucleic acid was stable in meat stored at around -20°C during the 15 wk. Serological and molecular analysis showed the transmission of infection by a majority of PRRSV positive meat pieces (5/9) fed orally to naïve recipients. The results confirmed a low prevalence of PRRSV in market's pig meat, and virus transmissibility by oral consumption to naïve recipients even after several weeks of storage in a commercial freezer. It occurred mainly with meat harboring the highest PRRSV RNA copies, in the range of 109 copies per 500 g of meat, with both wild type and vaccine-related strains.

Molecular Detection of Circovirus and Adenovirus in Feces of Fur Seals (Arctocephalus spp.)

In some regions, little is known about exposure to viruses in coastal marine mammals. The present study aimed to detect viral RNA or DNA in 23 free-ranging fur seals on the northern coastline of Rio Grande do Sul State, Brazil. Polymerase chain reaction was used to detect nucleic acids of circoviruses, adenoviruses, morbilliviruses, vesiviruses, and coronaviruses in the feces from twenty-one South American fur seals (Arctocephalus australis) and two Subantarctic fur seals (A. tropicalis). Adenovirus DNA fragments were detected in two South American fur seals; nucleotide sequences of these fragments revealed a high degree of similarity to human adenovirus type C. Circovirus DNA fragments were detected in six animals of the same species. Two were phylogenetically similar to the Circovirus genus, whereas the other four nucleotide fragments showed no similarity to any of the known genera within the family Circoviridae. RNA fragments indicating the presence of coronavirus, vesivirus, and morbillivirus were not detected. These findings suggest that adenoviruses and circoviruses are circulating in fur seal populations found along the coast of Rio Grande do Sul State, Brazil.

Detection of virus particles resembling circovirus and porcine circovirus 2a (PCV2a) sequences in feces of dogs

During routine electron microscopy of fecal samples from diarrheic dogs dated from 2000 virus particles resembling circovirus in shape and size were detected in two samples (V2177/00; V3374/00). Polymerase chain reaction (PCR) using primers specific for porcine circovirus type 2 (PCV2) amplified DNA recovered from both samples. Sequencing of PCR amplificates (V2177/00) obtained with PCV2-specific primer pairs revealed a genome size of 1768 bp. The nucleotide sequence was highly similar (98% nucleotide identity) to the PCV2a reference sequence.

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Electron microscopy has revealed circoviruses in two fecal samples of diarrheic dogs.

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PCV2-specific PCR amplified DNA extracted from the samples.

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By sequencing one sample a genome size of 1768 bp and a nucleotide sequence identity of 98% to PCV2a were achieved.

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This is the first time that PCV2 has been reported in dogs.