1
|
Ji C, Zhang Y, Feng Y, Zhang X, Gong F, Yao H, Sun X, Pan Z. Circular replication-associated protein-encoding single-stranded DNA virus with risk of spillover is widely prevalent in domestic animals in China. Virus Res 2024; 339:199204. [PMID: 37607596 PMCID: PMC10654594 DOI: 10.1016/j.virusres.2023.199204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/18/2023] [Accepted: 08/19/2023] [Indexed: 08/24/2023]
Abstract
Circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA viruses are highly diverse and have a broad range of hosts. In this study, we report the detection of Bo-Circo-like virus AH20-1 in the feces of diarrheal cattle. The virus has a circular genome of 3,912 nucleotides, three major putative open reading frames, and encodes a Rep gene of 310 amino acids. We found that the virus is closely related to the Bo-Circo-like virus CH strain, which belongs to the novel Kirkoviridae family. Furthermore, we conducted a nationwide surveillance program and found that the virus is prevalent in China (23.6%, 205/868), with the BCLa subtype being the predominant strain. Our findings suggest that the virus can infect sheep, highlighting the potential for cross-species transmission. Our pressure analysis indicates that the CRESS-DNA Kirkoviridae family has broad host adaptation, and that selection pressure played an important role in the evolution of its Rep genes. Our study underscores the need for continued epidemiological surveillance of this virus due to its widespread prevalence in our ruminant population and potential for cross-species transmission.
Collapse
Affiliation(s)
- Chengyuan Ji
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Yao Zhang
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Yiqiu Feng
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Xinqin Zhang
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Fengju Gong
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Huochun Yao
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Xueqiang Sun
- China Animal Health and Epidemiology Center, Key Laboratory of Animal Biosafety Risk Prevention and Control (South), Qingdao 266000, China.
| | - Zihao Pan
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China..
| |
Collapse
|
2
|
Zhang LH, Wang LQ, Li HX, Zhang HL, Zheng LL, Chen XM, Chen HY. Detection and genetic analysis of porcine circovirus-like virus in pigs with diarrhea between 2016 and 2021 in Henan and Shanxi provinces of China. Arch Virol 2023; 168:76. [PMID: 36709234 DOI: 10.1007/s00705-023-05701-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 12/06/2022] [Indexed: 01/29/2023]
Abstract
Porcine circovirus-like virus (PCLV) is a recently discovered virus that may be associated with diarrhea in pigs. To investigate the epidemic profile and genetic characteristics of this virus, 175 clinical samples (141 intestinal samples, 17 blood samples, and 17 fecal samples) were collected from diseased piglets during outbreaks of diarrhea from 33 pig farms in 19 cities of Henan and Shanxi provinces of China between 2016 and 2021 and were screened by PCR for the presence of PCLV. The results showed that the positive rate for PCLV was 32% (56/175) at the sample level, 60.6% (20/33) at the farm level, and 57.9% (11/19) at the city level, which varied from 5.88% to 44.12% between 2016 and 2021. It was also found that PCLV occurred in coinfections with porcine circovirus type 2 (PCV2), PCV3, PCV4, porcine epidemic diarrhea virus, and porcine reproductive and respiratory syndrome virus, but no nucleic acids were detected for transmissible gastroenteritis virus, porcine deltacoronavirus, or porcine rotavirus in piglets with diarrhea. Notably, PCLV was detected in 13 diarrheal piglets from four different farms that were negative for the other porcine viruses. These findings suggest that PCLV may be associated with porcine diarrhea and that it has been circulating in piglets in Henan and Shanxi provinces of China. In addition, the complete genomes of 13 PCLV strains were sequenced and found to share 35.4%-91.0% nucleotide sequence identity with sequences available in the GenBank database. Phylogenetic analysis based on Rep amino acid sequences revealed that the 13 PCLV strains from this study clustered in group 1 and were closely related to eight Chinese PCLV strains, Bo-Circo-like virus CH, American strains 21 and 22, and Hungarian strains 288_4 and 302_4, but they differed genetically from seven other foreign PCLV strains. The whole genome and rep gene of 13 PCLV strains in this study were 72.2%-82% and 83.8%-89.7% identical, respectively, to those of Bo-Circo-like virus strain CH, indicating that PCLV is a novel virus in pigs that may be involved in cross-species transmission. Evidence of a recombination event was found in the rep region of the 13 PCLV strains sequenced. This study enriches the epidemiological data on PCLV infection in pigs in China and lays a foundation for further study on the pathogenesis of PCLV.
Collapse
Affiliation(s)
- Liu-Hui Zhang
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China
| | - Lin-Qing Wang
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China
- Department of Life Science, Zhengzhou Normal University, Zhengzhou, 450044, Henan Province, People's Republic of China
| | - Hong-Xuan Li
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China
| | - Hong-Lei Zhang
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China
| | - Lan-Lan Zheng
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China
| | - Xi-Meng Chen
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China.
| | - Hong-Ying Chen
- Zhengzhou Major Pig Disease Prevention and Control Laboratory, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, People's Republic of China.
| |
Collapse
|
3
|
Ji C, Zeng M, Wei Y, Lv X, Sun Y, Ma J. Genetic characterization of four strains porcine circovirus-like viruses in pigs with diarrhea in Hunan Province of China. Front Microbiol 2023; 14:1126707. [PMID: 36937298 PMCID: PMC10014920 DOI: 10.3389/fmicb.2023.1126707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 02/13/2023] [Indexed: 03/05/2023] Open
Abstract
In this study, we detected a circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus [named Po-Circo-like (PCL) virus] in intestinal tissue and fecal samples of pigs. PCL virus contains a single-stranded DNA genome, and ORF1 encodes the Rep and not the typical capsid protein encoded in PCV. The Rep protein may be responsible for viral genome replication. In addition, PCL virus may be one of the pathogens causing diarrhea symptoms in pigs. We identified four strains of PCL virus in two different pig farms with severe diarrhea outbreaks in Hunan Province, China. The strains in this study share 85.7-99.7% nucleic acid identity and 84.7-100% amino acid identity with Rep of the reference strains. A multiple sequence alignment of these PCL viruses and Bo-Circo-like CH showed a identity of 93.2% for the Rep protein, and the nucleotide identity was 86.7-89.3%. Moreover, Bo-Circo-like CH and HN75, HN39-01, HN39-02 had similar stem-loop sequences. In conclusion, the present study is the first detailed report of the PCL virus in Hunan provinces, which is a potential new virus in pigs that might be involved in cross-species transmission. Further investigation is needed to determine the pathogenesis of this virus and its epidemiologic impact.
Collapse
Affiliation(s)
- Chihai Ji
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Health Aquaculture and Environmental Control, College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Meng Zeng
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Health Aquaculture and Environmental Control, College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Yingfang Wei
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Xiaocheng Lv
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Health Aquaculture and Environmental Control, College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Yuan Sun
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Health Aquaculture and Environmental Control, College of Animal Science, South China Agricultural University, Guangzhou, China
- Yuan Sun,
| | - Jingyun Ma
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Health Aquaculture and Environmental Control, College of Animal Science, South China Agricultural University, Guangzhou, China
- *Correspondence: Jingyun Ma,
| |
Collapse
|
4
|
Liu X, Zhang X, Xu G, Wang Z, Shen H, Lian K, Lin Y, Zheng J, Liang P, Zhang L, Liu Y, Song C. Emergence of porcine circovirus-like viruses associated with porcine diarrheal disease in China. Transbound Emerg Dis 2021; 68:3167-3173. [PMID: 34231316 PMCID: PMC9290044 DOI: 10.1111/tbed.14223] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/30/2021] [Accepted: 07/04/2021] [Indexed: 12/19/2022]
Abstract
Background The circular replication‐associated protein (Rep)‐encoding single‐stranded (CRESS) DNA virus emergence in diverse host has been associated with severe disease. Porcine circovirus‐like virus (Po‐Circo‐like [PCL] virus) is a CRESS DNA virus, the prevalence and pathogenicity of which are rarely studied. Methods We obtained two blood samples, four faecal samples, and two intestinal samples from a pig farm suffered from diarrheal disease in the delivery room in September 2020 and attempted to isolate and identify a causative pathogen. Subsequently, only PCL virus was positive, and qRT‐PCR was designed to detect the loading titre of PCL virus. We then initiated a heightened surveillance program on the pathogenicity and epidemiology of PCL virus. Results Six PCL virus strains, with severe diarrhoea and haemorrhagic enteritis, have been found in six different pig farms in Guangdong province, China. A multiple sequence alignment of these PCL viruses and bovine circovirus‐like virus/CH showed a similarity of 92.5‐94.8% for the Rep protein, indicating these PCL viruses are highly homologous to Bo‐Circo‐like virus associated with calf diarrhoea. There were striking similarities between the PCL virus and bovine circovirus‐like virus outbreaks in aetiological settings and Genomic sequence. We found that 11.2% (20/178) of diarrhoea samples and 13.3% (6/45) of pig farms were positive for PCL virus, suggesting that PCL virus may have spread widely in Pig farms. Moreover, this article underscores the risk of PCL virus spilling over and adapting to new species. Conclusions Porcine circovirus‐like virus was found to be associated with porcine diarrheal disease in China.
Collapse
Affiliation(s)
- Xianhui Liu
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Xinming Zhang
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Ge Xu
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Zhe Wang
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Hanqin Shen
- Wen's Foodstuff Group Co. Ltd, Guangdong Enterprise Key Laboratory for Animal Health and Environmental Control, Yunfu, P. R. China
| | - Kaiqi Lian
- School of Biotechnology and Food Science, Anyang Institute of Technology, Anyang, P. R. China
| | - Yihan Lin
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Jihao Zheng
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Pengshuai Liang
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Leyi Zhang
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Yanling Liu
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| | - Changxu Song
- College of Animal Science & National Engineering Center for Swine Breeding Industry, South China Agriculture University, Guangzhou, P. R. China
| |
Collapse
|
5
|
Computational based design and tracking of synthetic variants of Porcine circovirus reveal relations between silent genomic information and viral fitness. Sci Rep 2021; 11:10620. [PMID: 34012100 PMCID: PMC8134455 DOI: 10.1038/s41598-021-89918-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 04/29/2021] [Indexed: 12/17/2022] Open
Abstract
Viral genomes not only code the protein content, but also include silent, overlapping codes which are important to the regulation of the viral life cycle and affect its evolution. Due to the high density of these codes, their non-modular nature and the complex intracellular processes they encode, the ability of current approaches to decipher them is very limited. We describe the first computational-experimental pipeline for studying the effects of viral silent and non-silent information on its fitness. The pipeline was implemented to study the Porcine Circovirus type 2 (PCV2), the shortest known eukaryotic virus, and includes the following steps: (1) Based on the analyses of 2100 variants of PCV, suspected silent codes were inferred. (2) Five hundred variants of the PCV2 were designed to include various ‘smart’ silent mutations. (3) Using state of the art synthetic biology approaches, the genomes of these five hundred variants were generated. (4) Competition experiments between the variants were performed in Porcine kidney-15 (PK15) cell-lines. (5) The variant titers were analyzed based on novel next-generation sequencing (NGS) experiments. (6) The features related to the titer of the variants were inferred and their analyses enabled detection of various novel silent functional sequence and structural motifs. Furthermore, we demonstrate that 50 of the silent variants exhibit higher fitness than the wildtype in the analyzed conditions.
Collapse
|
6
|
Abstract
Viruses are the most abundant biological entities on Earth. In addition to their impact on animal and plant health, viruses have important roles in ecosystem dynamics as well as in the evolution of the biosphere. Circular Rep-encoding single-stranded (CRESS) DNA viruses are ubiquitous in nature, many are agriculturally important, and they appear to have multiple origins from prokaryotic plasmids. A subset of CRESS-DNA viruses, the cruciviruses, have homologues of capsid proteins encoded by RNA viruses. The genetic structure of cruciviruses attests to the transfer of capsid genes between disparate groups of viruses. However, the evolutionary history of cruciviruses is still unclear. By collecting and analyzing cruciviral sequence data, we provide a deeper insight into the evolutionary intricacies of cruciviruses. Our results reveal an unexpected diversity of this virus group, with frequent recombination as an important determinant of variability. The discovery of cruciviruses revealed the most explicit example of a common protein homologue between DNA and RNA viruses to date. Cruciviruses are a novel group of circular Rep-encoding single-stranded DNA (ssDNA) (CRESS-DNA) viruses that encode capsid proteins that are most closely related to those encoded by RNA viruses in the family Tombusviridae. The apparent chimeric nature of the two core proteins encoded by crucivirus genomes suggests horizontal gene transfer of capsid genes between DNA and RNA viruses. Here, we identified and characterized 451 new crucivirus genomes and 10 capsid-encoding circular genetic elements through de novo assembly and mining of metagenomic data. These genomes are highly diverse, as demonstrated by sequence comparisons and phylogenetic analysis of subsets of the protein sequences they encode. Most of the variation is reflected in the replication-associated protein (Rep) sequences, and much of the sequence diversity appears to be due to recombination. Our results suggest that recombination tends to occur more frequently among groups of cruciviruses with relatively similar capsid proteins and that the exchange of Rep protein domains between cruciviruses is rarer than intergenic recombination. Additionally, we suggest members of the stramenopiles/alveolates/Rhizaria supergroup as possible crucivirus hosts. Altogether, we provide a comprehensive and descriptive characterization of cruciviruses.
Collapse
|
7
|
Cao W, Cao H, Yi X, Zhuang Y. Development of a simple and high-yielding fed-batch process for the production of porcine circovirus type 2 virus-like particle subunit vaccine. AMB Express 2019; 9:164. [PMID: 31605297 PMCID: PMC6789058 DOI: 10.1186/s13568-019-0880-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 09/17/2019] [Indexed: 12/25/2022] Open
Abstract
The cap protein is encoded by the orf2 gene of porcine circovirus type 2 (PCV2) has the main antigen epitope of PCV2 and can form virus-like particles (VLPs), which are expressed in insect cells. PCV2-VLPs can effectively inhibit PCV2 replication as a subunit vaccine. In this study, a robust and reliable fed-batch process was successfully developed for the production of PCV2-VLPs by Sf9 cells. The feeding solution, feeding strategy, and cell density at infection were optimized to maximize the final PCV2-VLPs production yields. The cell density at infection and the volumetric PCV2-VLPs production reached 12 × 106 cells/mL and 110 mg/L, respectively, which yielded 3- and 3.6-fold enhancements compared to the batch culture. The PCV2-VLPs produced in fed-batch culture were not different from the PCV2-VLPs produced in a batch culture in an immunity test. A highly efficient production process was produced for PCV2-VLPs subunit vaccines, which could provide an effective means for the industrial production of PCV2 vaccines.
Collapse
Affiliation(s)
- Wenlong Cao
- School of Biotechnology, East China University of Science and Technology, Shanghai, 200237, China
| | - Hui Cao
- Zhejiang EBVAC Biotech Co., Ltd., Hangzhou, 310018, Zhejiang, China
| | - Xiaoping Yi
- School of Biotechnology, East China University of Science and Technology, Shanghai, 200237, China.
| | - Yingping Zhuang
- School of Biotechnology, East China University of Science and Technology, Shanghai, 200237, China
| |
Collapse
|
8
|
Specific functions of the Rep and Rep׳ proteins of porcine circovirus during copy-release and rolling-circle DNA replication. Virology 2015; 481:43-50. [PMID: 25768890 DOI: 10.1016/j.virol.2015.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 11/11/2014] [Accepted: 01/05/2015] [Indexed: 11/21/2022]
Abstract
The roles of two porcine circovirus replication initiator proteins, Rep and Rep׳, in generating copy-release and rolling-circle DNA replication intermediates were determined. Rep uses the supercoiled closed-circular genome (ccc) to initiate leading-strand synthesis (identical to copy-release replication) and generates the single-stranded circular (ssc) genome from the displaced DNA strand. In the process, a minus-genome primer (MGP) necessary for complementary-strand synthesis, from ssc to ccc, is synthesized. Rep׳ cleaves the growing nascent-strand to regenerate the parent ccc molecule. In the process, a Rep׳-DNA hybrid containing the right palindromic sequence (at the origin of DNA replication) is generated. Analysis of the virus particle showed that it is composed of four components: ssc, MGP, capsid protein and a novel Rep-related protein (designated Protein-3).
Collapse
|
9
|
Ge M, Yan A, Luo W, Hu YF, Li RC, Jiang DL, Yu XL. Epitope screening of the PCV2 Cap protein by use of a random peptide-displayed library and polyclonal antibody. Virus Res 2013; 177:103-7. [DOI: 10.1016/j.virusres.2013.06.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/25/2013] [Accepted: 06/26/2013] [Indexed: 10/26/2022]
|
10
|
Correlation of the cyclin A expression level with porcine circovirus type 2 propagation efficiency. Arch Virol 2013; 158:2553-60. [PMID: 23836398 DOI: 10.1007/s00705-013-1785-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 05/29/2013] [Indexed: 11/27/2022]
Abstract
Porcine circovirus type 2 (PCV2) is an important pathogen in swine, and it is assumed that PCV2 replication is cell cycle dependent (especially during S phase). However, the cellular molecules that regulate PCV2 replication have not been fully identified. Here, we cloned the porcine cyclin A (CycA) and CDK2 genes, the major regulators of the S phase, and established CycA or CDK2 overexpression and lower-expression cell lines. The propagation efficiency of strains PCV2a/CL or PCV2b/YJ in these cell lines was investigated using a capture enzyme-linked immunosorbent assay (ELISA) or an immunoperoxidase monolayer assay (IPMA), and the cell cycle was analyzed by flow cytometry. The results showed that CycA overexpression suppressed PCV2 replication. In contrast, CycA down-regulation by shRNA induced increases during the S and G2/M phases and resulted in increased PCV2 propagation. In contrast, overexpression or lower expression of CDK2 exhibited no significant influence on PCV2 replication. Furthermore, the subcellular localization of the PCV2 replicase protein (Rep) and capsid protein (Cap), CycA, and CDK2 in PK-15 cells was analyzed by confocal microscopy. The results showed that overexpression of CycA, rather than CDK2, altered normal nuclear localization of PCV2-Rep, which was transferred to the cytoplasm. In conclusion, PCV2 replication is both S- and G2/M-phase dependent and CycA, is an important regulator of the PCV2 life cycle.
Collapse
|
11
|
Hua T, Wang X, Bai J, Zhang L, Liu J, Jiang P. Attenuation of porcine circovirus type-2b by replacement with the Rep gene of porcine circovirus type-1. Virus Res 2013; 173:270-9. [PMID: 23454919 DOI: 10.1016/j.virusres.2013.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/18/2013] [Accepted: 02/18/2013] [Indexed: 10/27/2022]
Abstract
Porcine circovirus type-2 (PCV2) is the primary causative agent of porcine circovirus-associated diseases and has 4 main ORFs, ORF1 (Rep gene), ORF2 (Cap gene), ORF3 within ORF1, and ORF4, which is overlapped with ORF3, and 1 origin (Ori) of replication located between ORF1 and ORF2. The chimeric PCV1-2, containing the PCV2 capsid, PCV1 rep, and Ori genes, is attenuated in pigs. In order to verify the role of the Rep gene or Ori in the virulence of PCV2, 3 chimeric viruses [PCV2b-Ori1 (PCV1 Ori gene cloned into the backbone of PCV2b), PCV2b-rep1 (PCV1 Rep gene cloned into the backbone of PCV2b), and PCV2b-rep1-Ori1 (PCV1 Rep and Ori genes cloned into the backbone of PCV2b)] and 2 wild-type recombinant PCV2b and PCV1 were constructed and identified. The experimental results in piglets showed that clinical symptoms, viremia, viral load, lesions in lymphoid and lung tissues, and IL-10 and TNF-α expression levels in PBMCs in the PCV2b-rep1-Ori1 and PCV2b-rep1 groups were significantly decreased, compared to PCV2-infected piglets. Meanwhile, histological lesions of lymphoid and lung tissues, viral loads in lymphoid tissues, viremia, and TNF-α expression in PBMCs were not significantly different between groups PCV2b-Ori1 and PCV2b, suggesting that the Rep gene (ORF1) likely contributes to viral pathogenicity in vivo.
Collapse
Affiliation(s)
- Tao Hua
- Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | | | | | | | | | | |
Collapse
|
12
|
Wang YP, Liu D, Guo LJ, Tang QH, Wei YW, Wu HL, Liu JB, Li SB, Huang LP, Liu CM. Enhanced protective immune response to PCV2 subunit vaccine by co-administration of recombinant porcine IFN-γ in mice. Vaccine 2012; 31:833-8. [PMID: 23219694 DOI: 10.1016/j.vaccine.2012.11.062] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 11/15/2012] [Accepted: 11/21/2012] [Indexed: 11/24/2022]
Abstract
The capsid (Cap) protein of PCV2 is the major immunogenic protein that is crucial to induce PCV2-specific neutralizing antibodies and protective immunity; thus, it is a suitable target antigen for the research and development of genetically engineered vaccines against PCV2 infection. IFN-γ has exhibited potential efficacy as an immune adjuvant that enhances the immunogenicity of certain vaccines in experimental animal models. In this study, three recombinant proteins: PCV2-Cap protein, porcine IFN-γ (PoIFN-γ), and the fusion protein (Cap-PoIFN-γ) of PCV2-Cap protein and PoIFN-γ were respectively expressed in the baculovirus system, and analyzed by Western blot and indirect ELISA. Additionally, we evaluated the enhancement of the protective immune response to the Cap protein-based PCV2 subunit vaccine elicited by co-administration of PoIFN-γ in mice. Vaccination of mice with the PCV2-Cap+PoIFN-γ vaccine elicited significantly higher levels of PCV2-specific IPMA antibodies, neutralizing antibodies, and lymphocyte proliferative responses compared to the Cap-PoIFN-γ vaccine, the PCV2-Cap vaccine, and LG-strain. Following virulent PCV2 challenge, no viraemia was detected in all immunized groups, and the viral loads in lungs of the PCV2-Cap+PoIFN-γ group were significantly lower compared to the Cap-PoIFN-γ group, the LG-strain group, and the mock group, but slightly lower compared to the PCV2-Cap group. These findings suggested that PoIFN-γ substantially enhanced the protective immune response to the Cap protein-based PCV2 subunit vaccine, and that the PCV2-Cap+PoIFN-γ subunit vaccine potentially serves as an attractive candidate vaccine for the prevention and control of PCV2-associated diseases.
Collapse
Affiliation(s)
- Yi-Ping Wang
- Division of Swine Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Shan T, Li L, Simmonds P, Wang C, Moeser A, Delwart E. The fecal virome of pigs on a high-density farm. J Virol 2011; 85:11697-708. [PMID: 21900163 PMCID: PMC3209269 DOI: 10.1128/jvi.05217-11] [Citation(s) in RCA: 258] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 08/23/2011] [Indexed: 12/14/2022] Open
Abstract
Swine are an important source of proteins worldwide but are subject to frequent viral outbreaks and numerous infections capable of infecting humans. Modern farming conditions may also increase viral transmission and potential zoonotic spread. We describe here the metagenomics-derived virome in the feces of 24 healthy and 12 diarrheic piglets on a high-density farm. An average of 4.2 different mammalian viruses were shed by healthy piglets, reflecting a high level of asymptomatic infections. Diarrheic pigs shed an average of 5.4 different mammalian viruses. Ninety-nine percent of the viral sequences were related to the RNA virus families Picornaviridae, Astroviridae, Coronaviridae, and Caliciviridae, while 1% were related to the small DNA virus families Circoviridae, and Parvoviridae. Porcine RNA viruses identified, in order of decreasing number of sequence reads, consisted of kobuviruses, astroviruses, enteroviruses, sapoviruses, sapeloviruses, coronaviruses, bocaviruses, and teschoviruses. The near-full genomes of multiple novel species of porcine astroviruses and bocaviruses were generated and phylogenetically analyzed. Multiple small circular DNA genomes encoding replicase proteins plus two highly divergent members of the Picornavirales order were also characterized. The possible origin of these viral genomes from pig-infecting protozoans and nematodes, based on closest sequence similarities, is discussed. In summary, an unbiased survey of viruses in the feces of intensely farmed animals revealed frequent coinfections with a highly diverse set of viruses providing favorable conditions for viral recombination. Viral surveys of animals can readily document the circulation of known and new viruses, facilitating the detection of emerging viruses and prospective evaluation of their pathogenic and zoonotic potentials.
Collapse
Affiliation(s)
- Tongling Shan
- Blood Systems Research Institute, San Francisco, California
- Department of Laboratory Medicine, University of California at San Francisco, San Francisco, California
- Zoonosis and Comparative Medicine Group, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Linlin Li
- Blood Systems Research Institute, San Francisco, California
- Department of Laboratory Medicine, University of California at San Francisco, San Francisco, California
| | - Peter Simmonds
- Centre for Immunology, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Chunlin Wang
- Stanford Genome Technology Center, Stanford, California
| | - Adam Moeser
- College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Eric Delwart
- Blood Systems Research Institute, San Francisco, California
- Department of Laboratory Medicine, University of California at San Francisco, San Francisco, California
| |
Collapse
|
14
|
Cheung AK. Porcine circovirus: transcription and DNA replication. Virus Res 2011; 164:46-53. [PMID: 22036834 DOI: 10.1016/j.virusres.2011.10.012] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 10/14/2011] [Accepted: 10/15/2011] [Indexed: 12/18/2022]
Abstract
This review summarizes the molecular studies pertaining to porcine circovirus (PCV) transcription and DNA replication. The genome of PCV is circular, single-stranded DNA and contains 1759-1768 nucleotides. Both the genome-strand (packaged in the virus particle) and the complementary-strand (synthesized in the new host) encode viral proteins. Among a multitude of RNAs synthesized by alternate splicing, only rep and rep' are essential for virus DNA replication via the rolling-circle replication (RCR) mechanism. In contrast to other RCR biological systems which utilize only one multi-functional protein, Rep, to replicate their respective genomes, PCV requires two proteins, Rep and Rep'. During DNA synthesis, the PCV origin of DNA replication (Ori), which contains a pair of inverted repeats (palindrome), exists in a destabilized four-stranded configuration (the melting-pot model) and permits both the palindromic-strand and the complementary-strand to serve as templates simultaneously for initiation and termination. Inherent in the "melting-pot" model is the template-strand-switching mechanism. This mechanism is the basis for the "correction or conversion" of any mutated nucleotide sequences engineered into either arm of the palindrome and the incorporation of "illegitimate recombination" (addition or deletion of nucleotides) events that are commonly observed at the Ori of other RCR biological systems during DNA replication.
Collapse
Affiliation(s)
- Andrew K Cheung
- Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA 50010, USA.
| |
Collapse
|
15
|
Beach NM, Meng XJ. Efficacy and future prospects of commercially available and experimental vaccines against porcine circovirus type 2 (PCV2). Virus Res 2011; 164:33-42. [PMID: 22005075 DOI: 10.1016/j.virusres.2011.09.041] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 09/30/2011] [Accepted: 09/30/2011] [Indexed: 01/14/2023]
Abstract
Porcine circovirus type 2 (PCV2) is the causative agent of an economically significant collection of disease syndromes in pigs, now known as porcine circovirus associated diseases (PCVADs) in the United States or porcine circovirus diseases (PCVDs) in Europe. Inactivated and subunit vaccines based on PCV2a genotype are commercially available and have been shown to be effective at decreasing mortality and increasing growth parameters in commercial swine herds. Since 2003, there has been a drastic global shift in the predominant prevalence of PCV2b genotype in swine populations, concurrently in most but not all cases with increased severity of clinical disease. Although the current commercial vaccines based on PCV2a do confer cross-protection against PCV2b, novel experimental vaccines based on PCV2b genotype such as modified live-attenuated vaccines are being developed and may provide a superior protection and reduce vaccine costs. In this review, we discuss the current understanding of the impact of PCV2 infection on the host immune response, review the efficacy of the currently available commercial PCV2 vaccines in experimental and field conditions, and provide insight into novel experimental approaches that are useful in the development of next generation vaccines against PCV2.
Collapse
Affiliation(s)
- Nathan M Beach
- Department of Biomedical Sciences and Pathobiology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0913, USA
| | | |
Collapse
|
16
|
Association of an atypical alphasatellite with a bipartite New World begomovirus. Arch Virol 2010; 155:1843-7. [DOI: 10.1007/s00705-010-0760-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Accepted: 07/14/2010] [Indexed: 10/19/2022]
|
17
|
Replacement of the replication factors of porcine circovirus (PCV) type 2 with those of PCV type 1 greatly enhances viral replication in vitro. J Virol 2010; 84:8986-9. [PMID: 20573809 DOI: 10.1128/jvi.00522-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Porcine circovirus type 1 (PCV1), originally isolated as a contaminant of PK-15 cells, is nonpathogenic, whereas porcine circovirus type 2 (PCV2) causes an economically important disease in pigs. To determine the factors affecting virus replication, we constructed chimeric viruses by swapping open reading frame 1 (ORF1) (rep) or the origin of replication (Ori) between PCV1 and PCV2 and compared the replication efficiencies of the chimeric viruses in PK-15 cells. The results showed that the replication factors of PCV1 and PCV2 are fully exchangeable and, most importantly, that both the Ori and rep of PCV1 enhance the virus replication efficiencies of the chimeric viruses with the PCV2 backbone.
Collapse
|
18
|
Cheung AK. Homologous recombination plays minor role in excision of unit-length viral genomes from head-to-tail direct tandem repeats of porcine circovirus during DNA replication in Escherichia coli. Arch Virol 2007; 152:1531-9. [PMID: 17497233 DOI: 10.1007/s00705-007-0979-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 04/02/2007] [Indexed: 10/23/2022]
Abstract
In this report, we confirmed previous work that a theta-replicating bacterial plasmid containing 1.75 copies of genomic porcine circovirus (PCV) DNA in head-to-tail tandem (HTT) [a partial copy of PCV type 1 (PCV1), a complete copy of PCV type 2 (PCV2) and two origins of DNA replication (Ori)] yielded three different double-stranded DNA species when transformed into Escherichia coli: the input construct (U), the unit-length PCV1/PCV2 genome with a composite Ori lacking the plasmid vector (Q(RC)) and the remaining left-over 0.75 copy PCV1/PCV2 genome with a different composite Ori inserted in the plasmid vector (L(RC)). Replication of U was presumably via the theta-like replication mechanism utilizing the colicin E1 Ori, while derivation of L(RC) and Q(RC) was via the rolling-circle replication (RCR) copy-release mechanism and required the presence of two PCV Oris and the virus-encoded Rep protein. Essentially, excision of a unit-length PCV1/PCV2 genome (Q(RC)) via RCR from U yielded L(RC). Furthermore, we examined whether homologous recombination may also result in excision of a different type of unit-length PCV genome (Q(H)) from identical HTT constructs to generate L(H). Whereas the generation of L(RC) is Rep-protein-dependent, the generation of L(H) is Rep-protein-independent. Accordingly, the L(RC) and Q(RC) molecules derived from RCR possess different characteristics from the L(H) and Q(H) molecules generated via homologous recombination. In one of the studies in which both L(RC) and L(H) were generated simultaneously from the same HTT construct, out of 69 samples analyzed, 66 were derived via RCR and 3 were derived via homologous recombination. Thus, in comparison with RCR, homologous recombination plays a minor role in the excision of unit-length PCV genomes from HTT constructs in Escherichia coli.
Collapse
Affiliation(s)
- A K Cheung
- Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, Iowa 50010, USA.
| |
Collapse
|