Porcine Viruses

A special issue of Viruses (ISSN 1999-4915). This special issue belongs to the section "Animal Viruses".

Deadline for manuscript submissions: closed (1 March 2017) | Viewed by 220166

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Guest Editor
The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, UK
Interests: African swine fever virus; virus cell interactions; immune evasion; vaccines

E-Mail Website
Guest Editor
The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, UK
Interests: porcine reproductive and respiratory viruses; classical swine fever viruses; henipaviruses; immunity; vaccines
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Special Issue Information

Dear Colleagues,

Pig production is the fastest growing segment of the global livestock sector. Intensification of pig production has resulted in significant changes to traditional pig husbandry practices. Combined with urbanisation and ease of travel and transport, these changes have led to an environment conducive to increased emergence and spread of viral diseases. The past decade alone has seen the global emergence and re-emergence of porcine viruses with devastating consequnces: For example, in 2006, highly pathogenic porcine reproductive and respiratory syndrome viruses (PRRSV) spread rapidly across Southeast Asia killing millions of animals; since its introduction into the Causcusus in 2007, the African swine fever virus has  steadily spread to Eastern Europe; and in 2013-14, over 8 million pigs died when virulent porcine epidemic diarrhea virus (PEDV) swept North America. In this special issue we will explore our understanding of porcine viruses and how this may be exploited to improve the control of these pathogens of economic and agricultural significance.

Dr. Simon Graham
Dr. Linda Dixon
Guest Editors

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Keywords

  • Porcine viruses
  • evolution and molecular epidemiology
  • host-virus interactions
  • vaccines and diagnostics

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Published Papers (20 papers)

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Research

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1406 KiB  
Article
UK Pigs at the Time of Slaughter: Investigation into the Correlation of Infection with PRRSV and HEV
by Jean-Pierre Frossard, Sylvia Grierson, Tanya Cheney, Falko Steinbach, Bhudipa Choudhury and Susanna Williamson
Viruses 2017, 9(6), 110; https://doi.org/10.3390/v9060110 - 9 Jun 2017
Cited by 2 | Viewed by 6145
Abstract
Hepatitis E virus (HEV) and porcine reproductive and respiratory syndrome virus (PRRSV) and are both globally prevalent in the pig population. While HEV does not cause clinical disease in pigs, its zoonotic potential has raised concerns in the food safety sector. PRRS has [...] Read more.
Hepatitis E virus (HEV) and porcine reproductive and respiratory syndrome virus (PRRSV) and are both globally prevalent in the pig population. While HEV does not cause clinical disease in pigs, its zoonotic potential has raised concerns in the food safety sector. PRRS has become endemic in the United Kingdom (UK) since its introduction in 1991, and continues to cause considerable economic losses to the swine industry. A better understanding of the current prevalence and diversity of PRRSV and HEV in the UK, and their potential association, is needed to assess risks and target control measures appropriately. This study used plasma, tonsil, and cecal content samples previously collected from pigs in 14 abattoirs in England and Northern Ireland to study the prevalence of several pathogens including PRRSV and HEV. The diversity of PRRSV strains detected in these samples was analyzed by sequencing open reading frame 5 (ORF5), revealing no substantial difference in PRRSV strains from these clinically unaffected pigs relative to those from clinical cases of disease in the UK. Despite the potential immuno-modulatory effect of PRRSV infection, previously demonstrated to affect Salmonella and HEV shedding profiles, no significant association was found between positive PRRSV status and positive HEV status. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Redistribution of Endosomal Membranes to the African Swine Fever Virus Replication Site
by Miguel Ángel Cuesta-Geijo, Lucía Barrado-Gil, Inmaculada Galindo, Raquel Muñoz-Moreno and Covadonga Alonso
Viruses 2017, 9(6), 133; https://doi.org/10.3390/v9060133 - 1 Jun 2017
Cited by 18 | Viewed by 5900
Abstract
African swine fever virus (ASFV) infection causes endosomal reorganization. Here, we show that the virus causes endosomal congregation close to the nucleus as the infection progresses, which is necessary to build a compact viral replication organelle. ASFV enters the cell by the endosomal [...] Read more.
African swine fever virus (ASFV) infection causes endosomal reorganization. Here, we show that the virus causes endosomal congregation close to the nucleus as the infection progresses, which is necessary to build a compact viral replication organelle. ASFV enters the cell by the endosomal pathway and reaches multivesicular late endosomes. Upon uncoating and fusion, the virus should exit to the cytosol to start replication. ASFV remodels endosomal traffic and redistributes endosomal membranes to the viral replication site. Virus replication also depends on endosomal membrane phosphoinositides (PtdIns) synthesized by PIKfyve. Endosomes could act as platforms providing membranes and PtdIns, necessary for ASFV replication. Our study has revealed that ASFV reorganizes endosome dynamics, in order to ensure a productive infection. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
A Japanese Encephalitis Virus Vaccine Inducing Antibodies Strongly Enhancing In Vitro Infection Is Protective in Pigs
by Obdulio García-Nicolás, Meret E. Ricklin, Matthias Liniger, Nathalie J. Vielle, Sylvie Python, Philippe Souque, Pierre Charneau and Artur Summerfield
Viruses 2017, 9(5), 124; https://doi.org/10.3390/v9050124 - 22 May 2017
Cited by 23 | Viewed by 7638
Abstract
The Japanese encephalitis virus (JEV) is responsible for zoonotic severe viral encephalitis transmitted by Culex mosquitoes. Although birds are reservoirs, pigs play a role as amplifying hosts, and are affected in particular through reproductive failure. Here, we show that a lentiviral JEV vector, [...] Read more.
The Japanese encephalitis virus (JEV) is responsible for zoonotic severe viral encephalitis transmitted by Culex mosquitoes. Although birds are reservoirs, pigs play a role as amplifying hosts, and are affected in particular through reproductive failure. Here, we show that a lentiviral JEV vector, expressing JEV prM and E proteins (TRIP/JEV.prME), but not JEV infection induces strong antibody-dependent enhancement (ADE) activities for infection of macrophages. Such antibodies strongly promoted infection via Fc receptors. ADE was found at both neutralizing and non-neutralizing serum dilutions. Nevertheless, in vivo JEV challenge of pigs demonstrated comparable protection induced by the TRIP/JEV.prME vaccine or heterologous JEV infection. Thus, either ADE antibodies cause no harm in the presence of neutralizing antibodies or may even have protective effects in vivo in pigs. Additionally, we found that both pre-infected and vaccinated pigs were not fully protected as low levels of viral RNA were found in lymphoid and nervous system tissue in some animals. Strikingly, the virus from the pre-infection persisted in the tonsils throughout the experiment. Finally, despite the vaccination challenge, viral RNA was detected in the oronasal swabs in all vaccinated pigs. These latter data are relevant when JEV vaccination is employed in pigs. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Evaluation and Comparison of the Pathogenicity and Host Immune Responses Induced by a G2b Taiwan Porcine Epidemic Diarrhea Virus (Strain Pintung 52) and Its Highly Cell-Culture Passaged Strain in Conventional 5-Week-Old Pigs
by Yen-Chen Chang, Chi-Fei Kao, Chia-Yu Chang, Chian-Ren Jeng, Pei-Shiue Tsai, Victor Fei Pang, Hue-Ying Chiou, Ju-Yi Peng, Ivan-Chen Cheng and Hui-Wen Chang
Viruses 2017, 9(5), 121; https://doi.org/10.3390/v9050121 - 19 May 2017
Cited by 35 | Viewed by 8325
Abstract
A genogroup 2b (G2b) porcine epidemic diarrhea virus (PEDV) Taiwan Pintung 52 (PEDVPT) strain was isolated in 2014. The pathogenicity and host antibody responses elicited by low-passage (passage 5; PEDVPT-P5) and high-passage (passage 96; PEDVPT-P96) PEDVPT strains were compared in post-weaning PEDV-seronegative pigs [...] Read more.
A genogroup 2b (G2b) porcine epidemic diarrhea virus (PEDV) Taiwan Pintung 52 (PEDVPT) strain was isolated in 2014. The pathogenicity and host antibody responses elicited by low-passage (passage 5; PEDVPT-P5) and high-passage (passage 96; PEDVPT-P96) PEDVPT strains were compared in post-weaning PEDV-seronegative pigs by oral inoculation. PEDVPT-P5-inoculation induced typical diarrhea during 1–9 days post inoculation with fecal viral shedding persisting for 26 days. Compared to PEDVPT-P5, PEDVPT-P96 inoculation induced none-to-mild diarrhea and lower, delayed fecal viral shedding. Although PEDVPT-P96 elicited slightly lower neutralizing antibodies and PEDV-specific immunoglobulin G (IgG) and immunoglobulin A (IgA) titers, a reduction in pathogenicity and viral shedding of the subsequent challenge with PEDVPT-P5 were noted in both PEDVPT-P5- and PEDVPT-P96-inoculated pigs. Alignment and comparison of full-length sequences of PEDVPT-P5 and PEDVPT-P96 revealed 23 nucleotide changes and resultant 19 amino acid substitutions in non-structure proteins 2, 3, 4, 9, 14, 15, spike, open reading frame 3 (ORF3), and membrane proteins with no detectable deletion or insertion. The present study confirmed the pathogenicity of the PEDVPT isolate in conventional post-weaning pigs. Moreover, data regarding viral attenuation and potency of induced antibodies against PEDVPT-P5 identified PEDVPT-P96 as a potential live-attenuated vaccine candidate. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
TMPRSS2 and MSPL Facilitate Trypsin-Independent Porcine Epidemic Diarrhea Virus Replication in Vero Cells
by Wen Shi, Wenlu Fan, Jing Bai, Yandong Tang, Li Wang, Yanping Jiang, Lijie Tang, Min Liu, Wen Cui, Yigang Xu and Yijing Li
Viruses 2017, 9(5), 114; https://doi.org/10.3390/v9050114 - 18 May 2017
Cited by 23 | Viewed by 7144
Abstract
Type II transmembrane serine proteases (TTSPs) facilitate the spread and replication of viruses such as influenza and human coronaviruses, although it remains unclear whether TTSPs play a role in the progression of animal coronavirus infections, such as that by porcine epidemic diarrhea virus [...] Read more.
Type II transmembrane serine proteases (TTSPs) facilitate the spread and replication of viruses such as influenza and human coronaviruses, although it remains unclear whether TTSPs play a role in the progression of animal coronavirus infections, such as that by porcine epidemic diarrhea virus (PEDV). In this study, TTSPs including TMPRSS2, HAT, DESC1, and MSPL were tested for their ability to facilitate PEDV replication in Vero cells. Our results showed that TMPRSS2 and MSPL played significant roles in the stages of cell–cell fusion and virus–cell fusion, whereas HAT and DESC1 exhibited weaker effects. This activation may be involved in the interaction between TTSPs and the PEDV S protein, as the S protein extensively co-localized with TMPRSS2 and MSPL and could be cleaved by co-expression with TMPRSS2 or MSPL. Moreover, the use of Vero cells expressing TMPRSS2 and MSPL facilitated PEDV replication in the absence of exogenous trypsin. In sum, we identified two host proteases, TMPRSS2 and MSPL, which may provide insights and a novel method for enhancing viral titers, expanding virus production, and improving the adaptability of PEDV isolates in vitro. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Antigenic and Biological Characterization of ORF2–6 Variants at Early Times Following PRRSV Infection
by Alyssa B. Evans, Hyelee Loyd, Jenelle R. Dunkelberger, Sarah Van Tol, Marcus J. Bolton, Karin S. Dorman, Jack C. M. Dekkers and Susan Carpenter
Viruses 2017, 9(5), 113; https://doi.org/10.3390/v9050113 - 16 May 2017
Cited by 15 | Viewed by 5011
Abstract
Genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) challenges efforts to develop effective and broadly acting vaccines. Although genetic variation in PRRSV has been extensively documented, the effects of this variation on virus phenotype are less well understood. In the present [...] Read more.
Genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) challenges efforts to develop effective and broadly acting vaccines. Although genetic variation in PRRSV has been extensively documented, the effects of this variation on virus phenotype are less well understood. In the present study, PRRSV open reading frame (ORF)2–6 variants predominant during the first six weeks following experimental infection were characterized for antigenic and replication phenotype. There was limited genetic variation during these early times after infection; however, distinct ORF2–6 haplotypes that differed from the NVSL97-7895 inoculum were identified in each of the five pigs examined. Chimeric viruses containing all or part of predominant ORF2–6 haplotypes were constructed and tested in virus neutralization and in vitro replication assays. In two pigs, genetic variation in ORF2–6 resulted in increased resistance to neutralization by autologous sera. Mapping studies indicated that variation in either ORF2–4 or ORF5–6 could confer increased neutralization resistance, but there was no single amino acid substitution that was predictive of neutralization phenotype. Detailed analyses of the early steps in PRRSV replication in the presence and absence of neutralizing antibody revealed both significant inhibition of virion attachment and, independently, a significant delay in the appearance of newly synthesized viral RNA. In all pigs, genetic variation in ORF2–6 also resulted in significant reduction in infectivity on MARC-145 cells, suggesting variation in ORF2–6 may also be important for virus replication in vivo. Together, these data reveal that variation appearing early after infection, though limited, alters important virus phenotypes and contributes to antigenic and biologic diversity of PRRSV. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Porcine Epidemic Diarrhea Virus Induces Autophagy to Benefit Its Replication
by Xiaozhen Guo, Mengjia Zhang, Xiaoqian Zhang, Xin Tan, Hengke Guo, Wei Zeng, Guokai Yan, Atta Muhammad Memon, Zhonghua Li, Yinxing Zhu, Bingzhou Zhang, Xugang Ku, Meizhou Wu, Shengxian Fan and Qigai He
Viruses 2017, 9(3), 53; https://doi.org/10.3390/v9030053 - 19 Mar 2017
Cited by 68 | Viewed by 8789
Abstract
The new porcine epidemic diarrhea (PED) has caused devastating economic losses to the swine industry worldwide. Despite extensive research on the relationship between autophagy and virus infection, the concrete role of autophagy in porcine epidemic diarrhea virus (PEDV) infection has not been reported. [...] Read more.
The new porcine epidemic diarrhea (PED) has caused devastating economic losses to the swine industry worldwide. Despite extensive research on the relationship between autophagy and virus infection, the concrete role of autophagy in porcine epidemic diarrhea virus (PEDV) infection has not been reported. In this study, autophagy was demonstrated to be triggered by the effective replication of PEDV through transmission electron microscopy, confocal microscopy, and Western blot analysis. Moreover, autophagy was confirmed to benefit PEDV replication by using autophagy regulators and RNA interference. Furthermore, autophagy might be associated with the expression of inflammatory cytokines and have a positive feedback loop with the NF-κB signaling pathway during PEDV infection. This work is the first attempt to explore the complex interplay between autophagy and PEDV infection. Our findings might accelerate our understanding of the pathogenesis of PEDV infection and provide new insights into the development of effective therapeutic strategies. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Genetic Assessment of African Swine Fever Isolates Involved in Outbreaks in the Democratic Republic of Congo between 2005 and 2012 Reveals Co-Circulation of p72 Genotypes I, IX and XIV, Including 19 Variants
by Leopold K. Mulumba–Mfumu, Jenna E. Achenbach, Matthew R. Mauldin, Linda K. Dixon, Curé Georges Tshilenge, Etienne Thiry, Noelia Moreno, Esther Blanco, Claude Saegerman, Charles E. Lamien and Adama Diallo
Viruses 2017, 9(2), 31; https://doi.org/10.3390/v9020031 - 18 Feb 2017
Cited by 52 | Viewed by 8070
Abstract
African swine fever (ASF) is a devastating disease of domestic pigs. It is a socioeconomically important disease, initially described from Kenya, but subsequently reported in most Sub-Saharan countries. ASF spread to Europe, South America and the Caribbean through multiple introductions which were initially [...] Read more.
African swine fever (ASF) is a devastating disease of domestic pigs. It is a socioeconomically important disease, initially described from Kenya, but subsequently reported in most Sub-Saharan countries. ASF spread to Europe, South America and the Caribbean through multiple introductions which were initially eradicated—except for Sardinia—followed by re‑introduction into Europe in 2007. In this study of ASF within the Democratic Republic of the Congo, 62 domestic pig samples, collected between 2005–2012, were examined for viral DNA and sequencing at multiple loci: C-terminus of the B646L gene (p72 protein), central hypervariable region (CVR) of the B602L gene, and the E183L gene (p54 protein). Phylogenetic analyses identified three circulating genotypes: I (64.5% of samples), IX (32.3%), and XIV (3.2%). This is the first evidence of genotypes IX and XIV within this country. Examination of the CVR revealed high levels of intra-genotypic variation, with 19 identified variants. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Novel Approach for Isolation and Identification of Porcine Epidemic Diarrhea Virus (PEDV) Strain NJ Using Porcine Intestinal Epithelial Cells
by Wen Shi, Shuo Jia, Haiyuan Zhao, Jiyuan Yin, Xiaona Wang, Meiling Yu, Sunting Ma, Yang Wu, Ying Chen, Wenlu Fan, Yigang Xu and Yijing Li
Viruses 2017, 9(1), 19; https://doi.org/10.3390/v9010019 - 21 Jan 2017
Cited by 22 | Viewed by 8516
Abstract
Porcine epidemic diarrhea virus (PEDV), which is the causative agent of porcine epidemic diarrhea in China and other countries, is responsible for serious economic losses in the pork industry. Inactivated PEDV vaccine plays a key role in controlling the prevalence of PEDV. However, [...] Read more.
Porcine epidemic diarrhea virus (PEDV), which is the causative agent of porcine epidemic diarrhea in China and other countries, is responsible for serious economic losses in the pork industry. Inactivated PEDV vaccine plays a key role in controlling the prevalence of PEDV. However, consistently low viral titers are obtained during the propagation of PEDV in vitro; this represents a challenge to molecular analyses of the virus and vaccine development. In this study, we successfully isolated a PEDV isolate (strain NJ) from clinical samples collected during a recent outbreak of diarrhea in piglets in China, using porcine intestinal epithelial cells (IEC). We found that the isolate was better adapted to growth in IECs than in Vero cells, and the titer of the IEC cultures was 104.5 TCID50/0.1 mL at passage 45. Mutations in the S protein increased with the viral passage and the mutations tended towards attenuation. Viral challenge showed that the survival of IEC-adapted cultures was higher at the 45th passage than at the 5th passage. The use of IECs to isolate and propagate PEDV provides an effective approach for laboratory-based diagnosis of PEDV, as well as studies of the epidemiological characteristics and molecular biology of this virus. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Effective Detection of Porcine Cytomegalovirus Using Non-Invasively Taken Samples from Piglets
by Vladimir A. Morozov, Gerd Heinrichs and Joachim Denner
Viruses 2017, 9(1), 9; https://doi.org/10.3390/v9010009 - 12 Jan 2017
Cited by 20 | Viewed by 5655
Abstract
Shortage of human organs forced the development of xenotransplantation using cells, tissues, and organs from pigs. Xenotransplantation may be associated with the transmission of porcine zoonotic microorganisms, among them the porcine cytomegalovirus (PCMV). To prevent virus transmission, pigs have to be screened using [...] Read more.
Shortage of human organs forced the development of xenotransplantation using cells, tissues, and organs from pigs. Xenotransplantation may be associated with the transmission of porcine zoonotic microorganisms, among them the porcine cytomegalovirus (PCMV). To prevent virus transmission, pigs have to be screened using sensitive methods. In order to perform regular follow-ups and further breeding of the animals, samples for testing should be collected by low-invasive or non-invasive methods. Sera, ear biopsies, as well as oral and anal swabs were collected from ten 10-day-old Aachen minipigs (AaMP) and tested for PCMV using sensitive nested polymerase chain reaction (PCR) as well as uniplex and duplex real-time PCR. Porcine cytomegalovirus DNA was detected most frequently in oral and anal swabs. Comparison of duplex and uniplex real-time PCR systems for PCMV detection demonstrated a lower sensitivity of duplex real-time PCR when the copy numbers of the target genes were low (less 200). Therefore, to increase the efficacy of PCMV detection in piglets, early testing of oral and anal swabs by uniplex real-time PCR is recommended. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Article
Characterization of an Immunodominant Epitope in the Endodomain of the Coronavirus Membrane Protein
by Hui Dong, Xin Zhang, Hongyan Shi, Jianfei Chen, Da Shi, Yunnuan Zhu and Li Feng
Viruses 2016, 8(12), 327; https://doi.org/10.3390/v8120327 - 10 Dec 2016
Cited by 5 | Viewed by 5711
Abstract
The coronavirus membrane (M) protein acts as a dominant immunogen and is a major player in virus assembly. In this study, we prepared two monoclonal antibodies (mAbs; 1C3 and 4C7) directed against the transmissible gastroenteritis virus (TGEV) M protein. The 1C3 and 4C7 [...] Read more.
The coronavirus membrane (M) protein acts as a dominant immunogen and is a major player in virus assembly. In this study, we prepared two monoclonal antibodies (mAbs; 1C3 and 4C7) directed against the transmissible gastroenteritis virus (TGEV) M protein. The 1C3 and 4C7 mAbs both reacted with the native TGEV M protein in western blotting and immunofluorescence (IFA) assays. Two linear epitopes, 243YSTEART249 (1C3) and 243YSTEARTDNLSEQEKLLHMV262 (4C7), were identified in the endodomain of the TGEV M protein. The 1C3 mAb can be used for the detection of the TGEV M protein in different assays. An IFA method for the detection of TGEV M protein was optimized using mAb 1C3. Furthermore, the ability of the epitope identified in this study to stimulate antibody production was also evaluated. An immunodominant epitope in the TGEV membrane protein endodomain was identified. The results of this study have implications for further research on TGEV replication. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Review

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4128 KiB  
Review
Complex Virus–Host Interactions Involved in the Regulation of Classical Swine Fever Virus Replication: A Minireview
by Su Li, Jinghan Wang, Qian Yang, Muhammad Naveed Anwar, Shaoxiong Yu and Hua-Ji Qiu
Viruses 2017, 9(7), 171; https://doi.org/10.3390/v9070171 - 5 Jul 2017
Cited by 29 | Viewed by 11192
Abstract
Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is one of the most devastating epizootic diseases of pigs in many countries. Viruses are small intracellular parasites and thus rely on the cellular factors for replication. Fundamental aspects of CSFV–host interactions [...] Read more.
Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is one of the most devastating epizootic diseases of pigs in many countries. Viruses are small intracellular parasites and thus rely on the cellular factors for replication. Fundamental aspects of CSFV–host interactions have been well described, such as factors contributing to viral attachment, modulation of genomic replication and translation, antagonism of innate immunity, and inhibition of cell apoptosis. However, those host factors that participate in the viral entry, assembly, and release largely remain to be elucidated. In this review, we summarize recent progress in the virus–host interactions involved in the life cycle of CSFV and analyze the potential mechanisms of viral entry, assembly, and release. We conclude with future perspectives and highlight areas that require further understanding. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Review
Update on Senecavirus Infection in Pigs
by Raquel A. Leme, Alice F. Alfieri and Amauri A. Alfieri
Viruses 2017, 9(7), 170; https://doi.org/10.3390/v9070170 - 3 Jul 2017
Cited by 79 | Viewed by 11600
Abstract
Senecavirus A (SVA) is a positive-sense single-stranded RNA virus that belongs to the Senecavirus genus within the Picornaviridae family. The virus has been silently circulating in pig herds of the USA since 1988. However, cases of senecavirus-associated vesicular disease were reported in Canada [...] Read more.
Senecavirus A (SVA) is a positive-sense single-stranded RNA virus that belongs to the Senecavirus genus within the Picornaviridae family. The virus has been silently circulating in pig herds of the USA since 1988. However, cases of senecavirus-associated vesicular disease were reported in Canada in 2007 and in the USA in 2012. Since late 2014 and early 2015, an increasing number of senecavirus outbreaks have been reported in pigs in different producing categories, with this virus being detected in Brazil, China, and Thailand. Considering the novel available data on senecavirus infection and disease, 2015 may be a divisor in the epidemiology of the virus. Among the aspects that reinforce this hypothesis are the geographical distribution of the virus, the affected pig-producing categories, clinical signs associated with the infection, and disease severity. This review presents the current knowledge regarding the senecavirus infection and disease, especially in the last two years. Senecavirus epidemiology, pathogenic potential, host immunological response, diagnosis, and prophylaxis and control measures are addressed. Perspectives are focused on the need for complete evolutionary, epidemiological and pathogenic data and the capability for an immediate diagnosis of senecavirus infection. The health risks inherent in the swine industry cannot be neglected. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Review
Mechanisms of Adaptive Immunity to Porcine Reproductive and Respiratory Syndrome Virus
by Michael C. Rahe and Michael P. Murtaugh
Viruses 2017, 9(6), 148; https://doi.org/10.3390/v9060148 - 13 Jun 2017
Cited by 52 | Viewed by 9744
Abstract
The adaptive immune response is necessary for the development of protective immunity against infectious diseases. Porcine reproductive and respiratory syndrome virus (PRRSV), a genetically heterogeneous and rapidly evolving RNA virus, is the most burdensome pathogen of swine health and wellbeing worldwide. Viral infection [...] Read more.
The adaptive immune response is necessary for the development of protective immunity against infectious diseases. Porcine reproductive and respiratory syndrome virus (PRRSV), a genetically heterogeneous and rapidly evolving RNA virus, is the most burdensome pathogen of swine health and wellbeing worldwide. Viral infection induces antigen-specific immunity that ultimately clears the infection. However, the resulting immune memory, induced by virulent or attenuated vaccine viruses, is inconsistently protective against diverse viral strains. The immunological mechanisms by which primary and memory protection are generated and used are not well understood. Here, we summarize current knowledge regarding cellular and humoral components of the adaptive immune response to PRRSV infection that mediate primary and memory immune protection against viruses. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Review
African Swine Fever Virus: A Review
by Inmaculada Galindo and Covadonga Alonso
Viruses 2017, 9(5), 103; https://doi.org/10.3390/v9050103 - 10 May 2017
Cited by 441 | Viewed by 36627
Abstract
African swine fever (ASF) is a highly contagious viral disease of swine which causes high mortality, approaching 100%, in domestic pigs. ASF is caused by a large, double stranded DNA virus, ASF virus (ASFV), which replicates predominantly in the cytoplasm of macrophages and [...] Read more.
African swine fever (ASF) is a highly contagious viral disease of swine which causes high mortality, approaching 100%, in domestic pigs. ASF is caused by a large, double stranded DNA virus, ASF virus (ASFV), which replicates predominantly in the cytoplasm of macrophages and is the only member of the Asfarviridae family, genus Asfivirus. The natural hosts of this virus include wild suids and arthropod vectors of the Ornithodoros genus. The infection of ASFV in its reservoir hosts is usually asymptomatic and develops a persistent infection. In contrast, infection of domestic pigs leads to a lethal hemorrhagic fever for which there is no effective vaccine. Identification of ASFV genes involved in virulence and the characterization of mechanisms used by the virus to evade the immune response of the host are recognized as critical steps in the development of a vaccine. Moreover, the interplay of the viral products with host pathways, which are relevant for virus replication, provides the basic information needed for the identification of potential targets for the development of intervention strategies against this disease. Full article
(This article belongs to the Special Issue Porcine Viruses)
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Review
Porcine Circovirus Type 2 (PCV2) Vaccines in the Context of Current Molecular Epidemiology
by Anbu K. Karuppannan and Tanja Opriessnig
Viruses 2017, 9(5), 99; https://doi.org/10.3390/v9050099 - 6 May 2017
Cited by 124 | Viewed by 13424
Abstract
Porcine circovirus type 2 (PCV2) is an economically important swine pathogen and, although small, it has the highest evolution rate among DNA viruses. Since the discovery of PCV2 in the late 1990s, this minimalistic virus with a 1.7 kb single-stranded DNA genome and [...] Read more.
Porcine circovirus type 2 (PCV2) is an economically important swine pathogen and, although small, it has the highest evolution rate among DNA viruses. Since the discovery of PCV2 in the late 1990s, this minimalistic virus with a 1.7 kb single-stranded DNA genome and two indispensable genes has become one of the most important porcine pathogens, and presently is subjected to the highest volume of prophylactic intervention in the form of vaccines in global swine production. PCV2 can currently be divided into five different genotypes, PCV2a through PCV2e. It is well documented that PCV2 continues to evolve, which is reflected by changes in the prevalence of genotypes. During 2006, commercial vaccines for PCV2 were introduced on a large scale in a pig population mainly infected with PCV2b. Since 2012, the PCV2d genotype has essentially replaced the previously predominant PCV2b genotype in North America and similar trends are also documented in other geographic regions such as China and South Korea. This is the second major PCV2 genotype shift since the discovery of the virus. The potential increase in virulence of the emergent PCV2 genotype and the efficacy of the current vaccines derived from PCV2a genotype against the PCV2d genotype viruses has received considerable attention. This review attempts to synthesize the understanding of PCV2 biology, experimental studies on the antigenic variability, and molecular epidemiological analysis of the evolution of PCV2 genotypes. Full article
(This article belongs to the Special Issue Porcine Viruses)
246 KiB  
Review
Harnessing Local Immunity for an Effective Universal Swine Influenza Vaccine
by Elma Tchilian and Barbara Holzer
Viruses 2017, 9(5), 98; https://doi.org/10.3390/v9050098 - 5 May 2017
Cited by 18 | Viewed by 6872
Abstract
Influenza A virus infections are a global health threat to humans and are endemic in pigs, contributing to decreased weight gain and suboptimal reproductive performance. Pigs are also a source of new viruses of mixed swine, avian, and human origin, potentially capable of [...] Read more.
Influenza A virus infections are a global health threat to humans and are endemic in pigs, contributing to decreased weight gain and suboptimal reproductive performance. Pigs are also a source of new viruses of mixed swine, avian, and human origin, potentially capable of initiating human pandemics. Current inactivated vaccines induce neutralising antibody against the immunising strain but rapid escape occurs through antigenic drift of the surface glycoproteins. However, it is known that prior infection provides a degree of cross-protective immunity mediated by cellular immune mechanisms directed at the more conserved internal viral proteins. Here we review new data that emphasises the importance of local immunity in cross-protection and the role of the recently defined tissue-resident memory T cells, as well as locally-produced, and sometimes cross-reactive, antibody. Optimal induction of local immunity may require aerosol delivery of live vaccines, but it remains unclear how long protective local immunity persists. Nevertheless, a universal vaccine might be extremely useful for disease prevention in the face of a pandemic. As a natural host for influenza A viruses, pigs are both a target for a universal vaccine and an excellent model for developing human influenza vaccines. Full article
(This article belongs to the Special Issue Porcine Viruses)
2815 KiB  
Review
Classical Swine Fever—An Updated Review
by Sandra Blome, Christoph Staubach, Julia Henke, Jolene Carlson and Martin Beer
Viruses 2017, 9(4), 86; https://doi.org/10.3390/v9040086 - 21 Apr 2017
Cited by 186 | Viewed by 25574
Abstract
Classical swine fever (CSF) remains one of the most important transboundary viral diseases of swine worldwide. The causative agent is CSF virus, a small, enveloped RNA virus of the genus Pestivirus. Based on partial sequences, three genotypes can be distinguished that do not, [...] Read more.
Classical swine fever (CSF) remains one of the most important transboundary viral diseases of swine worldwide. The causative agent is CSF virus, a small, enveloped RNA virus of the genus Pestivirus. Based on partial sequences, three genotypes can be distinguished that do not, however, directly correlate with virulence. Depending on both virus and host factors, a wide range of clinical syndromes can be observed and thus, laboratory confirmation is mandatory. To this means, both direct and indirect methods are utilized with an increasing degree of commercialization. Both infections in domestic pigs and wild boar are of great relevance; and wild boars are a reservoir host transmitting the virus sporadically also to pig farms. Control strategies for epidemic outbreaks in free countries are mainly based on classical intervention measures; i.e., quarantine and strict culling of affected herds. In these countries, vaccination is only an emergency option. However, live vaccines are used for controlling the disease in endemically infected regions in Asia, Eastern Europe, the Americas, and some African countries. Here, we will provide a concise, updated review on virus properties, clinical signs and pathology, epidemiology, pathogenesis and immune responses, diagnosis and vaccination possibilities. Full article
(This article belongs to the Special Issue Porcine Viruses)
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422 KiB  
Review
Porcine Circoviruses and Xenotransplantation
by Joachim Denner and Annette Mankertz
Viruses 2017, 9(4), 83; https://doi.org/10.3390/v9040083 - 20 Apr 2017
Cited by 45 | Viewed by 8198
Abstract
Allotransplantation and xenotransplantation may be associated with the transmission of pathogens from the donor to the recipient. Whereas in the case of allotransplantation the transmitted microorganisms and their pathogenic effect are well characterized, the possible influence of porcine microorganisms on humans is mostly [...] Read more.
Allotransplantation and xenotransplantation may be associated with the transmission of pathogens from the donor to the recipient. Whereas in the case of allotransplantation the transmitted microorganisms and their pathogenic effect are well characterized, the possible influence of porcine microorganisms on humans is mostly unknown. Porcine circoviruses (PCVs) are common in pig breeds and they belong to porcine microorganisms that still have not been fully addressed in terms of evaluating the potential risk of xenotransplantation using pig cells, tissues, and organs. Two types of PCVs are known: porcine circovirus (PCV) 1 and PCV2. Whereas PCV1 is apathogenic in pigs, PCV2 may induce severe pig diseases. Although most pigs are subclinically infected, we do not know whether this infection impairs pig transplant functionality, particularly because PCV2 is immunosuppressive. In addition, vaccination against PCV2 is able to prevent diseases, but in most cases not transmission of the virus. Therefore, PCV2 has to be eliminated to obtain xenotransplants from uninfected healthy animals. Although there is evidence that PCV2 does not infect—at least immunocompetent—humans, animals should be screened using sensitive methods to ensure virus elimination by selection, Cesarean delivery, vaccination, or embryo transfer. Full article
(This article belongs to the Special Issue Porcine Viruses)
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2263 KiB  
Review
Porcine Rotaviruses: Epidemiology, Immune Responses and Control Strategies
by Anastasia N. Vlasova, Joshua O. Amimo and Linda J. Saif
Viruses 2017, 9(3), 48; https://doi.org/10.3390/v9030048 - 18 Mar 2017
Cited by 169 | Viewed by 17837
Abstract
Rotaviruses (RVs) are a major cause of acute viral gastroenteritis in young animals and children worldwide. Immunocompetent adults of different species become resistant to clinical disease due to post-infection immunity, immune system maturation and gut physiological changes. Of the 9 RV genogroups (A–I), [...] Read more.
Rotaviruses (RVs) are a major cause of acute viral gastroenteritis in young animals and children worldwide. Immunocompetent adults of different species become resistant to clinical disease due to post-infection immunity, immune system maturation and gut physiological changes. Of the 9 RV genogroups (A–I), RV A, B, and C (RVA, RVB, and RVC, respectively) are associated with diarrhea in piglets. Although discovered decades ago, porcine genogroup E RVs (RVE) are uncommon and their pathogenesis is not studied well. The presence of porcine RV H (RVH), a newly defined distinct genogroup, was recently confirmed in diarrheic pigs in Japan, Brazil, and the US. The complex epidemiology, pathogenicity and high genetic diversity of porcine RVAs are widely recognized and well-studied. More recent data show a significant genetic diversity based on the VP7 gene analysis of RVB and C strains in pigs. In this review, we will summarize previous and recent research to provide insights on historic and current prevalence and genetic diversity of porcine RVs in different geographic regions and production systems. We will also provide a brief overview of immune responses to porcine RVs, available control strategies and zoonotic potential of different RV genotypes. An improved understanding of the above parameters may lead to the development of more optimal strategies to manage RV diarrheal disease in swine and humans. Full article
(This article belongs to the Special Issue Porcine Viruses)
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