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16 pages, 681 KiB

Open AccessArticle

The Potential Role of Wild Suids in African Swine Fever Spread in Asia and the Pacific Region

by Madalene Oberin, Alison Hillman, Michael P. Ward, Caitlin Holley, Simon Firestone and Brendan Cowled

Viruses 2023, 15(1), 61; https://doi.org/10.3390/v15010061 - 24 Dec 2022

Cited by 5 | Viewed by 1901

Abstract

African swine fever (ASF) in Asia and the Pacific is currently dominated by ASF virus transmission within and between domestic pig populations. The contribution made by wild suids is currently not well understood; their distribution, density and susceptibility to the virus has raised [...] Read more.

African swine fever (ASF) in Asia and the Pacific is currently dominated by ASF virus transmission within and between domestic pig populations. The contribution made by wild suids is currently not well understood; their distribution, density and susceptibility to the virus has raised concerns that their role in the epidemiology of ASF in the region might be underestimated. Whilst in the Republic of Korea wild suids are considered important in the spread and maintenance of ASF virus, there is an apparent underreporting to official sources of the disease in wild suids from other countires and regions. A review of the current literature, an analysis of the official reporting resources and a survey of the World Organisation of Animal Health Member delegates in Asia and the Pacific were used to assess the potential role of wild suids in ASF outbreaks, and also to gain insight into what ASF management or control strategies are currently implemented for wild suids. Applying appropriate population control and management strategies can be increased in some areas, especially to assist in the conservation of endangered endemic wild suids in this region. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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22 pages, 4473 KiB

Open AccessArticle

Oronasal or Intramuscular Immunization with a Thermo-Attenuated ASFV Strain Provides Full Clinical Protection against Georgia 2007/1 Challenge

by Olivier Bourry, Evelyne Hutet, Mireille Le Dimna, Pierrick Lucas, Yannick Blanchard, Amélie Chastagner, Frédéric Paboeuf and Marie-Frédérique Le Potier

Viruses 2022, 14(12), 2777; https://doi.org/10.3390/v14122777 - 13 Dec 2022

Cited by 6 | Viewed by 1706

Abstract

African swine fever (ASF) is a contagious viral disease of suids that induces high mortality in domestic pigs and wild boars. Given the current spread of ASF, the development of a vaccine is a priority. During an attempt to inactivate the Georgia 2007/1 [...] Read more.

African swine fever (ASF) is a contagious viral disease of suids that induces high mortality in domestic pigs and wild boars. Given the current spread of ASF, the development of a vaccine is a priority. During an attempt to inactivate the Georgia 2007/1 strain via heat treatment, we fortuitously generated an attenuated strain called ASFV-989. Compared to Georgia, the ASFV-989 strain genome has a deletion of 7458 nucleotides located in the 5′-end encoding region of MGF 505/360, which allowed for developing a DIVA PCR system. In vitro, in porcine alveolar macrophages, the replication kinetics of the ASFV-989 and Georgia strains were identical. In vivo, specific-pathogen-free (SPF) pigs inoculated with the ASFV-989 strain, either intramuscularly or oronasally, exhibited transient hyperthermia and slightly decreased growth performance. Animals immunized with the ASFV-989 strain showed viremia 100 to 1000 times lower than those inoculated with the Georgia strain and developed a rapid antibody and cell-mediated response. In ASFV-989-immunized pigs challenged 2 or 4 weeks later with the Georgia strain, no symptoms were recorded and no viremia for the challenge strain was detected. These results show that the ASFV-989 strain is a promising non-GMO vaccine candidate that is usable either intramuscularly or oronasally. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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16 pages, 2976 KiB

Open AccessCommunication

Experimental Infection of Domestic Pigs with African Swine Fever Virus Isolated in 2019 in Mongolia

by Chester D. McDowell, Dashzeveg Bold, Jessie D. Trujillo, David A. Meekins, Cassidy Keating, Konner Cool, Taeyong Kwon, Daniel W. Madden, Bianca L. Artiaga, Velmurugan Balaraman, Ulaankhuu Ankhanbaatar, Batsukh Zayat, Jamie Retallick, Kimberly Dodd, Chungwon J. Chung, Igor Morozov, Natasha N. Gaudreault, Jayme A. Souza-Neto and Jürgen A. Richt

Viruses 2022, 14(12), 2698; https://doi.org/10.3390/v14122698 - 01 Dec 2022

Cited by 4 | Viewed by 1844

Abstract

African swine fever (ASF) is an infectious viral disease caused by African swine fever virus (ASFV), that causes high mortality in domestic swine and wild boar (Sus scrofa). Currently, outbreaks are mitigated through strict quarantine measures and the culling of affected [...] Read more.

African swine fever (ASF) is an infectious viral disease caused by African swine fever virus (ASFV), that causes high mortality in domestic swine and wild boar (Sus scrofa). Currently, outbreaks are mitigated through strict quarantine measures and the culling of affected herds, resulting in massive economic losses to the global pork industry. In 2019, an ASFV outbreak was reported in Mongolia, describing a rapidly progressing clinical disease and gross lesions consistent with the acute form of ASF; the virus was identified as a genotype II virus. Due to the limited information on clinical disease and viral dynamics within hosts available from field observations of the Mongolian isolates, we conducted the present study to further evaluate the progression of clinical disease, virulence, and pathology of an ASFV Mongolia/2019 field isolate (ASFV-MNG19), by experimental infection of domestic pigs. Intramuscular inoculation of domestic pigs with ASFV-MNG19 resulted in clinical signs and viremia at 3 days post challenge (DPC). Clinical disease rapidly progressed, resulting in the humane euthanasia of all pigs by 7 DPC. ASFV-MNG19 infected pigs had viremic titers of 10⁸ TCID₅₀/mL by 5 DPC and shed virus in oral secretions late in disease, as determined from oropharyngeal swabs. Whole-genome sequencing confirmed that the ASFV-MNG19 strain used in this study was a genotype II strain highly similar to other regional strains. In conclusion, we demonstrate that ASFV-MNG19 is a virulent genotype II ASFV strain that causes acute ASF in domestic swine. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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12 pages, 2068 KiB

Open AccessArticle

Indirect ELISA Using Multi–Antigenic Dominants of p30, p54 and p72 Recombinant Proteins to Detect Antibodies against African Swine Fever Virus in Pigs

by Dexin Li, Qin Zhang, Yutian Liu, Miaoli Wang, Lei Zhang, Liyuan Han, Xuefei Chu, Guofei Ding, Yingchao Li, Yanmeng Hou, Sidang Liu, Zhiliang Wang and Yihong Xiao

Viruses 2022, 14(12), 2660; https://doi.org/10.3390/v14122660 - 28 Nov 2022

Cited by 8 | Viewed by 1812

Abstract

African swine fever (ASF) caused by ASF virus (ASFV) is a fatal disease in pigs and results in great economic losses. Due to the lack of available vaccines and treatments, serological diagnosis of ASF plays a key role in the surveillance program, but [...] Read more.

African swine fever (ASF) caused by ASF virus (ASFV) is a fatal disease in pigs and results in great economic losses. Due to the lack of available vaccines and treatments, serological diagnosis of ASF plays a key role in the surveillance program, but due to the lack of knowledge and the complexity of the ASFV genome, the candidate target viral proteins are still being researched. False negativity is still a big obstacle during the diagnostic process. In this study, the high antigenic viral proteins p30, p54 and p72 were screened to find the antigenic dominant domains and the tandem His–p30–54–72 was derived. An indirect enzyme–linked immunosorbent assay (iELISA) coated with His–p30–54–72 was developed with a cut–off value of 0.371. A total of 192 clinical samples were detected by His–p30–54–72–coated indirect ELISA (iELISA) and commercial ASFV antibody kits. The results showed that the positive rate of His–p30–54–72–coated iELISA was increased by 4.7% and 14.6% compared with a single viral protein–based commercial ASFV antibody kits. These results provide a platform for future ASFV clinical diagnosis and vaccine immune effect evaluation. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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15 pages, 4641 KiB

Open AccessArticle

In Silico Characterization of African Swine Fever Virus Nucleoprotein p10 Interaction with DNA

by Claudia Istrate, Jéssica Marques, Pedro Bule, Sílvia Correia, Frederico Aires-da-Silva, Marlene Duarte, Ana Luísa Reis, Miguel Machuqueiro, Alexandre Leitão and Bruno L. Victor

Viruses 2022, 14(11), 2348; https://doi.org/10.3390/v14112348 - 25 Oct 2022

Cited by 2 | Viewed by 1859

Abstract

African swine fever virus (ASFV) is the etiological agent of a highly contagious, hemorrhagic infectious swine disease, with a tremendous sanitary and economic impact on a global scale. Currently, there are no globally available vaccines or treatments. The p10 protein, a structural nucleoprotein [...] Read more.

African swine fever virus (ASFV) is the etiological agent of a highly contagious, hemorrhagic infectious swine disease, with a tremendous sanitary and economic impact on a global scale. Currently, there are no globally available vaccines or treatments. The p10 protein, a structural nucleoprotein encoded by ASFV, has been previously described as capable of binding double-stranded DNA (dsDNA), which may have implications for viral replication. However, the molecular mechanism that governs this interaction is still unknown, mostly due to the lack of a structural model for this protein. In this work, we have generated an ab initio model of the p10 protein and performed extensive structural characterization, using molecular dynamics simulations to identify the motifs and residues regulating DNA recognition. The helix-turn-helix motif identified at the C-terminal region of the protein was shown to be crucial to the dsDNA-binding efficiency. As with other DNA-binding proteins, two distinct serine and lysine-rich regions found in the two helices were identified as key players in the binding to DNA, whose importance was later validated using experimental binding assays. Altogether, these findings may contribute to a better understanding of the p10 function in ASFV replication. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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21 pages, 1830 KiB

Open AccessArticle

Assessment of the Impact of a Toll-like Receptor 2 Agonist Synthetic Lipopeptide on Macrophage Susceptibility and Responses to African Swine Fever Virus Infection

by Giulia Franzoni, Susanna Zinellu, Elisabetta Razzuoli, Lorena Mura, Chiara G. De Ciucis, Livia De Paolis, Tania Carta, Antonio G. Anfossi, Simon P. Graham, Bernardo Chessa, Silvia Dei Giudici and Annalisa Oggiano

Viruses 2022, 14(10), 2212; https://doi.org/10.3390/v14102212 - 08 Oct 2022

Cited by 2 | Viewed by 1662

Abstract

Toll-like receptor 2 (TLR2) ligands are attracting attention as prophylactic and immunopotentiator agents against pathogens, including viruses. We previously reported that a synthetic diacylated lipopeptide (Mag-Pam2Cys_P48) polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. Here, we investigated its role in modulating monocyte-derived macrophage [...] Read more.

Toll-like receptor 2 (TLR2) ligands are attracting attention as prophylactic and immunopotentiator agents against pathogens, including viruses. We previously reported that a synthetic diacylated lipopeptide (Mag-Pam2Cys_P48) polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. Here, we investigated its role in modulating monocyte-derived macrophage (moMΦ) responses against African swine fever virus (ASFV), the etiological agent of one of the greatest threats to the global pig industry. Two ASFV isolates were compared: the attenuated NH/P68 and the virulent 26544/OG10. No effect on virus infection nor the modulation of surface markers’ expression (MHC I, MHC II DR, CD14, CD16, and CD163) were observed when Mag-Pam2Cys_P48 treated moMΦ were infected using a multiplicity of infection (MOI) of 1. Mag-Pam2Cys_P48 treated moMΦ released higher levels of IL-1α, IL-1β, IL-1Ra, and IL-18 in response to infection with NH/P68 ASFV compared to 26544/OG10-infected and mock-infected controls. Surprisingly, when infected using a MOI of 0.01, the virulent ASFV 26544/OG10 isolate replicated even slightly more efficiently in Mag-Pam2Cys_P48 treated moMΦ. These effects also extended to the treatment of moMΦ with two other lipopeptides: Mag-Pam2Cys_P80 and Mag-Pam2Cys_Mag1000. Our data suggested limited applicability of TLR2 agonists as prophylactic or immunopotentiator agents against virulent ASFV but highlighted the ability of the virulent 26544/OG10 to impair macrophage defenses. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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8 pages, 1900 KiB

Open AccessCommunication

The 24.5-kb Left Variable Region Is Not a Determinant for African Swine Fever Virus to Replicate in Primary Porcine Alveolar Macrophages

by Rui Luo, Tao Wang, Maowen Sun, Li Pan, Shujian Huang, Yun Sun and Hua-Ji Qiu

Viruses 2022, 14(10), 2119; https://doi.org/10.3390/v14102119 - 25 Sep 2022

Cited by 3 | Viewed by 1512

Abstract

African swine fever (ASF) is a widespread hemorrhagic and highly contagious infectious disease caused by African swine fever virus (ASFV), currently threatening the pig industry worldwide. Here, we demonstrated that the cell-adapted strain ASFV-P121 with a 24.5-kb deletion in the left variable region [...] Read more.

African swine fever (ASF) is a widespread hemorrhagic and highly contagious infectious disease caused by African swine fever virus (ASFV), currently threatening the pig industry worldwide. Here, we demonstrated that the cell-adapted strain ASFV-P121 with a 24.5-kb deletion in the left variable region (LVR) lost the ability to replicate in primary porcine alveolar macrophages (PAMs). To explore whether this deletion determines the inability of ASFV-P121 replication in PAMs, a mutant virus (ASFV-ΔLVR) with the same LVR deletion as ASFV-P121 was constructed based on the wild-type ASFV HLJ/18 (ASFV-WT). However, the growth titer of ASFV-ΔLVR only reduced 10-fold compared with ASFV-WT in PAMs. Furthermore, we found that the large deletion of the LVR does not affect the formation of virus factories and virion morphogenesis. These findings reveal important implications for analyzing the molecular mechanism of ASFV cell tropism change. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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17 pages, 2587 KiB

Open AccessArticle

Host Responses to Live-Attenuated ASFV (HLJ/18–7GD)

by Yuqin Fan, Weiye Chen, Chenggang Jiang, Xianfeng Zhang, Ying Sun, Renqiang Liu, Jingfei Wang, Decheng Yang, Dongming Zhao, Zhigao Bu and Xijun He

Viruses 2022, 14(9), 2003; https://doi.org/10.3390/v14092003 - 10 Sep 2022

Cited by 4 | Viewed by 2139

Abstract

African swine fever (ASF) is a highly contagious and fatal disease caused by the African swine fever virus. Recently, the multigene family and CD2v gene-deleted ASF vaccine candidate HLJ/18-7GD was found to be safe and effective in laboratory and clinical trials. However, the [...] Read more.

African swine fever (ASF) is a highly contagious and fatal disease caused by the African swine fever virus. Recently, the multigene family and CD2v gene-deleted ASF vaccine candidate HLJ/18-7GD was found to be safe and effective in laboratory and clinical trials. However, the immune-protective mechanisms underlying the effects of HLJ/18-7GD remain unclear. We assessed samples from pigs immunized with a single dose of 10⁶ TCID₅₀ HLJ/18-7GD. We found that pigs immunized with HLJ/18-7GD showed high levels of specific antibodies. T lymphocyte subsets (helper T cells (Th); cytotoxic T lymphocytes (CTL); double-positive T cells (DP-T cells)) were temporarily increased in peripheral blood mononuclear cells (PBMCs) after HLJ/18-7GD immunization. Once the HLJ/18-7GD-immunized pigs had been challenged with virulent HLJ/18, the percentage of Th, CTL, and DP-T cells increased significantly. PBMCs extracted from the pigs induced higher levels of CD8⁺ T cells after infection with the HLJ/18 strain in vitro. The levels of GM-CSF, IFN-γ, and TNF-α were upregulated at 7 days post-inoculation; this finding was contrary to the results obtained after HLJ/18 or HLJ/18ΔCD2v infection. The immune protection from HLJ/18-7GD resulted from many synergies, which could provide a theoretical basis for HLJ/18-7GD as a safe and effective ASF vaccine. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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9 pages, 782 KiB

Open AccessArticle

Usability of Immortalized Porcine Kidney Macrophage Cultures for the Isolation of ASFV without Affecting Virulence

by Ken-ichiro Kameyama, Tomoya Kitamura, Kota Okadera, Mitsutaka Ikezawa, Kentaro Masujin and Takehiro Kokuho

Viruses 2022, 14(8), 1794; https://doi.org/10.3390/v14081794 - 16 Aug 2022

Cited by 5 | Viewed by 1745

Abstract

Immortalized porcine kidney macrophage (IPKM) cells are highly susceptible to major African swine fever virus (ASFV) isolates. To clarify the compatibility of this cell line for ASFV isolation from biomaterials, animal experiments and in vitro isolation were performed. Pork products seized at international [...] Read more.

Immortalized porcine kidney macrophage (IPKM) cells are highly susceptible to major African swine fever virus (ASFV) isolates. To clarify the compatibility of this cell line for ASFV isolation from biomaterials, animal experiments and in vitro isolation were performed. Pork products seized at international airports were subjected to virus inoculation in pigs (in vivo) and IPKM cell cultures (in vitro) to examine the viability and virulence of the contaminating viruses. Moreover, the viruses isolated using IPKM cells were inoculated into pigs to assess the virulence shift from the original materials. All pigs that were inoculated with either homogenate samples of seized pork product or IPKM-isolated ASFVs developed typical symptoms of ASF and died (or were euthanized) within the term of the animal experiments. The success rate of virus isolation in IPKM cells was comparable to that observed in porcine primary alveolar macrophage (PAM) cells. The IPKM cell line would be an ideal tool for the isolation and propagation of live ASFVs with high efficiency and enhanced usability, such as immortal, proliferative, and adhesive properties. The isolated viruses retained biologically similar characteristics to those of the original ones during isolation in vitro. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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13 pages, 1921 KiB

Open AccessArticle

Development of an ELISA Method to Differentiate Animals Infected with Wild-Type African Swine Fever Viruses and Attenuated HLJ/18-7GD Vaccine Candidate

by Lulu Wang, Dan Fu, Weldu Tesfagaber, Fang Li, Weiye Chen, Yuanmao Zhu, Encheng Sun, Wan Wang, Xijun He, Yu Guo, Zhigao Bu and Dongming Zhao

Viruses 2022, 14(8), 1731; https://doi.org/10.3390/v14081731 - 06 Aug 2022

Cited by 7 | Viewed by 2356

Abstract

African swine fever (ASF) is a highly contagious hemorrhagic disease of pigs, posing a significant threat to the world pig industry. Several researchers are investigating the possibilities for developing a safe and efficient vaccine against ASF. In this regard, significant progress has been [...] Read more.

African swine fever (ASF) is a highly contagious hemorrhagic disease of pigs, posing a significant threat to the world pig industry. Several researchers are investigating the possibilities for developing a safe and efficient vaccine against ASF. In this regard, significant progress has been made and some gene-deleted ASFVs are reported as potential live attenuated vaccines. A seven-gene-deleted live attenuated vaccine candidate HLJ/18-7GD (among which CD2v is included) has been developed in our laboratory and reported to be safe and protective, and it is expected to be commercialized in the near future. There is an urgent need for developing a diagnostic method that can clearly discriminate between wild-type-ASFV-infected and vaccinated animals (DIVA). In the present study, a dual indirect ELISA based on p54 and CD2v proteins was successfully established to specifically distinguish serum antibodies from pigs infected with wild-type ASFV or possessing vaccine immunization. To evaluate the performance of the assay, a total of 433 serum samples from four groups of pigs experimentally infected with the wild-type HLJ/18 ASFV, immunized with the HLJ/18-7GD vaccine candidate, infected with the new lower virulent variant, and specific-pathogen-free pigs were used. Our results showed that the positive rate of immunized serum was 96.54% (p54) and 2.83% (CD2v), and the positive rate of the infection by wild-type virus was 100% (p54) and 97.8% (CD2v). Similarly, the positive rate to infection by the new low-virulent ASFV variant in China was 100% (p54) and 0% (CD2v), indicating the technique was also able to distinguish antibodies from wild-type and the new low-virulent ASFV variant in China. Moreover, no cross-reaction was observed in immune sera from other swine pathogens, such as CSFV, PEDV, PRRSV, HP-PRRSV, PCV2, and PrV. Overall, the developed dual indirect ELISA exhibited high diagnostic sensitivity, specificity, and repeatability and will provide a new approach to differentiate serum antibodies between wild virulent and CD2v-unexpressed ASFV infection, which will play a great role in serological diagnosis and epidemiological monitoring of ASF in the future. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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17 pages, 3217 KiB

Open AccessArticle

African Swine Fever Virus Manipulates the Cell Cycle of G0-Infected Cells to Access Cellular Nucleotides

by Hranush R. Avagyan, Sona A. Hakobyan, Arpine A. Poghosyan, Nane V. Bayramyan, Hranush H. Arzumanyan, Liana O. Abroyan, Aida S. Avetisyan, Lina A. Hakobyan, Elena M. Karalova and Zaven A. Karalyan

Viruses 2022, 14(8), 1593; https://doi.org/10.3390/v14081593 - 22 Jul 2022

Cited by 4 | Viewed by 1723

Abstract

African swine fever virus manipulates the cell cycle of infected G0 cells by inducing its progression via unblocking cells from the G0 to S phase and then arresting them in the G2 phase. DNA synthesis in infected alveolar macrophages starts at 10–12 h [...] Read more.

African swine fever virus manipulates the cell cycle of infected G0 cells by inducing its progression via unblocking cells from the G0 to S phase and then arresting them in the G2 phase. DNA synthesis in infected alveolar macrophages starts at 10–12 h post infection. DNA synthesis in the nuclei of G0 cells is preceded by the activation of the viral genes K196R, A240L, E165R, F334L, F778R, and R298L involved in the synthesis of nucleotides and the regulation of the cell cycle. The activation of these genes in actively replicating cells begins later and is less pronounced. The subsequent cell cycle arrest at the G2 phase is also due to the cessation of the synthesis of cellular factors that control the progression of the cell cycle–cyclins. This data describes the manipulation of the cell cycle by the virus to gain access to the nucleotides synthesized by the cell. The genes affecting the cell cycle simply remain disabled until the beginning of cellular DNA synthesis (8–9 hpi). The genes responsible for the synthesis of nucleotides are turned on later in the presence of nucleotides and their transcriptional activity is lower than that during virus replication in an environment without nucleotides. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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18 pages, 3438 KiB

Open AccessArticle

Cellular and Humoral Immune Responses after Immunisation with Low Virulent African Swine Fever Virus in the Large White Inbred Babraham Line and Outbred Domestic Pigs

by Lynnette C. Goatley, Rachel H. Nash, Catherine Andrews, Zoe Hargreaves, Priscilla Tng, Ana Luisa Reis, Simon P. Graham and Christopher L. Netherton

Viruses 2022, 14(7), 1487; https://doi.org/10.3390/v14071487 - 07 Jul 2022

Cited by 5 | Viewed by 2620

Abstract

African swine fever virus is currently present in all of the world’s continents apart from Antarctica, and efforts to control the disease are hampered by the lack of a commercially available vaccine. The Babraham large white pig is a highly inbred line that [...] Read more.

African swine fever virus is currently present in all of the world’s continents apart from Antarctica, and efforts to control the disease are hampered by the lack of a commercially available vaccine. The Babraham large white pig is a highly inbred line that could represent a powerful tool to improve our understanding of the protective immune responses to this complex pathogen; however, previous studies indicated differential vaccine responses after the African swine fever virus challenge of inbred minipigs with different swine leukocyte antigen haplotypes. Lymphocyte numbers and African swine fever virus-specific antibody and T-cell responses were measured in inbred and outbred animals after inoculation with a low virulent African swine fever virus isolate and subsequent challenge with a related virulent virus. Surprisingly, diminished immune responses were observed in the Babraham pigs when compared to the outbred animals, and the inbred pigs were not protected after challenge. Recovery of Babraham pigs after challenge weakly correlated with antibody responses, whereas protective responses in outbred animals more closely correlated with the T-cell response. The Babraham pig may, therefore, represent a useful model for studying the role of antibodies in protection against the African swine fever virus. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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13 pages, 1047 KiB

Open AccessEditor’s ChoiceArticle

Experimental Infections of Pigs with African Swine Fever Virus (Genotype II); Studies in Young Animals and Pregnant Sows

by Louise Lohse, Jens Nielsen, Åse Uttenthal, Ann Sofie Olesen, Bertel Strandbygaard, Thomas Bruun Rasmussen, Graham J. Belsham and Anette Bøtner

Viruses 2022, 14(7), 1387; https://doi.org/10.3390/v14071387 - 25 Jun 2022

Cited by 5 | Viewed by 2016

Abstract

African swine fever is an important viral disease of wild and domestic pigs. To gain further knowledge of the properties of the currently circulating African swine fever virus (ASFV), experimental infections of young pigs (approximately 8 weeks of age) and pregnant sows (infected [...] Read more.

African swine fever is an important viral disease of wild and domestic pigs. To gain further knowledge of the properties of the currently circulating African swine fever virus (ASFV), experimental infections of young pigs (approximately 8 weeks of age) and pregnant sows (infected at about 100 days of gestation) with the genotype II ASFV Georgia/2007 were performed. The inoculated young pigs developed typical clinical signs of the disease and the infection was transmitted (usually within 3–4 days) to all of the “in contact” animals that shared the same pen. Furthermore, typical pathogical lesions for ASFV infection were found at necropsy. Inoculation of pregnant sows with the same virus also produced rapid onset of disease from post-infection day three; two of the three sows died suddenly on post-infection day five, while the third was euthanized on the same day for animal welfare reasons. Following necropsy, the presence of ASFV DNA was detected in tonsils, spleen and lymph nodes of some of the fetuses, but the levels of viral DNA were much lower than in these tissues from the sows. Thus, only limited transplacental transmission occurred during the course of this experiment. These studies contribute towards further understanding about the spread of this important viral disease in domestic pigs. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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13 pages, 1824 KiB

Open AccessArticle

Serum Neutralizing and Enhancing Effects on African Swine Fever Virus Infectivity in Adherent Pig PBMC

by Jessica A. Canter, Theresa Aponte, Elizabeth Ramirez-Medina, Sarah Pruitt, Douglas P. Gladue, Manuel V. Borca and James J. Zhu

Viruses 2022, 14(6), 1249; https://doi.org/10.3390/v14061249 - 09 Jun 2022

Cited by 6 | Viewed by 2639

Abstract

African swine fever virus (ASFV) causes hemorrhagic fever with mortality rates of up to 100% in domestic pigs. Currently, there are no commercial vaccines for the disease. Only some live-attenuated viruses have been able to protect pigs from ASFV infection. The immune mechanisms [...] Read more.

African swine fever virus (ASFV) causes hemorrhagic fever with mortality rates of up to 100% in domestic pigs. Currently, there are no commercial vaccines for the disease. Only some live-attenuated viruses have been able to protect pigs from ASFV infection. The immune mechanisms involved in the protection are unclear. Immune sera can neutralize ASFV but incompletely. The mechanisms involved are not fully understood. Currently, there is no standardized protocol for ASFV neutralization assays. In this study, a flow cytometry-based ASFV neutralization assay was developed and tested in pig adherent PBMC using a virulent ASFV containing a fluorescent protein gene as a substrate for neutralization. As with previous studies, the percentage of infected macrophages was approximately five time higher than that of infected monocytes, and nearly all infected cells displayed no staining with anti-CD16 antibodies. Sera from naïve pigs and pigs immunized with a live-attenuated ASFV and fully protected against parental virus were used in the assay. The sera displayed incomplete neutralization with MOI-dependent neutralizing efficacies. Extracellular, but not intracellular, virions suspended in naïve serum were more infectious than those in the culture medium, as reported for some enveloped viruses, suggesting a novel mechanism of ASFV infection in macrophages. Both the intracellular and extracellular virions could not be completely neutralized. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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10 pages, 4096 KiB

Open AccessCommunication

Efficacy of Liming Forest Soil in the Context of African Swine Fever Virus

by Franziska Tanneberger, Ahmed Abd El Wahed, Melina Fischer, Paul Deutschmann, Hanna Roszyk, Tessa Carrau, Sandra Blome and Uwe Truyen

Viruses 2022, 14(4), 734; https://doi.org/10.3390/v14040734 - 31 Mar 2022

Cited by 3 | Viewed by 2056

Abstract

Since September 2020, Germany has experienced the first ever outbreak of African swine fever (ASF). The first known cases occurred exclusively in wild boar in forest areas in Brandenburg and Saxony; in July 2021, infected domestic pigs were also confirmed for the first [...] Read more.

Since September 2020, Germany has experienced the first ever outbreak of African swine fever (ASF). The first known cases occurred exclusively in wild boar in forest areas in Brandenburg and Saxony; in July 2021, infected domestic pigs were also confirmed for the first time. As wild boar are considered the main reservoir for the virus in the European region, an effective interruption of this infection chain is essential. In particular, the removal and safe disposal of infected carcasses and the direct disinfection of contaminated, unpaved ground are priorities in this regard. For the disinfection, highly potent as well as environmentally compatible disinfectants must be used, which are neither influenced in their effectiveness by the soil condition nor by increased organic contamination. Thus, in this study, slaked lime, milk of lime and quicklime (1% to 10% solutions) were selected for efficacy testing against the test virus recommended by the German Veterinary Society (DVG), Modified Vaccinia Ankara virus (MVAV), and ASF virus (ASFV) in conjunction with six different forest soils from Saxony in two different soil layers (top soil and mineral soil) each. In summary, 10% of any tested lime type is able to inactivate both MVAV and ASFV under conditions of high organic load and independent of the water content of the soil. At least a 4 log reduction of the virus titer in all tested forest soil types and layers and by all applied lime types was observed. In conclusion, the high efficacy and suitability of all tested lime products against both viruses and in the presence of high organic load in forest soil can be confirmed and will help to control ASF spread. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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Review

Jump to: Research

15 pages, 349 KiB

Open AccessReview

African Swine Fever Vaccinology: The Biological Challenges from Immunological Perspectives

by James J. Zhu

Viruses 2022, 14(9), 2021; https://doi.org/10.3390/v14092021 - 13 Sep 2022

Cited by 12 | Viewed by 3558

Abstract

African swine fever virus (ASFV), a nucleocytoplasmic large DNA virus (NCLDV), causes African swine fever (ASF), an acute hemorrhagic disease with mortality rates up to 100% in domestic pigs. ASF is currently epidemic or endemic in many countries and threatening the global swine [...] Read more.

African swine fever virus (ASFV), a nucleocytoplasmic large DNA virus (NCLDV), causes African swine fever (ASF), an acute hemorrhagic disease with mortality rates up to 100% in domestic pigs. ASF is currently epidemic or endemic in many countries and threatening the global swine industry. Extensive ASF vaccine research has been conducted since the 1920s. Like inactivated viruses of other NCLDVs, such as vaccinia virus, inactivated ASFV vaccine candidates did not induce protective immunity. However, inactivated lumpy skin disease virus (poxvirus) vaccines are protective in cattle. Unlike some experimental poxvirus subunit vaccines that induced protection, ASF subunit vaccine candidates implemented with various platforms containing several ASFV structural genes or proteins failed to protect pigs effectively. Only some live attenuated viruses (LAVs) are able to protect pigs with high degrees of efficacy. There are currently several LAV ASF vaccine candidates. Only one commercial LAV vaccine is approved for use in Vietnam. LAVs, as ASF vaccines, have not yet been widely tested. Reports thus far show that the onset and duration of protection induced by the LAVs are late and short, respectively, compared to LAV vaccines for other diseases. In this review, the biological challenges in the development of ASF vaccines, especially subunit platforms, are discussed from immunological perspectives based on several unusual ASFV characteristics shared with HIV and poxviruses. These characteristics, including multiple distinct infectious virions, extremely high glycosylation and low antigen surface density of envelope proteins, immune evasion, and possible apoptotic mimicry, could pose enormous challenges to the development of ASF vaccines, especially subunit platforms designed to induce humoral immunity. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

19 pages, 1187 KiB

Open AccessReview

Disinfectants against African Swine Fever: An Updated Review

by Maria Serena Beato, Federica D’Errico, Carmen Iscaro, Stefano Petrini, Monica Giammarioli and Francesco Feliziani

Viruses 2022, 14(7), 1384; https://doi.org/10.3390/v14071384 - 24 Jun 2022

Cited by 12 | Viewed by 4795

Abstract

African Swine Fever (ASF), a hemorrhagic disease with a high mortality rate in suids, is transmitted via direct and indirect contact with infectious animals and contaminated fomites, respectively. ASF reached Europe in 2014, affecting 14 of the 27 EU countries including, recently, the [...] Read more.

African Swine Fever (ASF), a hemorrhagic disease with a high mortality rate in suids, is transmitted via direct and indirect contact with infectious animals and contaminated fomites, respectively. ASF reached Europe in 2014, affecting 14 of the 27 EU countries including, recently, the Italian peninsula. The fast and unprecedented spread of ASF in the EU has highlighted gaps in knowledge regarding transmission mechanisms. Fomites, such as contaminated clothing and footwear, farming tools, equipment and vehicles have been widely reported in the spread of ASF. The absence of available vaccines renders biosecurity measures, cleaning and disinfection procedures an essential control tool, to a greater degree than the others, for the prevention of primary and secondary introductions of ASF in pig farms. In this review, available data on the virucidal activity of chemical compounds as disinfectants against the ASF virus (ASFV) are summarized together with laboratory methods adopted to assess the virucidal activity. Full article

(This article belongs to the Special Issue African Swine Fever Virus 2.0)

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