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12 pages, 1547 KiB

Open AccessArticle

Disease Course of Korean African Swine Fever Virus in Domestic Pigs Exposed Intraorally, Intranasally, Intramuscularly, and by Direct Contact with Infected Pigs

by Ki-Hyun Cho, Seong-Keun Hong, Da-Young Kim, Hyun-Joo Sohn, Dae-Sung Yoo, Hae-Eun Kang and Yeon-Hee Kim

Viruses 2024, 16(3), 433; https://doi.org/10.3390/v16030433 - 11 Mar 2024

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Abstract

African swine fever (ASF) is a fatal contagious disease affecting swine. The first Korean ASF virus (ASFV) isolate (Korea/Pig/Paju1/2019) was used to compare the disease course of ASFV in pigs inoculated via the four routes. In the challenge experiment, domestic pigs were infected [...] Read more.

African swine fever (ASF) is a fatal contagious disease affecting swine. The first Korean ASF virus (ASFV) isolate (Korea/Pig/Paju1/2019) was used to compare the disease course of ASFV in pigs inoculated via the four routes. In the challenge experiment, domestic pigs were infected via the intraoral (IO) and intranasal (IN) routes with a 10⁶ 50% hemadsorbing dose (HAD₅₀) and an intramuscular (IM) injection of 10³ HAD₅₀. In the direct contact (DC) group, five naïve pigs were brought into direct contact with two IM-ASFV-infected pigs. IO-, IN-, and IM-inoculated pigs showed similar disease courses, whereas DC pigs had comparable ASF syndrome after a 7-day latent period. The disease course in the DC route, one of the most common routes of infection, was not significantly different from that in the IO and IN routes. IM and DC groups differed in terms of the severity of fever and hemorrhagic lesions in the lymph nodes and spleen, indicating that the IM route, suitable for early vaccine development trials, is not appropriate for studying the ASFV infection mechanism, including early stage of infection, and IO and IN challenges with a designated dose can be alternatives in trials for assessing ASFV pathogenicity and vaccine efficacy investigations. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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22 pages, 10731 KiB

Open AccessArticle

Identification of a Potential Entry-Fusion Complex Based on Sequence Homology of African Swine Fever and Vaccinia Virus

by Jesús Urquiza, Miguel Ángel Cuesta-Geijo, Isabel García-Dorival, Óscar Fernández, Ana del Puerto, José Fernando Díaz and Covadonga Alonso

Viruses 2024, 16(3), 349; https://doi.org/10.3390/v16030349 - 23 Feb 2024

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Abstract

African swine fever virus (ASFV) belongs to the family of Asfarviridae, part of the group of nucleocytoplasmic large DNA viruses (NCLDV). Little is known about the internalization of ASFV in the host cell and the fusion membrane events that take place at [...] Read more.

African swine fever virus (ASFV) belongs to the family of Asfarviridae, part of the group of nucleocytoplasmic large DNA viruses (NCLDV). Little is known about the internalization of ASFV in the host cell and the fusion membrane events that take place at early stages of the infection. Poxviruses, also members of the NCLDV and represented by vaccinia virus (VACV), are large, enveloped, double-stranded DNA viruses. Poxviruses were considered unique in having an elaborate entry-fusion complex (EFC) composed of 11 highly conserved proteins integrated into the membrane of mature virions. Recent advances in methodological techniques have again revealed several connections between VACV EFC proteins. In this study, we explored the possibility of an analogous ASFV EFC by identifying ten candidate proteins exhibiting structural similarities with VACV EFC proteins. This could reveal key functions of these ASFV proteins, drawing attention to shared features between the two virus families, suggesting the potential existence of an ASFV entry-fusion complex. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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15 pages, 1893 KiB

Open AccessArticle

Generation of High-Quality African Swine Fever Virus Complete Genome from Field Samples by Next-Generation Sequencing

by Chuan Shi, Qinghua Wang, Yutian Liu, Shujuan Wang, Yongqiang Zhang, Chunju Liu, Yongxin Hu, Dongxia Zheng, Chengyou Sun, Fangfang Song, Xiaojing Yu, Yunling Zhao, Jingyue Bao and Zhiliang Wang

Viruses 2024, 16(2), 312; https://doi.org/10.3390/v16020312 - 18 Feb 2024

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Abstract

African swine fever (ASF) is a lethal contagious viral disease of domestic pigs and wild boars caused by the African swine fever virus (ASFV). The pandemic spread of ASF has caused severe effects on the global pig industry. Whole-genome sequencing provides crucial information [...] Read more.

African swine fever (ASF) is a lethal contagious viral disease of domestic pigs and wild boars caused by the African swine fever virus (ASFV). The pandemic spread of ASF has caused severe effects on the global pig industry. Whole-genome sequencing provides crucial information for virus strain characterization, epidemiology analysis and vaccine development. Here, we evaluated the performance of next-generation sequencing (NGS) in generating ASFV genome sequences from clinical samples. Thirty-four ASFV-positive field samples including spleen, lymph node, lung, liver and blood with a range of Ct values from 14.73 to 25.95 were sequenced. For different tissue samples collected from the same sick pigs, the proportion of ASFV reads obtained from the spleen samples was 3.69–9.86 times higher than other tissues. For the high-viral-load spleen samples (Ct < 20), a minimum of a 99.8% breadth of ≥10× coverage was revealed for all the samples. For the spleen samples with Ct ≥ 20, 6/12 samples had a minimum of a 99.8% breadth of ≥10× coverage. A high average depth of sequencing coverage was also achieved from the blood samples. According to our results, high-quality ASFV whole-genome sequences could be obtained from the spleen or blood samples with Ct < 20. The high-quality ASFV genome sequence generated in this study was further used for the high-resolution phylogenetic analysis of the ASFV genomes in the early stage of the ASF epidemic in China. Our study demonstrates that NGS may act as a useful tool for efficient ASFV genome characterization, providing valuable information for disease control. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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10 pages, 782 KiB

Open AccessArticle

Stability of Genotube^® Swabs for African Swine Fever Virus Detection Using Loop-Mediated Isothermal (LAMP) Laboratory Testing on Samples Stored without Refrigeration

by Dianne Phillips, Felisiano da Conceicao, Joanita Bendita da Costa Jong, Grant Rawlin and Peter Mee

Viruses 2024, 16(2), 263; https://doi.org/10.3390/v16020263 - 07 Feb 2024

Viewed by 780

Abstract

African swine fever (ASF) is a transboundary viral disease which causes high mortality in pigs. In many low- and middle-income countries and in remote areas where diagnostic surveillance for ASF virus (ASFV) is undertaken, access to trained animal health technicians, sample collection, cold [...] Read more.

African swine fever (ASF) is a transboundary viral disease which causes high mortality in pigs. In many low- and middle-income countries and in remote areas where diagnostic surveillance for ASF virus (ASFV) is undertaken, access to trained animal health technicians, sample collection, cold chain storage and transport of samples to suitably equipped laboratories can be limiting when traditional sampling and laboratory tests are used. Previously published studies have demonstrated that alternative sampling matrices such as swabs and filter papers can be tested using PCR without refrigeration for up to a week. This study used Genotube^® swabs stored in temperate and tropical climates without refrigeration for four weeks after collection to demonstrate there was no change in test performance and results using loop-mediated isothermal amplification (LAMP) ASFV detection on a series of pig serum samples including serum spiked with a synthetic ASFV positive control, naturally acquired ASFV positive serum from Timor-Leste and negative ASFV serum samples. The use of Genotube^® swabs for ASFV detection for surveillance purposes, coupled with testing platforms such as LAMP, can provide an alternative to traditional testing methodology where resources are limited and time from collection to testing of samples is prolonged. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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12 pages, 1482 KiB

Open AccessArticle

Optimizing Vaccination Strategies against African Swine Fever Using Spatial Data from Wild Boars in Lithuania

by Vincenzo Gervasi, Marius Masiulis, Paulius Bušauskas, Silvia Bellini and Vittorio Guberti

Viruses 2024, 16(1), 153; https://doi.org/10.3390/v16010153 - 19 Jan 2024

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Abstract

African swine fever (ASF) is one of the most severe suid diseases, impacting the pig industry and wild suid populations. Once an ASF vaccine is available, identifying a sufficient density of vaccination fields will be crucial to achieve eradication success. In 2020–2023, we [...] Read more.

African swine fever (ASF) is one of the most severe suid diseases, impacting the pig industry and wild suid populations. Once an ASF vaccine is available, identifying a sufficient density of vaccination fields will be crucial to achieve eradication success. In 2020–2023, we live-trapped and monitored 27 wild boars in different areas of Lithuania, in which the wild boars were fed at artificial stations. We built a simulation study to estimate the probability of a successful ASF vaccination as a function of different eco-epidemiological factors. The average 32-day home range size across all individuals was 16.2 km² (SD = 16.9). The wild boars made frequent visits of short durations to the feeding sites rather than long visits interposed by long periods of absence. A feeding site density of 0.5/km² corresponded to an expected vaccination rate of only 20%. The vaccination probability increased to about 75% when the feeding site density was 1.0/km². Our results suggest that at least one vaccination field/km² should be used when planning an ASF vaccination campaign to ensure that everyone in the population has at least 5–10 vaccination sites available inside the home range. Similar studies should be conducted in the other ecological contexts in which ASF is present today or will be present in the future, with the objective being to estimate a context-specific relationship between wild boar movement patterns and an optimal vaccination strategy. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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14 pages, 2180 KiB

Open AccessArticle

The Long-Jumping of African Swine Fever: First Genotype II Notified in Sardinia, Italy

by Silvia Dei Giudici, Federica Loi, Sonia Ghisu, Pier Paolo Angioi, Susanna Zinellu, Mariangela Stefania Fiori, Francesca Carusillo, Diego Brundu, Giulia Franzoni, Giovanni Maria Zidda, Paolo Tolu, Ennio Bandino, Stefano Cappai and Annalisa Oggiano

Viruses 2024, 16(1), 32; https://doi.org/10.3390/v16010032 - 23 Dec 2023

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Abstract

African swine fever (ASF) is a devastating infectious disease of domestic pigs and wild boar that is spreading quickly around the world and causing huge economic losses. Although the development of effective vaccines is currently being attempted by several labs, the absence of [...] Read more.

African swine fever (ASF) is a devastating infectious disease of domestic pigs and wild boar that is spreading quickly around the world and causing huge economic losses. Although the development of effective vaccines is currently being attempted by several labs, the absence of globally recognized licensed vaccines makes disease prevention and early detection even more crucial. ASF has spread across many countries in Europe and about two years ago affected the Italian susceptible population. In Italy, the first case of ASF genotype II in wild boar dates back to January 2022, while the first outbreak in a domestic pig farm was notified in August 2023. Currently, four clusters of infection are still ongoing in northern (Piedmont-Liguria and Lombardy), central (Lazio), and southern Italy (Calabria and Campania). In early September 2023, the first case of ASFV genotype II was detected in a domestic pig farm in Sardinia, historically affected by genotype I and in the final stage of eradication. Genomic characterization of p72, p54, and I73R/I329L genome regions revealed 100% similarity to those obtained from isolates that have been circulating in mainland Italy since January 2022 and also with international strains. The outbreak was detected and confirmed due to the passive surveillance plan on domestic pig farms put in place to provide evidence on genotype I’s absence. Epidemiological investigations suggest 24 August as the most probable time of ASFV genotype II’s arrival in Sardinia, likely due to human activities. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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14 pages, 3853 KiB

Open AccessArticle

Evaluation of the Deletion of the African Swine Fever Virus Gene O174L from the Genome of the Georgia Isolate

by Elizabeth Ramirez-Medina, Lauro Velazquez-Salinas, Ayushi Rai, Nallely Espinoza, Alyssa Valladares, Ediane Silva, Leeanna Burton, Edward Spinard, Amanda Meyers, Guillermo Risatti, Sten Calvelage, Sandra Blome, Douglas P. Gladue and Manuel V. Borca

Viruses 2023, 15(10), 2134; https://doi.org/10.3390/v15102134 - 23 Oct 2023

Viewed by 1194

Abstract

African swine fever virus (ASFV) is a structurally complex, double-stranded DNA virus, which causes African swine fever (ASF), a contagious disease affecting swine. ASF is currently affecting pork production in a large geographical region, including Eurasia and the Caribbean. ASFV has a large [...] Read more.

African swine fever virus (ASFV) is a structurally complex, double-stranded DNA virus, which causes African swine fever (ASF), a contagious disease affecting swine. ASF is currently affecting pork production in a large geographical region, including Eurasia and the Caribbean. ASFV has a large genome, which harbors more than 160 genes, but most of these genes’ functions have not been experimentally characterized. One of these genes is the O174L gene which has been experimentally shown to function as a small DNA polymerase. Here, we demonstrate that the deletion of the O174L gene from the genome of the virulent strain ASFV Georgia2010 (ASFV-G) does not significantly affect virus replication in vitro or in vivo. A recombinant virus, having deleted the O174L gene, ASFV-G-∆O174L, was developed to study the effect of the O174L protein in replication in swine macrophages cultures in vitro and disease production when inoculated in pigs. The results demonstrated that ASFV-G-∆O174L has similar replication kinetics to parental ASFV-G in swine macrophage cultures. In addition, animals intramuscularly inoculated with 10² HAD₅₀ of ASFV-G-∆O174L presented a clinical form of the disease that is indistinguishable from that induced by the parental virulent strain ASFV-G. All animals developed a lethal disease, being euthanized around day 7 post-infection. Therefore, although O174L is a well-characterized DNA polymerase, its function is apparently not critical for the process of virus replication, both in vitro and in vivo, or for disease production in domestic pigs. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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12 pages, 2629 KiB

Open AccessArticle

Developing an Indirect ELISA for the Detection of African Swine Fever Virus Antibodies Using a Tag-Free p15 Protein Antigen

by Zhi Wu, Huipeng Lu, Dewei Zhu, Jun Xie, Fan Sun, Yan Xu, Hua Zhang, Zhijun Wu, Wenlong Xia and Shanyuan Zhu

Viruses 2023, 15(9), 1939; https://doi.org/10.3390/v15091939 - 16 Sep 2023

Cited by 2 | Viewed by 1110

Abstract

African swine fever (ASF) is one of the most severe diseases caused by the ASF virus (ASFV), causing massive economic losses to the global pig industry. Serological tests are important in ASF epidemiological surveillance, and more antigen targets are needed to meet market [...] Read more.

African swine fever (ASF) is one of the most severe diseases caused by the ASF virus (ASFV), causing massive economic losses to the global pig industry. Serological tests are important in ASF epidemiological surveillance, and more antigen targets are needed to meet market demand for ASFV antibody detection. In the present study, ASFV p15 protein was fusion-expressed in Escherichia coli (E. coli) with elastin-like polypeptide (ELP), and the ELP-p15 protein was purified using a simple inverse transition cycling (ITC) process. The ELP tag was cleaved off using tobacco etch virus protease (TEVp), resulting in a tag-free p15 protein. Western blot analysis demonstrated that the p15 protein reacted strongly with ASFV-positive serum. The p15 protein was used as a coating antigen in an indirect ELISA (iELISA) for detecting ASFV antibodies. The p15-iELISA method demonstrated high specificity to ASFV-positive sera, with a maximum detection dilution of 1:1600. Moreover, the method exhibited good reproducibility, with less intra-assay and inter-assay CV values than 10%. Therefore, p15-iELISA offers a novel approach for accurately detecting ASFV antibodies with significant clinical application potential. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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Review

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23 pages, 2241 KiB

Open AccessReview

Functional Landscape of African Swine Fever Virus–Host and Virus–Virus Protein Interactions

by Katarzyna Magdalena Dolata, Gang Pei, Christopher L. Netherton and Axel Karger

Viruses 2023, 15(8), 1634; https://doi.org/10.3390/v15081634 - 27 Jul 2023

Cited by 2 | Viewed by 2027

Abstract

Viral replication fully relies on the host cell machinery, and physical interactions between viral and host proteins mediate key steps of the viral life cycle. Therefore, identifying virus–host protein–protein interactions (PPIs) provides insights into the molecular mechanisms governing virus infection and is crucial [...] Read more.

Viral replication fully relies on the host cell machinery, and physical interactions between viral and host proteins mediate key steps of the viral life cycle. Therefore, identifying virus–host protein–protein interactions (PPIs) provides insights into the molecular mechanisms governing virus infection and is crucial for designing novel antiviral strategies. In the case of the African swine fever virus (ASFV), a large DNA virus that causes a deadly panzootic disease in pigs, the limited understanding of host and viral targets hinders the development of effective vaccines and treatments. This review summarizes the current knowledge of virus–host and virus–virus PPIs by collecting and analyzing studies of individual viral proteins. We have compiled a dataset of experimentally determined host and virus protein targets, the molecular mechanisms involved, and the biological functions of the identified virus–host and virus–virus protein interactions during infection. Ultimately, this work provides a comprehensive and systematic overview of ASFV interactome, identifies knowledge gaps, and proposes future research directions. Full article

(This article belongs to the Special Issue African Swine Fever Virus 4.0)

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