EFFECTS OF MODERATELY VIRULENT AFRICAN SWINE FEVER VIRUS ON INTERLEUKIN-10 PRODUCTION

A characteristic feature of African swine fever virus (ASFV) is the ability to escape from host immune response, affecting macrophages and replicating in them. Besides, ASFV - specific antibodies do not completely neutralize the virus. Cytokines are important factors for various viral infection pathologies. The virulence of ASFV isolates may depend on the capacity to regulate cytokine expression by macrophages. Thus, when comparing in vitro and in vivo cytokine production by macrophages, it was established that infection with low virulent virus isolates leads to an immune response with a predominance of cytokines involved in cellular immunity, such as INF-α and IL-12p40, as compared with infection with highly virulent isolates. The aim of this paper was to study the effect of African swine fever virus on the production of IL-10, a pleiotropic cytokine that inhibits synthesis of cytokines and shows a strong antiinflammatory effect. For this, 12 piglets were experimentally infected intramuscularly with a continuous cell culture-adapted ASFV isolate Vero25 at a dose of 10 HAdU per animal followed by control infection of surviving animals with the reference virus isolate Arm 07 at a dose of 1,000 HAdU per animal. Temperature measurements were taken and blood sampling to obtain serum was conducted during the experiment. IL-10 amount in blood sera was determined using Invitrogen test systems (Thermo Fisher, USA). A higher IL-10 level (15.8–173 pg/ml) was observed in blood sera of dead animals infected with a moderately virulent virus, as compared with surviving pigs (4–5 pg/ml). No correlation between the speed of appearance of specific antibodies and IL-10 serum levels has been established. No noticeable effect of the IL-10 serum level prior to infection on the survival rate of animals has been observed. Further studies are needed to establish a causal relationship, including study of the expression of various cytokines during infection with both low- and highly virulent virus isolates.

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African Swine Fever Virus Georgia 2007 with a Deletion of Virulence-Associated Gene9GL(B119L), when Administered at Low Doses, Leads to Virus Attenuation in Swine and Induces an Effective Protection against Homologous Challenge

Journal of Virology ◽

10.1128/jvi.00969-15 ◽

2015 ◽

Vol 89 (16) ◽

pp. 8556-8566 ◽

Cited By ~ 55

Author(s):

Vivian O'Donnell ◽

Lauren G. Holinka ◽

Peter W. Krug ◽

Douglas P. Gladue ◽

Jolene Carlson ◽

...

Keyword(s):

African Swine Fever Virus ◽

Genetically Modified ◽

African Swine Fever ◽

Fever Virus ◽

The Caucasus ◽

Caucasus Region ◽

Homologous Virus ◽

Virulent Virus ◽

Virulent Phenotype ◽

Highly Virulent

ABSTRACTAfrican swine fever virus (ASFV) is the etiological agent of an often lethal disease of domestic pigs. Disease control strategies have been hampered by the unavailability of vaccines against ASFV. Since its introduction in the Republic of Georgia, a highly virulent virus, ASFV Georgia 2007 (ASFV-G), has caused an epizootic that spread rapidly into Eastern European countries. Currently no vaccines are available or under development to control ASFV-G. In the past, genetically modified ASFVs harboring deletions of virulence-associated genes have proven attenuated in swine, inducing protective immunity against challenge with homologous parental viruses. Deletion of the gene9GL(open reading frame [ORF] B119L) in highly virulent ASFV Malawi-Lil-20/1 produced an attenuated phenotype even when administered to pigs at 10650% hemadsorption doses (HAD50). Here we report the construction of a genetically modified ASFV-G strain (ASFV-G-Δ9GLv) harboring a deletion of the9GL(B119L) gene. Like Malawi-Lil-20/1-Δ9GL, ASFV-G-Δ9GL showed limited replication in primary swine macrophages. However, intramuscular inoculation of swine with 104HAD50of ASFV-G-Δ9GL produced a virulent phenotype that, unlike Malawi-Lil-20/1-Δ9GL, induced a lethal disease in swine like parental ASFV-G. Interestingly, lower doses (102to 103HAD50) of ASFV-G-Δ9GL did not induce a virulent phenotype in swine and when challenged protected pigs against disease. A dose of 102HAD50of ASFV-G-Δ9GLv conferred partial protection when pigs were challenged at either 21 or 28 days postinfection (dpi). An ASFV-G-Δ9GL HAD50of 103conferred partial and complete protection at 21 and 28 dpi, respectively. The information provided here adds to our recent report on the first attempts toward experimental vaccines against ASFV-G.IMPORTANCEThe main problem for controlling ASF is the lack of vaccines. Studies on ASFV virulence lead to the production of genetically modified attenuated viruses that induce protection in pigs but only against homologous virus challenges. Here we produced a recombinant ASFV lacking virulence-associated gene9GLin an attempt to produce a vaccine against virulent ASFV-G, a highly virulent virus isolate detected in the Caucasus region in 2007 and now spreading though the Caucasus region and Eastern Europe. Deletion of9GL, unlike with other ASFV isolates, did not attenuate completely ASFV-G. However, when delivered once at low dosages, recombinant ASFV-G-Δ9GL induces protection in swine against parental ASFV-G. The protection against ASFV-G is highly effective after 28 days postvaccination, whereas at 21 days postvaccination, animals survived the lethal challenge but showed signs of ASF. Here we report the design and development of an experimental vaccine that induces protection against virulent ASFV-G.

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Analysis of genetic markers of variability of African swine fever virus isolates isolated in the Russian Federation

Veterinary Medicine Journal ◽

10.30896/0042-4846.2020.23.2.14-19 ◽

2020 ◽

Vol 23 (2) ◽

pp. 14-19

Author(s):

A.K. Sibgatullova ◽

◽

M.V. Nefedeva ◽

D.A. Kudryashov ◽

M.E. Vlasov ◽

...

Keyword(s):

Genetic Markers ◽

Russian Federation ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus ◽

The Russian Federation ◽

Virus Isolates

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GS-441524 inhibits African swine fever virus infection in vitro

Antiviral Research ◽

10.1016/j.antiviral.2021.105081 ◽

2021 ◽

pp. 105081

Author(s):

Zhao Huang ◽

Lang Gong ◽

Zezhong Zheng ◽

Qi Gao ◽

Xiongnan Chen ◽

...

Keyword(s):

Virus Infection ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus

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Differential Effect of the Deletion of African Swine Fever Virus Virulence-Associated Genes in the Induction of Attenuation of the Highly Virulent Georgia Strain

Viruses ◽

10.3390/v11070599 ◽

2019 ◽

Vol 11 (7) ◽

pp. 599 ◽

Cited By ~ 14

Author(s):

Elizabeth Ramirez-Medina ◽

Elizabeth Vuono ◽

Vivian O’Donnell ◽

Lauren G. Holinka ◽

Ediane Silva ◽

...

Keyword(s):

Protective Immunity ◽

Gene Deletion ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Early Death ◽

Fever Virus ◽

Differential Behavior ◽

Viral Genes ◽

The Uk ◽

Highly Virulent

African swine fever virus (ASFV) is the etiological agent of an often lethal disease of domestic pigs, African swine fever (ASF). The ASFV Georgia 2007 isolate (ASFV-G) is responsible for the current epidemic situation in Europe and Asia. Genetically modified ASFVs containing deletions of virulence-associated genes have produced attenuated phenotypes and induced protective immunity in swine. Here we describe the differential behavior of two viral genes, NL (DP71L) and UK (DP96R), both originally described as being involved in virus virulence. Deletion of either of these genes efficiently attenuated ASFV strain E70. We demonstrated that deletion of the UK gene from the ASFV-G genome did not decrease virulence when compared to the parental virus. Conversely, deletion of the NL gene produced a heterogeneous response, with early death in one of the animals and transient fever in the other animals. With this knowledge, we attempted to increase the safety profile of the previously reported experimental vaccine ASFV-GΔ9GL/ΔUK by deleting the NL gene. A triple gene-deletion virus was produced, ASFV-GΔ9GL/ΔNL/ΔUK. Although ASFV-GΔ9GL/ΔNL/ΔUK replicated in primary cell cultures of swine macrophages, it demonstrated a severe replication deficiency in pigs, failing to induce protection against challenge with parental ASFV-G.

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Role of African swine fever virus (ASFV) proteins EP153R and EP402R in reducing viral persistence and virulence from attenuated BeninΔDP148R

10.1101/2021.04.16.439957 ◽

2021 ◽

Author(s):

Vlad Petrovan ◽

Anusyah Rathakrishnan ◽

Muneeb Islam ◽

Lynnette Goatley ◽

Katy Moffat ◽

...

Keyword(s):

Virus Replication ◽

Vaccine Development ◽

African Swine Fever Virus ◽

Clinical Signs ◽

African Swine Fever ◽

Viral Persistence ◽

Fever Virus ◽

Post Immunization

The limited knowledge on the role of many of the approximately 170 proteins encoded by African swine fever virus restricts progress towards vaccine development. In this study we investigated the effect of deleting combinations of different genes from a previously attenuated virus, BeninΔDP148R on: virus replication in macrophages, virus persistence and clinical signs post immunization, and induction of protection against challenge. Deletion of either EP402R or EP153R genes individually or in combination from BeninΔDP148R did not reduce virus replication in vitro. However, deletion of EP402R dramatically reduced viral persistence in vivo, whilst maintaining high levels of protection against challenge. The additional deletion of EP153R (BeninΔDP148RΔEP153RΔEP402R) further attenuated the virus and no viremia or clinical signs were observed post immunization. This was associated with decreased protection and detection of moderate levels of challenge virus in blood. Interestingly, the deletion of EP153R alone from BeninΔDP148R did not result in further virus attenuation and a slight increase in virus genome copies in blood was observed at different times post immunization when compared with BeninΔDP148R. These results show that EP402R and EP153R have a synergistic role in promoting viremia, however EP153R alone does not seem to have a major impact on virus levels in blood.

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Deletion of a CD2-Like Gene, 8-DR, from African Swine Fever Virus Affects Viral Infection in Domestic Swine

Journal of Virology ◽

10.1128/jvi.72.4.2881-2889.1998 ◽

1998 ◽

Vol 72 (4) ◽

pp. 2881-2889 ◽

Cited By ~ 74

Author(s):

M. V. Borca ◽

C. Carrillo ◽

L. Zsak ◽

W. W. Laegreid ◽

G. F. Kutish ◽

...

Keyword(s):

Viral Infection ◽

Mononuclear Cells ◽

African Swine Fever Virus ◽

Disease Onset ◽

African Swine Fever ◽

Fever Virus ◽

Parental Virus ◽

Viral Virulence

ABSTRACT An African swine fever virus (ASFV) gene with similarity to the T-lymphocyte surface antigen CD2 has been found in the pathogenic African isolate Malawi Lil-20/1 (open reading frame [ORF] 8-DR) and a cell culture-adapted European virus, BA71V (ORF EP402R) and has been shown to be responsible for the hemadsorption phenomenon observed for ASFV-infected cells. The structural and functional similarities of the ASFV gene product to CD2, a cellular protein involved in cell-cell adhesion and T-cell-mediated immune responses, suggested a possible role for this gene in tissue tropism and/or immune evasion in the swine host. In this study, we constructed an ASFV 8-DR gene deletion mutant (Δ8-DR) and its revertant (8-DR.R) from the Malawi Lil-20/1 isolate to examine gene function in vivo. In vitro, Δ8-DR, 8-DR.R, and the parental virus exhibited indistinguishable growth characteristics on primary porcine macrophage cell cultures. In vivo,8-DR had no obvious effect on viral virulence in domestic pigs; disease onset, disease course, and mortality were similar for the mutant Δ8-DR, its revertant 8-DR.R, and the parental virus. Altered viral infection was, however, observed for pigs infected with Δ8-DR. A delay in spread to and/or replication of Δ8-DR in the draining lymph node, a delay in generalization of infection, and a 100- to 1,000-fold reduction in virus titers in lymphoid tissue and bone marrow were observed. Onset of viremia for Δ8-DR-infected animals was significantly delayed (by 2 to 5 days), and mean viremia titers were reduced approximately 10,000-fold at 5 days postinfection and 30- to 100-fold at later times; moreover, unlike in 8-DR.R-infected animals, the viremia was no longer predominantly erythrocyte associated but rather was equally distributed among erythrocyte, leukocyte, and plasma fractions. Mitogen-dependent lymphocyte proliferation of swine peripheral blood mononuclear cells in vitro was reduced by 90 to 95% following infection with 8-DR.R but remained unaltered following infection with Δ8-DR, suggesting that 8-DR has immunosuppressive activity in vitro. Together, these results suggest an immunosuppressive role for 8-DR in the swine host which facilitates early events in viral infection. This may be of most significance for ASFV infection of its highly adapted natural host, the warthog.

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African Swine Fever Virus Infection of Porcine Aortic Endothelial Cells Leads to Inhibition of Inflammatory Responses, Activation of the Thrombotic State, and Apoptosis

Journal of Virology ◽

10.1128/jvi.75.21.10372-10382.2001 ◽

2001 ◽

Vol 75 (21) ◽

pp. 10372-10382 ◽

Cited By ~ 31

Author(s):

Isabelle Vallée ◽

Stephen W. G. Tait ◽

Penelope P. Powell

Keyword(s):

Endothelial Cells ◽

African Swine Fever Virus ◽

African Swine Fever ◽

Surface Expression ◽

Fever Virus ◽

Parp Cleavage ◽

Aortic Endothelial Cells ◽

Porcine Aortic Endothelial Cells ◽

Aortic Endothelial

ABSTRACT African swine fever (ASF) is an asymptomatic infection of warthogs and bushpigs, which has become an emergent disease of domestic pigs, characterized by hemorrhage, lymphopenia, and disseminated intravascular coagulation. It is caused by a large icosohedral double-stranded DNA virus, African swine fever virus (ASFV), with infection of macrophages well characterized in vitro and in vivo. This study shows that virulent isolates of ASFV also infect primary cultures of porcine aortic endothelial cells and bushpig endothelial cells (BPECs) in vitro. Kinetics of early and late gene expression, viral factory formation, replication, and secretion were similar in endothelial cells and macrophages. However, ASFV-infected endothelial cells died by apoptosis, detected morphologically by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling and nuclear condensation and biochemically by poly(ADP-ribose) polymerase (PARP) cleavage at 4 h postinfection (hpi). Immediate-early proinflammatory responses were inhibited, characterized by a lack of E-selectin surface expression and interleukin 6 (IL-6) and IL-8 mRNA synthesis. Moreover, ASFV actively downregulated interferon-induced major histocompatibility complex class I surface expression, a strategy by which viruses evade the immune system. Significantly, Western blot analysis showed that the 65-kDa subunit of the transcription factor NF-κB, a central regulator of the early response to viral infection, decreased by 8 hpi and disappeared by 18 hpi. Both disappearance of NF-κB p65 and cleavage of PARP were reversed by the caspase inhibitor z-VAD-fmk. Interestingly, surface expression and mRNA transcription of tissue factor, an important initiator of the coagulation cascade, increased 4 h after ASFV infection. These data suggest a central role for vascular endothelial cells in the hemorrhagic pathogenesis of the disease. Since BPECs infected with ASFV also undergo apoptosis, resistance of the natural host must involve complex pathological factors other than viral tropism.

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An African swine fever virus ORF with similarity to C-type lectins is non-essential for growth in swine macrophages in vitro and for virus virulence in domestic swine

Journal of General Virology ◽

10.1099/0022-1317-80-10-2693 ◽

1999 ◽

Vol 80 (10) ◽

pp. 2693-2697 ◽

Cited By ~ 28

Author(s):

J. G. Neilan ◽

M. V. Borca ◽

Z. Lu ◽

G. F. Kutish ◽

S. B. Kleiboeker ◽

...

Keyword(s):

African Swine Fever Virus ◽

African Swine Fever ◽

Fever Virus ◽

Virus Infectivity ◽

Mrna Transcription ◽

Host Cell Interactions ◽

Lectin Family ◽

Virus Replication Cycle ◽

Domestic Swine

An African swine fever virus (ASFV) ORF, 8CR, with similarity to the C-type lectin family of adhesion proteins has been described in the pathogenic isolate Malawi Lil-20/1. The similarity of 8CR to cellular and poxvirus genes associated with cell adhesion, cell recognition and virus infectivity suggested that 8CR may be of significance to ASFV–host cell interactions. Sequence analysis of the 8CR ORF from additional pathogenic ASFV isolates demonstrated conservation among isolates from both pig and tick sources. Northern blot analysis demonstrated 8CR mRNA transcription late in the virus replication cycle. A Malawi Lil-20/1 8CR deletion mutant (Δ8CR) was constructed to analyse 8CR function further. The growth characteristics in vitro of Δ8CR in porcine macrophage cell cultures were identical to those observed for parental virus. In domestic swine, Δ8CR exhibited an unaltered parental Malawi Lil- 20/1 disease and virulence phenotype. Thus, although well conserved among pathogenic ASFV field isolates, 8CR is non-essential for growth in porcine macrophages in vitro and for virus virulence in domestic swine.

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