African horse sickness virus NS4 protein is an important virulence factor and interferes with JAK-STAT signaling during viral infection.
Abstract: African horse sickness virus (AHSV) non-structural protein NS4 is a nucleocytoplasmic protein that is expressed in the heart, lung, and spleen of infected horses, binds dsDNA, and colocalizes with promyelocytic leukemia nuclear bodies (PML-NBs). The aim of this study was to investigate the role of AHSV NS4 in viral replication, virulence and the host immune response. Using a reverse genetics-derived virulent strain of AHSV-5 and NS4 deletion mutants, we showed that knockdown of NS4 expression has no impact in cell culture, but results in virus attenuation in infected horses. RNA sequencing (RNA-seq) was used to investigate the transcriptional response in these horses, to see how the lack of NS4 mediates the transition of the virus from virulent to attenuated. The presence of NS4 was shown to result in a 24 hour (h) delay in the transcriptional activation of several immune system processes compared to when the protein was absent. Included in these processes were the RIG-I-like, Toll-like receptor, and JAK-STAT signaling pathways, which are key pathways involved in innate immunity and the antiviral response. Thus, it was shown that AHSV NS4 suppresses the host innate immune transcriptional response in the early stages of the infection cycle. We investigated whether AHSV NS4 affects the innate immune response by impacting the JAK-STAT signaling pathway specifically. Using confocal laser scanning microscopy (CLSM) we showed that AHSV NS4 disrupts JAK-STAT signaling by interfering with the phosphorylation and/or translocation of STAT1 and pSTAT1 into the nucleus. Overall, these results showed that AHSV NS4 is a key virulence factor in horses and allows AHSV to overcome host antiviral responses in order to promote viral replication and spread.
Copyright © 2021. Published by Elsevier B.V.
Publication Date: 2021-04-01 PubMed ID: 33812899DOI: 10.1016/j.virusres.2021.198407Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research examines the role of African horse sickness virus NS4 protein in viral replication, virulence and host immune response. The study shows NS4 suppresses the activation of key immune response pathways, thus making it a significant factor in the virulence of the virus in horses.
Introduction
- The researchers aim to investigate the role of AHSV non-structural protein NS4 in viral replication, virulence, and the horse’s immune response to infection.
- NS4 is found in the heart, lungs, and spleen of infected horses and has been shown to bind dsDNA.
Methods
- A virulent strain of AHSV-5 and NS4 deletion mutants were used to determine the impact of NS4 on the virus and the infected host.
- RNA sequencing was implemented to study the transcriptional response in horses and see how the absence of NS4 affected the transition of the virus from virulent to attenuated.
- Confocal laser scanning microscopy was used to examine how the NS4 protein affects the innate immune response, specifically the JAK-STAT signaling pathway.
Results & Discussion
- The absence of NS4 in the virus did not impact cell cultures but did result in virus attenuation in infected horses, indicating its role in virulence.
- The presence of NS4 led to a 24-hour delay in the transcriptional activation of several immune system processes, which included RIG-I-like, Toll-like receptor, and JAK-STAT signaling pathways that are key to innate immunity and antiviral response.
- This indicates that AHSV NS4 suppresses the host innate immune transcriptional response early in the infection cycle.
- Further analysis showed that AHSV NS4 disrupts the JAK-STAT signaling, a crucial immunity response pathway, by hindering the phosphorylation and/or translocation of STAT1 and pSTAT1 into the nucleus.
- In conclusion, the study shows that the AHSV NS4 protein plays a significant role in the virulence of the virus in horses by suppressing the host’s immune response and promoting viral replication.
Cite This Article
APA
Wall GV, Wright IM, Barnardo C, Erasmus BJ, van Staden V, Potgieter AC.
(2021).
African horse sickness virus NS4 protein is an important virulence factor and interferes with JAK-STAT signaling during viral infection.
Virus Res, 298, 198407.
https://doi.org/10.1016/j.virusres.2021.198407 Publication
Researcher Affiliations
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, 0002, South Africa.
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa.
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa.
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa.
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, 0002, South Africa.
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa; Department of Biochemistry, Focus Area for Human Metabolomics, North-West University, Potchefstroom, South Africa. Electronic address: christiaan@deltamune.co.za.
MeSH Terms
- African Horse Sickness
- African Horse Sickness Virus / genetics
- Animals
- Horses
- Signal Transduction
- Viral Nonstructural Proteins / genetics
- Viral Nonstructural Proteins / metabolism
- Virulence Factors / genetics
- Virulence Factors / metabolism
Citations
This article has been cited 5 times.- Zhang M, Wang XF, Guo SF, Wang L, Fu BF, Wang JW, Song YF, Yang XY, Hao SY, Zhang QY, Zhang B, Yang CH. Identification and Genetic Characterization of a Strain of African Horse Sickness Virus Serotype 1 and Its Safety Evaluation in a Mouse Model. Microorganisms 2025 Oct 6;13(10).
- Xu B, Jiang C, Di L, Zhou L, Wang Z, Tang Y, Fang R, Wang H. Novel Duck Orthoreovirus σA Protein Inhibits Interferon Signaling by Impeding STAT1/STAT2 Nuclear Translocation. Transbound Emerg Dis 2025;2025:8440800.
- Ma X, Zhang Y, Na L, Qi T, Ma W, Guo X, Wang XF, Wang X. Identification and Characterization of Linear Epitopes of Monoclonal Antibodies Against African Horse Sickness Virus Serotype 1 VP2 Protein. Viruses 2024 Nov 15;16(11).
- Mohd Jaafar F, Belhouchet M, Monsion B, Bell-Sakyi L, Mertens PPC, Attoui H. Orbivirus NS4 Proteins Play Multiple Roles to Dampen Cellular Responses. Viruses 2023 Sep 12;15(9).
- Clemmons EA, Alfson KJ, Dutton JW 3rd. Transboundary Animal Diseases, an Overview of 17 Diseases with Potential for Global Spread and Serious Consequences. Animals (Basel) 2021 Jul 8;11(7).
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