Antiviral activity of ISG15 against classical swine fever virus replication in porcine alveolar macrophages via inhibition of autophagy by ISGylating BECN1

Abstract

Interferons (IFNs) induce the expression of interferon-stimulated genes (ISGs) for defense against numerous viral infections, including classical swine fever virus (CSFV). However, the mechanisms underlying the effect of ISGs on CSFV infection are rarely reported. In this study, we demonstrate that IFN-α treatment induces upregulation of ISG15 and thus attenuates CSFV replication. To determine whether ISG15 is critical for controlling CSFV replication, we established porcine alveolar macrophages (PAMs) with stable overexpression or knockdown of ISG15. Overexpression of Flag-ISG15 significantly prevented CSFV replication, whereas loss of ISG15 led to abnormal proliferation of CSFV. Furthermore, upregulated ISG15 promoted beclin-1 (BECN1) ISGylation and dysfunction and subsequently inhibited autophagy, which is indispensable for CSFV replication. In addition, HECT and RLD domain containing E3 ubiquitin protein ligase 5 (HERC5), which functions to catalyze conjugation of ISG15 protein, was confirmed to interact with BECN1. Collectively, these results indicate that IFN-α restricts CSFV replication through ISG15-mediated BECN1 ISGylation and autophagy inhibition, providing insight into the mechanism of CSFV replication control by type I IFN. This mechanism may not be the only antiviral mechanism of ISG15; nonetheless, this study may contribute to the development of CSFV treatment and prevention strategies.

Targeting hub genes and pathways of innate immune response in COVID-19: A network biology perspective

“…Coronaviruses engages in interactions with [50,51]. The antiviral activity of ISG15 has been shown in several viruses including human cytomegalovirus [52], HIV [53], West Nile virus [54], swine fever virus [55], MERS-CoV [56], and SARS-CoV [57].…”

Anti-Classical Swine Fever Virus Strategies

“…(1) Once viral infection occurs, the type I interferon (IFN) path-way might be triggered, resulting in the expression of hundreds of interferon-stimulated genes (ISGs). Proteins encoded by ISGs, such as ISG15 [34], Viperin (RSAD2) [35,36], NRAMP1, NT5C3A, CXCL10, OAS1 [37], Mx (porcine Mx1, porcine Mx2, human MxA, and mouse Mx1) [38][39][40], GBP1 [41], pOASL [42], and IFITM family (IFITM1, IFITM2, and IFITM3) [43], have been shown to have anti-CSFV effects. Additionally, ISGs have been further used in the research of transgenic pigs resistant to CSFV.…”

“…( 1) Both IFNs and IFN-stimulated genes (ISGs) are important for the host to resist viral infection. IFNα/γ [34,108,109] and recombinant protein encoded by ISGs, such as porcine Mx1 fused to HIV Tat protein transduction domain (PTD-poMx1) [40,110], have anti-CSFV effects. The effect of IFN-α treatment on CSFV infection in swine was reported for the first time by Fernandez-Sainz et al [109].…”

More than Meets the ISG15: Emerging Roles in the DNA Damage Response and Beyond

“…HyperISGylation can even induce aberrant autophagy under genotoxic stress, at least in certain pathological circumstances [ 112 , 113 ]. By contrast, ISG15 can also have a negative effect on autophagy e.g., by ISGylation, and subsequent inhibition, of positive autophagy regulators ( Figure 3 , Section 5) [ 114 , 115 , 116 ]. In certain circumstances ISGylation can also protect proteins from lysosomal degradation, challenging the notion that ISG15 simply serves as a tag for selective autophagy [ 117 ].…”