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Title:Cytokine modulations by type I interferon suppression-negative and NF-κB activation-negative Porcine Reproductive and Respiratory Syndrome Virus
Author(s):Kim, Jineui
Advisor(s):Yoo, Dongwan; Lau, Gee; Wang, Leyi
Contributor(s):Yoo, Dongwan
Department / Program:Pathobiology
Discipline:VMS - Pathobiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):PRRSV
PRDC
type I IFN
NF-κB
cytokine modulations
Abstract:Porcine reproductive and respiratory syndrome virus (PRRSV) suppresses innate immunity, namely, type I interferons (IFNs-α/β) during infection and predisposes infected hosts to secondary bacterial infections. PRRSV also activates NF-κB signaling such that the secondary infection may trigger enhanced expression of proinflammatory cytokines. This series of cellular processes may result in severe porcine respiratory disease complex. Among the PRRSV proteins, nsp1β has been identified as the potent IFN antagonist, and leucine at position 135 in SAP (SAF-A/B, Acinus, and PIAS) motif is determined as the active residue for IFN suppression. For NF-κB activation, the viral nucleocapsid (N) protein has been found as the effector protein, and the nuclear localization signal (NLS) in N overlaps the NF-κB activation domain. In the present study, IFN suppression and NF-κB activation functions were eliminated individually from PRRSV by reverse genetics and extralong inverse PCR, and mutant viruses were generated: type I IFN suppression-negative PRRSV (P1β-∆135), NF-κB activation-negative PRRSV (PN-∆NLS), and both type I IFN suppression-negative and NF-κB activation-negative PRRSV (PD-∆135-NLS). These mutant viruses were then examined in cells for their immunological phenotype. Macrophages or MARC-145 cells were infected with wild-type or individual mutant PRRSVs alone or coinfected with Streptococcus suis (S. suis) Intracellular survival of S. suis was measured in coinfection groups, and NF-κB luciferase assays and RT-qPCR were used to determine cytokines modulations. PD-∆135-NLS most significantly attenuated the TNF-α, IL-1β, IL-6, and IL-8 expressions compared to those of wild-type PRRSV. The viability of S. suis was increased, and TNF-α and IL-1β were significantly upregulated in cells coinfected with wild-type PRRSV and S. suis compared to S. suis alone. In contrast, PD-∆135-NLS and S. suis coinfection did not enhance the infectivity of S. suis and the TNF-α and IL-1β productions compared to wild-type PRRSV and S. suis coinfection. Our study demonstrates that the SAP motif- and NLS motif- double mutant PRRSV attenuated the expression of proinflammatory cytokines compared to wild-type PRRSV. This finding supports the hypothesis that the mutant PRRSV may relieve the clinical severity of porcine respiratory disease complex caused by coinfections of PRRSV and other swine pathogens.
Issue Date:2020-07-22
Type:Thesis
URI:http://hdl.handle.net/2142/108726
Rights Information:Copyright 2020 Jineui Kim
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08


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