Kinetics of the West Nile virus induced transcripts of selected cytokines and Toll-like receptors in equine peripheral blood mononuclear cells.

Muhammad Jasim Uddin,Helle Bielefeldt-Ohmann,Richard A Bowen,Angela Bosco-Lauth,Willy W Suen,Airn-Elizabeth Hartwig,Roy A Hall

doi:10.1186/s13567-016-0347-8

Muhammad Jasim Uddin, Helle Bielefeldt-Ohmann + Show 5 more

Open Access

https://doi.org/10.1186/s13567-016-0347-8

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Abstract

West Nile virus (WNV) is one of the most common causes of epidemic viral encephalitis in horses worldwide. Peripheral blood mononuclear cells (PBMCs) are amongst the first to encounter the virus following a mosquito bite. This study aimed to elucidate the transcription kinetics of cytokine, Toll-like receptor (TLRs) and TLRs-associated genes following WNV challenge of equine PBMCs. PBMCs were challenged with an Australian strain of WNV (WNVNSW2011) and transcriptomes were quantified at 2, 6, 12 and 24 h post-infection (pi) using qRT-PCR. Type I and II interferons (IFNα, β and γ) mRNA transcription increased following WNV exposure, as did the transcripts for IL1α, IL1β, IL6, IL8, and IL22, but with slightly varying kinetics. TLR1, 3, 5, 7-9 transcripts were also upregulated in equine PBMCsin response to WNV challenge, as were those for MyD88, NF-κB, TRAF3, STAT1 and 2, IRF3 and 7, ISG15, as well as SOCS1 and 3 compared to the control cells. Expression of selected genes in the draining lymph node, spleen and brain (medulla oblongata) of experimentally infected horses was also assessed and transcription of most of these genes was also upregulated here. Although qRT-PCR detected higher viral RNA at 24 h pi compared to 6 h pi, the virus did not replicate productively in equine PBMCs. The up-regulation of gene-transcription for selected cytokines, IFNs, TLRs and TLRs-associated molecules suggests their involvement in virus recognition and control of WNV infection in the horse.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0347-8) contains supplementary material, which is available to authorized users.

Highlights

West Nile virus (WNV), a mosquito-borne flavivirus, is widely distributed throughout Africa, the Middle East, Asia, Southern Europe, the Americas and Australia [1]
IL22 mRNA expression was 75 fold higher in WNV-stimulated Periph‐ eral blood mononuclear cells (PBMCs) compared to mock-inoculated PBMCs, whereas steady state expression of TNFα and IL12 mRNA was observed over times (Additional file 1A)
TLR1, 3, 5, 7 and 9 mRNA expressionsall became upregulated within 2–24 h of in vitro virus challenge of horse PBMCs suggestive of their involvement in the WNV-induced innate immune response in this species

Summary

Introduction

West Nile virus (WNV), a mosquito-borne flavivirus, is widely distributed throughout Africa, the Middle East, Asia, Southern Europe, the Americas and Australia [1]. The host must recognise invasion and develop an effective antiviral immune response. This response is initiated in infected cells after detection of virus by specific, conserved host molecules, such as Toll-like receptors (TLRs) which trigger signalling cascades that induce the activation of transcription factor NF-κB, IFN regulatory factors (IRFs), including IFNs and hundreds of different IFN-stimulated effector genes (ISGs) [8]. The ISG products include antiviral effector molecules and immunomodulatory cytokines that serve to restrict virus replication and modulate the adaptive immune response [15]. These signalling pathways have been studied predominantly in mice (reviewed in [8]), with only limited studies in horses [18]. While WNVNY99 causes severe neuropathology and death in mice, WNVKUN mostly causes only subclinical infection in horses and rabbits [23]

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