Regulation of Viral Replication, Apoptosis and Pro-Inflammatory Responses by 17-AAG during Chikungunya Virus Infection in Macrophages.

Tapas Nayak,Laishram Singh,Soma Chattopadhyay,Subhasis Chattopadhyay,Abhishek Kumar,Subhransu Sahoo,Prabhudutta Mamidi

doi:10.3390/v9010003

Abstract

Chikungunya virus (CHIKV) infection has re-emerged as a major public health concern due to its recent worldwide epidemics and lack of control measures. Although CHIKV is known to infect macrophages, regulation of CHIKV replication, apoptosis and immune responses towards macrophages are not well understood. Accordingly, the Raw264.7 cells, a mouse macrophage cell line, were infected with CHIKV and viral replication as well as new viral progeny release was assessed by flow cytometry and plaque assay, respectively. Moreover, host immune modulation and apoptosis were studied through flow cytometry, Western blot and ELISA. Our current findings suggest that expression of CHIKV proteins were maximum at 8 hpi and the release of new viral progenies were remarkably increased around 12 hpi. The induction of Annexin V binding, cleaved caspase-3, cleaved caspase-9 and cleaved caspase-8 in CHIKV infected macrophages suggests activation of apoptosis through both intrinsic and extrinsic pathways. The pro-inflammatory mediators (TNF and IL-6) MHC-I/II and B7.2 (CD86) were also up-regulated during infection over time. Further, 17-AAG, a potential HSP90 inhibitor, was found to regulate CHIKV infection, apoptosis and pro-inflammatory cytokine/chemokine productions of host macrophages significantly. Hence, the present findings might bring new insight into the therapeutic implication in CHIKV disease biology.

Highlights

Chikungunya virus (CHIKV), a mosquito borne re-emerging Alphavirus, belonging to the Togaviridae family, is endemic mainly in Africa, India, China and many other parts of Asia [1,2,3,4]
The expression pattern of these two CHIKV proteins was assessed by Flow Cytometry (FC) and it was observed that, both nsP2 and E2 were detected as early as 4 hpi, while the highest level of proteins were noticed at 8 hpi followed by Viruses 2016, 8, 339
The current study provides thatalteration there is an alterationresponses in immune responses of mouse (Raw264.7 cell line)

Summary

Introduction

Chikungunya virus (CHIKV), a mosquito borne re-emerging Alphavirus, belonging to the Togaviridae family, is endemic mainly in Africa, India, China and many other parts of Asia [1,2,3,4]. It was first isolated from Tanzania (formerly Tanganyika), Africa in 1952 during an epidemic of dengue-like illness [5]. Aedes mosquitoes and maintained in two distinct transmission cycles: urban cycle between human and mosquitoes and sylvatic cycle within forest dwelling mosquitoes and non-human primates [17] It is an enveloped virus, containing 11.8 kb long single stranded positive sense RNA genome with two open reading frames (ORF). The 50 ORF codes for non-structural proteins, nsP1-4, mainly involved in viral replication and 30 ORF codes for three major structural proteins, capsid, E1 and E2 [18]

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