Please cite this article in press as: Adhya, D., et al., Histone deacetylase inhibition by Japanese encephalitis virus in monocyte/macrophages: A novel viral immune evasion strategy. Immunobiology (2013), http://dx.doi.org/10.1016/j.imbio.2013.04.018 ARTICLE IN PRESS G Model IMBIO-51034; No. of Pages 13 Immunobiology xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Immunobiology jou rn al hom ep age: www.elsevier.com/locate/imbio Histone deacetylase inhibition by Japanese encephalitis virus in monocyte/macrophages: A novel viral immune evasion strategy Dwaipayan Adhya 1 , Kallol Dutta 2 , Kiran Kundu, Anirban Basu ∗ National Brain Research Centre, Manesar, Haryana 122051, India a r t i c l e i n f o Article history: Received 29 November 2012 Accepted 21 April 2013 Available online xxx Keywords: Antigen presentation Histone deacetylase Immune evasion Inflammation Interferon Japanese encephalitis virus Macrophage a b s t r a c t Japanese encephalitis virus (JEV) is a common cause of encephalitis in humans who are dead-end hosts producing negligible viremia. The virus reaches the brain and causes massive inflammation. Our study seeks to understand the virus–host interaction using the murine monocyte/macrophage cell line RAW264.7, an antigen presenting cell involved in eliciting an innate immune response. We have dis- covered several interesting phenomena occurring in JEV-infected RAW264.7 cells which diverge from established observations. JEV remains inside RAW264.7 and appears to have little negative effect on cell viability. Expression studies of major histocompatibility complexes (MHC) and co-stimulatory molecules show inhibition of antigen presentation. There is enhanced immune suppression creating an anti-viral milieu. Expression of pro-inflammatory cytokines and chemokines is suppressed along with increased expression of anti-inflammatory molecules. Histone deacetylases (HDACs) have known inflammatory properties. In our study, through modulation of HDACs JEV seems to induce a crucial anti-inflammatory and anti-viral role in host macrophages. © 2013 Elsevier GmbH. All rights reserved. Introduction Viruses share a unique relationship with their hosts. Organisms which have developed mechanisms to avoid or limit virus infec- tion are favored by natural selection. On the other hand, there are numerous viruses with well-developed mechanisms to evade host’s natural defenses (Lobo et al. 2009). Japanese encephalitis virus (JEV) is a neurotropic flavivirus that is endemic to a vast geographical realm, mostly affecting children below the age of 15 years. According to the WHO, JEV causes approximately 10,000–15,000 deaths annually (Solomon et al. 2008). Considering the fact that only 1 out of 300 infected individuals is symptomatic for Japanese encephalitis (JE) (Mathur et al. 1992), the actual number of infected in the population could be Abbreviations: APC, antigen-presenting cell; CCL-2, chemokine (C-C motif) ligand 2; EGCG, epigallocatechin gallate; HDAC, histone deacetylase; IDO, indoleamine 2,3-dioxygenase; IFN, interferon; IL-6, interleukin 6; IRF3, Interferon regulatory factor 3; JEV, Japanese encephalitis virus; MHC, major histocompati- bility complex; NFB, nuclear factor kappa B; P38MAPK, p38 mitogen-activated protein kinases; RSAD2, radical S-adenosyl methionine domain-containing protein 2; STAT1, signal transducer and activator of transcription 1; TNF, tumor necrosis factor-alpha; VPA, valproic acid. ∗ Corresponding author. Tel.: +91 124 2845225; fax: +91 124 2338910/28. E-mail address: anirban@nbrc.ac.in (A. Basu). 1 Current address: Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK. 2 Current address: Department of Psychiatry and Neuroscience, Research Center of the University Hospital Center of Quebec, Laval University, Canada. much higher. It is possible that the virus evades immune detection and persists within the host for a significantly long period of time. Virus latency and recurrence of infection has been reported in human patients of JE (Sharma et al. 1991), and peripheral blood mononuclear cells have been implicated in such processes. JEV can survive within peripheral macrophages (Aleyas et al. 2009; Dutta et al. 2010), but whether it is related with avoidance of immune detection is unknown. The macrophage being an antigen presenting cell (APC) should express viral antigens on its surface via class I MHC molecules for their detection by T cells. Multiple studies have shown that JEV infection causes up-regulation of MHC-I, though none of these studies involved APCs (Abraham and Manjunath 2006; Abraham et al. 2008, 2010; Das et al. 2009; King and Kesson 1998). However, it has been observed that JEV infection failed to upregulate co-stimulatory and MHC-II molecules in dendritic cells (Aleyas et al. 2009). Also, certain viruses have developed ways to bypass the MHC-I antigen presentation pathway and subsequently escape T cell-mediated killing (Coscoy and Ganem 2000; Fruh et al. 1995; Wiertz et al. 1996). However, there is little data in favor of such mechanisms in flaviviral infection of macrophages. Macrophages are cells produced by the differentiation of mono- cytes. Microglial cells, originating from the same lineage also differentiate from monocytes before settling into their antigen pre- senting role in the central nervous system (Ritter et al. 2006). Studies on microglial response to JEV infection have shown a significantly elevated activation state with increased release of pro- inflammatory mediators such as TNF, IL-6 and CCL-2 inducing neuronal death (Ghoshal et al. 2007). 0171-2985/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.imbio.2013.04.018