SHORT COMMUNICATION NEW MICROBIOLOGICA, 39, 2, 139-142, 2016, ISN 1121-7138 Antiviral activity of human Vδ2 T-cells against WNV includes both cytolytic and non-cytolytic mechanisms Chiara Agrati 1,2 , Concetta Castilletti 2 , Eleonora Cimini 1 , Antonella Romanelli 1 , Daniele Lapa 2 , Serena Quartu 2 , Federico Martini 1 , Maria Rosaria Capobianchi 2 1 Cellular Immunology Laboratory; 2 Laboratory of Virology, “L. Spallanzani” National Institute for Infectious Diseases (INMI), Rome, Italy West Nile virus (WNV) is a re-emerging pathogen responsi- ble for fatal outbreaks of meningoencephalitis in humans. This plus-sense, single-stranded neurotropic flavivirus has been representing a public health concern in North Amer- ica for more than a decade (Campbell et al., 2002; Kramer et al., 2008). Infections in humans mainly result from mos- quito bites, but may also be acquired through blood trans- fusion, organ transplantation and breast feeding (2002a; 2002b; Campbell et al., 2002; Charatan, 2002). Although human infection is usually asymptomatic, life-threaten- ing neurological disease including encephalitis can ensue, particularly in the elderly and in immunocompromised hosts (Chowers et al., 2001; Nash et al., 2001). At present, there is no specific therapeutic agent available for either treatment or approved human vaccine for prevention. The analysis of WNV pathogenesis and host immune re- sponse has mainly been performed using the mouse model of WNV infection (Beasley et al., 2002; Kramer et al., 2001). In this system, both innate and adaptive immune systems contribute to WNV infection control (Diamond et al., 2003a). In fact, B cells and specific antibodies are critical in controlling viral dissemination (Diamond et al., 2003b; Roehrig et al., 2001), while αβ T-cells provide long-lasting protective immunity and contribute to host survival fol- Corresponding author: Maria Rosaria Capobianchi E-mail: maria.capobianchi@inmi.it ©2016 by EDIMES - Edizioni Internazionali Srl. All rights reserved lowing WNV infection (Sitati et al., 2006). Among innate immune cells, gδ T-cells provide a rapid response during WNV infection in mice, limiting the viral load and protect- ing the host from lethal encephalitis (Wang, 2011; Wang et al., 2013). Murine gδ T-cells expand quickly in response to WNV infection, produce significant amounts of IFN-g (Wang et al., 2003) and promote the maturation of den- dritic cells, resulting in an improved CD4 T-cell response (Fang et al., 2010). Moreover, gδ T-cell-deficient mice have a reduced CD8+ T-cell memory response and are more sus- ceptible to secondary WNV infection, suggesting a role of murine gδ T-cells in linkage of innate immunity to adap- tive immune responses (Wang et al., 2006). Although the murine model represents an effective experimental model to investigate WNV pathogenesis and host immunity, gδ T-cell subsets show substantial differences between mice and humans. In humans, gδ T-cells account for approxi- mately 1%-5% of circulating T-cells, and most of them bear the Vg9Vδ2 T-cell receptor (TCR) (Born et al., 2006; Carding et al., 2002). Specifically, proliferative, cytotoxic, and cytokine responses of the human Vδ2 T cell subset are induced by both nonpeptidic antigens, and nitrogen-con- taining bisphosphonates (N-BPs), such as zoledronic acid (ZA) (Dieli et al., 2003; Hayday, 2000). Vδ2 T-cells can be easily activated in vivo by N-BP, and have been proposed as a target for innovative approaches to the immunother- apy of viral infections (Deniger et al., 2014; Poccia et al., 2005b). Notably, human Vδ2 T-cells are known to exert broad antiviral activities against different viruses through both cytolytic and non-cytolytic mechanisms (Agrati et al., 2006a; Agrati et al., 2006b; Poccia et al., 1999; 2005a; SUMMARY West Nile virus (WNV) causes a severe central nervous system infection in humans, primarily in the elderly and immunocompromised subjects. Human gδ T-cells play a critical role in the immune response against viruses, and studies of WNV meningoencephalitis in laboratory mice described a role of gδ T-cells in the protective immune response. Aim of this study was to analyze the cytolytic and non-cyto- lytic antiviral activity of human Vδ2 T-cells against WNV replication. The anti-WNV activity of soluble factor released by zoledronic acid (ZA)-activated Vδ2 T-cell lines and the cytotoxic capability of Vδ2 T-cell lines against WNV-infected cells were tested in vitro. The activation of Vδ2 T-cell lines was able to inhibit WNV replication through the release of soluble factors. IFN-g is massively released by activated Vδ2 T-cell lines and is involved in the anti-WNV activity. Moreover, the Vδ2 T-cell lines can efficiently kill WNV-infected cells possibly through perforin-mediated mechanism. Altogether, our results provide insight into the effector functions of human Vδ2 T-cells against WNV. The possibility to target these cells by ZA, a commercially available drug used in humans, could potentially offer a new immunotherapeutic strategy for WNV infection. Received December 9, 2015 Accepted March 11, 2016 Key words: Innate immunity, gδ T-cells, IFN-g, cytotoxicity.