Author's personal copy Vaccine 32 (2014) 949–956 Contents lists available at ScienceDirect Vaccine jou rn al hom ep age: www.elsevier.com/locat e/vaccine Recombinant chimeric Japanese encephalitis virus/tick-borne encephalitis virus is attenuated and protective in mice Hong-Jiang Wang a,1 , Xiao-Feng Li a,1 , Qing Ye a , Shi-Hua Li a , Yong-Qiang Deng a , Hui Zhao a , Yan-Peng Xu a , Jie Ma a , E-De Qin a , Cheng-Feng Qin a,b,∗ a Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China b Graduate School, Anhui Medical University, Hefei, China a r t i c l e i n f o Article history: Received 9 July 2013 Received in revised form 14 November 2013 Accepted 18 December 2013 Available online 4 January 2014 Keywords: Tick-borne encephalitis virus Japanese encephalitis virus Vaccine Chimeric flavivirus a b s t r a c t Tick-borne encephalitis virus (TBEV) represents one of the most dangerous human pathogens circulating in Europe and East Asia. No effective treatment for TBEV infection currently exists, and vaccination is the primary preventive measure. Although several inactivated vaccines have been licensed, the develop- ment of novel vaccines against TBEV remains a high priority in disease-endemic countries. In the present study, a live chimeric recombinant TBEV (ChinTBEV) was created by substituting the major structural genes of TBEV for the corresponding regions of Japanese encephalitis virus (JEV) live vaccine strain SA14- 14-2. The resulting chimera had a small-plaque phenotype, replicated efficiently in both mammalian and mosquito cells. The preliminary data from in vitro passaging indicated the potential for stability of ChinTBEV. ChinTBEV also exhibited significantly attenuated neuroinvasiveness in mice upon either intraperitoneal or subcutaneous inoculation in comparison with its parental TBEV. Importantly, a sin- gle immunisation with ChinTBEV elicited TBEV-specific IgG and neutralising antibody responses in a dose-dependent manner, providing significant protection against lethal TBEV challenge in mice. Taken together, the results of this proof-of-concept study indicate that ChinTBEV can be further developed as a potential vaccine candidate against TBEV infection. Moreover, the construction of this type of flavivirus chimera using a JEV vaccine strain as the genetic backbone represents a universal vaccine approach. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Tick-borne encephalitis (TBE) is the most serious tick- transmitted human infection in Europe and Asia, accounting for approximately 8500 human cases annually [1–5]. During the last few decades, new endemic foci and a great increase in TBE morbidity have been reported in many European and Asian countries [6,7]. This infection is characterised by typical neurolog- ical complications, such as meningitis, meningoencephalitis and encephalomyelitis/radiculitis, in both children and adults [3]. The causative agent, TBE virus (TBEV), belongs to the genus Flavivirus within the family Flaviviridae, which also contains other impor- tant human pathogens, including yellow fever virus (YFV), dengue virus (DENV), Japanese encephalitis virus (JEV) and West Nile virus (WNV). TBEV contains an approximately 11-kb positive-sense single-stranded RNA genome flanked by 5 ′ - and 3 ′ -untranslated regions (UTRs) and encodes a polyprotein that is proteolytically ∗ Corresponding author at: Department of Virology, Beijing Institute of Microbi- ology and Epidemiology, Beijing 100071, China. Tel.: +86 1066948604. E-mail addresses: qincf@bmi.ac.cn, chengfeng qin@126.com (C.-F. Qin). 1 These authors contribute equally to this work. cleaved into three structural proteins (C, prM and E) and seven nonstructural proteins. TBEV can be divided into three genetically related subtypes: the European, Siberian and Far Eastern subtypes [8]. No effective treatment for TBEV infection is currently avail- able. Currently, vaccination offers the most effective protection against TBE, and the vaccine has been introduced into many disease-endemic countries. There are at least four inactivated, cell culture-derived vaccines currently available, including Encepur ® and TBE-Immun ® , which are manufactured in Western Europe, as well as TBE-Moscow vaccine ® and EnceVir ® , which are manufac- tured in Russia [9,10]. Although the current vaccination schedules using these inactivated vaccines have led to a dramatic decline in the annual incidence of the disease [11], the requirement of multiple doses for primary and booster immunisations and the relatively high cost influence the success of TBEV immunisation programmes. Moreover, post-vaccination fever has been well doc- umented, particularly in young children [12,13]. Although rare, vaccination failures have also been reported with use of the current inactivated TBEV vaccines [14–20]. In addition to killed vaccines, live attenuated vaccines have been demonstrated to induce long-term immunity at low cost. Two prominent flavivirus vaccines, the yellow fever live vaccine (strain 0264-410X/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.vaccine.2013.12.050