The virus’s non-structural (NS) proteins induce cell-mediated immune responses that may also play a protective role [20], [21], [22] and [23]. We previously designed and optimized a recombinant subunit vaccine against BTV-8 composed of VP2 from BTV-8 and NS1 and NS2 from BTV-2, with a Libraries VP7-based DIVA characteristic [24] that can potentially be used to detect antibodies in samples from animals infected with IWR-1 any serotype [25]. We determined that, in cattle, this vaccine induced strong neutralizing antibody titers, VP2-, NS1-, and NS2-specific antibodies, and cellular immune responses to NS1

[26] that may contribute to a successful multi-serotype vaccine [27]. Here, we aimed to evaluate the clinical and virological protective efficacy of the experimental vaccine against virulent BTV-8 challenge in cattle and to verify its DIVA compliancy using existing Selleckchem Cobimetinib diagnostic assays. Recombinant VP2 of BTV-8 and NS1 and NS2 of BTV-2 were produced and purified as described previously [26]. Each 2.5 ml subunit vaccine

(SubV) dose contained 150 μg each of purified VP2, NS1, and NS2 and 450 μg AbISCO®-300 (Isconova AB, Sweden), an immunostimulating complex (ISCOM)-based adjuvant. To induce both a viremia and clinical signs associated to BTV, the challenge virus consisted of two viral cell suspensions of BTV-8 strain isolated from a BTV-8-viremic cow during a 2007 outbreak in France, on (i) embryonated chicken eggs (ECE) and passaged twice on baby hamster kidney (BHK-21) cells (BHK suspension; 6 × 106 of 50% tissue culture infective dose (TCID50)/ml, or (ii) Culicoides-derived (KC) cells (kindly provided by the Pirbright

Institute, UK) followed by one passage on the same cell line for virus amplification (KC suspension). The KC suspension was analyzed by RT-qPCR (Adiavet™ BTV Realtime ADI352, Adiagene, France) and resulted in a Ct value of 14.1. Twelve conventionally reared female Holstein calves aged 6–12 months were housed in the Biosecurity Level 3 animal facilities of the National Institute of Agricultural Research (INRA) Research Center (Nouzilly, France). The not calves originated from the same BVDV- and BHV1-free herd, were seronegative for BTV antibodies, and were not previously vaccinated against BTV. Animals were divided randomly into two groups (n = 6) and housed in the same room, separated by a fence. All procedures were approved by the ethical review board of Val de Loire (CEEA VdL, committee number n°19, file number 2012-08-01). Animals were immunized subcutaneously on the left side of the neck at a 3-week interval with SubV or with 450 μg AbISCO®-300 in PBS (Control). Three weeks after second vaccination all animals were subcutaneously inoculated with 2.5 ml each of BTV-8 preparations on the right (BHK suspension) and left (KC suspension) sides of the neck (post-infection day 0 (PID0)).