Disabled infectious single animal (DISA) vaccine against Bluetongue by deletion of viroporin-like NS3/NS3a expression is effective, safe, and enables differentiation of infected from vaccinated animals (DIVA)

Authors: FEENSTRA, FEMKE - Utrecht University; VAN GENNIP, RENE - Utrecht University; VAN DE WATER, SANDRA - Utrecht University; Drolet, Barbara; MARIS-VELDHUIS, MIEKE - Utrecht University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/12/2015
Publication Date: 10/6/2015
Citation: Feenstra, F., Van Gennip, R., Van De Water, S., Drolet, B.S., Maris-Veldhuis, M. 2015. Disabled infectious single animal (DISA) vaccine against Bluetongue by deletion of viroporin-like NS3/NS3a expression is effective, safe, and enables differentiation of infected from vaccinated animals (DIVA). Meeting Abstract. 12: 153.

Interpretive Summary:

Technical Abstract: The prototype virus species of the genus Orbivirus (family Reoviridae) is bluetongue virus (BTV) consisting of at least 27 serotypes. Bluetongue is a noncontagious haemorrhagic disease of ruminants spread by competent species of Culicoides biting midges in large parts of the world leading to huge economic losses. The best strategy for combatting arboviral diseases is vaccination. Currently, live-attenuated and inactivated vaccines for a few serotypes are available, however, each having their specific disadvantages. Outer capsid VP2 protein of orbiviruses is the main serotype determining protein inducing neutralizing immune responses. Serogroup specific VP7 protein and non-structural protein NS3/NS3a are also immunogenic but antibodies are not neutralizing. NS3/NS3a is a viroporin-like membrane associated protein involved in virus release, cytopathogenic effect, and interferon antagonism. BTV release from insect cells is non-lytic, whereas release from mammalian cells occurs via both lytic and non-lytic pathways. We show that NS3/NS3a is not essential for virus replication in vitro. Knockout of NS3/NS3a lead to delayed virus release from mammalian cells with strongly reduced cytopathogenic effect, whereas release from insect cells is very low. BTV without NS3/NS3a replicates only locally in vivo in sheep not causing viremia, is completely avirulent, and induces sterile immunity against virulent BTV. Virus propagation in competent C. sonorensis midges in vivo is strongly abolished, indicating that spread by the insect vector is highly unlikely. Taken together, NS3/NS3a deletion is a powerful safety element of live-attenuated replicating vaccine by blocking arthropod transmission, and the BTV NS3/NS3a knockout mutant is therefore named “Disabled Infectious Single Animal (DISA) vaccine”. Since the immune response against NS3/NS3a is absent in vaccinated ruminants, DISA vaccine also enables detection of infected animals in vaccinated populations (differentiation of infected from vaccinated animals (DIVA), which is an important tool for disease control and livestock trade purposes. We studied VP2 exchange to apply the BT DISA vaccine platform for more serotypes, and demonstrate that single VP2 exchange is limited. Therefore, BT DISA vaccines with chimeric VP2 proteins containing predicted neutralizing epitopes were developed and used to immunize sheep. Neutralizing humoral responses against both involved serotypes were raised suggesting a broader application and the potential of bivalent BT DISA vaccines. Development of DISA vaccines for the orbivirus species African horse sickness virus is in progress. We propose that our DISA strategy might be also applicable for other arthropod-borne viruses in order to block spread of replicating vaccines.