Plant‐made E2 glycoprotein single‐dose vaccine protects pigs against classical swine fever

Abstract

Classical Swine Fever Virus (CSFV) causes classical swine fever, a highly contagious hemorrhagic fever affecting both feral and domesticated pigs. Outbreaks of CSF in Europe, Asia, Africa and South America had significant adverse impacts on animal health, food security and the pig industry. The disease is generally contained by prevention of exposure through import restrictions (e.g. banning import of live pigs and pork products), localized vaccination programmes and culling of infected or at-risk animals, often at very high cost. Current CSFV-modified live virus vaccines are protective, but do not allow differentiation of infected from vaccinated animals (DIVA), a critical aspect of disease surveillance programmes. Alternatively, first-generation subunit vaccines using the viral protein E2 allow for use of DIVA diagnostic tests, but are slow to induce a protective response, provide limited prevention of vertical transmission and may fail to block viral shedding. CSFV E2 subunit vaccines from a baculovirus/insect cell system have been developed for several vaccination campaigns in Europe and Asia. However, this expression system is considered expensive for a veterinary vaccine and is not ideal for wide-spread deployment. To address the issues of scalability, cost of production and immunogenicity, we have employed an Agrobacterium-mediated transient expression platform in Nicotiana benthamiana and formulated the purified antigen in novel oil-in-water emulsion adjuvants. We report the manufacturing of adjuvanted, plant-made CSFV E2 subunit vaccine. The vaccine provided complete protection in challenged pigs, even after single-dose vaccination, which was accompanied by strong virus neutralization antibody responses.

A classical swine fever virus E2 fusion protein produced in plants elicits a neutralizing humoral immune response in mice and pigs

“…The expected size of the E2 recombinant protein is 64 kD; therefore, the strong band appeared to be larger than expected. We assume that this is due to N-glycosylation since E2 protein has putative 7 N-glycosylation sites (Laughlin et al 2019). Consistent with this, previous studies reported that CBD-fused E2 recombinant proteins have several N-glycosylation sites and are larger than expected when expressed in plants (Park et al 2019;Sohn et al 2018).…”

“…In addition, Arabidopsis thaliana-derived E2 antibodies in a mouse can recognize the native E2 protein suggesting that structure of plant-produced E2 is comparable to native E2 protein (Sohn et al 2018). In addition, transient expression of recombinant E2 protein from the leaves of Nicotiana benthamiana or from the leaves of transgenic N. benthamiana lines generates antibodies that can neutralize CSFV in pigs and protect them against subsequent challenge with CSFV (Laughlin et al 2019;Park et al 2019).…”

A neutralizing monoclonal antibody-based competitive ELISA for classical swine fever C-strain post–vaccination monitoring

“…The authors suggested that as cELISA proved to be nearly as sensitive and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for CDV or PDV cases [23]. The glycoprotein E2 exposed on the outer surface of CSFV is the major immuno-protective antigen of C-strain vaccine that is responsible for inducing neutralizing antibodies and eliciting protective immunity against CSFV [13][14][15][16][17][18][19][20]. Thus, it is not surprising that E2 protein has been successfully used to develop ELISAs to measure anti-CSFV antibody response in pigs after vaccination [13][14][15][16].…”

“…Virus neutralization test (VNT) is considered as the gold standard for serological monitoring and efficacy evaluation of CSF vaccines. However, it has several limitations including time-consuming, requirement of cell culture, the need for live virus manipulation, and relatively expensive [2,[18][19][20][21]. Here, we described a competitive ELISA (cELISA) developed with a neutralizing anti-E2 monoclonal antibody.…”

A neutralizing monoclonal antibody-based competitive ELISA for classical swine fever C-strain post–vaccination monitoring

“…In this study, we developed a neutralizing mAb based cELISA with the emphasis on the replacement of and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for CDV or PDV cases [23]. The glycoprotein E2 exposed on the outer surface of CSFV is the major immuno-protective antigen of C-strain vaccine that is responsible for inducing neutralizing antibodies and eliciting protective immunity against CSFV [13][14][15][16][17][18][19][20]. Thus, it is not surprising that E2 protein has been successfully used to develop ELISAs to measure anti-CSFV antibody response in pigs after vaccination [13][14][15][16].…”