Novel Japanese encephalitis virus NS1-based vaccine: Truncated NS1 fused with E. coli heat labile enterotoxin B subunit

Abstract

Background: Current vaccines against Japanese encephalitis virus (JEV) of flaviviruses have some disadvantages, such as the risk of virulent reversion. Non-structural protein NS1 is conserved among flaviviruses and confers immune protection without the risk of antibody-dependent enhancement (ADE). Therefore, NS1 has become a promising vaccine candidate against flaviviruses. Methods: A NS1-based vaccine (LTB-NS1 Δ63 ) with a truncated NS1 protein (NS1 Δ63 ) fused to E. coli heat-labile enterotoxin B subunit (LTB) was expressed in E.coli and explored for its ability to induce immune responses. Safety of LTB-NS1 Δ63 was assessed by determining its toxicity in vitro and in vivo. Protective capability of LTB-NS1 Δ63 and its-induced antisera was evaluated in the mice challenged with JEV by analyzing mortality and morbidity. Findings: LTB-NS1 Δ63 induced immune responses to a similar level as LTB-NS1, but more robust than NS1 Δ63 alone, particularly in the context of oral immunization of mice. Oral vaccination of LTB-NS1 Δ63 led to a higher survival rate than that of NS1 Δ63 or live-attenuated JEV vaccine SA14À14À2 in the mice receiving lethal JEV challenge. LTB-NS1 Δ63 protein also significantly decreases the morbidity of JEV-infected mice. In addition, passive transfer of LTB-NS1 Δ63 -induced antisera provides a protection against JEV infection in mice. Interpretation: NS1 Δ63 bears JEV NS1 antigenicity. Besides, LTB-NS1 Δ63 could serve as a novel protein-based mucosa vaccine targeting JEV and other flaviviruses.

Protective Immune Responses Induced by an mRNA-LNP Vaccine Encoding prM-E Proteins against Japanese Encephalitis Virus Infection

“…Over the past years, SA14-14-2 vaccines for humans have been broadly used in many countries where JE is endemic, as well as inactivated or liveattenuated vaccines for swine [26]. New inactivated vaccines, recombinant protein subunit vaccines and DNA vaccines against JEV were reported in recent years [7,8,27]. However, there are no related reports on mRNA vaccines of JE.…”

“…However, the incidence in adults has increased in recent years, suggesting that a live-attenuated vaccine may not provide long-term effective protection [3][4][5]. In addition, the populations in some Asian countries are worried about the safety of live vaccines and choose inactivated vaccines which are relatively less effective [6] Other types of JEV vaccines, such as recombinant protein subunit vaccines and DNA vaccines, have been previously reported to show effective protection in mice [7,8]. For example, virus-like particles containing E protein were secreted into the culture medium and immunized mice after purification.…”

Molecular pathogenesis of Japanese encephalitis and possible therapeutic strategies

“…Hence, as an early marker of infection, the NS1 protein can be targeted to develop drugs, vaccines, and monoclonal antibodies to inhibit JEV pathogenesis. Notably, an NS1-based vaccine was developed recently by fusing a truncated NS1 protein with the Escherichia coli heat-labile enterotoxin subunit [ 59 ].…”

“…5 a and b). NS1 is a 48-kDa protein that mainly exists as a homodimer [ 66 ] that interacts with the envelope (E) protein [ 52 , 68 ], NS4A protein [ 59 ], and NS5 protein [ 69 ] and is co-localised with the viral genomic RNA [ 52 ]. It is therefore essential for stabilising the RC by creating a scaffold on the ER membrane.…”

“…Keeping the disadvantages of previous vaccines in mind, Wan et al have developed an NS1-based vaccine (LTB-NS1 Δ63 ) by fusing the truncated NS1 protein of JEV with the heat-labile enterotoxin B subunit of E. coli . They also tested the vaccine for its immunogenicity and toxicity through in vitro and in vivo experiments and found that mice inoculated with LTB-NS1 Δ63 showed a higher survival rate than those receiving the live attenuated SA14-14-2 vaccine when challenged with a lethal dose of JEV [ 59 ].…”