An Advax-adjuvanted Inactivated Cell-culture Japanese Encephalitis Vaccine Induces Broadly Neutralising Anti-flavivirus Antibodies and T-cell Immunity and Provides Single Dose Protection

ccJE+Advax is an inactivated cell culture Japanese encephalitis (JE) vaccine formulated with Advax™, a novel polysaccharide adjuvant based on delta inulin. This vaccine has previously shown promise in murine and equine studies and the current study sought to better understand its mechanism of action and assess the feasibility of single dose vaccine protection. Mice immunised with ccJE-Advax had higher serum neutralisation titres than those immunised with ccJE alone or with alum adjuvant. ccJE+Advax induced extraordinarily broad cross-neutralising antibodies against multiple flaviviruses including West Nile virus (WNV), Murray Valley Encephalitis Virus (MVEV), St Louis Encephalitis virus (SLE) and Dengue-1 and -2 viruses. Notably, the DENV-2 cross-neutralising antibodies from ccJE+Advax immunised mice uniquely had no DENV-2 antibody dependent enhancement (ADE) activity, by contrast to high ADE activity seen with DENV-1 cross-reactive antibodies induced by mbJE or ccJE alone or with alum adjuvant. JEV-stimulated splenocytes from ccJE+Advax immunised mice showed increased IL-17 and IFN-γ production, consistent with a mixed Th1 and Th17 response, whereas ccJE-alum was associated with production of mainly Th2 cytokines. There is an ongoing lack of human vaccines against particular flaviviruses, including WNV, SLE and MVEV. Given its ability to provide single-dose JEV protection as well as to induce broadly neutralising antibodies free of ADE activity, ccJE+Advax vaccine could be highly useful in all situations where rapid protection is desirable but ADE needs to be avoided, e.g. during a local outbreak or for use in travellers or the military requiring rapid travel to JEV endemic regions.

Safety and immunogenicity of inactivated Japanese encephalitis vaccine derived from Vero cell. Phase III, double-blind, randomized, control trial (JECEVAX, VABIOTECH, Vietnam)

Japanese encephalitis (JE) is one of the most important infectious disease in Southeast Asia and the Pacifc region and more than 3 billion people are living in endemic areas. The annual incidence is estimated to be 60,000 cases/year of which 15,000 deaths, 50% of the people survive with neurological sequelae. Since 1997, Vietnam has produced and used mouse brain - derived (MB) inactivated Japanese encephalitis vaccine (JEVAX®) for children 1 - 5 years of age under the Expanded programme on immunization (EPI). In 2006, VABIOTECH started the research and development of vero cell-derived inactivated JE vaccine (JECEVAX). The clinical trial phases I, II & IIB were conducted successfully and the phase III was completed in January 2019. The study participants included 655 healthy infants aged 9 - 24 months were immunized with JECEVAX testing vaccine, and JEVAX® control vaccine. The results showed that both vaccines were safe with good tolerability in children. The seroconversion rates of JECEVAX (n = 547) were 99.6 - 100%, compared with JEVAX® (n =108) were 99 - 100%. The GMT titer of JECEVAX and JEVAX® after the second dose was 2.07log and 2.02log after the third dose, the neutralizing antibody (PRNT50) increased to 3.04log and 3.19log respectively. The registration dossier with the MOH of Vietnam is being fnalized before scaling up the production to prevent JE disease with JECEVAX high qualifed second generation vaccine.

Effectiveness of the SA 14-14-2 Live-Attenuated Japanese Encephalitis Vaccine in Myanmar

Myanmar is an endemic country for the Japanese encephalitis virus (JEV), and the SA-14-14-2 live-attenuated JEV vaccine was first introduced as a catch-up vaccination campaign in 2017. To determine the effectiveness of vaccination by means of neutralizing antibody titers against JEV, a cross-sectional descriptive study was conducted among five to 15-year-old monastic school children in Mandalay, Myanmar. A total of 198 students who had received vaccines were recruited, and single-time investigation of anti-JEV IgG and neutralizing antibodies against wild-type JEV were determined using anti-JEV IgG ELISA and plaque reduction neutralization tests (PRNT50). All students 100% (198/198) showed positive results on the anti-JEV IgG ELISA, and 87% (172/198) of the students had neutralizing antibodies against JEV six months after immunization. The geometric mean titers of both IgG antibodies and neutralizing antibodies increased with the participants’ age groups, and statistically significant differences in anti-JEV IgG titers were noted across age groups. In this study, we could not investigate the persistence of neutralizing antibodies as only single-time blood collection was done. This study, which is the first report of JEV vaccination among children in Myanmar, showed similar neutralizing antibody production rates among vaccinated individuals as did studies in other countries.

Assessment of gene and protein similarities of Beijing-1 vaccine producing strain with Japanese encephalitis virus strains circulating in Vietnam

Since 2006, the inactivated Japanese encephalitis vaccine has been studied and produced by the VABIOTECH company from the Beịing-1 strain on Vero cells. Vaccines produced from the materseed and working seed virus have been evaluated at laboratory and clinical scale in humans. The results showed that the vaccine was safe and created 100% protective antibodies after the booster dose. To officially put this vaccine into production and mass use, the master seed virus BV-MSV-0210 and working seed virus BV-WSV-0310 with the reference standard strain JEV Beijing-Kanonji has been tested for genetic stability. By the method of Sanger sequencing and genetic analysis software, we have evaluated the similarity of nucleotide and proteinsequencesof the E antigen-encoding gene. The results showed that the seed virus similarity of amino acids and nucleotides is 100% compared with the reference strain. Thus, it can be concluded, the seed virus has antigen stability. Nucleotide and amino acid gene sequences of E genomic regions of the two seed lots were compared with virus strains isolated from human, pig and mosquito in Vietnam. The results showed that the nucleotide similarity of seed virus compared with the JEV strains isolated from humans ranged from 86.67 to 97.54%; from pigs is 87.47 to 88.33%, and from mosquitoes is 86.05 to 99%. Meanwhile, the amino acid similarity of the seed virus with the JEV strains isolated from humans ranged from 96.73 to 99.02%; from pigs is 98.00 to98.40% and from mosquitoes 94.55 to 98.40%. The sequence of amino acids in the epitope producing neutralizing antibodies of the seed virus did not differ from that of the JEV strain circulating in humans isolated in 2014.