A replication-defective Japanese encephalitis virus (JEV) vaccine candidate with NS1 deletion confers dual protection against JEV and West Nile virus in mice

Abstract

In our previous study, we have demonstrated in the context of WNV-ΔNS1 vaccine (a replication-defective West Nile virus (WNV) lacking NS1) that the NS1 trans-complementation system may offer a promising platform for the development of safe and efficient flavivirus vaccines only requiring one dose. Here, we produced high titer (10 7 IU/ml) replication-defective Japanese encephalitis virus (JEV) with NS1 deletion (JEV-ΔNS1) in the BHK-21 cell line stably expressing NS1 (BHK NS1) using the same strategy. JEV-ΔNS1 appeared safe with a remarkable genetic stability and high degrees of attenuation of in vivo neuroinvasiveness and neurovirulence. Meanwhile, it was demonstrated to be highly immunogenic in mice after a single dose, providing similar degrees of protection to SA14-14-2 vaccine (a most widely used live attenuated JEV vaccine), with healthy condition, undetectable viremia and gradually rising body weight. Importantly, we also found JEV-ΔNS1 induced robust cross-protective immune responses against the challenge of heterologous West Nile virus (WNV), another important member in the same JEV serocomplex, accounting for up to 80% survival rate following a single dose of immunization relative to mock-vaccinated mice. These results not only support the identification of the NS1-deleted flavivirus vaccines with a satisfied balance between safety and efficacy, but also demonstrate the potential of the JEV-ΔNS1 as an alternative vaccine candidate against both JEV and WNV challenge.

Flavivirus NS1 and Its Potential in Vaccine Development

“…All of the mice inoculated with WT JEV died within 10 days of inoculation, whereas all of the mice inoculated with JEV-∆NS1 survived without neurological signs. A single immunization was able to confer protection from WT JEV equivalent to the licensed JEV SA14-14-2 vaccine and provided dose-dependent protection against infection from WT WNV [137]. These studies identify a novel vaccine platform that shows promising results for effective flavivirus vaccine development.…”

Japanese encephalitis in Bali, Indonesia: ecological and socio-cultural perspectives

“…Japanese encephalitis (JE) is a potentially fatal, zoonotic viral disease caused by JE virus (JEV) [1]. The virus is grouped within the family Flaviviridae, along with other arthropod-borne flaviviruses, including Dengue virus, West Nile virus (WNV), Tick-borne encephalitis virus (TBEV), St. Louis encephalitis virus and yellow fever virus (YFV) [2]. JEV is an enveloped, icosahedral virus, with a diameter of approximately 50 nm, and consists of a single-stranded positive-sense ribonucleic acid genome [3], of approximately 11 kb in length [4].…”

Rational design of West Nile virus vaccine through large replacement of 3′ UTR with internal poly(A)

“…In contrast, the mice infected with WNV-poly(A) all survived (Fig 2A ) without any visible signs of disease, and the body weights gradually increased during the 14-day observation period (Fig 2B). The 50% lethal dose (LD 50 ) of WNV-poly(A) is above 10 7 PFU, which is $ 100,000-time higher than that of the WT WNV strain (LD 50 = 16 PFU) (Zhang et al, 2020). It is notable that the viremia was only observed in the mice infected with the highest dose of WNV-poly(A) (10 7 PFU) on day one post-infection (Fig 2C).…”

“…Hybridization and visualization were performed using the DIG Northern Starter Kit I (Roche). The sequences of probe for detection were the same as described before (Zhang et al, 2020).…”

“…(ii) For immunization and challenge experiments, groups of 4-to 6-week-old C57BL/6 mice (n = 5 per group) were immunized i.p with 10 4 -10 7 PFU of WNV-poly(A), PBS (negative control), or mock (untreated). At different time points, the titers of total anti-WNV IgG antibodies and neutralizing antibodies in mouse serum were examined by ELISA and PRNT assay, respectively, as described previously (Zhang et al, 2016;Zhang et al, 2019;Li et al, 2020). At 30 or 170 days post-immunization, mice were challenged i.p with 3 × 10 7 PFU of WT WNV.…”