Preparation and immunogenic properties of a recombinant West Nile subunit vaccine

Abstract

While several West Nile vaccines are being developed, none are yet available for humans. In this study aimed at developing a vaccine for humans, West Nile virus (WNV) envelope protein (E) and non-structural protein 1 (NS1) were produced in the Drosophila S2 cell expression system. The Cterminal 20% of the E protein, which contains the membrane anchor portion, was deleted, thus allowing for efficient secretion of the truncated protein (80E) into the cell culture medium. The proteins were purified by immunoaffinity chromatography (IAC) using monoclonal antibodies that were flavivirus envelope protein group specific (for the 80E) or flavivirus NS1 group specific (for NS1). The purified proteins were produced in high yield and used in conjunction with adjuvant formulations to vaccinate mice. The mice were tested for both humoral and cellular immune responses by a plaque reduction neutralization test and ELISA, and by lymphocyte proliferation and cytokine production assays, respectively. The results revealed that the 80E and the NS1 proteins induced both high-titered ELISA and neutralizing antibodies in mice. Splenocytes from immunized mice, cultured in vitro with the vaccine antigens as stimulants, showed excellent proliferation and production of cytokines . The level of antigen-stimulated lymphocyte proliferation and cytokine production was comparable to the level obtained from mitogen (phytohemagglutinin or pokeweed) stimulation, indicating a robust cellular response as well. These findings are encouraging and warrant further in vivo studies to determine the protective efficacy of the WNV vaccine candidate.

Efficacy and durability of a recombinant subunit West Nile vaccine candidate in protecting hamsters from West Nile encephalitis

“…The production and purification of the vaccine antigens are described in detail in the accompanying paper [5]. Briefly, West Nile virus carboxy-truncated envelope protein (80E) and nonstructural protein 1 (NS1) were produced in an insect cell (Drosophila) expression system.…”

“…b 12 μg of ISCOMATRIX ® adjuvant per dose present in all groups; "mock antigen" = equivalent of 10 μg of 80E purified by IAC from an induced "mock" 80E transformed S2 cell line, i.e., S2 cells transformed with plasmid DNA without the prM80E insert [5]. c p value = 0.022 relative to group 1 (Fisher exact probability test).…”

Recent advances in human flavivirus vaccines

“…Immunising mice, hamsters and rhesus macaques with HBV-002 induced high titres of neutralising antibodies and protected animals against WNV challenges [43][44][45]. A phase I clinical study was initiated in 25 flavivirus-naïve volunteers.…”

Complex Adenovirus-Mediated Expression of West Nile Virus C, PreM, E, and NS1 Proteins Induces both Humoral and Cellular Immune Responses

“…These proteins are followed by the nonstructural (NS) proteins NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5 (17,63). It is now well known that the majority of antibodies elicited during a flavivirus infection are directed to epitopes within the E and NS1 proteins (12,50). However, most immunological studies have focused on the E protein because it induces neutralizing antibody responses (7,8,27,28,33).…”

“…A number of approaches for the development of a WNV vaccine have been investigated, such as the use of an inactivated virus (35,52,61,62), subunit particles (47,84,85), naked DNA (24,35,48,70,71,91), cross-protection immunity induced by Japanese encephalitis virus vaccination (1,77,88), live-, attenuated virus (51,78,79,89), recombinant virus (3,25,39,50,58,74,78,79,86), and virus replicons (2). Currently, only ChimeriVax-WNV, a vaccine based on a recombinant virus that expresses the preM and E proteins of WNV in an attenuated yellow fever virus backbone, has completed phase I clinical trials (58;Acambis, 2007), and others are in preclinical development (34,70,71).…”