A VLP-based vaccine targeting domain III of the West Nile virus E protein protects from lethal infection in mice - PubMed (original) (raw)
A VLP-based vaccine targeting domain III of the West Nile virus E protein protects from lethal infection in mice
Gunther Spohn et al. Virol J. 2010.
Abstract
Background: Since its first appearance in the USA in 1999, West Nile virus (WNV) has spread in the Western hemisphere and continues to represent an important public health concern. In the absence of effective treatment, there is a medical need for the development of a safe and efficient vaccine. Live attenuated WNV vaccines have shown promise in preclinical and clinical studies but might carry inherent risks due to the possibility of reversion to more virulent forms. Subunit vaccines based on the large envelope (E) glycoprotein of WNV have therefore been explored as an alternative approach. Although these vaccines were shown to protect from disease in animal models, multiple injections and/or strong adjuvants were required to reach efficacy, underscoring the need for more immunogenic, yet safe DIII-based vaccines.
Results: We produced a conjugate vaccine against WNV consisting of recombinantly expressed domain III (DIII) of the E glycoprotein chemically cross-linked to virus-like particles derived from the recently discovered bacteriophage AP205. In contrast to isolated DIII protein, which required three administrations to induce detectable antibody titers in mice, high titers of DIII-specific antibodies were induced after a single injection of the conjugate vaccine. These antibodies were able to neutralize the virus in vitro and provided partial protection from a challenge with a lethal dose of WNV. Three injections of the vaccine induced high titers of virus-neutralizing antibodies, and completely protected mice from WNV infection.
Conclusions: The immunogenicity of DIII can be strongly enhanced by conjugation to virus-like particles of the bacteriophage AP205. The superior immunogenicity of the conjugate vaccine with respect to other DIII-based subunit vaccines, its anticipated favourable safety profile and low production costs highlight its potential as an efficacious and cost-effective prophylaxis against WNV.
Figures
Figure 1
Electron micrograph of purified AP205 VLPs. Purified AP205 VLPs were adsorbed onto carbon-Formvar-coated grids, stained with 2% phosphotungstic acid and subjected to transmission electron microscopy.
Figure 2
Production and characterization of the DIII-C-AP205 conjugate vaccine. A Derivatized AP205 (dAP205), DIII-C, and the dialysed conjugate vaccine (DIII-C-AP205) were analyzed by reducing, denaturing SDS-PAGE (left panel). Corresponding amounts of derivatized AP205, DIII-C, and of the non-dialysed (nd) conjugate vaccine were also analysed by non-reducing, non-denaturing SDS-PAGE (right panel). For identification of the coupling bands, proteins were separated on reducing, denaturing SDS-PAGE, blotted on nitrocellulose and detected with AP205- and His-tag- specific antibodies (middle panels). Bands corresponding to AP205-crosslinked DIII-C are indicated by arrows. The 27 kDa band which is visible in the SDS-PAGE and in the His-tag-specific Western Blot corresponds to dimeric DIII-C (*). B Size exclusion chromatography. A superdex 75 column was calibrated with a molecular weight (MW) calibration kit and then loaded sequentially with the indicated proteins. AP205 VLPs and the conjugate vaccine DIII-C-AP205 elute in the void volume of the column (V0, 40 ml) while purified DIII-C elutes at 72.4 ml.
Figure 3
Immunogenicity of DIII-C-AP205. Groups of female BALB/c mice (n = 4) were immunized subcutaneously three times (days 0, 14, and 28, arrows) with either 50 μg of DIII-C-AP205 or a mixture of the corresponding amounts of free DIII-C protein (13.6 μg) and free AP205 VLPs (36.4 μg) in the absence of adjuvants. DIII-C-specific IgG antibody titers were measured at the indicated time points. The dashed line indicates the detection limit. Shown are group means ± SEM.
Figure 4
Immunization with DIII-C-AP205 protects from lethal WNV infection. A Induction of neutralizing antibodies. Groups of female C57BL/6 mice (n = 8) were immunized subcutaneously on days 0, 14 and 28 with 50 μg DIII-C-AP205 either in the absence or presence of Alum as adjuvant or with 50 μg AP205 VLPs in the absence of adjuvant. A fourth group was immunized once with 50 μg DIII-C-AP205 in Alum on day 28. Virus-neutralizing titers of individual sera were measured on day 42. The dashed line indicates the detection limit. Shown are individual titers and group means. B Protection from WNV challenge. Two weeks after the last vaccine injection mice were challenged with a lethal dose of WNV (arrow). Statistical significance of differences in survival curves was calculated by log-rank test using GraphPad-Prism (***p < 0.001 vs. 3xAP205 control). p.i.= post infection C and D Viral titers were determined 3 and 7 days post infection (p.i.) in blood of infected animals. Shown are individual titers and group means. The Mann-Whitney test was used to assess statistical significance (**p < 0.01, ***p < 0.001 vs. 3xAP205 control).
References
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