A West Nile Virus Recombinant Protein Vaccine That Coactivates Innate and Adaptive Immunity

Abstract

A chimeric protein West Nile virus (WNV) vaccine capable of delivering both innate and adaptive immune signals was designed by fusing a modified version of bacterial flagellin (STF2 Delta ) to the EIII domain of the WNV envelope protein. This fusion protein stimulated interleukin-8 production in a Toll-like receptor (TLR)-5-dependent fashion, confirming appropriate in vitro TLR5 bioactivity, and also retained critical WNV-E-specific conformation-dependent neutralizing epitopes as measured by enzyme-linked immunosorbent assay. When administered without adjuvant to C3H/HeN mice, the fusion protein elicited a strong WNV-E-specific immunoglobulin G antibody response that neutralized viral infectivity and conferred protection against a lethal WNV challenge. This potent EIII-specific immune response requires a direct linkage of EIII to STF2 Delta , given that a simple mixture of the 2 components failed to induce an antibody response or to provide protection against virus challenge. The presence of a functional TLR5 gene in vivo is also required--TLR5-deficient mice elicited only a minimal antigen-specific response. These results confirm that vaccines designed to coordinately regulate the innate and adaptive immune responses can induce protective immune responses without the need for potentially toxic adjuvants. They also support the further development of an effective WNV vaccine and novel monovalent and multivalent vaccines for related flaviviruses.

Deletion of Flagellin’s Hypervariable Region Abrogates Antibody-Mediated Neutralization and Systemic Activation of TLR5-Dependent Immunity

“…The deleted flagellin FliC ⌬174 -400 also retains adjuvant properties when administered s.c, suggesting that mucosal and dermal responses behave similarly and thus differ from the systemic response (data not shown). Studies with the S. typhimurium flagellin FljB (which harbors a similar deletion in the hypervariable region) have been recently performed with a view to using this type of molecule as an Ag carrier (14,21). Similar findings were obtained using the deleted flagellin FljB as a carrier for foreign Ags in s.c. immunization (21).…”

“…Various authors have reported that flagellins are potent systemic and mucosal adjuvants that elicit 1) serum and/or secretory Ab responses and 2) Th1 and Th2 cell responses to both the flagellins themselves and coadministered Ags (14,17,21,22).…”

Recent progress in West Nile virus diagnosis and vaccination

“…Minke et al demonstrated that Recombitek ® Equine West Nile, that expresses the prM/E genes of lineage 1 strain in a recombinant canarypox virus, could protect horses against a contemporary neurovirulent lineage 2 WNV isolate [123]. Finally, Yamshchikov et al reported that an attenuated non-epidemic West Nile virus strain of lineage 2 can be used as an effective vaccine against a virulent epidemic strain of lineage 1 in mice [124]. …”

Potential adjuvantic properties of innate immune stimuli

“…116 As described above, as a consequence of the potent effects of flagellin on both the innate and adaptive limbs of the immune system, the protein has indeed been demonstrated to have potent adjuvantic effects in experimental vaccine constructs. [117][118][119][120][121][122] However, the safety profile of flagellin is yet to be unequivocally established. Of particular note, it has been observed that the administration of flagellin at doses comparable to or lower than that of bacterial LPS induces prominent local and systemic immune/inflammatory responses in vivo.…”