Incorporation of GM-CSF or CD40L Enhances the Immunogenicity of Hantaan Virus-Like Particles.

A safe and effective Hantaan virus (HTNV) vaccine is highly desirable because HTNV causes an acute and often fatal disease (hemorrhagic fever with renal syndrome, HFRS). Since the immunity of the inactivated vaccine is weak and the safety is poor, HTNV virus-like particles (VLPs) offer an attractive and safe alternative. These particles lack the viral genome but are perceived by the immune system as virus particles. We hypothesized that adding immunostimulatory signals to VLPs would enhance their efficacy. To accomplish this enhancement, we generated chimeric HTNV VLPs containing glycosylphosphatidylinositol (GPI)-anchored granulocyte macrophage colony-stimulating factor (GM-CSF) or CD40 ligand (CD40L) and investigated their biological activity in vitro. The immunization of mice with chimeric HTNV VLPs containing GM-CSF or CD40L induced stronger humoral immune responses and cellular immune responses compared to the HTNV VLPs and Chinese commercial inactivated hantavirus vaccine. Chimeric HTNV VLPs containing GM-CSF or CD40L also protected mice from an HTNV challenge. Altogether, our results suggest that anchoring immunostimulatory molecules into HTNV VLPs can be a potential approach for the control and prevention of HFRS.

Induction of Hantaan virus-specific immune responses in C57BL/6 mice by immunization with a modified recombinant adenovirus containing the chimeric gene, GcS0.7.

Hantavirus glycoprotein Gc is one of the main components that contribute to the generation of humoral immune responses, while the nucleocapsid protein (NP) is involved in cellular immune responses through the induction of antibody-dependent cytotoxic T cells. In this study, a chimeric gene, GcS0.7, which encodes a fusion protein containing Gc and truncated NP, was constructed as a candidate for Hantaan virus (HTNV) vaccine development. The chimeric gene was cloned into an adenoviral vector in conjunction with the powerful hybrid cytomegalovirus (CMV) enhancer/chicken ß-actin (CAG) promoter or the woodchuck hepatitis virus (WHV) post-transcriptional regulatory element (WPRE), or both. Both elements increased the expression level of the fusion protein. The rAd-GcS0.7-pCAG group demonstrated the highest fusion protein expression level, with a 2.3-fold increase compared with the unmodified adenoviral vector. To further evaluate the humoral and cellular immunity induced by the recombinant adenovirus, the antibody titers, interferon (IFN)-γ secretion level and cytotoxic T cell ratio were detected in immunized mice. The strongest HTNV­specific humoral and cellular immune responses were detected in the rAd-GcS0.7­pCAG group. The immunogenicity of these recombinant adenoviruses was compared with that of the inactivated vaccine through a series of immunological assays. In terms of the cellular immune responses, the rAd-GcS0.7-pCAG group even exceeded those induced by the vaccine control. The CAG hybrid promoter improved not only the expression level, but also the immunogenicity of the fusion protein, and may thus provide a promising strategy for HTNV vaccine research.