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.

Modification of the adenoviral transfer vector enhances expression of the Hantavirus fusion protein GnS0.7 and induces a strong immune response in C57BL/6 mice.

Hantavirus glycoproteins (Gn and Gc) are significant components of vaccines for haemorrhagic fever with renal syndrome (HFRS); however, they are not effective due to weak immunogenicity and low levels of production in expression systems. To circumvent this problem, a 0.7-kb fragment of the S segment was fused to Gn, and a hybrid CAG promoter/enhancer in conjunction with (or without) the WPRE (Woodchuck hepatitis virus post-transcriptional regulatory element) was used to improve the expression of fusion protein GnS0.7 in the adenoviral expression system. The expression level of the fusion protein as well as the response of mice immunized with recombinant adenoviruses containing GnS0.7 was investigated. In addition, a series of immunological assays were conducted to determine the immunogenicity of the recombinant adenoviruses. The results showed that the recombinant adenovirus with the CAG promoter/enhancer (rAd-GnS0.7-pCAG) expressed approximately 2.1-fold more GnS0.7 than the unmodified recombinant adenovirus containing GnS0.7 (rAd-GnS0.7-pShuttle). This enhanced expression level was also higher than for other modified recombinant adenoviruses studied. Animal experiments showed that rAd-GnS0.7-pCAG induced a stronger Hantaan virus (HTNV)-specific humoral and cellular immune response in mice, with the cellular immune response to the GnS0.7 being stronger than the HFRS vaccine control. These results demonstrate that the CAG promoter/enhancer improved significantly the expression of the chimeric gene GnS0.7 in the adenovirus expression system. These findings may have significant implications for the development of genetically engineered vaccines for HFRS.

[Construction and expression of the eukaryotic expression vector carrying HSV-1 gC glycoprotein gene].

AIM: To stably express herpes simplex virus type 1 (HSV-1) glycoprotein C (gC) in Chinese hamster ovary cells (CHO-K1). METHODS: The eukaryotic expression vector pCI-mCMV-gC-1-IRES-DHFR-L22R was constructed and transfected into CHO-K1 cells by Lipofectamine 2000. The transfected cells were selected by G418 and methotrexate (MTX). The expression of HSV-1 gC was analyzed by Slot blot. HSV-1 gC proteins were purified with His-Ni Sepharose and then detected by Western blot. RESULTS: The eukaryotic expression vector pCI-mCMV-gC-1-IRES-DHFR-L22R was constructed successfully. CHO-K1 cells stably expressing HSV-1 gC proteins were established and confirmed by Western blot. CONCLUSION: The HSV-1 gC proteins have been expressed successfully and have good bioactivity. The results make it possible for further study and clinical use of HSV-1 gC.

[Construction and identification of a new type of recombinant adenovirus containing S0.7 gene of Hantavirus].

AIM: To construct a adenovirus vector containing the 0.7 kb fragment of S gene of Hantavirus, CAG promoter, and WPRE (mRNA-stabilizing post-transcriptional regulatory element from the woodchuck hepatitis virus). METHODS: The fragments of CAG and WPRE were synthesized according to GenBank, and inserted into the plasmid pShuttle-S0.7 to create a transfer vector pShuttle-S0.7-CAG-WPRE. The S0.7-CAG-WPRE fragment was then cloned into Adeno-X; Viral DNA by PI-Sce I and I-Ceu I digestion. The recombinant adenovirus DNA was linearized by Pac I, transfected into HEK 293 cells via Lipofectamine; 2000, and the titer of the recombinant adenovirus was determined by Adeno-X; Rapid Titer Kit. The expressed product of S0.7-CAG-WPRE fragment was detected by immunofluorescence assay. RESULTS: The sequence of S0.7-CAG-WPRE fragment was confirmed by sequencing, and the recombinant adenovirus containing S0.7-CAG-WPRE was titered at 10(13); pfu/L. HEK293 cells transfected with recombinant adenoviruses were detected positive by immunofluorescence assay using a specific mAb 1A8 against Hantavirus nucleoprotein. CONCLUSION: The recombinant adenovirus containing the 0.7 kb fragment of S segment of Hantavirus, CAG promoter, WPRE was constructed.