Construction of a Eukaryotic Expression Plasmid Encoding Partial S Gene Fragments of the SARS-CoV and Its Potential Utility as a DNA Vaccine

Abstract

The spike (S) protein, a main surface antigen of the SARS coronavirus (SARS-CoV), is considered to be one of the most important protective antigen candidates for targets for vaccine design against the virus. In this study, a secreted recombinant expression plasmid, pVAX-S1, encoding the partial S protein with a signal peptide, was constructed and used to immunize BALB/c mice through electroporation. It was demonstrated that the eukaryotic expression vector pVAX-S1 was successfully constructed by restriction enzyme and sequence analysis. The expressed protein could be detected specifically by Western blot analysis. The serum IgG level of the vaccine group mice was significantly higher than that of the corresponding control group at day 14 after vaccination (P < 0.05). The vaccine group demonstrated significantly higher S1 protein lymphocyte proliferation index (LPI) than the control groups (P < 0.05). Furthermore, in the experimental group, a decrease in the ratio of CD4(+) to CD8(+) T-lymphocytes and an increase level of IFN-gamma in serum were observed. However, interleukin-4 (IL-4) was not detectable in two groups. These results strongly demonstrated that the pVAX-S1 plasmid could induce humoral and cellular immune responses in mice, and may be a potential candidate for a DNA vaccine against the SARS coronavirus.

Vaccination of mice with recombinant baculovirus expressing spike or nucleocapsid protein of SARS-like coronavirus generates humoral and cellular immune responses

“…To date, several vaccines have been tested in pre-clinical or clinical studies, including vector-based DNA vaccines (Bisht et al, 2004;He et al, 2005;Okada et al, 2005;Wang et al, 2005;Yang et al, 2004), combination of whole killed virus and DNA vaccines (Zakhartchouk et al, 2005), inactivated whole virus vaccines (He et al, 2004;Spruth et al, 2006), and other recombinant proteins and their fragments. The majority of these vaccines target SARS-CoV structural proteins, particularly the S and N proteins.…”

Emerging Respiratory Viruses: Challenges and Vaccine Strategies

“…DNA vaccines have demonstrated strong induction of immune responses to viral pathogens in animal models, specifically in mice; however, clinical data on DNA vaccines in human subjects are limited. DNA vaccines encoding the S, N, M, and E proteins of SARS-CoV have been evaluated in mice (74,92,99,216,234,241,242,244). Vaccination with S-, M-, and N-encoding DNA vaccines induced both humoral and cellular immune responses, with some variation in the relative levels of induction (92,216).…”

A recombinant baculovirus-expressed S glycoprotein vaccine elicits high titers of SARS-associated coronavirus (SARS-CoV) neutralizing antibodies in mice

“…There are also several subunit vaccines in pre-clinical development, targeting SARS-CoV structural proteins, including the spike (S) and nucleocapsid (N) proteins. Other vaccine candidates include vector-based DNA vaccines [7][8][9][10][11], a combination of whole killed virus and DNA vaccines [12], inactivated whole virus vaccines [13,14], a combination of DNA and S-peptide vaccines [15], and other recombinant proteins and their fragments.…”