Enhanced Induction of SARS-CoV Nucleocapsid Protein-Specific Immune Response Using DNA Vaccination followed by Adenovirus Boosting in BALB/c Mice

Abstract

Objective: To investigate immunogenicity in the induction of humoral and cellular immune responses to genetic vaccines of the recombinant severe acute respiratory syndrome-associated coronavirus (SARS-CoV)-N gene expressing the same protein plasmid, pcDNA3.1-N, and replication-defective adenoviral vector, rAd-N, in a pcDNA3.1-N prime-rAd-N boost regimen and the reverse sequence in a rAd-N prime-pcDNA3.1-N boost regimen. Method: After the mice had been immunized intramuscularly and/or intraperitoneally with pcDNA3.1-N and rAd-N in prime-triple boost immunization, humoral and cellular immune responses were detected. Results: After detection, different levels of anti-N humoral and cellular responses are shown compared to controls. The humoral immune response was induced more effectively by the DNA priming and recombinant adenovirus boosting regimen and the reverse sequence of heterogeneous combinations. There is a significant difference between heterogeneous and homologous vaccinations. However, the cytotoxic T lymphocyte (CTL) response was not significantly altered by the different prime-boost immunizations or the recombinant adenovirus of pcDNA3.1-N prime-rAd-N boost regimen alone, but lymphoproliferation and interferon-γ (IFN-γ) secretion were all enhanced by heterologous combination immunizations compared to homologous combinations. For the reverse sequence immunization regimen, lymphoproliferation, IFN-γ and CTL responses were all significantly weaker compared with pcDNA3.1-N prime-rAd-N boost regimen. Conclusion: Taken together, of all the combinations, the prime-triple boost immunization of pcDNA3.1-N/pcDNA3.1-N/pcDNA3.1-N/rAd-N can effectively induce SARS-CoV-N-specific and strong humoral and cellular immune responses in mice. The present results suggest that DNA immunization followed by recombinant adenovirus boosting could be used as a potential SARS-CoV vaccine in the induction of an enhanced humoral and cellular immune response.

Intranasal Vaccination of Recombinant Adeno-Associated Virus Encoding Receptor-Binding Domain of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) Spike Protein Induces Strong Mucosal Immune Responses and Provides Long-Term Protection against SARS-CoV Infection

“…Therefore, the function of the RBD-rAAV vector is not affected by the insert size limitation. Further studies are warranted to determine the immune responses of RBD-rAAV in the presence of long-term RBD Ag expression and using different vaccination regimens, e.g., priming with DNA vaccine expressing the RBD and boosting with RBD-rAAV, as the adenovirus vector-based vaccine strategies (66).…”

Induction of T-cell response by a DNA vaccine encoding a novel HLA-A*0201 severe acute respiratory syndrome coronavirus epitope

“…Subunit vaccines containing HLA-A*0201 restricted peptides is highly effective for the induction of strong cytotoxic T-cell response against infectious virus [6]. Among the four structure proteins of the SARS-CoV, the S and N proteins are the major targets for vaccine research studies due to their potency in triggering immune responses [7][8][9][10][11][12][13][14]. The S protein contains 1256 amino acids and is involved in viral entry through angiotensin-converting enzyme 2 receptor on host cell surface [15,16] and the N protein contains 422 amino acids and is involved in the viral RNA packaging [17,18].…”

Newly Emerging Human Coronaviruses: Animal Models and Vaccine Research for SARS, MERS, and COVID-19

“…Further, heterologous prime-boost immunization with DNA vaccines and inactivated SARS-CoV induced strong CD4 + T cell and Ab responses ( 126 ). Meanwhile, DNA vaccines encoding SARS-CoV N proteins induced Abs and T cell responses in mice, but their protective efficacy has not been fully investigated ( 127 128 ). In MERS vaccine studies, immunization of full-length or S1 subunit-expressing plasmids also induced neutralizing Abs and T cell responses in mice, camels, and NHPs ( 114 129 130 ), while also alleviating clinical symptoms upon MERS-CoV infection in a rhesus macaque model ( 129 ).…”