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Clinical and Vaccine Immunology, January 2009, p. 73-77, Vol. 16, No. 1
1071-412X/09/$08.00+0 doi:10.1128/CVI.00261-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Science, Wuhan 430071, People's Republic of China,1 Graduate University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China2
Received 18 July 2008/ Returned for modification 21 August 2008/ Accepted 25 October 2008
Vaccine development for severe acute respiratory syndrome coronavirus (SARS-CoV) has mainly focused on the spike (S) protein. However, the variation of the S gene between viruses may affect the efficacy of a vaccine, particularly for cross-protection against SARS-like CoV (SL-CoV). Recently, a more conserved group-specific open reading frame (ORF), the 3a gene, was found in both SARS-CoV and SL-CoV. Here, we studied the immunogenicity of human SARS-CoV 3a and bat SL-CoV 3a DNA vaccines in mice through electroporation immunization followed by enzyme-linked immunosorbent, enzyme-linked immunospot, and flow cytometry assays. Our results showed that high levels of specific humoral responses were induced by SARS-CoV 3a and SL-CoV 3a DNA vaccines. Furthermore, a strong Th1-based cellular immune response was stimulated by both DNA vaccines. The vaccines stimulated gamma interferon production mainly by CD8+ T cells and interleukin-2 (IL-2) mainly by CD4+ T cells. Of interest, the frequency of IL-2-positive cells elicited by the SARS-CoV 3a DNA vaccine was significantly higher than that elicited by the SL-CoV 3a DNA vaccine. In summary, our study provides a reference for designing cross-protective DNA vaccines based on the group-specific ORFs of CoVs.
Published ahead of print on 5 November 2008.
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