Characterization of cytotoxic T‐lymphocyte epitopes and immune responses to SARS coronavirus spike DNA vaccine expressing the RGD‐integrin‐binding motif

Poh, W.P.; Narasaraju, T.; Pereira, N.A.; Zhong, F.; Phoon, M.C.; Macary, P.A.; Wong, S.H.; Lu, J.; Koh, D.R.; Chow, Vincent T.K.

Integrins are critical for initiating T‐cell activation events. The integrin‐binding motif Arg‐Gly‐Asp (RGD) was incorporated into the pcDNA 3.1 mammalian expression vector expressing the codon‐optimized extracellular domain of SARS coronavirus (SARS‐CoV) spike protein, and tested by immunizing C57BL/6 mice. Significant cell‐mediated immune responses were characterized by cytotoxic T‐lymphocyte (51)Cr release assay and interferon‐gamma secretion ELISPOT assay against RMA‐S target cells presenting predicted MHC class I H2‐Kb epitopes, including those spanning residues 884–891 and 1116–1123 within the S2 subunit of SARS‐CoV spike protein. DNA vaccines incorporating the Spike‐RGD/His motif or the Spike‐His construct generated robust cell‐mediated immune responses. Moreover, the Spike‐His DNA vaccine construct generated a significant antibody response. Immunization with these DNA vaccine constructs elicited significant cellular and humoral immune responses. Additional T‐cell epitopes within the SARS‐CoV spike protein that may contribute to cell‐mediated immunity in vivo were also identified. J. Med. Virol. 81:1131–1139, 2009. © 2009 Wiley‐Liss, Inc.