S2 protein  N/A  Freund’s  S.C.  BALB/c mice  Elicits SARS-CoV S2-specific Abs (IgG, 1:1.6 × 103) in mice with no neutralizing activity  Induces SARS-CoV S2-specific cellular immune responses (IFN-γ and IL-4) in mice  N/A  Guo et al., 2005