FIG. 2.

Systemic anti-SARS S protein response following mucosal immunization. Groups of 12 mice were immunized orally (open) or intranasally (closed) with either wild-type (circles) or a mixture of recombinant (inverted triangles) L. casei. (Left) Kinetics of anti-SARS S serum IgG response. ELISA was performed in triplicate using pooled peptides shown in Table 1, and titers are defined as the reciprocal of the maximum dilution of sera that yielded an absorbance equal to that of preimmune samples. Immunization periods are indicated by bars below the x axis. (Right) Isotype profiles of anti-SARS S serum antibodies. Serum samples collected on day 84 postimmunization were used. End point titers were calculated as the reciprocals of serum dilutions yielding the same optical density as a 1/50 dilution of a pooled preimmune serum. The data are presented as means ± standard deviations. Statistical comparisons between groups were made by the Mann-Whitney U test.