Mucosal immune response. Titers of intestinal secretory IgA (sIgA) (A) and virginal sIgA (B) obtained after vaccination with a co-mixture of all the four strains. The responses measured against each LI protein by an indirect ELISA using individual recombinant proteins as coating antigens. Each data points represent mean ± standard deviation (sd) of 10 mice/group. *P < 0.05. wpi: week post-immunization. ns: non-significant.