Secretory IgA responses to S. enterica serovar Typhimurium LPS and SOMPs and to rPspA. The data represent anti-LPS, -SOMP, and -rPspA IgA antibody levels in vaginal secretions of BALB/c mice orally immunized with χ8501(pYA3493) (vector control) and χ8501(pYA3494) (expressing rPspA) at weeks 4, 6, 8, and 10 after immunization.