Western blot of serum samples collected the day before the i.n. challenge. C. trachomatis MoPn EB were used as the antigen. Lane 1, molecular weight standards. Lanes 2 to 7, sera from mice immunized with MOMP, CpG, and alum once (lane 2); with ovalbumin, CpG, and alum once (lane 3); with MOMP, CpG, and alum three times (lane 4); with ovalbumin, CpG, and alum three times (lane 5); with C. trachomatis MoPn EB (lane 6); or with saline (lane 7). Lane 8, control monoclonal antibody 40 to the C. trachomatis MoPn MOMP.