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. 2021 Jul 15;89(8):e00121-21. doi: 10.1128/IAI.00121-21

FIG 1.

FIG 1

OmpV induces protective immunity against S. Typhimurium infection. (A, B) Intraperitoneal immunization of mice with purified OmpV protects against systemic infection (A) but does not protect against gastrointestinal infection (B) of S. Typhimurium. Mice were immunized intraperitoneally at an interval of 7 days. Buffer was used for the control mice. Following 14 days after the last dose, mice were challenged with S. Typhimurium SL1344 intraperitoneally (A) or through the oral route (B), and survival was monitored until day 7 (A) or day 21 (B). (C, D) A high titer of IgG (C) and IgA (D) was observed in the serum of mice immunized intraperitoneally with OmpV (C) and in the stools of mice immunized orally with OmpV-proteoliposome (PL) (D). Mice were immunized intraperitoneally with four doses of OmpV, and buffer was used for the control mice (C). Mice were immunized with four doses of OmpV-proteoliposome (PL), and liposomes were used for control mice (D). Following 14 days after the last dose of immunization, serum and stool samples were obtained from the immunized and control mice (n = 3 mice/group, 3 biological replicates). (E) Oral immunization of mice with OmpV-proteoliposome (PL) protects against gastrointestinal infection of S. Typhimurium. Mice were immunized with OmpV-proteoliposome (PL). Following the last dose, mice were given gastrointestinal infection with oral challenge of S. Typhimurium SL1344, and survival was monitored. Mice immunized with liposomes were taken as controls. For panels A, B, and E, n = 12 mice/group (4 mice per group per experiment were taken, and 3 biological replicates were done). A Kaplan-Meier plot of cumulative mortality was prepared to compare the survival rate. (F) Similar intestinal length was observed in the naive noninfected mice as well as the infected mice immunized with OmpV-proteoliposome (PL). Mice were immunized with OmpV-proteoliposome (PL), and, after the last dose, mice were given gastrointestinal infection with S. Typhimurium SL1344. After 5 days of infection, the intestines and spleens of these mice were removed, observed, and matched with noninfected naive mice (n = 3 mice/group).