Figure 6. Protective efficacy of subsp. novicida vaccination against subsequent subsp. tularensis challenge in Fischer 344 rats.
Groups of Fischer 344 rats (n = 6) were vaccinated intratracheally with 102 or 105 CFU of subsp. novicida in PBS or mock vaccinated with PBS alone. (A) Thirty days later, rats were challenged intratracheally with subsp. tularensis (104 CFU) and monitored daily for morbidity and mortality. *P = 0.182, **P<0.05 (B) Fourteen days after vaccination with 105 CFU of subsp. novicida or PBS alone, rats were sacrificed, cervical lymph nodes removed, and whole cell populations were recalled with 105 CFU of UV-inactivated subsp. novicida, media alone, or the unrelated antigen HEL for 72 hr. Culture supernatants were analyzed for antigen-specific IFN-γ production. *P<0.001 (C) Thirty days after vaccination with 105 CFU of subsp. novicida or PBS alone, blood was collected and sera were prepared. Sera were analyzed for antigen-specific total antibody (Ig H & L), IgG1, and IgG2a, as well as reaction to the unrelated antigen HEL by ELISA. Results are represented as 50% binding titers. Results are representative of two separate experiments. *P<0.01, **P = 0.118.