Survival of secondary lethal systemic Francisella LVS challenge depends largely on interferon gamma

Microbes Infect. 2010 Jan;12(1):28-36. doi: 10.1016/j.micinf.2009.09.012. Epub 2009 Sep 23.


Although survival of primary infection with the live vaccine strain (LVS) of Francisella tularensis depends on interferon gamma (IFN-gamma), the relative importance of IFN-gamma to secondary protective immunity in vivo has not been clearly established. Here we examine the role of IFN-gamma in T cell priming and expression of vaccine-induced protection against lethal intraperitoneal challenge of mice. Large amounts of IFN-gamma were detected between days 3 and 7 in the sera of LVS-immunized mice, while relatively small amounts were found transiently after secondary LVS challenge. Consistent with the production of this cytokine, mice lacking IFN-gamma (gamma interferon knockout, GKO, mice) could not be successfully vaccinated with LVS or an attenuated mglA mutant of F. novicida to withstand secondary Francisella LVS challenge. Further, splenocytes from such primed mice did not adoptively transfer protection to naive GKO recipient mice in vivo, nor control the intramacrophage growth of LVS in vitro. Finally, LVS-immune WT mice depleted of IFN-gamma prior to intraperitoneal challenge survived only the lowest doses of challenge. Thus successful priming of protective LVS-immune T cells, as well as complete expression of protection against Francisella during secondary challenge, depends heavily on IFN-gamma.

MeSH terms

  • Adoptive Transfer
  • Animals
  • Bacterial Vaccines / immunology
  • Francisella tularensis / immunology*
  • Interferon-gamma / blood
  • Interferon-gamma / deficiency
  • Interferon-gamma / immunology*
  • Lethal Dose 50
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Survival Analysis
  • Tularemia / immunology*
  • Tularemia / mortality*
  • Vaccination / methods


  • Bacterial Vaccines
  • Interferon-gamma