A heterologous prime-boost vaccination strategy comprising the Francisella tularensis live vaccine strain capB mutant and recombinant attenuated Listeria monocytogenes expressing F. tularensis IglC induces potent protective immunity in mice against virulent F. tularensis aerosol challenge.

ABSTRACT: Francisella tularensis, the causative agent of tularemia, is a category A bioterrorism agent. A vaccine that is safer and more effective than the currently available unlicensed F. tularensis live vaccine strain (LVS) is needed to protect against intentional release of aerosolized F. tularensis, the most dangerous type of exposure. In this study, we employed a heterologous prime-boost vaccination strategy comprising intradermally administered LVS ?capB (highly attenuated capB-deficient LVS mutant) as the primer vaccine and rLm/iglC (recombinant attenuated Listeria monocytogenes expressing the F. tularensis immunoprotective antigen IglC) as the booster vaccine. Boosting LVS ?capB-primed mice with rLm/iglC significantly enhanced T cell immunity; their splenic T cells secreted significantly more gamma interferon (IFN-?) and had significantly more cytokine (IFN-? and/or tumor necrosis factor [TNF] and/or interleukin-2 [IL-2])-producing CD4(+) and CD8(+) T cells upon in vitro IglC stimulation. Importantly, mice primed with LVS ?capB or rLVS ?capB/IglC, boosted with rLm/iglC, and subsequently challenged with 10 50% lethal doses (LD50) of aerosolized highly virulent F. tularensis Schu S4 had a significantly higher survival rate and mean survival time than mice immunized with only LVS ?capB (P < 0.0001); moreover, compared with mice immunized once with LVS, primed-boosted mice had a higher survival rate (75% versus 62.5%) and mean survival time during the first 21 days postchallenge (19 and 20 days for mice boosted after being primed with LVS ?capB and rLVS ?capB/IglC, respectively, versus 17 days for mice immunized with LVS) and maintained their weight significantly better (P < 0.01). Thus, the LVS ?capB-rLm/iglC prime-boost vaccination strategy holds substantial promise for a vaccine that is safer and at least as potent as LVS.

SUBMITTER: Jia Q 

PROVIDER: S-EPMC3647989 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature