Intranasal Interleukin-12 Treatment Promotes Antimicrobial Clearance and Survival in PulmonaryFrancisella tularensissubsp.novicidaInfection

Abstract

Francisella tularensis is a highly virulent facultative intracellular bacterium and is considered a potential biological warfare agent. Inhalation tularemia can lead to the development of bronchopneumonia, which is frequently fatal without medical intervention. Treatment strategies that directly target the respiratory mucosa may extend the efficacy of therapy, particularly for the medical management of acute aerosol exposure. To this end, we describe an intranasal (i.n.) strategy for the treatment of pulmonary Francisella infection in mice that uses a combinatorial approach with the conventional antibiotic gentamicin and interleukin 12 (IL-12). The i.n. administration of IL-12 alone promoted bacterial clearance and extended the time to death but did not prevent mortality against lethal pulmonary challenge with Francisella tularensis subsp. novicida. However, i.n. treatment with gentamicin and IL-12 therapeutically at 8 and 24 h after challenge markedly enhanced the rate of survival (70 to 100%) against pulmonary infection compared to the rates of survival for animals treated with antibiotic alone (17%) or IL-12 alone (0%). A delay in combinatorial therapy over a span of 4 days progressively decreased the efficacy of this treatment regimen. This combinatorial treatment was shown to be highly dependent upon the induction of endogenous gamma interferon and may also involve the activation of natural killer cells. Together, these findings suggest that IL-12 may be a potent adjunct for chemotherapy to enhance drug effectiveness against pulmonary Francisella infection.

Induction of innate immunity by lipid A mimetics increases survival from pneumonic plague

“…Our findings are consistent with similar in vivo and in vitro studies showing that protection against bacterial pathogens can be enhanced by IL-12 administration (Pammit et al, 2004) or other TLR inducers (Honko & Mizel, 2004;Montminy et al, 2006). The advantage of inducing the non-specific innate immune response is in its potential for protection against a broad spectrum of infectious agents.…”

Intranasal Vaccination with a Defined AttenuatedFrancisella novicidaStrain Induces Gamma Interferon-Dependent Antibody-Mediated Protection against Tularemia

“…Mice were first anesthetized with 3% isoflurane using a rodent anesthesia system (Harvard Apparatus, Holliston, MA) (38,40) and then inoculated intranasally with 10 6 CFU of KKF24 in 25 l of phosphate-buffered saline (PBS). Mock-vaccinated animals were treated with PBS alone.…”

“…Single-cell suspensions were prepared (1 ϫ 10 6 cells/well for spleen cells and 2 ϫ 10 5 cells/well for lymph node cells) and cultured in Dulbecco's modified Eagle's medium supplemented with 10% (vol/vol) fetal calf serum (Mediatech, Fairfax, VA), with or without increasing concentrations (10 3 CFU to 10 5 CFU) of UV-inactivated KKF24 for 72 h. Cells were also cultured with the unrelated antigen hen egg lysozyme (HEL). Culture supernatants were removed for IFN-␥, IL-12, and IL-4 analysis using BD OptEIA kits (BD Pharmingen, San Diego, CA) according to the manufacturer's instructions and as described previously (40). Briefly, culture supernatants or recombinant murine standards were incubated for 2 h in 96-well plates that were precoated overnight with 100 l of anti-IFN-␥, anti-IL-12, or anti-IL-4 capture antibody.…”

“…Humans infected by F. tularensis usually acquire the disease by contact with infected animals or vectors (ticks), exposure to contaminated food and water, or aerosol exposure (21,48 (50). An additional species, F. novicida, has low virulence for humans but shares a high degree of antigenic and genetic similarities with F. tularensis types A and B (22) and maintains high virulence in mice (33,40), thus making F. novicida infections of mice an attractive model for tularemia vaccine development.…”

In VivoMechanisms Involved in Enhanced Protection Utilizing an Fc Receptor-Targeted Mucosal Vaccine Platform in a Bacterial Vaccine and Challenge Model

“…This is in accordance with previous studies showing that both subunits of IL-12 (p35 and p40) are essential in resolving pulmonary F. tularensis infection, while the administration of recombinant IL-12 i.n. facilitates bacterial clearance from the lungs of infected mice (38)(39)(40). Therefore, it is likely that targeting iFT to Fc␥R on DCs (and potentially macrophages as well) increases the levels of IL-12 in vivo, which drives EM T cell differentiation that is long-lived and possesses TH1 phenotype characteristics.…”