173. Electroporation-Mediated FER Gene Delivery in the Resolution of Severe Gram Negative Pneumonia

Abstract

Introduction: The emergence of multi drug resistant bacterial pneumonia is a major concern among Intensive Care Units across the nation. Severely injured patients including those with lung contusion (LC) and requiring mechanical ventilation are particularly vulnerable in developing above forms of virulent pneumonia (PNA). The continued deterioration of these patients evolves into highly mortal Acute Respiratory Distress Syndrome. A recent GWAS study showed that FER expression, a non-receptor cytosolic tyrosine-kinase, was associated with survival from pneumonia and sepsis. We elected to study the role of FER gene in a murine model of bacterial PNA. We hypothesized that electroporation-mediated (EP) delivery of the FER gene would decrease mortality in severe PNA complicated by trauma. Methods: Two separate PNA models were created in C57Bl/6 mice by airway inoculation of 500 CFU of Klebsiella sp., in naive (Primary PNA) or after blunt trauma-induced lung contusion (Secondary PNA). Treatment group(s) consisted on delivering naked plasmid DNA encoding FER to the lung (pFER) followed by square wave EP at 200 V/cm, eight 10 ms pulses, 1 s apart using external forelimb flat electrodes, either before or after insult. These plasmids were delivered with appropriate controls (saline EP {EP-sham} and plasmids encoding the Na+/K+-ATPase- which has shown favorable response in sterile inflammatory conditions {pPump}). 7-day survival curves were recorded. Specific readouts included parameters of lung inflammation (Histology, Bronchial Alveolar Lavage [BAL], Taq-man PCR) and infection (blood-lung bacterial quantification) at 24 and 72 hrs. Results: Survival was markedly improved by pFER treatment, both in primary and secondary bacterial PNA as compared to EP-sham or pPump controls. (Figure 1 leftFigure 1 left). Assessed parameters of inflammation showed also favorable changes being more prominent in secondary bacterial PNA, as visualized by H-E staining (Figure 1 rightFigure 1 right). With pFER treatment there was a robust recruitment of monocytes in BAL (~20 fold increase over LC+PNA control, p<0.0001), with cells showing activation of bactericidal Fizz (~110 fold change over LC + PNA control, p<0.0001) and NOS (~160 fold change over LC + PNA, p<0.0001) genes. Blood and lung, bacterial counts were significantly decreased in the pFER group with some animals able to completely clear the lung of infection (Figure 2Figure 2). Conclusion: EP-mediated delivery of the FER gene significantly improved mouse survival in severe primary and secondary models of bacterial PNA. Mechanisms include recruitment of monocytes, activation of lung immune cells and improved bacterial clearance.View Large Image | Download PowerPoint SlideView Large Image | Download PowerPoint Slide