Background Ionizing radiation induces lipid peroxidation and forms reactive oxygen species (ROS) within the cell. Due to their highly reactive state, ROS have short diffusion distances and quickly transfer unbalanced electrons to neighboring molecules. This transfer cycle continues until it finally culminates in the generation of reactive alkenals such as 4-hydroxynonenal (4HNE). Under normal conditions, intracellular 4HNE levels are controlled by conjugation to glutathione and are actively transported from the cell; RLIP76 protein has been determined to be the major transport protein involved in the efflux of 4HNE-conjugates. Radiation induces significant oxidative stress, and the increased levels of 4HNE conjugates overwhelm transport capacity. When this occurs, further conjugation is inhibited and free 4HNE levels rise, triggering apoptosis. It was hypothesized that adding exogenous RLIP76 protein would reduce 4HNE levels and correspondingly increase the recovery from acute radiation syndrome (ARS) or completely protect individuals exposed to lethal doses of radiation. Methods The National Institutes of Health has developed animal models of ARS so that medical countermeasures can be tested in accordance with the FDA Animal Rule, since testing in people is clearly not ethical. One of these models, the C57BL/6 mouse, has been successfully utilized by Terapio to evaluate the efficacy of recombinant human RLIP76 encapsulated in liposomes (RLIP76-PL). These studies were 30-day survival studies of mice exposed to total body irradiation of 7.45-8.75 Gy. Administration of RLIP76-PL was subcutaneous or intramuscular on a prophylactic (administered up to 20 h prior to irradiation) or therapeutic (administered up to 36 h after irradiation) schedule. Results As a prophylactic, there was 100% survival compared to 33% of the controls when mice were given three doses and exposed to 8.1 Gy. As a therapeutic, the drug is not administered until 24hrs after irradiation and remarkably, there is 92% survival compared to 8% of the controls. Conclusions Combined data of many studies show that when compared to controls, treated mice exposed to LD50s, LD70s, or LD90s resulted in survival ranging from 50-80% over the controls. RLIP76-PL is a strong candidate to protect the population from acute radiation exposure.

The battlefield risk from toxic industrial chemicals, materials, or threat agents is aerosol exposure. In most cases, this is not the natural route of exposure, so we must rely on animal models to predict disease course in humans. Deposition patterns for small (1µm) and large (8µm) particles were easily predicted, but effect on disease course for Ricinus communis (ricin) was unknown. Ricin small particle: Guinea Pig (GP) - histopathologic findings (lung) were absent at 1-hr timepoint, but present by 6-hr. Ricin deposition at 6-hr was less than that at the 1-hr timepoint. After 24 hr, pulmonary changes represented significant progression of disease and amount of ricin in lungs was significantly decreased. After 48 hr, there was advanced progression of disease and amount of ricin in the lungs was comparable to 24-hr timepoint. Ricin large particle: GP - minor changes in large airways represented early pathological effects of aerosol ricin exposure at all timepoints; significantly diminished compared to pathology of small particles. Compared to small particle, abundant ricin antigen was detected in nasal cavity at these timpoints. The cohort of GP exposed to large particle ricin euthanized at 1-hr and 6-hr postchallenge contained abundant ricin antigen in large pulmonary airways and nasal passages. In contrast, only small amounts of ricin antigen were detected in lungs of GP exposed to large particle ricin euthanized at 48-hr; furthermore, immunopositive staining was absent in the nasal cavity and contiguous airway passages. Ricin small particle: African green monkey (AGM) - Lung pathology at 4 or 8-hr post-exposure was normal, but at 16, 24, and 36-hr, progression of changes due to acute ricin intoxication was present. Deposition patterns were similar to small particle in GP. Ricin large particle: three AGM survived without developing clinical signs of illness. Both the GP and AGM were most susceptible and disease progression most severe after inhalational exposure to a 1µm aerosol. Although some GP were susceptible to large particles, there was a delayed time to death, compared to death due to a small particle aerosol. AGM were not affected by an 8µm aerosol. These different outcomes are important for risk assessment of human health factors on the battlefield.