A Rodent Model of Sulfur Mustard Hematologic Toxicity for the Efficacy Evaluation of Candidate Medical Countermeasures

Abstract

Introduction While exposure to sulfur mustard (SM) is commonly associated with the production of vesicating dermal, ocular, and respiratory injuries, systemic damage to bone marrow and lymphatic tissue can decrease critical immune cell populations leading to higher susceptibility to life-threatening infection and septicemia. There are currently no approved medical countermeasures for SM-induced myelosuppression. An intravenous SM challenge model was developed in adult rats as a preliminary proof-of-principle platform to evaluate the efficacy of candidate immunostimulants. Materials and Methods Adult male and female Sprague Dawley rats were exposed to SM through tail vein injection. Toxicity progression was monitored through clinical observations, body weights, body temperatures, hematology, serum clinical chemistry, and flow cytometry of blood and bone marrow samples. Results Following SM exposure, overt toxicity progression was characterized by weight loss, changes in body temperature, and manifestation of toxic clinical signs (diarrhea, lethargy, hunched posture, rough hair coat, respiratory distress, and death). Drastic alterations in complete blood cell profiles included an early-onset lymphopenia followed by a delayed-onset neutropenia and thrombocytopenia. Only transient changes in serum clinical chemistry parameters were observed. Flow cytometry analysis of circulating blood revealed that B-cells were more predominantly affected by SM exposure than T-cells. Challenge with SM resulted in loss of hematopoietic and mesenchymal stem cell populations in the bone marrow. Conclusions The small animal model developed in this study replicates many key aspects of human SM exposures and should serve as a relevant, rapid, and cost-effective platform to screen candidate medical countermeasures for SM-induced hematologic toxicity.

Granulocyte Colony-Stimulating Factor (Neupogen®; Filgrastim) Accelerates Neutrophil Recovery in a Rodent Model of Sulfur Mustard-Induced Hematologic Toxicity

“…The current study was undertaken to evaluate the efficacy of filgrastim, specifically Neupogen®, in a recently published rodent model of SM hematologic toxicity. 20 Although this IV model of SM intoxication is not representative of a real-world exposure scenario, the temporal progression of hematologic toxicity following SM exposure observed in IV challenged rats aligns with clinical findings, characterized by an early-onset lymphopenia followed by a delayed-onset neutropenia and thrombocytopenia. 5 Consequently, monitoring potential treatment-induced changes in immune cell populations and/or resultant clinical symptoms after SM exposure in this model provides a platform to assess effectiveness of candidate MCMs.…”

“…Of note, due to surgical scheduling/animal availability, the vendor for Sprague-Dawley rats in this study was different from that used in previous model development work. 20 While analysis of baseline CBC profiles between vendor sources revealed significant differences (data not shown), most notably higher baseline WBC, lymphocyte, and neutrophil counts in rats obtained from Charles River Laboratories (CRL), it is unclear if this contributed to the lower mortality observed in this study using Sprague-Dawley rats sourced from CRL. Regardless, further study will be required to better define appropriate SM challenge levels that provide a reliable lethal background in vehicle-treated animals from which to measure countermeasure effectiveness.…”

“…Purity analysis, preparation of SM dosing solutions at 1.5 mg/mL in ethanol/propylene glycol, dose confirmation analysis, and intravenous (IV) tail vein dose administration were performed as previously described. 20 Neupogen® Treatment Neupogen® (filgrastim), manufactured by Amgen® (Thousand Oaks, CA), was purchased by NIH and provided to Battelle by SRI International (Lot #1098089). Animals received Neupogen® treatment by the subcutaneous (SC) route as a single daily injection at 41 μg/kg/d (see the Results section for dosing justification).…”

“…SM challenge was performed at 2.11 mg/kg which represented a revised LD 50 estimated based on continued work from previous efforts. 20 Treatment was initiated at approximately 1 d after challenge.…”

Overlapping Science in Radiation and Sulfur Mustard Exposures of Skin and Lung: Consideration of Models, Mechanisms, Organ Systems, and Medical Countermeasures: Overlapping science in radiation and sulfur mustard injuries to lung and skin

“…The program has a robust pipeline of funding to address other areas of concern during a radiation emergency, including the development of de-corporation agents that are amenable to mass casualty use, and the identification of biomarkers of radiation injury to triage and guide patient management and predict severity of late radiation-induced health outcomes. 4 The CCRP, which focuses on discovery research and early development, has supported the development of many animal models, 5 including those addressing ocular, 6 hematologic, 4 and lung 5 injuries arising from SM exposure. The program has also provided guidance and funding to allow the transition of many products to BARDA for further development.…”