A novel sulfur mustard (HD) vapor inhalation exposure model of pulmonary toxicity for the efficacy evaluation of candidate medical countermeasures

Abstract

Objective

To develop a novel inhalation exposure system capable of delivering a controlled inhaled HD dose through an endotracheal tube to anesthetized rats to investigate the lung pathophysiology and evaluate potential medical countermeasures.

Materials and methods

Target HD vapor exposures were generated by a temperature-controlled vapor generator, while concentration was monitored near real-time by gas chromatography. Animal breathing parameters were monitored real-time by in-line EMKA/SciReq pulmonary analysis system. Individual exposures were halted when the target inhaled doses were achieved. Animals were observed daily for clinical observations and lethality with scheduled termination at 28 days post-exposure. Upon scheduled or unscheduled death, animals underwent a gross necropsy and lung and trachea were collected for histopathology.

Results

Controlled HD concentrations ranged from 60 to 320 mg/m³. Delivered inhaled doses range from 0.3 to 3.20 mg/kg with administered doses within 3% of the target. The 28-day inhaled LD₅₀ is 0.80 mg/kg (95% CI = 0.42–1.18 mg/kg). Post exposure respiratory abnormalities were observed across all dose levels though the higher dose levels had earlier onset and higher frequency of occurrence. Histopathologic alterations were not qualitatively altered in accordance with dose but instead showed a relationship to an animals’ time of death, with early deaths demonstrating acute damage and later deaths displaying signs of repair.

Discussion/Conclusion

This novel exposure system administers targeted HD inhaled doses to generate a small animal model that can be used to evaluate physiological toxicities of inhaled HD on the lungs and for evaluation of potential medical countermeasure treatments.

Keywords:

• Rats
• inhalation exposure
• inhaled dose
• methods
• sulfur mustard vapor
• lethality

Acknowledgements

The views expressed in this article are those of the authors and do not reflect the official policy of the NIAID, NIH, HHS, or the U.S. Government. No official support or endorsement of this article by the NIAID, NIH, HHS, or the U.S. Government is intended or should be inferred. The sponsor participated in the development of the concept of the reported study, contributed to its design and the interpretation of the data, the decision to submit it for publication and the preparation of the manuscript. The sponsor also made similar contributions to other studies occurring at Battelle during the same time frame.

Ethical approval

The experimental protocol was approved by the Institutional Animal Care and Use Committee at Battelle. All procedures were conducted in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals and the Animal Welfare Act of 1966 (P.L. 89-544), as amended.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Chemical Countermeasures Research Program (CCRP), National Institute of Allergy and Infectious Diseases (NIAID), and the National Institutes of Health Office of the Director (NIH OD) through an interagency agreement (AOD18012-001-00000) between the NIH and U.S. Department of Health and Human Services Program Support Center (HHS PSC) and prepared under the auspices of the CCRP/NIAID/NIH – contract No. HHSP233201500095I/HHSP23337001T (PSC180304).