The New Zealand white rabbit animal model of acute radiation syndrome: hematopoietic and coagulation-based parameters by radiation dose following supportive care

Abstract

Purpose

Animal models that accurately reflect human responses to radiation injury are needed for advanced mechanistic investigation and development of effective therapeutics. The rabbit is an established animal model accepted by the FDA for studies of cardiovascular disease, lipid metabolism, the development of anticoagulants, testing of bone implants, and the development of treatments for infectious diseases such as HIV. The purpose of this study was to investigate the New Zealand White (NZW) Rabbit model as a model of acute radiation exposure because of its established similarity to human vascular, immune, and coagulation responses.

Materials and methods

Two sequential studies were performed in a total of 81 male NZW rabbits, 16–20 weeks of age. All animals underwent clinical observations and peripheral blood analyses following a single dose of 0, 6, 7, 8, 8.5, 9, or 10 Gy of total body irradiation via a 6 MV Linear accelerator photon source on day 0. Animals were treated with timed release fentanyl patch (days 0–30), subcutaneous hydration (day 1, Study 2 only), and oral sulfamethoxazole/trimethoprim 30 mg/kg once daily (days 3–30) and were followed for 30 days or to time of mortality.

Results

Study 1 revealed the estimated LD30, −50, −70, and −90 with 95% confidence intervals (CI) at 30 days to be 6.7 (CI: 5.9–7.4), 7.3 (CI: 6.7–7.8), 7.9 (CI: 7.3–8.4), and 8.8 (CI: 7.9–9.7) Gy, respectively. In study 2, a survey of blood coagulation and biochemical parameters were performed over time and necropsy. Complete blood counts taken from animals exposed to 7, 8, or 10 Gy, demonstrated dose-dependent depletion of lymphocytes, neutrophils, and platelets. Platelet counts recovered to baseline levels in survivors by day 30, whereas lymphocyte and neutrophil counts did not. Decedent animals demonstrated grade 3 or 4 neutropenia and lymphopenia at time of death; 64% of the decedents experienced a 30% or greater drop in hematocrit. Decedent animals demonstrated more than 100% increases from serum baseline levels of blood urea nitrogen, creatinine, aspartate aminotransferase, and triglyceride levels at the time of death whereas survivors on average demonstrated modest or no elevation.

Conclusion

This NZW rabbit model demonstrates dose-dependent depletion of hematopoietic parameters. The LD_50/30 of 7.8 Gy (95% CI: 6.6–8.4) with supportive care appears to be close to the ranges reported for rhesus macaques (5.25–7.44 Gy) and humans (6–8 Gy) with supportive care. These findings support the utility of the NZW rabbit model for further mechanistic investigation of acute radiation exposure and medical countermeasure testing.

Keywords:

• Rabbit
• total body irradiation
• radiation injury
• hematopoietic response
• acute radiation syndrome
• dose response

Acknowledgments

Funding for this project has been provided in whole or in part by the Biomedical Advanced Research and Development Authority, Office of the Assistant Secretary for Preparedness and Response, Office of the Secretary, Department of Health and Human Services, under contract no. HHS0100201500008I.

Authors contributions

Paredes, Lindeblad, and Bartholomew wrote the paper. Lindeblad, Bartholomew, Moulder, Nanda, and Lyubimov designed the study. Paredes, Patil, Hong, Smith, Mousefeiris, and Bosland conducted data acquisition. Paredes, Patil, Neal, Nanda, Mousafeiris, Bosland, Lyubimov, and Bartholomew analyzed the data.

Disclosure statement

The authors have no conflicts of interest to report.

Additional information

Notes on contributors

Andre Paredes

Andre Paredes, PhD, is a Research Assistant Professor in the Department of Surgery at the University of Illinois at Chicago. He received is PhD in Bioengineering in 2018. His research interest are in photomedicine, innate immunity, and radiation biology.

Matthew Lindeblad

Mr. Matthew Lindeblad is the Director of the Toxicology Research Laboratory (TRL) at the University of Illinois at Chicago over. He served as a Co-PI or Study Director on contracts for more than 22 years, including BARDA (radiation studies in mice, rabbits, mini-pigs and monkeys), NIAID, NCI, DOD, and CDC.

Rachana Patil

Rachana Patil, MS, is a Research Scientist at Pediatrics Stem Cell Transplant Division at Stanford University. She has 8 years of experience in technical project leadership, laboratory management, and other academic services. Her research improves outcomes of allogeneic hematopoietic stem cell transplant in children with various leukemia and genetic disorders.

Matthew D. Neal

Matthew D. Neal, MD FACS is the Roberta G. Simmons Associate Professor of Surgery at the University of Pittsburgh. He is the Director of the Pittsburgh Trauma Research Center and is a practicing trauma surgeon. His research focuses on mechanisms of hemostasis, coagulopathy, and thrombosis, funded by NIH and DoD.

Yuanfan Hong

Yuanfan Hong is a Research Scientist at the Transplantation Biology Research Laboratory at the University of Illinois. She has over 10 years of experience in cellular and molecular assays, laboratory management and data analytics. Her research focuses on radiation biology and cellular therapeutics.

Brett Smith

Brett Smith is a Licensed Radiophysicist at the University of Illinois with a clinical interest in radiation therapeutics. Additional interests include large and small animal models of radiation exposure.

Joy P. Nanda

Joy P. Nanda, DSc, MS, MHS, MBA, is a Community, Behavioral, and Statistical Epidemiologist from Johns Hopkins with over four decades of experience in teaching, research, mentoring, and other academic/community services/consultations on epidemiological and biostatistical methodologies. Joy currently devotes his time in COVID-19 recovery evaluation and community engaged translational research.

Vasileios Mousafeiris

Vasileios Mousafeiris is an MD and Surgery Resident. He received his MSc in Medicinal chemistry and Pathology in 2018. His main research interests include tissue regeneration, radiology and cancer profile.

John Moulder

John Moulder, PhD is Professor Emeritus of Radiation Oncology at the Medical College of Wisconsin. His primary research interest is the development of methods to detect, prevent and treat injuries from radiation exposure. A secondary interest is explaining radiation exposure risks to those who are not radiation experts.

Maarten C. Bosland

Maarten C. Bosland, DVSc, PhD, is a Professor in the Department of Pathology at the University of Illinois at Chicago. He is a laboratory animal pathologist providing pathology services to investigators. His research interests include hormonal carcinogenesis, prostate cancer, cancer chemoprevention, and experimental pathology conducting NIH and DoD-funded projects.

Alexander Lyubimov

Alexander Lyubimov, MD, PhD, DABT, is a Research Associate Professor, Department of Pharmacology at UIC. He has received his PhD in Toxicology in 1989. His interests are drug development, efficacy and toxicity of the new drugs for many different indications, including cancer, acute radiation syndrome, diabetes, thrombosis, sepsis, etc.

Amelia Bartholomew

Amelia Bartholomew is Chief of Translational Research and Professor of Surgery and Bioengineering at the University of Illinois Chicago. She is interested in hematopoietic, coagulopathic and inflammatory responses following total body radiation. Additional interests include cellular therapeutics in tissue regeneration and cancer treatments.