Total body irradiation models in NHPs – consideration of animal sex and provision of supportive care to advance model development

Abstract

Purpose: Harmonized animal models are an indispensable tool for the development of safe and effective medical countermeasures (MCMs) against radiation injury, and rhesus macaques (referred herein as NHPs) play a critical role in FDA approval of radiation medical countermeasures for acute and delayed radiation syndromes. Reliance on such models requires that they be well characterized, which consists, in part, of a reproducible dose to mortality response relationship (DRR). However, data describing the DRR for both male and female NHPs from the same study are scarce. Furthermore, the level of supportive care and the use of blood transfusions may shift the DRR, yet such information can be difficult to compare across publications. To address these knowledge gaps, the DRRs of two different NHP total body irradiation (TBI) models are compared in this paper, one which is reliant on the use of male animals provided blood transfusions, and the other which incorporates both sexes wherein animals are not provided transfusions. Materials and methods: Studies were conducted using NHPs (Macacca mulatta) receiving TBI, with survival reported over a 60 days. Two primary studies, incorporating both male and female animals not receiving blood transfusions as a provision of supportive care, were compared to two previously published studies, which incorporated only male animals provided blood transfusions as a part of the supportive care regimen. Criterion for euthanasia, and all other provisions of supportive care were comparable. Linear probit plots estimating the lethal dose (LD) and upper and lower limits of the 95% confidence interval (CI) for 10, 30, 50, 70 and 90% mortality, were compared between individual studies and the two models presented. Results: Comparison of probit estimates reveals two important findings. (1) Females have higher mortality than males at identical radiation doses, and (2) blood transfusions increased survival of male animals at lower doses but not at high doses of radiation exposure. Conclusions: The use of single sex animal models may lead to an incomplete understanding of potential sex differences in the dose to mortality response of the TBI model. Consistent use of both sexes and type of supportive care will improve the transferability and reliability of NHP-TBI models currently in use, assist in the selection of radiation doses for single dose lethality studies, and allow investigators to determine the effectiveness of a particular MCM.

Acute Radiation Effects, the H-ARS in the Non-human Primate: A Review and New Data for the Cynomolgus Macaque with Reference to the Rhesus Macaque

“…Additionally, a recent analysis of research site-specific datasets noted as "historical" and "range-finding" provided DRRs using 60 Co gamma radiation plus medical management. The datasets showed that adult, male rhesus macaque, (a) were more sensitive to the lethal H-ARS than the datasets published above and that, (b) female rhesus macaques were markedly more sensitive than the male counterparts (Beach et al, 2020). Four of the studies noted previously, posted equivalent DRRs and slopes that estimated LD50/60 values that ranged from 7.43 to 7.54 Gy for male rhesus administered full supportive care (Farese et al, 2012;Thrall et al, 2015;Yu et al, 2015;Thrall et al, 2020) .…”

“…The respective datasets are described below. A cumulative comparison will be made relative to respective published studies, DRRs and cellular kinetics that characterized the H-ARS for rhesus macaques exposed to bilateral or rotational TBI with 2 Mev x radiation, 60 Co gamma radiation and LINAC-derived photons or x rays (Dalrymple et al, 1965;Farese et al, 2012;MacVittie et al, 2015b;Thrall et al, 2015;Yu et al, 2015;Beach et al, 2020;Thrall et al, 2020) Drouet M and Herodin F (data herein); cynomolgus and rhesus macaques, 8.0 Gy, 7 Gy, 6.5 Gy, unilateral, AP, TBI 60 Co gamma radiation, plus medical management.…”

“…The established and validated DRR for male rhesus macaques, exposed to bilateral, uniform TBI and administered medical management, resulted an LD50/60 that ranged from 6.7 Gy to 7.54 Gy with a cellular hematologic response and morbidity characteristic of the H-ARS 38 (Farese et al, 2012;MacVittie et al, 2012a;Thrall et al, 2015;Yu et al, 2015;Beach et al, 2020). The established slopes for the mortality DRR in rhesus macaques provided the database for estimated comparative mortality relative to that noted within the cynomolgus exposure protocols (Fig 7a,b).…”

“…Recent studies have emphasized the delayed effects of acute exposure (DEARE) characterized by the prolonged GI injury, immune suppression and injury to the lung, kidney and heart (MacVittie et al, 2012a;Garofalo et al, 2014;MacVittie et al, 2014;de Faria et al, 2015;Cohen et al, 2017;Cohen et al, 2019;Parker et al, 2019a;Parker et al, 2019b). Models of the GI-, H-ARS and lung-DEARE have been developed via total-body irradiation (TBI), whole thorax lung irradiation (WTLI) and partial-body irradiation (PBI) with marginal bone marrow (BM) sparing (Bertho et al, 2005a;Bertho et al, 2005b;Farese et al, 2012;MacVittie et al, 2012a;Garofalo et al, 2014;MacVittie et al, 2014;Thrall et al, 2015;Yu et al, 2015;Thrall et al, 2019;Accardi et al, 2020;Beach et al, 2020). The models have been validated through established dose response relationships (DRR), respective slopes, lethal dose (LD) values, response to radiation of varied quality, e.g., 60 Co gamma-, 250 kVp to 1 MV x ray, 6 MV LINAC derived photon-and mixed gammma/neutron-radiation, uniform, non-uniform, homogeneous and non-homogeneous exposure geometry, natural history and associated co-morbidities (MacVittie et al, 2015b;Singh and Olabisi, 2017;MacVittie et al, 2019;MacVittie et al, 2020a).…”

Pharmacokinetic and metabolomic studies with a BIO 300 Oral Powder formulation in nonhuman primates

“…Four sex matched NHPs ( Macaca mulatta ; Chinese sub-strain) weighing 4.0–8.3 kg and approximately 2–5 years old were used in this PK study. Young adult animals were used for this PK and metabolomics study because they are used in efficacy studies of H-ARS in NHPs exposed to TBI 44 – 46 . The animal study was conducted at Citoxlab, A Charles River Company (Laval, QC, Canada).…”