Characterization and pathogenesis of aerosolized eastern equine encephalitis in the common marmoset (Callithrix jacchus).
Licensed antiviral therapeutics and vaccines to protect against eastern equine encephalitis virus (EEEV) in humans currently do not exist. Animal models that faithfully recapitulate the clinical characteristics of human EEEV encephalitic disease, including fever, drowsiness, anorexia, and neurological signs such as seizures, are needed to satisfy requirements of the Food and Drug Administration (FDA) for clinical product licensing under the Animal Rule.



In an effort to meet this requirement, we estimated the median lethal dose and described the pathogenesis of aerosolized EEEV in the common marmoset (Callithrix jacchus). Five marmosets were exposed to aerosolized EEEV FL93-939 in doses ranging from 2.4 × 101PFU to 7.95 × 105PFU.



The median lethal dose was estimated to be 2.05 × 102PFU. Lethality was observed as early as day 4 post-exposure in the highest-dosed marmoset but animals at lower inhaled doses had a protracted disease course where humane study endpoint was not met until as late as day 19 post-exposure. Clinical signs were observed as early as 3 to 4 days post-exposure, including fever, ruffled fur, decreased grooming, and leukocytosis. Clinical signs increased in severity as disease progressed to include decreased body weight, subdued behavior, tremors, and lack of balance. Fever was observed as early as day 2-3 post-exposure in the highest dose groups and hypothermia was observed in several cases as animals became moribund. Infectious virus was found in several key tissues, including brain, liver, kidney, and several lymph nodes. Clinical hematology results included early neutrophilia, lymphopenia, and thrombocytopenia. Key pathological changes included meningoencephalitis and retinitis. Immunohistochemical staining for viral antigen was positive in the brain, retina, and lymph nodes. More intense and widespread IHC labeling occurred with increased aerosol dose.



We have estimated the medial lethal dose of aerosolized EEEV and described the pathology of clinical disease in the marmoset model. The results demonstrate that the marmoset is an animal model suitable for emulation of human EEEV disease in the development of medical countermeasures.
United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Virology Division, Frederick, MD, 21702, USA.
Aimee I
AI
Porter
United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Virology Division, Frederick, MD, 21702, USA. rerwincohen@gmail.com.
Rebecca A
RA
Erwin-Cohen
Pathology Division, Frederick, MD, 21702, USA.
Nancy
N
Twenhafel
Pathology Division, Frederick, MD, 21702, USA.
Taylor
T
Chance
Center for Aerobiological Sciences, Frederick, MD, 21702, USA.
Steven B
SB
Yee
Research Support Division, Frederick, MD, 21702, USA.
Steven J
SJ
Kern
Diagnostic Systems Division, Frederick, MD, 21702, USA.
David
D
Norwood
Diagnostic Systems Division, Frederick, MD, 21702, USA.
Laurie J
LJ
Hartman
United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Virology Division, Frederick, MD, 21702, USA.
Michael D
MD
Parker
United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Virology Division, Frederick, MD, 21702, USA.
Pamela J
PJ
Glass
Center for Aerobiological Sciences, Frederick, MD, 21702, USA.
Luis
L
DaSilva
D000336:Aerosols; D000818:Animals; D001774:Blood Chemical Analysis; D001921:Brain / Q000473:pathology / Q000821:virology; D002144:Callithrix / Q000821:virology*; D004195:Disease Models, Animal; D004663:Encephalitis Virus, Eastern Equine / Q000472:pathogenicity*; D020242:Encephalomyelitis, Eastern Equine / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary* / Q000821:virology*; D005260:Female; D007109:Immunity; D007150:Immunohistochemistry; D007668:Kidney / Q000821:virology; D007928:Lethal Dose 50; D008099:Liver / Q000821:virology; D008198:Lymph Nodes / Q000821:virology; D008297:Male; D012367:RNA, Viral / Q000032:analysis / Q000302:isolation & purification; D016019:Survival Analysis; D019562:Viral Load; D010948:Viral Plaque Assay
D000336:Aerosols; D012367:RNA, Viral
Alphavirus; Animal model; Immunity; Nonhuman primate; Pathogenesis