Comparison of Monkeypox Virus Clade Kinetics and Pathology within the Prairie Dog Animal Model Using a Serial Sacrifice Study Design

Abstract

Monkeypox virus (MPXV) infection of the prairie dog is valuable to studying systemic orthopoxvirus disease. To further characterize differences in MPXV clade pathogenesis, groups of prairie dogs were intranasally infected (8 × 103 p.f.u.) with Congo Basin (CB) or West African (WA) MPXV, and 28 tissues were harvested on days 2, 4, 6, 9, 12, 17, and 24 postinfection. Samples were evaluated for the presence of virus and gross and microscopic lesions. Virus was recovered from nasal mucosa, oropharyngeal lymph nodes, and spleen earlier in CB challenged animals (day 4) than WA challenged animals (day 6). For both groups, primary viremia (indicated by viral DNA) was seen on days 6–9 through day 17. CB MPXV spread more rapidly, accumulated to greater levels, and caused greater morbidity in animals compared to WA MPXV. Histopathology and immunohistochemistry (IHC) findings, however, were similar. Two animals that succumbed to disease demonstrated abundant viral antigen in all organs tested, except for brain. Dual-IHC staining of select liver and spleen sections showed that apoptotic cells (identified by TUNEL) tended to colocalize with poxvirus antigen. Interestingly splenocytes were labelled positive for apoptosis more often than hepatocytes in both MPXV groups. These findings allow for further characterization of differences between MPXV clade pathogenesis, including identifying sites that are important during early viral replication and cellular response to viral infection.

Characterization of Monkeypox virus infection in African rope squirrels (Funisciurus sp.)

“…Lymphoplasmacytic interstitial pneumonia was also similar to that seen in other rodents [ 20 , 21 , 39 ]. Unlike other sciurids, such as ground squirrels and prairie dogs, the rope squirrels did not have hepatic or splenic lesions [ 39 , 40 ]. A large majority of the rope squirrels did have renal tubular degeneration with perivascular lymphoid and plasmacytic inflammation [ 41 ].…”

Characterization of Monkeypox virus dissemination in the black-tailed prairie dog (Cynomys ludovicianus) through in vivo bioluminescent imaging

“…Samples taken during necropsy included submandibular and mesenteric lymph nodes, tongue, heart/lung pluck, spleen, stomach, kidneys, gonads, bladder, large and small intestines, lesion tissue, and blood. Tissues were selected and processed as previously reported [19, 20]. Instruments were cleaned and decontaminated with 5% MicroChem Plus and 70% Ethanol between collections of tissue types.…”

“…Use of this animal model has allowed us to identify informative stages of monkeypox disease such as the first occurrence of viable virus shedding following intranasal inoculation starts from the oral cavity at day 6 post infection. The presence of viremia (in this case demonstrated by the presence of virus DNA within the blood starting at day 6 post infection); and finally the production of anti-orthopoxvirus antibodies begins by day 13 post infection, which generally occurs at approximately the same time as cutaneous lesion development (day 9–13 post infection) [19–21]. This similar incubation time before development of skin lesions (a key characteristic of human monkeypox), make them an ideal animal model to study MPXV pathogenesis and therapeutic testing (especially in the ability to treat animals at rash onset), unlike other animal models such as CAST/EiJ mice and African dormice, which do not develop skin lesions.…”

IMVAMUNE® and ACAM2000® Provide Different Protection against Disease When Administered Postexposure in an Intranasal Monkeypox Challenge Prairie Dog Model

“…These studies were conducted approximately 2 years apart with animals from the same geographical region, with similar weights and the same female to male ratio. Animals in the 2× LD 50 study were 2 years older than the animals used in the 170× LD 50 study, but other animal studies in our lab have not indicated that age is a factor in the pathogenesis of MPXV [32,40,58]. Animal husbandry was performed as previously described [40,66] and in accordance with CDC Institutional Animal Care and Use Committee (IACUC)-approved protocol 1718DAMPRAC.…”