FIG. 3.

Macroscopic and histological lesions observed in naïve monkeys infected with MPXV. (A) Macroscopic and histological lesions in the skin, lungs, and pancreas in the IN-Naïve group. Papulovesicular lesions were observed in the skin (a), and nodular and granulomatous lesions were present in the lungs (b) and pancreas (c). (d) The edges of the cutaneous lesions were characterized by epithelial cell swelling, epidermal hyperplasia, hyperkeratosis, necrosis, and infiltration of inflammatory cells. (e) Nodular and granulomatous lesions in the lungs were characterized by destruction of alveolar structures, necrosis, edema, proliferating fibroblasts, and infiltration of inflammatory cells. (f) Nodular and granulomatous lesions in the pancreas were characterized by extensive necrosis with infiltration of inflammatory cells and proliferating fibroblasts. (g to i) In these lesions, MPXV antigens were demonstrated by IHC analyses, indicating that they were caused by MPXV infection. (B) Macroscopic and histological lesions in the thymus, stomach, and colon in the SC-Naïve group. (a to c) Multiple nodular lesions were present in the thymus, and papilliform and granular lesions with hemorrhaging were seen in the lumens of the stomach and colon. (d) The lesions in the thymus were characterized by granulomatous inflammation and proliferation of fibrous tissue consisting of fibroblastic cells, histiocytes, and microvascular structures. (e) The histology in the stomach consisted of necrotic changes with inflammatory cells including neutrophils. (f) The submucosal area of the colon consisted of fibroblastic tissues with granulomatous inflammation characterized by infiltration of inflammatory cells. The mucosal membranes showed ulceration. (g to i) In these lesions, MPXV antigens were demonstrated by IHC analyses, indicating that they were caused by MPXV infection.