Origin, Evolution, and Virulence of Porcine Deltacoronaviruses in the United States

Ma, Yuanmei; Zhang, Yu; Liang, Xueya; Lou, Fangfei; Oglesbee, Michael; Krakowka, Steven; Li, Jianrong

Gn piglets infected by the PdCV MI strain were similar to those described for PdCV Ohio CVM1 (Table 1) . Extensive villous atrophy, necrosis, and blunting were observed in the small intestine of all Gn piglets infected by the PdCV MI strain, including the two Gn piglets infected via indirect contact. Villous atrophy was more severe in the jejunum and ileum than in the duodenum for all PdCV MI-infected Gn piglets (Table 1; Histology of extraintestinal tissues. Histological changes associated with PdCV Ohio CVM1 infection were not seen in any other organs except the lung. In the lung, mild multifocal bronchial-to-bronchiolar-centric areas of nonsuppurative interstitial pneumonia were identified by 48 h p.i. (Fig. 4A and B) . Convincing histologic evidence of epithelial cell necrosis or syncytia was not seen (data not shown). Similarly, the PdCV MI strain caused mild interstitial pneumonia in Gn piglets. No histologic lesions were found in other organs of piglets infected by the PdCV MI strain. Viral antigen distribution in gnotobiotic piglets infected with the PdCV CVM1 or MI strain. Deparaffinized PdCV CVM1infected tissue sections or PEDV-infected tissue sections were stained with convalescent-phase serum from a PdCV-infected sow or monospecific polyclonal antiserum raised against PEDV in Gn piglets (Fig. 5) . PdCV convalescent-phase serum stained infected mucosal epithelia from only PdCV-infected piglets (Fig. 5E) ; anti-PEDV stained infected epithelial cells from only PEDV-infected Gn piglets (Fig. 5A) . Bronchial epithelial cells from PdCV-infected piglets contained a horseradish peroxidase (HRP) reaction product in the 72-h-p.i. lung sections (data not shown). A large number of antigens were detected in the jejunum and ileum in PdCV MI-infected Gn piglets on day 3 p.i. (see Fig. S5 in the supplemental material). These data demonstrate that (i) PdCV replicates in the epithelium of the small intestine and (ii) PdCV does not cross-react serologically with PEDV.