Coxsackievirus-cell interactions that initiate infection in porcine ileal explants

Coxsackievirus B5 (CB5) labeled with tritiated uridine was used to trace the interaction of the virus with explant cultures of porcine ileum. Similarly labeled human poliovirus 1 (PO 1), which is not specifically retained by porcine tissue, was used as a control. The explant procedure employed could maintain ileal tissue in a differentiated state for up to 48 hours. Porcine ileum was acquired from both young (4-6 week-old) and adult (9-11 month-old) animals. Inoculated explants of either absorptive or lymphoid tissue were incubated at temperatures selected to permit either viral adsorption or penetration and elution to occur. Retention of radioactive virus was quantitated by liquid scintillation counting and localized by autoradiography. Only in absorptive tissue explants from young animals did adsorption of CB5 at 6 degrees C exceed penetration at 37 degrees C. This suggested that incubation at 6 degrees C may not be an appropriate condition for studying enterovirus adsorption in explants. CB5 penetrated most efficiently into lymphoid tissue explants from young animals, indicating that these tissues could discriminate between CB5 and PO 1. In explants from adults, CB5 penetrated equally well into lymphoid and absorptive tissues. Virus penetrated into the absorptive epithelial cells and, possibly, the lamina propria near the villous tips. Low efficiency of penetration, and the non-critical function of these target cells, may help account for the characteristic lack of gastrointestinal symptoms in enterovirus infections.