The four remaining pigs were orally infected with virus suspension diluted in a total volume of 5 ml PBS and containing 2 9 10 7 rotavirus particles (as determined by negative-stain semi-quantitative electron microscopy) of strain RV277 [45] . The virus suspension was prepared from the contents of the small and large intestine of a rotavirus-infected gnotobiotic piglet [32] . The above applied oral dose caused severe diarrhea from 24 hpi (hours post infection) in 3-week-old gnotobiotic piglets [32] . Infected piglets were housed in their isolators under the same conditions as described above for another period of 12 (two piglets) or 18 h (two piglets) before they were transported to the necropsy room. Immediately after arrival in the necropsy room, 10 ml of EDTA blood for hematological analysis was collected from the jugular vein. Subsequently, animals were killed by barbiturate overdose and their intestines were taken out. The jejunum was opened and rinsed with cold saline, and 10 cm of mucosa in the middle of the jejunum was scraped off with a glass slide, frozen in liquid nitrogen, and kept at -70°C until RNA and DNA extraction. An adjacent part of the collected jejunum was fixed in 4% formaldehyde and used to determine the villus height and crypt depth. Villus and crypt dimensions were determined on hematoxylin-eosinstained 5-lm tissue sections [34] . During the experiment, fecal samples were collected at 0, 12 and 18 hpi from the rectum for determination of the percent dry matter [18] . Fecal samples were tested for the presence or absence of rotavirus by ELISA [33] . The germ-free status of each piglet was confirmed by analyzing throat saliva and feces samples, collected on days 6, 12 and 19, and on the day of slaughter, for the presence of microorganisms.