Table 2.

Histopathologic findings after inoculation of gnotobiotic pigs with original and tissue-culture-grown PDCoV OH-FD22

Pig no. and age (days) at inoculation	Inoculation virus	PID* at euthanasia	VH:CD*, mean	Antigen detection in formalin-fixed, paraffin-embedded tissues (IF* results)†
				Duodenum	Jejunum	Ileum	Cecum/colon	MLN*	Other internal organs
PDCoV-inoculated
1 (14)	OH-FD22-P5	3	1.3 (0.2)	-	+++	+++	±	±	-
2 (14)	OH-FD22-P5	28	5.0 (0.8)	NA*	NA	NA	NA	NA	NA
3 (14)	OH-FD22-P20	3	1.4 (0.2)	±	+++	+++	±	±	-
4 (14)	OH-FD22-P20	24	4.3 (0.6)	± (lamina propria)	+ (lamina propria)	+ (lamina propria and Peyer’s patch)	± (lamina propria)	+	-
5 (14)	OH-FD22-P40	3	2.7 (0.6)	±	+++	+++	±	±	-
6 (14)	OH-FD22-P40	23	3.4 (0.8)	± (lamina propria)	+ (lamina propria)	+ (lamina propria and Peyer’s patch)	± (lamina propria)	++	-
Ref. 1 (14)	OH-FD22 (original)	5	ND*	-	+++	+++	±	-	-
Ref. 2 (14)	OH-FD22 (original)	.	.	.	.	.	.	.	.
Ref. 3 (14)	OH-FD22 (original)	3	3.6 (1.7)	±	+++	+++	±	-	-
Negative control
7 (14)	.	3	5.6 (0.5)	-	-	-	-	-	-
8 (14)	.	24	4.0 (0.2)	-	-	-	-	-	-

* PID, postinoculation days; VH:CD, ratio of villous height to crypt depth; IF, immunofluorescence staining; MLN, mesenteric lymph node; ND, not determined due to autolysis at the tips of jejunal villi; NA, not applicable

^†Detected by immunofluorescence staining. ±, <1 % of epithelial or immune cells showed staining; +, 1 %–29 % of epithelial or immune cells showed staining; ++, 30 %–59 % of epithelial or immune cells showed staining; +++, 60 %–100 % of epithelial or immune cells showed staining; -, no cells showed staining in the intestinal section, as described [12] or in the MLN section per microscope area, at ×200 magnification