Table 1.
Summary of clinical signs, viral RNA titers in the feces and serum samples, and histopathologic and immunofluorescent (IF) staining results from 10-day-old gnotobiotic pigs inoculated orally with 8.7 log10 GE/pig of the IPEC-J2 cell culture-passaged PDCoV (OH-FD22-P8-I-P4) or mock at post-inoculation day (PID) 1 to 5.
| Group | Pig no. |
Viral RNA titer, log10 GE/mL, by PIDa |
Mean jejunal VH:CD ratio (SD)c |
PDCoV antigen detection by IF staining in FFPE tissuesc, d |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 | D | MJ | I | C | ||||
| PDCoV-inoculated | 1 |
Feces (score)b | <4.6 (1) | 10.0 (3) | 6.7 (3) | 7.3 (3) | 7.1 (3) | 7.9 (3) | 1.4 (0.3) |
+ | ++ or +++ | + | ± |
| Serum | <3.6 | 4.4 | . | . | . | 4.4 | |||||||
| 2 |
Feces (score) | <4.6 (1) | 9.9 (3) | 8.0 (3) | 7.6 (3) | 6.9 (3) | 9.3 (3) | 1.3 (0.2) |
+ | +++ | + | ± | |
| Serum | <3.6 | 4.0 | . | . | . | 5.0 | |||||||
| Mock-inoculated | 3 (15e) |
Feces (score) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | 5.7 (0.4) | − | − | − | − |
| Serum | <3.6 | <3.6 | . | . | . | <3.6 | |||||||
| 4 (13e) |
Feces (score) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | . | . | ND |
ND | ||||
| Serum | <3.6 | <3.6 | . | <3.6 | . | . | |||||||
| 5 (13e) |
Feces (score) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | . | . | ND |
ND | ||||
| Serum | <3.6 | <3.6 | . | <3.6 | . | . | |||||||
| 6 (13e) |
Feces (score) | <4.6 (0) | <4.6 (0) | <4.6 (0) | <4.6 (0) | . | . | ND |
ND | ||||
| Serum | <3.6 | <3.6 | . | <3.6 | . | . | |||||||
GE, genomic equivalent; VH:CD ratio, villous height to crypt depth ratio; SD, standard deviation; FFPE, formalin-fixed, paraffin-embedded; D, duodenum; MJ, mid-jejunum; I, ileum; C, colon; ND, not determined.
Detected by real-time reverse transcription PCR with a detection limit of 4.6 log10 GE/ml for fecal samples and 3.6 log10 GE/ml for serum samples.
Fecal consistency was scored as follows: 0 = solid; 1 = pasty; 2 = semi-liquid; 3 = liquid, with scores of 2 or more considered diarrheic.
Euthanasia was done at PID 5.
Detected by IHC in multiple tissue sections, resulting in a range of IF score. +/- (few), <1% of villous epithelial cells showed staining; + (low), 1%–29% of villous epithelial cells showed staining; ++ (moderate), 30%–59% of villous epithelial cells showed staining; +++ (high), 60%–100% villous epithelial cells showed staining; and -, no cells showed staining.
Pig age (days) at euthanasia. Note that the negative control pigs 4–6 were euthanized at PID 3 to establish other immunologic assays using mononuclear cells isolated from the small intestine.