Seronegative pregnant sows and 26-day-old, PEDV-
seronegative weaned, Large White × Duroc crossbred pigs were
obtained from a PEDV-free specific pathogen free (SPF) (confirmed
by history, lack of qRT-PCR-PEDV positive fecal samples and
PEDV antibodies) swine herd of The Ohio State University. The
SPF OSU herd was also seronegative for antibodies to porcine
respiratory and reproductive syndrome virus, PRCV, TGEV and
porcine circovirus type 2. The sows farrowed naturally and nursed
their piglets until the end of the study. The four experimental
groups in the study were as follows. Group 1: PEDV inoculated
9-day-old suckling pigs (n = 9); Group 2: MEM only inoculated
9-day-old suckling pigs (n = 11); Group 3: PEDV inoculated 26-
day-old weaned pigs (n = 11); Group 4: MEM only inoculated
26-day-old weaned pigs (n = 9). All experimental procedures on
animals were approved by the Institutional Animal Care and Use
Committee of The Ohio State University. Pigs in PEDV groups
were inoculated orally with PEDV inoculum [8.9 log10 GE (genomic
equivalents) (≈2.9 log10 plaque forming unit)/pig] and pigs in
MEM only inoculated groups received MEM. The inoculation dose
was based on a previous pathogenicity study in our lab (Jung
et al., 2014). Following PEDV inoculation, pigs were monitored for
clinical signs daily until necropsy. Diarrhea was assessed by sco-
ring fecal consistency. Fecal consistency was scored as, 0 = solid;
1 = pasty; 2 = semi-liquid; 3 = liquid, with scores of 2 or more
considered diarrheic. Inoculated and mock pigs (n = 3-4/group at
each time-point) were euthanized for immunological studies at an
acute stage on post inoculation day (PID) 1 and at a later stage (PID
5) of infection. Blood samples were taken at PID 1 (n = 6-8 pigs per
group), PID 3 (n = 4-8 pigs per group) and PID 5 (from euthanized
pigs, n = 3-4 per group) and separate serum aliquots were prepared
for cytokine analysis and viral RNA quantification.