We have a field isolate of PEDv. We have been trying to propagate it in Vero cells for a year now. We have tried many types of inoculation media, ranging from DMEM supplemented with BSA and trypsin, and DMEM + tryptose phosphate broth + yeast extract + trypsin (with or without polybrene). We have detected PEDv by sequencing a segment of the S gene from PEDv propagated in DMEM + tryptose phosphate broth (0.3%) + yeast extract (0.02%) + trypsin (2 ug/mL) + polybrene (4 ug/mL). However, we found that titer was very low (~ 40 TCID50/mL), and the virus seems to be weaker after several passages, as shown by the lack of CPE in our recent experiments.
Could anyone please suggest us a way to solve this problem. Thank you very much for your time.