The Growth Kinetics of Porcine Epidemic Diarrhea Virus strain Pingtung 52

Porcine epidemic diarrhea (PED) is a highly contagious disease caused by porcine epidemic diarrhea virus (PEDV) infection, characterized by watery diarrhea, vomiting, dehydration, and weight loss in swine (1). PEDV has an enveloped, single-stranded, positive-sense RNA genome of ≈28 kb, belongs to the order Nidovirale, the family Coronaviridae, genus Alphacoronavirus (1). PEDV was adapted to serial propagation in Vero cell cultures by adding trypsin to the medium (2). The growth and titers with different multiplicity of infection (MOI) of PEDV in Vero cell culture were characterized in this study.

Vero cells were grown in minimum essential medium (MEM) (Gibco) supplemented with 10% fetal bovine serum, 1% Penicillin/Streptomycin (10,000 Units and 10 mg per ml) and maintained at 37 ºC in a humidified 5% CO2 incubator. When PEDV strain Pingtung 52 was inoculated to Vero cells, minimum essential medium supplemented with 0.3% tryptose phosphate broth, 0.02% yeast extract, and 10 μg/ml trypsin. The MOI of one-step and multi-step growth kinetics were 5 and 0.1, respectively. At 0, 4, 6, 8, 12, 24, 36, 48, and 72 hours post infection (hpi), the cell culture fluids were collected after 3 freeze-thaw cycles and tested for PEDV titers by real-time PCR.

The one-step (MOI 5) and multi-step (MOI 0.1) growth kinetics of PEDV strain Pingtung 52 in Vero cells revealed that Pingtung 52 has a short replicative cycle in Vero cells (6-8 h). Both growth kinetics showed a lag phase of about 6 h during virus replication, followed by exponential growth that lasted 30 h. The viral titer of multi-step growth kinetics was lower than that of one-step growth kinetics until 24 hpi. Virus yields of both growth kinetics reached the top at 36 hpi and the multi-step growth kinetic had exceeded by 0.5 log10. A typical coronavirus induced cytopathic effect appeared at 12 hpi, and near hundred percent of multinucleated cells were observed at 24 hpi.

The results of this study indicate that PEDV strain Pingtung 52 displayed similar growth kinetics with other PEDV isolates.

Disclosure of Interest: None Declared.