Experimental PRRSV Infection in Piglets

Healthy, 6-week-old, landrace piglets that were free of PRRSV, classic swine fever virus (CSFV), pseudorabies virus (PRV), porcine circovirus type 2 (PCV2) and M. hyopneumoniae infections were obtained from Beijing Center for SPF Swine Breeding & Management. All piglets were confirmed to be negative for PRRSV and PCV2 antibodies, as determined using commercial ELISA kits and using RT-PCR or PCR for viral nucleic acid detection in sera. The animals were raised in the animal facilities at China Agricultural University (CAU). For the first batch of animal trials, forty-five piglets were randomly divided into nine groups. The animals in each group (n = 5) were separately raised in different isolation rooms. Each piglet in each infection group was intranasally administered with 2 ml of each virus containing 2×10⁵ TCID₅₀ (RvJXwn, RvJH1a, RvJH1b, RvJHSP, RvHB-1/3.9, RvHJ1a, RvHJ1b or RvHJSP). Each piglet in the control group was mock-inoculated with the same dose of MARC-145 cell culture supernatant. For the second batch of animal trials, fifty-five piglets were randomly allotted to eleven groups (n = 5). Each piglet in each infection group was intranasally inoculated with 2 ml of each virus containing 2×10⁵ TCID₅₀ (RvJHn9, RvJHn10, RvJHn9n10, RvJHn9n10n11, RvHJn9, RvHJn10, RvHJn9n10 or RvHJn9n10n11). The piglets in the control group were mock inoculated with 2 ml of MARC-145 cell culture supernatant. All the survived piglets were euthanized and necropsied on day 21 post-inoculation (pi).