Genetic and immunogenicity analysis of porcine circovirus type 2 strains isolated in central China.

Porcine circovirus type 2 (PCV2) is an economically important pathogen in domestic pigs and wild boars all around the world. To understand the molecular epidemiology of PCV2 strains circulating in central China and to provide a potential vaccine candidate strain, we analyzed the genetic variations of 46 PCV2 isolates circulating from 2009 to 2016 in Henan Province (24 detected in the field from 2009-2013 and 22 from 2013-2016) and evaluated the efficacy of an isolate as a vaccine candidate strain in a mouse model. We found that PCV2b was the predominant genotype and PCV2b-1C was the main subtype. The PCV2 isolate DF-1, which had a virus titer of 106.5 TCID50/mL and a stable genome, was selected and used to immunize Kunming mice. Enzyme-linked immunosorbent assay (ELISA), immunoperoxidase monolayer assay (IPMA), and virus neutralization test (VNT) results indicated that the DF-1 vaccine candidate strain could elicit a level of specific antibodies and neutralizing antibodies similar to those induced by a commercial vaccine. Polymerase chain reaction (PCR) detection of virus in vaccinated mice after challenge revealed that DF-1 vaccination was effective in clearing the virus in different tissues. Hence, the PCV2 isolate DF-1, a circulating subtype of PCV2b-1C, might be used as a potential vaccine candidate strain.