Development of real-time PCR assay for detection of porcine circovirus-like virus P1 in domestic pigs in China

BACKGROUND The porcine circovirus-like agent P1 is a newly discovered DNA virus with a single-stranded circular genome that is highly homologous to that of porcine circovirus type 2. P1 infection can cause symptoms resembling postweaning multisystemic wasting syndrome. This study aims to develop a rapid, sensitive and specific method to detect P1. RESULTS A pair of primers was designed and used to amplify a 119 bp DNA fragment to generate a recombinant plasmid which was served as the standard. A SYBR I qPCR protocol was established using the P1 recombinant plasmid standard and the sensitivity, specificity and stability of this method was analyzed. The results demonstrate a strong correlation with P1 recombinant plasmid titers when virus DNA copy numbers fall in between 10(0) ~ 10(9) copies/μL. This method doesn't detect pseudo rabies, porcine parvovirus or porcine reproductive and respiratory syndrome virus; moreover it can distinguish porcine circovirus type 2 from P1 by melting temperature analysis. Coefficient of variation for each batch of reaction is less than 5%. The serum virus titers of P1 positive in this study were measured by this protocol to be 10(3) to 10(7) copies/mL. CONCLUSIONS The established qPCR is sensitive, specific, and reliable, which could be a useful tool when applied to quantification of P1 in a variety of samples from infected pigs.