Single-step multiplex conventional and real-time reverse transcription polymerase chain reaction assays for simultaneous detection and subtype differentiation of Influenza A virus in swine.

Because pigs are considered intermediate hosts for the emergence of novel influenza virus reassortants with associated zoonotic potential, monitoring and characterization of circulating influenza viruses in pigs are important for adequate control of infection. For this, rapid molecular diagnostic methods other than immunoassays are needed. Three novel single-step multiplex reverse transcription polymerase chain reaction (RT-PCR) assays were developed in the current study for simultaneous detection and subtype differentiation of Influenza A virus in pigs. A conventional single-step pentaplex RT-PCR was designed for concomitant detection of the generic matrix (M) gene, hemagglutinin H1 and H3, and neuraminidase N1 and N2 genes of Swine influenza virus (SIV). In the other 2 single-step tetraplex real-time RT-PCR assays, the primers and fluorescent probes were targeted for the simultaneous detection of common M, H1, H3, and N2 SIV genes (first assay), and for M, H1, and H3 SIV genes and the H5 gene of highly pathogenic avian influenza virus of Eurasian lineage (second assay). The real-time RT-PCR assays had detection sensitivity limits ranging from 10(1) to 10(3) copies of respective in vitro RNA transcripts of M, H1, H3, H5, and N2 genes. The multiplex assays were evaluated by using SIV isolates, clinical specimens, and the appropriate synthetic template. The recent H1N1 pandemic strain isolated from pigs also was tested in simplex RT-PCR and real-time RT-PCR assays with the H1 primers and probes. The efficacy of the multiplex RT-PCR and real-time RT-PCR shows the suitability of multiplex RT-PCR and real-time RT-PCR for rapid subtype identification and monitoring in North American pigs of Influenza A virus.