Isolation and Genetic Characterization of H1N2 Subtype of Influenza A Virus from Pigs in Korea

ABSTRACT

In order to investigate swine influenza virus (SIV) infection in South Korea, 180 nasal swabs from pigs with respiratory symptoms of 18 different farms were collected between November 2001 and February 2002. Of the 180 swabs, 52 were positive for SIV by a multiplex reverse transcription-polymerase chain reaction (RT-PCR) assay. Positive samples were then subtyped by two multiplex RT-PCR assays, and 43 and 9 samples were found to be H1N2 and H3N2, respectively. SIV was isolated from the positive samples using embryonated chicken eggs. Two H1N2 isolates designated as A/Sw/ Korea/CY01/02 and A/Sw/Korea/CY02/02 were genetically characterized. Comparison of the nucleotide sequences between the two isolates showed 99.6% to 99.9% nucleotide identity of each gene segment. Pairwise sequence analysis of the hemagglutinin (HA)1 gene segments indicated that HA genes of the Korean isolates were more closely related to those of the US H1N2 isolates (94.5% to 97.9% amino acid identity) than those of the Japanese H1N2 isolates (82.4% to 93.7% amino acid identity). Amino acid sequences of the Korean isolate (A/Sw/Korea/CY02/02) showed high homology with the US H1N2 isolates; neuraminidase (NA) (97.4~99.2%), matrix (98.8~99.9%), nucleoprotein (97.6~ 98.0%), non-structural (96.8~98.6%), PA (97.9~98.7%), PB1 (98.3~99.6%) and PB2 (97.8~98.9%) genes.