Molecular Characterization of an H1N2 Swine Influenza Virus Isolated in Miyazaki, Japan, in 2006

Abstract

ABSTRACT. Swine influenza virus (SIV) was isolated from a farm in Miyazaki Prefecture in Japan in July 2006. An isolate was genetically subtyped as H1N2 and was designated A/swine/Miyazaki/1/2006 (H1N2). The nucleotide sequences of all eight viral RNA segments were determined, and then phylogenetic analysis was performed using the neighbor-joining method. All segments were shown to be closely related to those of Japanese SIV H1N2 isolates, which have been circulating since the 1980s. The results indicate the persistence of the SIV H1N2 subtype in the Japanese pig population for more than two decades and emphasize the importance of continuous surveillance for SIV.

Alterations in receptor-binding properties of swine influenza viruses of the H1 subtype after isolation in embryonated chicken eggs

“…Phylogenetic analysis of HA gene sequences of both viruses obtained by direct sequencing of the nasal swabs revealed that they belonged to the classical swine H1 lineage (data not shown). N1 and other internal genes of Rat101942 resided in the Eurasian avian-like swine lineage (data not shown), as did previously characterized Thai H1N1 isolates (Takemae et al, 2008).…”

“…The inoculated cells were incubated for more than 48 h at 37 uC in 5 % CO 2 until the cytopathogenic effect appeared. Haemagglutinating agents arising from the same swab in both an embryonated egg and MDCK cells were identified as H1N1 by the PCR method using specific primers designed in a previous study (Takemae et al, 2008). They were designated A/swine/Ratchaburi/NIAH101942/2008 (H1N1) (Rat101942).…”

“…RT-PCR, direct sequencing of the PCR products and phylogenetic analysis of the viruses obtained in this study were carried out as described previously (Takemae et al, 2008). The TCID 50 ml 21 values on MDCK cells and the EID 50 ml 21 values at 37 uC of the viruses used were determined.…”

“…In addition, human H1 egg-adapted variants with either 190DAN or 225DAG/N in the HA1 molecule always had increased affinity for Neu5Aca2,3Gal-containing receptors (Gambaryan et al, 1999). as well as the H1N2 SIVs in Japan, have retained 225D since 1999 and 2003 (Choi et al, 2002;Karasin et al, 2000;Saito et al, 2008;Yassine et al, 2009), respectively, whereas most of the classical SIVs circulating before the late 1990s had 225G ; other data from GenBank). It has been suspected that the classical swine H1 protein retained 225G due to egg adaptation (Gambaryan et al, 2005), coinciding with the fact that many laboratories used embryonated eggs for SIV isolation before the 1990s (Kida et al, 1994;Olsen et al, 2000).…”

“…Three subtypes, H1N1, H1N2 and H3N2, have been predominantly circulating in pig populations over several decades (Van Reeth, 2007). However, these subtypes have genetically distinctive characters in different geographical locations, and complicated genetic diversity has thus been demonstrated even among the same subtypes (Brown et al, 1998;Campitelli et al, 1997;Guan et al, 1996;Karasin et al, 2006;Olsen et al, 2006b;Saito et al, 2008;Takemae et al, 2008;Vincent et al, 2008;Webby et al, 2000;Yu et al, 2009). Because of the segmented nature of the genome, co-infection with more than two influenza viruses of different origins in a single host allows viruses to exchange their genes, resulting in this genetic diversity (Olsen et al, 2006a).…”