Abstract
BackgroundThe objective of this study is to investigate the pathogenesis of swine influenza virus (SIV) subtype H1N1 and H3N2 (Thai isolates) in 22-day-old SPF pigs.ResultsThe study found that all pigs in the infected groups developed typical signs of flu-like symptoms on 1–4 days post- infection (dpi). The H1N1-infected pigs had greater lung lesion scores than those of the H3N2-infected pigs. Histopathological lesions related to swine influenza-induced lesions consisting of epithelial cells damage, airway plugging and peribronchial and perivascular mononuclear cell infiltration were present in both infected groups. Immunofluorescence and immunohistochemistry using nucleoprotein specific monoclonal antibodies revealed positive staining cells in lung sections of both infected groups at 2 and 4 dpi. Virus shedding was detected at 2 dpi from both infected groups as demonstrated by RT-PCR and virus isolation.ConclusionThe results demonstrated that both SIV subtypes were able to induce flu-like symptoms and lung lesions in weanling pigs. However the severity of the diseases with regards to lung lesions both gross and microscopic lesions was greater in the H1N1-infected pigs. Based on phylogenetic analysis, haemagglutinin gene of subtype H1N1 from Thailand clustered with the classical H1 SIV sequences and neuraminidase gene clustered with virus of avian origin, whereas, both genes of H3N2 subtype clustered with H3N2 human-like SIV from the 1970s.
Highlights
The objective of this study is to investigate the pathogenesis of swine influenza virus (SIV) subtype H1N1 and H3N2 (Thai isolates) in 22-day-old SPF pigs
Since different subtypes of the influenza type A viruses isolated from pigs are found to cause different pathogenic levels in pigs, the objective of this study is to investigate the pathogenesis of SIV (Thai isolates) subtype H1N1 (A/swine/ Thailand/HF6/05) and H3N2 (A/swine/Thailand/S1/05) in weanling SPF pigs
The results showed that the nucleotide sequences of the HA [GenBank:FJ688266] gene of A/Thailand/HF6/ 05 (H1N1) belonged to the classical swine H1 lineage and the NA [GenBank:FJ688267] gene belonged to avian N1 lineage, and both HA [GenBank:FJ688268] and NA [GenBank:FJ688269] genes of A/Thailand/S1/05 (H3N2) belonged to the human H3N2 lineage
Summary
The objective of this study is to investigate the pathogenesis of swine influenza virus (SIV) subtype H1N1 and H3N2 (Thai isolates) in 22-day-old SPF pigs. Swine influenza is an acute, highly contagious, respiratory disease caused by type A influenza virus infection. Three main subtypes currently circulating in the pig population are classical swine influenza virus (SIV) and reassortant viruses of H1N1, H3N2 and H1N2 [1]. Pigs can be infected with other subtypes of influenza A viruses. Pig plays a substantially important role in the ecology of influenza A virus [2] since they can act as a 'mixing vessel'. When co-infections among human, avian or swine influenza viruses occur within a specific host, any new subtype can be produced by antigenic reassortment [3]
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