Genetic variations of nucleoprotein gene of influenza A viruses isolated from swine in Thailand

Kamol Suwannakarn,Sujira Parchariyanon,Nattakarn Thippamom,Alongkorn Amonsin,Roongroje Thanawongnuwech,Yong Poovorawan,Donreuthai Sreta,Sudarat Damrongwatanapokin,Pravina Kitikoon,Apiradee Theamboonlers

doi:10.1186/1743-422x-7-185

Kamol Suwannakarn, Sujira Parchariyanon + Show 8 more

Open Access

https://doi.org/10.1186/1743-422x-7-185

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Abstract

BackgroundInfluenza A virus causes severe disease in both humans and animals and thus, has a considerably impact on economy and public health. In this study, the genetic variations of the nucleoprotein (NP) gene of influenza viruses recovered from swine in Thailand were determined.ResultsTwelve influenza A virus specimens were isolated from Thai swine. All samples were subjected to nucleotide sequencing of the complete NP gene. Phylogenetic analysis was conducted by comparing the NP gene of swine influenza viruses with that of seasonal and pandemic human viruses and highly pathogenic avian viruses from Thailand (n = 77). Phylogenetic analysis showed that the NP gene from different host species clustered in distinct host specific lineages. The NP gene of swine influenza viruses clustered in either Eurasian swine or Classical swine lineages. Genetic analysis of the NP gene suggested that swine influenza viruses circulating in Thailand display 4 amino acids unique to Eurasian and Classical swine lineages. In addition, the result showed 1 and 5 amino acids unique to avian and human lineages, respectively. Furthermore, nucleotide substitution rates showed that the NP gene is highly conserved especially in avian influenza viruses.ConclusionThe NP gene sequence of influenza A in Thailand is highly conserved within host-specific lineages and shows amino acids potentially unique to distinct NP lineages. This information can be used to investigate potential interspecies transmission of influenza A viruses. In addition, the genetic variations of the NP gene will be useful for monitoring the viruses and preparing effective prevention and control strategies for potentially pandemic influenza outbreaks.

Highlights

Influenza A virus causes severe disease in both humans and animals and has a considerably impact on economy and public health
The 12 swine influenza isolates were identified as subtypes H1N1 (n = 6), H1N2 (n = 1) and H3N2 (n = 5) based on RT-PCR using subtype specific primers
In conclusion, our study provided the nucleotide sequences of the NP gene of 12 Thai swine influenza viruses of subtypes H1N1, H1N2 and H3N2

Summary

Introduction

Influenza A virus causes severe disease in both humans and animals and has a considerably impact on economy and public health. Influenza A virus poses a serious threat to public health worldwide, the virus circulating in humans and animal species such as birds, pigs and horses. The 8 gene segments of the pandemic (H1N1) 2009 virus originated from human lineage (PB1), avian lineage (PB2, PA), Eurasian swine lineage (NA, M) and classical swine lineage (HA, NP, NS) [14,15]. This serves as an example that certain influenza A strains can harbor an NP gene that might not be host specific, such as the S-OIV in humans. The NP gene of S-OIV has been suggested to originate from the classical swine influenza virus

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