﻿Complete Genome Sequence of an Avian-Like H4N8 Swine Influenza
Virus Discovered in Southern China
Shuo Su, Wen-bao Qi, Ji-dang Chen, Nan Cao, Wan-jun Zhu, Li-guo Yuan, Heng Wang, and Gui-hong Zhang
College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, China
We report here the complete genomic sequence of an avian-like H4N8 swine influenza virus containing an H5N1 avian influenza
virus segment from swine in southern China. Phylogenetic analyses of the sequences of all eight viral RNA segments demon-
strated that these are wholly avian influenza viruses of the Asia lineage. To our knowledge, this is the first report of interspecies
transmission of an avian H4N8 influenza virus to domestic pigs under natural conditions.
Influenza A virus can infect various hosts, including migratory
waterfowl, resident birds, horses, swine, dogs, sea mammals,
and humans. Among these species, swine serve as an important
component of the human-animal interface and play an important
role in influenza evolution and ecology (2). Although pigs can be
simultaneously infected with avian influenza viruses and human
influenza viruses, the viruses can exchange genes and produce new
variants, which suggests that pigs have become mixing vessels for
influenza viruses (3). However, in nature, interspecies transmis-
sion of avian viruses to pigs is not often documented (1).
In October 2011, an avian-like H4N8 swine influenza virus was
isolated from a commercial pig farm during an outbreak of severe
respiratory diseases in pigs in Guangdong Province, Southern
China. The strain had hemagglutination (HA) activity, and the
HA titers ranged from 128 to 256. Subsequently, nucleotide se-
quences of the eight viral genes were amplified through reverse
transcriptase PCR (RT-PCR). The amplified products were puri-
fied and cloned into the pMD18-T vector (TaKaRa) and se-
quenced with an ABI 3730 XL genome sequencer. Sequences were
assembled and manually edited to produce the final genome se-
quence. The strain was identified as subtype H4N8.
The results showed that the virus was avian-like H4N8 swine
influenza virus, whose HA gene had the highest homology with
that of A/avian/Japan/8K10185/2008(H4N6) (99%) and whose
NA gene had the highest homology with that of A/chicken/
Guangxi/2117/2010(H3N8) (98%). The NP gene was phyloge-
netically close to those in H5N1 avian influenza viruses. Accord-
ingly, the nomenclature for this isolate was A/swine/Guangdong/
K4/2011(H4N8). Phylogenetic analyses of the sequences of all
eight viral RNA segments demonstrated that these are wholly
avian influenza viruses of the Asia lineage. The nucleotide se-
quence identity between each segment of A/swine/Guangdong/
K4/2011(H4N8) and its potential progenitor identified in the
public database varied from 97% to 99%. Finding an NP gene
fragment ostensibly of avian influenza (H5N1) virus in this strain
implies that subtype H5N1 viruses may be able to contribute genes
to virus pathogenic processes in pigs in Southern China.
The amino acid sequence at the cleavage site in the HA mole-
cule is PEKASR/GLF, indicating that it is a low-pathogenicity
avian influenza virus. Analysis of potential N-glycosylation sites of
HA protein showed that this virus has four potential N-glycosyla-
tion sites at positions 18, 34, 178, and 310. This virus has Q226 and
G228 (H3 numbering) in the receptor-binding site in the HA pro-
tein, which preferentially bind to an avian-origin receptor. The
analysis of PB2 protein showed that it has 627E and 701D, with no
substitutions.
In the past decades, many influenza pandemic strains were
reported to emerge in Southern China. This is the first report of
avian-like H4N8 swine influenza virus containing an H5N1 avian
influenza virus segment in Southern China. This finding further
confirms that this area is critical for the emergence of novel influ-
enza A viruses.
Nucleotide sequence accession numbers. The GenBank ac-
cession numbers of A/Swine/Guangdong/K4/2011(H4N8) are
JX151007 to JX151014.
ACKNOWLEDGMENTS
This work was supported by the International Sci &Tech Cooperation
Program (2010DFB33920) and the Modern Agricultural Industry Tech-
nology System (CARS-36).
The funding organizations had no role in the study design, data col-
lection and analysis, ownership of the materials, or preparation of the
manuscript.
REFERENCES
1. Peiris JSM, et al. 2001. Cocirculation of avian H9N2 and contemporary
"human" H3N2 influenza A viruses in pigs in southeastern China: potential
for genetic reassortment? J. Virol. 75:9679­9686.
2. Scholtissek C. 1990/1991. Pigs as "mixing vessels" for the creation of new
pandemic influenza A viruses. Med. Princ. Pract. 2:65­71.
3. Vijaykrishna D, et al. 2010. Reassortment of pandemic H1N1/2009 influ-
enza A virus in swine. Science 328:1529.
Received 12 June 2012 Accepted 13 June 2012
Address correspondence to Guihong Zhang, guihongzh@scau.edu.cn.
S.S. and W.-B.Q. contributed equally to this study.
Copyright © 2012, American Society for Microbiology. All Rights Reserved.
doi:10.1128/JVI.01475-12
GENOME ANNOUNCEMENT
9542 jvi.asm.org Journal of Virology p. 9542 September 2012 Volume 86 Number 17
