Molecular evolution of influenza A viruses circulated in Fujian Province, China

April 1, 2008

Fujian Center for Disease Control & Prevention, China, reported the molecular evolution of influenza A (H3N2) viruses in Fujian Province, south of China during the period 1996¨D2004 and demonstrated some key codons responsible for antigenic drift. The study is reported in Issue 51 of the Science in China Series C: Life Science because of its significant impact.

The FJ/411/02-like virus strains caused influenza epidemics worldwide in the 2003£­04 influenza seasons. It has been shown that the viruses causing pandemics, and even year-to-year epidemics, emerge from Asia. So it is important to do surveillance and analyses of the mutation of HA1 gene of influenza virus in south of China. A/Fujian/411/2002(H3N2)-like influenza virus was recommended as one of the compositions of 2003-04 trivalent influenza vaccine for the south hemisphere and 2004-05 trivalent influenza vaccine for the north hemisphere.

Phylogenetic analysis was carried out for genes encoding hemagglutinin1 (HA1) of influenza A virus (14 new and 11 previously reported reference sequences) in this study. Phylogenetic analysis confirmed that progressive drifts occurred among our H3N2 influenza isolates over the eight flu seasons. The mutations of HA1 genes occurred from time to time, which were responsible for about four times of antigenic drift of influenza H3N2 viruses in Fujian, China.

The data demonstrated that amino acid changes were limited to some key codons at or near antibody binding sites A through E on the HA1 molecule. "The changes at the antibody binding site B or A or sialic acid receptor binding site 226 were critical for antigenic drift," noted principal investigator WenQiong Xiu, associate professor of the Department of Virology at the Fujian Center for Disease Control & Prevention, China. "The antigenic sites might change and the key codons for antigenic drift might change as influenza viruses evolve."

The study involved many experiments. The influenza strains of Fujian were directly isolated from clinical samples grown in MDCK cells or embryonated chicken eggs. Then viral RNA was extracted from the isolating fluids and was amplified by RT-PCR . Sequencing was performed and the nucleotide sequences were determined. Finally, sequence alignment and phylogenetic analysis of the sequencing data was carried out.

We also found that potential glycosylation sites were accumulated with evolution. Influenza viruses are volatile in order to survive in human body, and the viability was indeed a heritable trait of codons. The HA three-dimensional structure remains constant during antigenic drift, presumably so that the biological function of HA can be maintained. Amino acid changes in natural isolates were principally chosen from changeable substitutions that do not disrupt HA activity.

The main conclusion reported by the investigators is that it is important to monitor new H3 isolates for mutations in the positively selected codons of HA1 gene in south of Asia.

Reference: Xiu WQ, Wen YW, Shen XN, Xie JF, Yang SQ, Wu BS, Wang MA. Molecular evolution of influenza A (H3N2) viruses circulated in Fujian Province, China during the 1996-2004 period. Science in China Series C: Life Sciences 2008; 51(4): 1-8

Source: Science in China Press

Explore further: H7N9 influenza vaccine clinical trials begin

Related Stories

H7N9 influenza vaccine clinical trials begin

March 15, 2018
Two new clinical trials testing an experimental vaccine to prevent influenza caused by an H7N9 influenza virus are now enrolling volunteers at sites across the United States. The Phase 2 studies, sponsored by the National ...

Scientists seek super-shot for flu 100 years after pandemic

January 17, 2018
The descriptions are haunting.

Explainer: What is H7N9 bird flu?

February 10, 2014
Australia's federal Department of Health has advised general practitioners to be on the lookout for potential cases of the H7N9 strain of influenza A, or bird flu, following a spate of deaths in China.

Studies showing how bird flu viruses could adapt to humans offer surveillance and vaccine strategies

June 6, 2013
Bird flu viruses are potentially highly lethal and pose a global threat, but relatively little is known about why certain strains spread more easily to humans than others. Two studies published today in the journal Cell identify ...

Novel avian influenza A virus has potential for both virulence and transmissibility in humans

September 10, 2013
A new study has found that a novel avian-origin H7N9 influenza A virus, which has recently emerged in humans, attaches moderately or abundantly to the epithelium of both the upper and lower respiratory tracts. This pattern ...

Evidence of host adaptation of avian-origin influenza A virus

May 15, 2013
The connection between human avian-origin influenza A (H7N9) virus infection and environmental sources of the virus were determined based on clinical data, epidemiology, and virological characteristics of the three early ...

Recommended for you

Switch discovered to convert blood vessels to blood stem cells in embryonic development

March 20, 2018
A switch has been discovered that instructs blood vessel cells to become blood stem cells during embryonic development in mice. Using single-cell technology, researchers from the Wellcome Sanger Institute in Cambridge and ...

Scientists discover new causes of cellular decline in prematurely aging kids

March 19, 2018
In a recent paper published in Cell Reports, Saint Louis University researchers have uncovered new answers about why cells rapidly age in children with a rare and fatal disease. The data points to cellular replication stress ...

Don't blame adolescent social behavior on hormones

March 19, 2018
Reproductive hormones that develop during puberty are not responsible for changes in social behavior that occur during adolescence, according to the results of a newly published study by a University at Buffalo researcher.

Stem cells treat macular degeneration

March 19, 2018
In July 2015, 86-year-old Douglas Waters developed severe age-related macular degeneration (AMD). He struggled to see things clearly, even when up close.

Measuring neutrophil motility could lead to accurate sepsis diagnosis

March 19, 2018
A microfluidic device developed by Massachusetts General Hospital (MGH) investigators may help solve a significant and persistent challenge in medicine—diagnosing the life-threatening complication of sepsis. In their paper ...

Democratizing science: Researchers make neuroscience experiments easier to share, reproduce

March 16, 2018
Over the past few years, scientists have faced a problem: They often cannot reproduce the results of experiments done by themselves or their peers.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.