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Expansion of genotypic diversity and establishment of 2009 H1N1 pandemic-origin internal genes in pigs in China.

ABSTRACT: Two-way transmission of influenza viruses between humans and swine has been frequently observed, and the occurrence of the 2009 H1N1 pandemic influenza virus (pdm/09) demonstrated that swine-origin viruses could facilitate the genesis of a pandemic strain. Although multiple introductions to and reassortment in swine of the pdm/09 virus have been repeatedly reported in both Eurasia and the Americas, its long-term impact on the development of swine influenza viruses (SIVs) has not been systematically explored. Our comprehensive evolutionary studies of the complete genomes of 387 SIVs obtained from 2009 to 2012 by influenza virus surveillance in China revealed 17 reassortant genotypes with pdm/09-origin genes. Even though the entire 2009 pandemic virus and its surface genes cannot persist, its internal genes have become established and are now the predominant lineages in pigs in the region. The main persistent pdm/09-origin reassortant forms had at least five pdm/09-origin internal genes, and their surface genes were primarily of European avian-like (EA) or human H3N2-like SIV origin. These findings represent a marked change in the evolutionary patterns and ecosystem of SIVs in China. It is possible that the pdm/09-origin internal genes are in the process of replacing EA or triple-reassortant-like internal genes. These alterations in the SIV gene pool need to be continually monitored to assess changes in the potential for SIV transmission to humans.Shortly after the emergence of the 2009 pandemic H1N1 (pdm/09) influenza virus, it was transmitted from humans to pigs and this continues to occur around the world. Many reassortants between pdm/09-origin viruses and enzootic swine influenza viruses (SIVs) have been detected. However, the long-term impact of pdm/09-origin viruses on the SIV gene pool, which could lead to the generation of influenza viruses with the potential to infect humans, has not been systematically examined. From extensive surveillance of SIVs over a 38-month period in southern China, it was found that although neither complete pdm/09 viruses nor their surface genes could persist in pigs, their internal genes did persist. Over the survey period, these internal genes became predominant, potentially replacing those of the enzootic SIV lineages. The altered diversity of the SIV gene pool needs to be closely monitored for changes in the potential for SIV transmission to humans.

SUBMITTER: Liang H

PROVIDER: S-EPMC4178866 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Expansion of genotypic diversity and establishment of 2009 H1N1 pandemic-origin internal genes in pigs in China.

Liang Huyi H Lam Tommy Tsan-Yuk TT Fan Xiaohui X Chen Xinchun X Zeng Yu Y Zhou Ji J Duan Lian L Tse Maying M Chan Chung-Hei CH Li Lifeng L Leung Tak-Ying TY Yip Chun-Hung CH Cheung Chung-Lam CL Zhou Boping B Smith David K DK Poon Leo Lit-Man LL Peiris Malik M Guan Yi Y Zhu Huachen H

Journal of virology 20140709 18

<h4>Unlabelled</h4>Two-way transmission of influenza viruses between humans and swine has been frequently observed, and the occurrence of the 2009 H1N1 pandemic influenza virus (pdm/09) demonstrated that swine-origin viruses could facilitate the genesis of a pandemic strain. Although multiple introductions to and reassortment in swine of the pdm/09 virus have been repeatedly reported in both Eurasia and the Americas, its long-term impact on the development of swine influenza viruses (SIVs) has n ...[more]

PMID: 25008935

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Project description:In June 2009, the World Health Organization declared the first influenza pandemic of the 21st century, due to the emergence and rapid spread of new swine origin H1N1 influenza A virus. In contrast to seasonal influenza infections, which typically cause morbidity and mortality in the elderly, this virus caused severe infection in young adults and not the elderly. This phenomenon was attributed to the presence of cross-neutralizing antibodies acquired by older individuals from previous exposure to swine origin influenza. However, this hypothesis could not be empirically tested using clinical data. To address this question, we investigated viral replication and the development of the immune response in naï12 years old) and aged (20 to 24 years old) female rhesus macaques infected with A/California/04/2009 (H1N1), one of the circulating pandemic strains in 2009. We compared viral loads as well as the kinetics and magnitude of the adaptive immune response in peripheral blood and bronchoalveolar lavage samples (BAL) collected longitudinally for 99 days post-infection. Although, adult animals exhibited earlier T cell responses in peripheral blood, aged animals generated a robust T cell response with comparable kinetics and magnitude as those observed in young animals in BAL. Moreover, aged animals generated a higher hemagglutination inhibition titer compared to young animals. We also measured the concentration of several cytokines in BAL supernatant. With the exception of IL-8, which was higher in aged animals, we found no differences in IFNa, IFNb, TNFa, IL-1r, IL-6, IL-15, IL-17, or MCP1 levels. Finally, we compared gene expression infection using microarray analysis of BAL samples taken on days 0, 4, 7, 10, and 14 pi. Our analyses revealed that the largest difference in host response between aged and young animals was detected day 4 post-infection, with significant enrichment for genes associated with inflammation, the innate immune response, and T cell activation in aged animals. The ability of aged animals to generate a robust immune response, especially antibody response, following infection with 2009 H1N1 virus could explain the lack of morbidity normally observed with seasonal influenza viruses in this vulnerable population.

Dataset Information

Expansion of genotypic diversity and establishment of 2009 H1N1 pandemic-origin internal genes in pigs in China.

Publications

Expansion of genotypic diversity and establishment of 2009 H1N1 pandemic-origin internal genes in pigs in China.

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