Two different genotypes of H1N2 swine influenza virus isolated in northern China and their pathogenicity in animals.

During 2006 and 2007, two swine-origin triple-reassortant influenza A (H1N2) viruses were isolated from pigs in northern China, and the antigenic characteristics of the hemagglutinin protein of the viruses were examined. Genotyping and phylogenetic analyses demonstrated different emergence patterns for the two H1N2 viruses, Sw/Hebei/10/06 and Sw/Tianjin/1/07. Sequences for the other genes encoding the internal proteins were compared with the existing data to determine their origins and establish the likely mechanisms of genetic reassortment. Sw/Hebei/10/06 is an Sw/Indiana/9K035/99-like virus, whereas Sw/Tianjin/1/07 represents a new H1N2 genotype with surface genes of classic swine and human origin and internal genes originating from the Eurasian avian-like swine H1N1 virus. Six-week-old female BALB/c mice infected with the Sw/HeB/10/06 and Sw/TJ/1/07 viruses showed an average weight loss of 12.8% and 8.1%, respectively. Healthy six-week-old pigs were inoculated intranasally with either the Sw/HeB/10/06 or Sw/TJ/1/07 virus. No considerable changes in the clinical presentation were observed post-inoculation in any of the virus-inoculated groups, and the viruses effectively replicated in the nasal cavity and lung tissue. Based on the results, it is possible that the new genotype of the swine H1N2 virus that emerged in China may become widespread in the swine population and pose a potential threat to public health.

Immunogenicity and efficacy of a recombinant adenovirus expressing hemagglutinin from the H5N1 subtype of swine influenza virus in mice.

The H5N1 influenza viruses infect a range of avian species and have recently been isolated from humans and pigs. In this study we generated a replication-defective recombinant adenovirus (rAd-H5HA-EGFP) expressing the hemagglutinin (HA) gene of H5N1 A/Swine/Fujian/1/2001 (SW/FJ/1/01) and evaluated its immunogenicity and protective efficacy in BALB/c mice. The recombinant virus induced high levels of hemagglutination inhibition (HI) antibody at a median tissue culture infective dose of 10(8) or 10(7). Compared with mice in the control groups, the mice vaccinated with rAd-H5HA-EGFP did not show apparent weight loss after challenge with either the homologous SW/FJ/1/01 or the heterologous H5N1 A/Chicken/Hunan/77/2005 (CK/HuN/77/05). Replication of the challenge virus was partially or completely inhibited, and viruses were detected at significantly lower numbers in the organs of the vaccinated mice, all of which survived the challenge with CK/HuN/77/05, whereas most of the control mice did not. These results indicate that rAd-H5HA-EGFP can provide effective immune protection from highly pathogenic H5N1 viruses in mice and is therefore a promising new candidate vaccine against H5N1 influenza in animals.

Les virus de l'influenza de type H5N1 infectent une grande variété d'espèces aviaires et ont récemment été isolés des humains et des porcs. Dans la présente étude nous avons généré un adénovirus recombinant défectueux pour la réplication (rAd-H5HA-EGFP) exprimant le gène de l'hémagglutinine (HA) du virus H5N1 A/Porc/Fujian/1/2001 (SW/FJ/1/01) et évalué son immunogénicité et son activité protectrice chez des souris BALB/c. Le virus recombinant induisit des titres élevés d'anticorps inhibant l'hémagglutination (HI) à une dose médiane infectant les cultures cellulaires de 108 ou 107. Comparativement aux souris des groupes témoins, les souris vaccinées avec rAd-H5HA-EGFP n'ont pas montré de perte de poids apparente après une infection défi avec soit le virus homologue SW/FJ/1/01 ou le virus H5N1 hétérologue A/Poulet/Hunan/77/2005 (CK/HuN/77/05). La réplication du virus de l'infection défi fut partiellement ou complètement inhibée, et les virus furent détectés à une charge virale significativement inférieure dans les organes des souris vaccinées, qui ont toutes survécu à l'infection défi avec le virus CK/HuN/77/05, ce qui ne fut pas le cas de la majorité des souris témoins. Ces résultats indiquent que rAd-H5HA-EGFP peut fournir une protection efficace contre des virus H5N1 hautement pathogènes chez les souris et est ainsi un nouveau vaccin candidat prometteur contre l'influenza H5N1 chez les animaux.(Traduit par Docteur Serge Messier).

H7N9 influenza viruses are transmissible in ferrets by respiratory droplet.

A newly emerged H7N9 virus has caused 132 human infections with 37 deaths in China since 18 February 2013. Control measures in H7N9 virus-positive live poultry markets have reduced the number of infections; however, the character of the virus, including its pandemic potential, remains largely unknown. We systematically analyzed H7N9 viruses isolated from birds and humans. The viruses were genetically closely related and bound to human airway receptors; some also maintained the ability to bind to avian airway receptors. The viruses isolated from birds were nonpathogenic in chickens, ducks, and mice; however, the viruses isolated from humans caused up to 30% body weight loss in mice. Most importantly, one virus isolated from humans was highly transmissible in ferrets by respiratory droplet. Our findings indicate nothing to reduce the concern that these viruses can transmit between humans.

Co-circulation of pandemic 2009 H1N1, classical swine H1N1 and avian-like swine H1N1 influenza viruses in pigs in China.

The pandemic A/H1N1 influenza viruses emerged in both Mexico and the United States in March 2009, and were transmitted efficiently in the human population. They were transmitted occasionally from humans to other mammals including pigs, dogs and cats. In this study, we report the isolation and genetic analysis of novel viruses in pigs in China. These viruses were related phylogenetically to the pandemic 2009 H1N1 influenza viruses isolated from humans and pigs, which indicates that the pandemic virus is currently circulating in swine populations, and this hypothesis was further supported by serological surveillance of pig sera collected within the same period. Furthermore, we isolated another two H1N1 viruses belonging to the lineages of classical swine H1N1 virus and avian-like swine H1N1 virus, respectively. Multiple genetic lineages of H1N1 viruses are co-circulating in the swine population, which highlights the importance of intensive surveillance for swine influenza in China.

Human infection from avian-like influenza A (H1N1) viruses in pigs, China.

In investigating influenza in an immunodeficient child in China, in December 2010, we found that the influenza virus showed high sequence identity to that of swine. Serologic evidence indicated that viral persistence in pigs was the source of infection. Continued surveillance of pigs and systemic analysis of swine influenza isolates are needed.

Reassortant H1N1 influenza virus vaccines protect pigs against pandemic H1N1 influenza virus and H1N2 swine influenza virus challenge.

Influenza A (H1N1) virus has caused human influenza outbreaks in a worldwide pandemic since April 2009. Pigs have been found to be susceptible to this influenza virus under experimental and natural conditions, raising concern about their potential role in the pandemic spread of the virus. In this study, we generated a high-growth reassortant virus (SC/PR8) that contains the hemagglutinin (HA) and neuraminidase (NA) genes from a novel H1N1 isolate, A/Sichuan/1/2009 (SC/09), and six internal genes from A/Puerto Rico/8/34 (PR8) virus, by genetic reassortment. The immunogenicity and protective efficacy of this reassortant virus were evaluated at different doses in a challenge model using a homologous SC/09 or heterologous A/Swine/Guangdong/1/06(H1N2) virus (GD/06). Two doses of SC/PR8 virus vaccine elicited high-titer serum hemagglutination inhibiting (HI) antibodies specific for the 2009 H1N1 virus and conferred complete protection against challenge with either SC/09 or GD/06 virus, with reduced lung lesions and viral shedding in vaccine-inoculated animals compared with non-vaccinated control animals. These results indicated for the first time that a high-growth SC/PR8 reassortant H1N1 virus exhibits properties that are desirable to be a promising vaccine candidate for use in swine in the event of a pandemic H1N1 influenza.

Two genotypes of H1N2 swine influenza viruses appeared among pigs in China.

BACKGROUND: H1N2 is one of the main subtypes of influenza, which circulates in swine all over the world. OBJECTIVES: To investigate the prevalence and genetic of H1N2 in swine of China. STUDY DESIGN: Two H1N2 swine influenza viruses were isolated from Tianjin and Guangdong province of China in 2004 and 2006, respectively. The molecular evolution of eight gene segments was analyzed. RESULT: A/Swine/Tianjin/1/2004 has low identity with A/Swine/Guangdong/2006; in the phylogenetic tree of PA gene, A/Swine/Guangdong/1/2006 and A/Swine/Guangxi/1/2006 along with the H1N2 swine isolates of North America formed a cluster; and A/Swine/Tianjin/2004 and A/Swine/Zhejiang/2004, along with the classical H1N1 swine isolates formed another cluster; except that NA gene of A/Swine/Tianjin/1/2004 fell into the cluster of the H3N2 human influenza virus, indicating the reassortment between H3N2 human and H1N1 swine influenza viruses. CONCLUSION: Two different genotypes of H1N2 appeared among pigs in China. A/swine/Guangdong/1/06 was probably from H1N2 swine influenza viruses of North America; while A/swine/Tianjin/1/04 maybe come from reassortments of classical H1N1 swine and H3N2 human viruses prevalent in North America.

Recombinant fowlpox virus vector-based vaccine completely protects chickens from H5N1 avian influenza virus.

With the widespread presence of influenza virus H5N1 in poultry and wildlife species, particularly migrating birds, vaccination has become an important control strategy for avian influenza (AI). In this study, the immune efficacy and hemagglutination inhibition (HI) antibody responses induced by a recombinant fowlpox virus (FPV) vector-based rFPV-HA-NA vaccine was evaluated in SPF and commercial chickens. Four-week old SPF chickens vaccinated with one dose of vaccine containing 2 x 10(3) plaque forming units (PFU) of virus were completely protected from H5N1 AI virus 1 week after vaccination, and protective immunity lasted for at least 40 weeks. Two-week old commercial layer chickens were vaccinated with the rFPV-HA-NA vaccine and boosted with the same dose of vaccine following an interval of 18 weeks. The HI antibody titers higher than 4log2 lasted for 52 weeks after the booster immunization. We also examined the efficacy of the rFPV-HA-NA vaccine in SPF chickens administrated by different routes. The results showed that effective application of rFPV-HA-NA vaccine in poultry may be restricted to wing-web puncture, intramuscular or subcutaneous injection. These results demonstrate that the rFPV-HA-NA vaccine is effective in the prevention of infection of H5N1 AI virus.