Efficacy evaluation of two commercial modified-live virus vaccines against a novel recombinant type 2 porcine reproductive and respiratory syndrome virus.

NADC30-like porcine reproductive and respiratory syndrome virus (PRRSV) causing clinical disease outbreaks has been recently reported in China. The recombination occurring among PRRSV strains could lead to the emergence of novel and more virulent viruses. In our previous study, a novel recombinant type 2 PRRSV (TJnh1501) between NADC30-like and modified-live virus (MLV)-like derived from the Chinese highly pathogenic PRRSV was shown to have higher pathogenicity than NADC30-like PRRSV. It remains unknown whether the emergence of the novel recombinant PRRSV strain can lead to variable protection efficacy of the MLV vaccines. In this paper, two typical commercial MLV vaccines were used to evaluate their efficacy to block TJnh1501 infection and onset of clinical symptoms. Our results showed that both MLV vaccines could shorten the period of fever and reduce viral loads in sera, but were not able to reduce the clinical signs and lung lesions indicating that the two commercial MLV vaccines provide limited cross-protection efficacy against the novel recombinant type 2 PRRSV infection. This study gives valuable suggestions for the use of MLV vaccines to control PRRSV infection in the field.

Novel triple-reassortant H1N1 swine influenza viruses in pigs in Tianjin, Northern China.

Pigs are susceptible to both human and avian influenza viruses and therefore have been proposed to be mixing vessels for the generation of pandemic influenza viruses through reassortment. In this study, for the first time, we report the isolation and genetic analyses of three novel triple-reassortant H1N1 swine influenza viruses from pigs in Tianjin, Northern China. Phylogenetic analysis showed that these novel viruses contained genes from the 2009 pandemic H1N1 (PB2, PB1, PA and NP), Eurasian swine (HA, NA and M) and triple-reassortant swine (NS) lineages. This indicated that the reassortment among the 2009 pandemic H1N1, Eurasian swine and triple-reassortant swine influenza viruses had taken place in pigs in Tianjin and resulted in the generation of new viruses. Furthermore, three human-like H1N1, two classical swine H1N1 and two Eurasian swine H1N1 viruses were also isolated during the swine influenza virus surveillance from 2009 to 2013, which indicated that multiple genetic lineages of swine H1N1 viruses were co-circulating in the swine population in Tianjin, China. The emergence of novel triple-reassortant H1N1 swine influenza viruses may be a potential threat to human health and emphasizes the importance of further continuous surveillance.