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Title: Polymorphisms in the hemagglutinin gene influenced the viral shedding of pandemic 2009 influenza virus in swine

Author
item Lorusso, Alessio
item Ciacci-zanella, Janice - Embrapa-Pigs And Poultry
item Zanella, Eraldo - Universidad De Passo Fundo
item Pena, Lindomar - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item Perez, Daniel - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item Lager, Kelly
item Rajao, Daniela - Universidade Federal De Minas Gerais
item Loving, Crystal
item Kitikoon, Pravina
item Vincent, Amy

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2014
Publication Date: 12/1/2014
Citation: Lorusso, A., Ciacci-Zanella, J.R., Zanella, E.L., Pena, L., Perez, D.R., Lager, K.M., Rajao, D.S., Loving, C.L., Kitikoon, P., Vincent, A.L. 2014. Polymorphisms in the hemagglutinin gene influenced the viral shedding of pandemic 2009 influenza virus in swine. Journal of General Virology. 95(Pt 12):2618-2626.

Interpretive Summary: In this study we showed that minimal amino acid changes in the HA protein of influenza A viruses (IAV) may have important implications for transmission in the natural host. IAV contain negative stranded RNA genomes that are prone to errors during replication and this is a natural component of IAV evolution. The contribution of influenza virus sequence variants for transmission and replication during infection is poorly understood. In the present study examined the ability of such naturally occurring variants found in the hemagglutinin (HA) gene of two 2009 pandemic H1N1 IAV isolates, A/California/04/2009 (Ca/09) and A/Mexico/4108/2009 (Mx/09). These genetic changes resulted in predicted amino acid changes in the HA protein and one of these changes was readily selected in vivo in primary infected and contact naïve pigs when inoculated with Ca/09. By reverse genetics we engineered Ca/09 and Mx/09 genomes by introducing the Ca/09 HA with the two naturally occurring variations. One of these engineered viruses resulted in higher efficiency of transmission in naive pigs. This efficiency appeared to be more likely through an advantage in cell surface attachment of the virus rather than replication efficiency. Although these mutations occur within the receptor binding pocket and in one of the serologic antigenic sites of the HA protein, they did not affect serologic cross-reactivity.

Technical Abstract: The contribution of influenza virus quasi-species for transmission efficiency and replication is poorly understood. In the present study we show that naturally occurring polymorphisms present in the hemagglutinin (HA) gene of two 2009 pandemic H1N1 isolates, A/California/04/2009 (Ca/09) and A/Mexico/4108/2009 (Mx/09) resulted in amino acid changes at position 186 (S to P) and 194 (L to I) of the mature HA1 protein. P186, not present in 2009 pandemic H1N1 (H1N1pdm09) consensus sequence, is readily selected in vivo in primary infected and contact naïve pigs when inoculated with Ca/09. By reverse genetics we engineered Ca/09 and Mx/09 genomes by introducing the Ca/09 HA in two naturally occurring variants expressing S186/I194 (HA-S/I) and P186/L194 (HA-P/L), respectively. The combination P186/L194 resulted in higher efficiency of transmission in naive pigs in either Ca/09 or Mx/09 backbones. This efficiency appeared to be more likely through an advantage in cell surface attachment rather than replication efficiency. Although these mutations occur within the receptor binding pocket and the Sb antigenic site, they did not affect serologic cross-reactivity.