Emerging Infectious Disease ISSN: 1080-6059

Multiple Reassortment between Pandemic (H1N1) 2009 and Endemic Influenza Viruses in Pigs, United States

Mariette F. Ducatez, Ben Hause, Evelyn Stigger-Rosser, Daniel Darnell, Cesar Corzo, Kevin Juleen, Randy Simonson, Christy Brockwell-Staats, Adam Rubrum, David Wang, Ashley Webb, Jeri-Carol Crumpton, James Lowe, Marie Gramer, and Richard J. Webby

Author affiliations: Author affiliations: St. Jude Children’s Research Hospital, Memphis, Tennessee, USA (M.F. Ducatez, E. Stigger-Rosser, D. Darnell, C. Brockwell-Staats, A. Rubrum, D. Wang, A. Webb, J.-C. Crumpton, R.J. Webby); Newport Laboratories, Worthington, Minnesota, USA (B. Hause, R. Simonson); University of Minnesota College of Veterinary Medicine, Saint Paul, Minnesota, USA (C. Corzo, K. Juleen, M. Gramer); and Carthage Veterinary Services, Carthage, Illinois, USA (J. Lowe)

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Figure 3

Replication of North American reassortant and endemic swine influenza viruses on swine testicle (ST) cells and in ferrets. A) The growth of 6 endemic swine viruses and 3 reassortant viruses (sw/MN/239105/09, sw/MN/239106/10, and sw/NC/239108/10) from 2009–2010 were analyzed in vitro. One curve corresponds to 1 isolate. Black lines and symbols indicate swine pandemic influenza reassortant viruses; red lines and symbols indicate swine triple reassortant (TR) influenza viruses. The progeny viruses

Figure 3. Replication of North American reassortant and endemic swine influenza viruses on swine testicle (ST) cells and in ferrets. A) The growth of 6 endemic swine viruses and 3 reassortant viruses (sw/MN/239105/09, sw/MN/239106/10, and sw/NC/239108/10) from 2009–2010 were analyzed in vitro. One curve corresponds to 1 isolate. Black lines and symbols indicate swine pandemic influenza reassortant viruses; red lines and symbols indicate swine triple reassortant (TR) influenza viruses. The progeny viruses released from infected ST cultures were collected at the indicated time points and titrated in ST cells by performing a 50% tissue culture infectious dose (TCID₅₀) assay. Negative TCID₅₀ titers were given the value 0.5; log₁₀ TCID₅₀ >8.5 were given the value 8.5. B) Virus titers in the upper respiratory tract (nasal washes) of ferrets infected with 10⁶ 50% egg infectious dose (EID₅₀) pandemic (H1N1) 2009 TN/560/09 (35); 10⁶ TCID₅₀ swine TR influenza virus sw/TX/4199/98; or 10⁶ EID₅₀ swine pandemic reassortant virus sw/MN/239105/09. Values are the mean ± SD for 4, 3, and 5 ferrets for TN/560/09, sw/TX/4199/98, and sw/MN/239105/09, respectively.

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