The H5 HA and N1 NA of the reassortant H5N1 2003 and 2004
ca vaccine viruses were derived from influenza A/HK/213/2003 (H5N1 2003
wt) and A/VN/1203/2004 (H5N1 2004
wt) viruses, respectively, and the internal protein genes came from the AA
ca donor virus. The H5N1 1997 reassortant vaccine candidate's H5 HA was derived from A/HK/491/1997 (H5N1 1997
wt), its N1 NA from A/HK/486/1997 (H5N1), and the remaining gene segments from AA
ca. A/Beijing/262/95
ca (H1N1), which was generated by MedImmune Vaccines for seasonal influenza, was used as a control in evaluating the neurotropism of the viruses. A/New Caledonia/99
ca (H1N1) was generated by MedImmune Vaccines and was used as a control for evaluating vaccine efficacy in ferrets. A/Ann Arbor/6/60 (H2N2)
wt (AA
wt) and AA
ca viruses were obtained from MedImmune Vaccines. Additional influenza A viruses used for challenge studies were A/Vietnam/JPHN30321/2005 (H5N1), which belongs to clade 1 [4 (
link)], and A/Indonesia/05/2005 (H5N1), which belongs to clade 2 (R. Donis, Influenza Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, United States, personal communication). The
wt H5N1 viruses used in this study were kindly provided by N. Cox and A. Klimov, Influenza Branch, Centers for Disease Control and Prevention.
Virus stocks for the
wt viruses were propagated in the allantoic cavity of 9- to 11-day-old embryonated specific pathogen-free (SPF) hen's eggs at 37 °C. The allantoic fluids from eggs inoculated with
wt viruses were harvested 24 h postinoculation and tested for hemagglutinating activity. Eggs inoculated with
ca reassortant viruses were incubated at 33 °C and were harvested 3 d postinoculation. Infectious allantoic fluids were pooled, divided into aliquots, and stored at −80 °C until use. The 50% tissue culture infectious dose (TCID
50) for each virus was determined by serial titration of virus in Madin-Darby canine kidney (MDCK) cells and calculated by the method developed by Reed and Muench [22 ].
All experiments, including animal studies with infectious
wt H5 avian influenza viruses and the reassortant viruses, were conducted using enhanced BSL-3 containment procedures in laboratories approved for use by the USDA and Centers for Disease Control and Prevention. Animal experiments were approved by the National Institutes of Health Animal Care and Use Committee. Experimental studies in chickens were approved by the USDA (SEPRL) Animal Care and Use Committee.
Suguitan AL J.r., McAuliffe J., Mills K.L., Jin H., Duke G., Lu B., Luke C.J., Murphy B., Swayne D.E., Kemble G, & Subbarao K. (2006). Live, Attenuated Influenza A H5N1 Candidate Vaccines Provide Broad Cross-Protection in Mice and Ferrets. PLoS Medicine, 3(9), e360.