Genetic analysis of nonstructural genes (NS1 and NS2) of H9N2 and H5N1 viruses recently isolated in Israel Caroline Banet-Noach Æ Alexander Panshin Æ Natalia Golender Æ Lubov Simanov Æ Ezra Rozenblut Æ Shimon Pokamunski Æ Michael Pirak Æ Yevgenii Tendler Æ Maricarmen Garcı´a Æ Boris Gelman Æ Ruslan Pasternak Æ Shimon Perk Received: 26 June 2006 / Accepted: 10 November 2006 / Published online: 15 December 2006 Ó Springer Science+Business Media, LLC 2006 Abstract The avian influenza virus subtype H9N2 affects wild birds, domestic poultry, swine, and humans; it has circulated amongst domestic poultry in Israel during the last 6 years. The H5N1 virus was recorded in Israel for the first time in March 2006. Nonstructural (NS) genes and NS proteins are impor- tant in the life cycle of the avian influenza viruses. In the present study, NS genes of 21 examples of H9N2 and of two examples of H5N1 avian influenza viruses, isolated in Israel during 2000–2006, were completely sequenced and phylogenetically analyzed. All the H9N2 isolates fell into a single group that, in turn, was subdivided into three subgroups in accordance with the time of isolation; their NS1 and NS2 proteins possessed 230 and 121 amino acids, respectively. The NS1 protein of the H5N1 isolates had five amino acid deletions, which was typical of highly pathogenic H5N1 viruses isolated in various countries during 2005–2006. Com- parative analysis showed that the NS proteins of the H9N2 Israeli isolates contained few amino acid sequences associated with high pathogenicity or human host specificity. Keywords Avian influenza virus Á Genetic analysis Á H9N2 Á H5N1 Á NS genes Introduction Avian influenza virus (AIV) H9N2 and H5N1 subtypes are considered the most probable precursors of a pandemic influenza virus [1]. During the last 10 years the highly pathogenic H5N1 influenza virus has been responsible for killing more than 140 million poultry birds and more than 100 humans in Asia, Europe, and Africa [2]. The first outbreak of H5N1 in Israel was recorded in March 2006, and more than 1 million poultry birds were killed to stem its spread (see: Avian influenza in Israel. Follow-up report No. 4 (final report), Disease Information 27, July 2006, Vol. 19, No. 30). The H9N2 subtype was dominant amongst the influenza viruses circulating among the Israeli avian population from 2000 and, although this virus was characterized as low-pathogenic, it caused substantial damage to the Israeli poultry-farming industry [3]. During the last 10 years influenza viruses of serotype H9N2 have been isolated from outbreaks in poultry in several countries: Germany, Italy, Ireland, Saudi Ara- bia, Iran, Pakistan, China, Hong Kong, South Africa, and the United States [4–8]. It was shown that cross- reactive cellular immunity induced by the H9N2 influenza viruses protected chickens from lethal infec- tion with the H5N1 influenza virus in the Hong Kong markets in 1997 but permitted virus shedding in their C. Banet-Noach Á A. Panshin (&) Á N. Golender Á L. Simanov Á E. Rozenblut Á B. Gelman Á R. Pasternak Á S. Perk Division of Avian and Aquatic Diseases, Kimron Veterinary Institute, P.O.B. 12, Beit Dagan, ZC 50250, Israel e-mail: alexpan@moag.gov.il S. Pokamunski Á M. Pirak Poultry Veterinary Services, Beit Dagan, Israel Y. Tendler Rambam Medical Center, Haifa, Israel M. Garcı ´a Poultry Diagnostic and Research Center, College of Veterinary Medicine, The University of Georgia, Athens, GA, USA 123 Virus Genes (2007) 34:157–168 DOI 10.1007/s11262-006-0057-9