|Jadhao, Samadhan - Emory University, School Of Medicine|
Submitted to: International Symposium on Avian Influenza
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2015
Publication Date: 4/12/2015
Citation: Pantin Jackwood, M.J., Jadhao, S., Wasilenko, J.L., Shepherd, E.M., Smith, D.M., Suarez, D.L. 2015. NS1 gene truncations partially attenuate H5N1 highly pathogenic avian influenza viruses in chickens [abstract]. 9th International Symposium on Avian Influenza, Athens, Georgia. p. 85.
Technical Abstract: The polybasic amino acid sequence in the hemagglutinin (HA) protein of H5 and H7 avian influenza (AI) viruses determines the high pathogenicity (HP) phenotype in chickens. The NS1 protein plays an important role in blocking the induction of antiviral defenses and other regulatory functions and thus can contribute to the pathogenesis of HPAI viruses. In this study, we investigated whether the HP phenotype of H5N1 HPAI viruses in chickens can be modulated by truncation of the NS1 protein. Using reverse genetics (rg) we generated three sets of viruses based on different H5N1 HPAIV; A/egret/Hong Kong/7/02, A/chicken/Indonesia/7/03, and A/duck/Vietnam/201/05. The rg derived viruses (rgH5N1) preserved the wild type polybasic amino acid sequence at the H5 HA cleavage site. For each virus, two different length truncations were introduced in the carboxyl terminus region of NS1. Chickens were intranasally inoculated with 10^6 embryo infective dose 50 of one of the nine rgH5N1 viruses and morbidity, mortality, virus shedding, and cytokine gene expression in spleen and lungs assessed. Chickens inoculated with NS1-truncated viruses survived for longer than those inoculated with the full length-NS1 rgH5N1 viruses; however this attenuation varied among the three sets of viruses, with less attenuation observed with the A/chicken/Indonesia/7/03 NS1-truncated viruses. Virus shedding and virus replication in tissues also reflected the attenuated phenotype induced by NS1 truncation. The blocking effect of NS1 on the innate immune response as the mechanism of attenuation was not confirmed since expression of innate immune related genes (IFN type 1 and 2, IL-6 and MX1) in spleen and lung 24 hours after virus inoculation directly correlated with viral titers in these organs.