Please cite this article in press as: Kreijtz JHCM, et al. Low pathogenic avian influenza A(H7N9) virus causes high mortality in ferrets upon intratracheal challenge: A model to study intervention strategies. Vaccine (2013), http://dx.doi.org/10.1016/j.vaccine.2013.06.071 ARTICLE IN PRESS G Model JVAC-14407; No. of Pages 5 Vaccine xxx (2013) xxx–xxx Contents lists available at ScienceDirect Vaccine jou rn al hom ep age: www.elsevier.com/locat e/vaccine Low pathogenic avian influenza A(H7N9) virus causes high mortality in ferrets upon intratracheal challenge: A model to study intervention strategies J.H.C.M. Kreijtz a , E.J.B. Veldhuis Kroeze b , K.J. Stittelaar b , L. de Waal b , G. van Amerongen b , S. van Trierum a , P. van Run a , T. Bestebroer a , T.Kuiken a , R.A.M. Fouchier a , G.F. Rimmelzwaan a,b , A.D.M.E. Osterhaus a,b,∗ a Department of Viroscience, Erasmus MC, Rotterdam, The Netherlands b Viroclinics Biosciences, Rotterdam, The Netherlands a r t i c l e i n f o Article history: Received 24 May 2013 Accepted 20 June 2013 Available online xxx Keywords: H7N9 Avian influenza A Intervention strategies a b s t r a c t Infections with low pathogenic avian influenza (LPAI) A(H7N9) viruses have caused more than 100 hos- pitalized human cases of severe influenza in China since February 2013 with a case fatality rate exceeding 25%. Most of these human infections presented with severe viral pneumonia, while limited information is available currently on the occurrence of mild and subclinical cases. In the present study, a ferret model for this virus infection in humans is presented to evaluate the pathogenesis of the infection in a mam- malian host, as ferrets have been shown to mimic the pathogenesis of human infection with influenza viruses most closely. Ferrets were inoculated intratracheally with increasing doses (>10 e5 TCID50) of H7N9 influenza virus A/Anhui/1/2013 and were monitored for clinical and virological parameters up to four days post infection. Virus replication was detected in the upper and lower respiratory tracts while animals developed fatal viral pneumonia. This study illustrates the high pathogenicity of LPAI-H7N9 virus for mammals. Furthermore, the intratracheal inoculation route in ferrets proofs to offer a solid model for LPAI-H7N9 virus induced pneumonia in humans. This model will facilitate the development and assess- ment of clinical intervention strategies for LPAI-H7N9 virus infection in humans, such as preventive vaccination and the use of antivirals. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Avian influenza viruses have crossed the species barrier on sev- eral occasions and with varying impact on human health. From February 2013 onward several human cases with severe respiratory illness were reported from South-East China. The causative agents were rapidly characterized and subtyped as low pathogenic avian influenza (LPAI) A(H7N9) viruses that most likely were the result of multiple reassortment events of at least two avian influenza viruses [1,2]. Although the exact source of the human infections with this apparently avian influenza virus remains to be elucidated, sequence analysis has indicated that the viruses have been circu- lating for a longer period before they recently surfaced [3,4], Since the first reported human cases, the virus has infected at least 131 humans of which 32 succumbed to the infection with a predilection ∗ Corresponding author at: Department of Viroscience, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Tel.: +31 10 7044066; fax: +31 10 7044760. E-mail addresses: a.osterhaus@erasmusmc.nl, eva.editorialassistant.vaccine@gmail.com (A.D.M.E. Osterhaus). for older male individuals [5–8]. It is the largest outbreak of avian influenza in humans since the introduction of highly pathogenic avian influenza (HPAI) A(H5N1) viruses in the human population that thus far has resulted in over 600 reported cases with a hos- pitalized case fatality rate of approximately 60%. The majority of the humans infected with LPAI-H7N9 virus have presented with severe viral pneumonia and became critically ill [2]. The virus has been classified as being low pathogenic based on the genotype (the hemagglutinin does not contain a multi-basic cleavage site) and based on the results of intravenous pathogenicity index (IVPI) testing in chickens and data from poultry and wild birds. How- ever, the clinical manifestation of LPAI-H7N9 virus infection in humans shows a higher pathogenic phenotype. To further explore this discrepancy and elucidate the pathogenesis of the infection in mammals, we established a model for LPAI-H7N9 virus-induced pneumonia in ferrets (Mustela Putorius furo). The ferret model has been used to elucidate the severity of lower respiratory tract infec- tions with various influenza A virus subtypes [9]. Preliminary data on intranasal inoculation of ferrets with avian influenza A(H7N9) indicates that the virus causes only mild disease (unpublished data) in these animals. However, we have demonstrated in the past that 0264-410X/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.vaccine.2013.06.071