Vaccine 31 (2013) 5075–5081 Contents lists available at ScienceDirect Vaccine jou rn al hom ep age: www.elsevier.com/locat e/vaccine Cross-clade protection against H5N1 HPAI strains recently isolated from commercial poultry in Egypt with a single dose of a baculovirus based vaccine M.S. Beato a,∗,1 , M. Realpe-Quintero b,1 , F. Bonfante a , M. Mancin c , S. Ormelli a , C. Terregino a , C. Gonzalez-Hernandez b , I. Capua a a OIE/FAO and National Reference Laboratory for Newcastle Disease and Avian Influenza, OIE Collaborating Centre for Infectious Diseases at the Human-Animal Interface, Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), Viale dell’Università 10, 35020 Legnaro (PD), Italy b Research and Development Department, Boehringer Ingelheim Vetmedica, Mexico c Public Health and Risk Analysis Department, Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), Viale dell’Università 10, 35020 Legnaro (PD), Italy a r t i c l e i n f o Article history: Received 21 February 2013 Received in revised form 19 August 2013 Accepted 27 August 2013 Available online 7 September 2013 Keywords: H5N1 Baculovirus Egypt a b s t r a c t The current avian influenza epidemic in Egypt caused by circulation of genetically and antigenically diverse H5N1 HPAI viruses in poultry is controlled by applying vaccination among other measures. In this context, the use of a DIVA (differentiating infected from vaccinated animals) vaccination strategy utilizing a vaccine capable of inducing protection against multiple antigenic variants may result as an additional control tool to the existing ones. In this study the efficacy of a single-shot recombinant baculovirus-based vaccine in specific-pathogen-free chickens was tested by experimental challenge with genetically and antigenically diverse H5N1 HPAI viruses belonging to clades 2.2.1 and 2.2.1.1, which have been circulating in Egypt since 2010. A single dose of vaccine, administration at 10 days of age, was shown to confer 100% clinical protection, with a decrease or suppression of virus shedding. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype have been enzootic in poultry in Egypt since 2008. The infection was first identified in early 2006 and quickly spread to 22 Governorates despite the use of stamping out and movement control measures. Eventually, vaccination with inactivated whole- virus vaccines was introduced as an additional measure to control infections in industrial and backyard sectors [1]. Phylogenetic studies of Egyptian H5N1 HPAI viruses showed that two genetically distinct groups co-circulated between 2008 and 2010 [2], which were recently shown to belong to clades 2.2.1 and 2.2.1.1 [3]. Antigenic cartography studies showed that the clade 2.2.1 and 2.2.1.1 H5N1 viruses also represented antigenically dis- tinct clusters designated A and B, respectively [4]. Additional studies investigated the antigenic diversity of Egyp- tian H5N1 HPAI viruses isolated between 2009 and 2011 by using monoclonal antibodies [5] and confirmed the antigenic diversity of clade 2.2.1 and 2.2.1.1 viruses. ∗ Corresponding author. Tel.: +39 049 8084371; fax: +39 049 8084360. E-mail address: msbeato@izsvenezie.it (M.S. Beato). 1 These authors equally contributed. Field investigations showed that vaccination had a limited effect in controlling the spread of infection because of failures associated with improper vaccination technique, poor biosecurity, presence of maternally derived antibodies to the H5 avian influenza virus and emergence of antigenic variant H5N1 viruses [6–9]. Addition- ally, vaccination trials showed that some vaccine preparations did not protect clinically and virologically against H5N1 variant viruses isolated in 2008 and 2009 [8,10,11]. This suggested that the anti- genic diversity of Egyptian H5N1 viruses may have played a role in the failure of vaccines to control infections in the field. The H5N1 virus remains enzootic in Egypt despite the use of more than 917 million doses of vaccine to control infections in the poultry pop- ulation, which in 2010, consisted of more than 545 million birds [12]. The current epidemic of HPAI H5N1 in Egypt may benefit from a vaccination strategy with a broad-spectrum vaccine that would allow application of the DIVA (Differentiating Infected from Vac- cinated Animals) strategy. Such a strategy is fundamental for progressive control of HPAI infection and eventual eradication and it is applicable using different methods. Sub-unit vaccines that elicit an immune response against the haemagglutinin allow the appli- cation of the DIVA concept enabling the detection of field-exposed animals by means of serological assays [13]. These tests detect antibodies directed against viral proteins different from the ones contained in the vaccine preparations. 0264-410X/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.vaccine.2013.08.073