Virus Research 127 (2007) 17–25 Isolation of recombinant type 2 vaccine-derived poliovirus (VDPV) from a Nigerian child  Festus Adu a,∗ , Jane Iber b , David Bukbuk c , Nicksy Gumede d , Su-Ju Yang b , Jaume Jorba b , Ray Campagnoli b , Waidi Folorunso Sule a , Chen-Fu Yang b , Cara Burns b , Mark Pallansch b , Tekena Harry c , Olen Kew b a National Poliovirus Laboratory, Department of Virology, College of Medicine, University of Ibadan, UCH, Ibadan, Oyo State, Nigeria b Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, G-10, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA c National Poliovirus Laboratory, Immunology Department, University of Maiduguri, Maiduguri, Nigeria d WHO Regional Reference Unit for Polio, National Institute for Communicable Diseases, No. 1 Modderfontein Road, Sandringham 2131, South Africa Received 10 January 2007; received in revised form 26 February 2007; accepted 13 March 2007 Available online 20 April 2007 Abstract A type 2 vaccine-derived poliovirus (VDPV), differing from Sabin 2 at 2.5% (22/903) of VP1 nucleotide (nt) positions, was isolated from an incompletely immunized 21-month-old Nigerian child who developed acute flaccid paralysis in 2002. Sequences upstream of nt position 620 (within the 5 ′ -untranslated region [5 ′ -UTR]) and downstream of nt position 5840 (in the 3C pro region) were derived from species C enteroviruses unrelated to the oral poliovirus vaccine (OPV) strains. The two substitutions associated with the attenuated phenotype had either recombined out (A 481 → G in the 5 ′ -UTR) or reverted (Ile 143 → Thr in VP1). The VDPV isolate had lost the temperature sensitive phenotype of Sabin 2 and it was antigenically distinct from the parental OPV strain, having amino acid substitutions in or near neutralizing antigenic sites 1 and 3. The date of the initiating OPV dose, calculated from the number of synonymous substitutions in the capsid region, was estimated to be ∼16 to 18 months before onset of paralysis, a finding inconsistent with the most recent mass OPV campaign (conducted 12 days before onset of paralysis) as being the source of infection. Although no related type 2 VDPVs were detected in Nigeria or elsewhere, the VDPV was found in an area where conditions favor VDPV emergence and spread. © 2007 Elsevier B.V. All rights reserved. Keywords: Vaccine-derived poliovirus; VDPV; Oral poliovaccine; Nigeria 1. Introduction A remaining challenge to the World Health Organization (WHO) Global Polio Eradication Initiative is the continued circulation of wild poliovirus in Nigeria (Centers for Disease Control and Prevention, 2005b, 2006a,b, 2007). Wild poliovirus type 1 has spread from reservoirs in northern Nigeria (and south-  The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the funding agency. ∗ Corresponding author. Tel.: +80 23242768/234 2 241 0034; fax: +234 2 241 0749. E-mail addresses: akitikori@yahoo.com, ibadan-lab@ng.afro.who.int (F. Adu). ern Niger) to 18 previously polio-free countries in 2002–2005, from Guinea in the west to Indonesia at the southeastern rim of Asia, resulting in over 1200 cases associated with the imported virus since 2002 (Centers for Disease Control and Prevention, 2006b). Moreover, northern Nigeria remains by far the world’s largest reservoir for wild poliovirus type 3, with 244 polio wild poliovirus type 3 cases reported in 2005 and 278 wild type 3 cases reported in 2006 (Centers for Disease Control and Prevention, 2007; for updates see: www.polioeradication.org). Despite these severe challenges, a major milepost to polio eradi- cation has been the disappearance of indigenous wild poliovirus type 2, last found in West Africa in 1997, and last found any- where in the world (in Uttar Pradesh, India) in 1999 (World Health Organization, 2001). Thus, in Nigeria, as in other parts 0168-1702/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.virusres.2007.03.009