Nucleotide variation in Sabin type 2 poliovirus from an immunodeficient patient with poliomyelitis Gabriele Buttinelli, 1 Valentina Donati, 1 Stefano Fiore, 1 Jill Marturano, 1 Alessandro Plebani, 2 Paolo Balestri, 3 Anna Rosa Soresina, 2 Rossella Vivarelli, 3 Francis Delpeyroux, 4 Javier Martin 5 and Lucia Fiore 1 Correspondence Lucia Fiore fiore@iss.it 1 Laboratory of Virology, Istituto Superiore di Sanita ` , Viale Regina Elena 299, 00161 Rome, Italy 2 Department of Pediatrics, University of Brescia, Italy 3 Pediatrics Unit, University of Siena, Italy 4 Epidemiologie Moleculaire des Enterovirus, Institut Pasteur, Paris, France 5 NIBSC, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK Received 13 November 2002 Accepted 4 February 2003 The molecular and antigenic properties of a Sabin-like type 2 poliovirus, isolated from the stool samples of a 2-year-old agammaglobulinaemic child who developed paralysis 1 year after receiving the third dose of oral poliovirus vaccine, were analysed. The virus revealed 0?88 % genome variation in the VP1 region compared with the standard reference strain, compatible with replication of the virus in the intestine over approximately 1 year. The typical mutations in the 59NCR and VP1 associated with reversion to neurovirulence for Sabin type 2 poliovirus were found. Despite this, the virus was characterized by both PCR and ELISA tests as Sabin-like and showed temperature sensitivity and neurovirulence in transgenic mice typical of the Sabin type 2 vaccine strain. Gammaglobulin replacement therapy led rapidly to virus clearance, which, when combined with treatment with the antiviral drug pleconaril, stopped virus excretion; no further virus shedding occurred. This is the first case of poliomyelitis and long-term excretion from an immunodeficient patient to be reported in Italy through the active ‘Acute Flaccid Paralysis’ surveillance system. INTRODUCTION As global poliomyelitis eradication approaches, Europe is moving towards stopping poliovirus vaccination with oral polio vaccine (OPV). Whereas disease caused by wild polio- virus is decreasing, vaccine-associated paralytic poliomyelitis (VAPP), although rare, is causing increasing concern. Even more worrying is the fact that VAPP outbreaks, reported recently in the Caribbean and the Philippines, have been caused by highly mutated and neurovirulent Sabin-like type 1 polioviruses (Kew et al., 2002; CDC, 2002a). This emphasizes the need for an appropriate strategy to dismiss OPV after wild poliovirus eradication (Hull et al., 1997). Long-term excretors of poliovirus, like immunodeficient patients, are an additional concern, as they may ensure poliovirus persistence and new infections in the unvacci- nated population in the post-eradication era. Prolonged intestinal replication of the virus in these subjects could increase the chances of reversion to neurovirulence and trans- missibility characteristics typical of wild poliovirus strains. In Italy, OPV vaccination was made compulsory for 3- month-old infants in 1966 and high immunization coverage has been achieved thereafter. The Ministry of Health (Italy) has documented more than 95 % immunization coverage for children of less than 5 years of age. The last two cases of paralytic disease due to indigenous wild poliovirus were reported in 1982 (Novello et al., 1987); since then, three imported poliomyelitis cases from Iran, India and Libya (the last in 1988) due to wild virus have been reported and investigated. With the exception of the cases cited above, only VAPP cases (two of which were contacts of vaccines) have occurred in Italy (Fiore et al., 1999, 2000). Active surveillance of acute flaccid paralysis (AFP) was established in Italy in 1997 following WHO indications. To comply with an active surveillance system, hospitals are contacted by the local Regional Reference Centres every 15 days and asked to provide information on AFP cases admitted. The incidence rate found over the 5 years of activity was good and performance indicators improved with time (Fiore et al., 2000). In Italy, a combination of inactivated polio vaccine (IPV) and OPV was adopted in May 1999 to reduce the number of VAPP cases, while keeping high levels of protection against possible wild virus importation, also related to the constant, often illegal, immigration flow from endemic countries. 0001-8974 G 2003 SGM Printed in Great Britain 1215 Journal of General Virology (2003), 84, 1215–1221 DOI 10.1099/vir.0.18974-0