Characterization of a new genotype and serotype of infectious bronchitis virus in Western Africa

1 Institute of Immunology, National Public Health Laboratory, CRP-Santé, 20A rue Auguste Lumière, L-1950 Luxembourg 2 Istituto Zooprofilattico sperimentale della Lombardia e dell'Emilia Romagna, Reparto di virologia e sierologia specializzata, Via Bianchi 9, 25124 Brescia, Italy 3 Department of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria 4 Food Safety, Drug Residues/Animal Diseases Surveillance and Intervention, Department of Veterinary Public Health and Preventive Medicine, University of Ibadan, Ibadan, Nigeria 5 Department Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, Sokoto, Nigeria 6 LABOCEL, Direction des Laboratoires Vétérinaires, Niamey, Niger Correspondence Claude P. Muller claude.muller{at}LNS.ETAT.LU Between 2002 and 2007, more than 1000 chickens from commercial farms, live bird markets and backyard farms in Nigeria and Niger were tested for the presence of the infectious bronchitis virus (IBV) genome. Phylogenetic analysis of full-length sequences of the spike 1 ( S1 ) gene revealed a new genotype of IBV that we refer to as ‘IBADAN’. The minimum genetic distance to the closest ‘non-IBADAN’ strains (UK/7/93 at the nucleotide level; H120 and M41 at the amino acid level) reached 24 and 32 % at the nucleotide and amino acid levels, respectively. The full genome of the IBADAN reference strain (NGA/A116E7/2006) had a genetic distance of 9.7–16.4 % at the nucleotide level with all available fully sequenced strains. As IBV S1 plays a major role in antigenicity, the antigenic relatedness of NGA/A116E7/2006 was compared with strains of other serotypes. NGA/A116E7/2006 did not cross-react with antisera against IT02, M41, D274, Connecticut or 793/B strains in virus neutralization assays. NGA/A116E7/2006 cross-reacted with the QX-like strain ITA/90254/2005 but only to a low level (antigenic relatedness of 33 %), suggesting that IBADAN also represents a new serotype. A comparison of S1 sequences identified several amino acids that may play a role in IBV antigenicity. Despite the absence of obvious clinical signs in poultry infected by IBADAN strains, it is important to test the cross-protection of current vaccine strains. Present address: St Jude Children's Research Hospital, Department of Infectious Diseases, Division of Virology, 262 Danny Thomas Place, MS330, Memphis, TN 38105, USA. The GenBank/EMBL/DDBJ accession numbers for the complete genome sequences of NGA/A116E7/2006 and ITA/90254/2005 are FN430415 and FN43041