RESUMEN
The complete nucleotide sequences of the S1 and N genes of three Japanese and one Taiwanese field strains of IBV are reported. These Japanese strains were found to have S1 sequences most similar to those of Australian strains and N sequences most similar to those of North American strains. This result suggested that these Japanese strains might all be recombinant viruses derived from recombination of Australia- and North America-related viruses. Moreover, the S1 proteins of all these Japanese and Taiwanese strains exhibit only a limited sequence homology to strains of Massachusetts and Connecticut serotypes that have been commonly used as vaccine strains. This result high lightens the importance of development of vaccines based on the local strains of IBV.