Identificazioni di marker molecolari per la differenziazione di un vaccino IBV genotipo QX

IBV genotype QX causes suf cient disease in Europe for several commercial com- panies to have started developing live attenuated vaccines. Here, one of those vac- cines (L1148) was fully consensus sequenced alongside its progenitor eld strain (1148-A) to determine vaccines markers, thereby enabling detection on farms. Twenty eight single nucleotide substitutions were associated with the 1148-A atten- uation, of which any combination can identify vaccine L1148 in the eld. Sixteen substitutions resulted in amino acid coding changes of which half were in spike. One change in the 1b gene altered the normally highly conserved nal 5 nucleotides of the transcription regulatory sequence of the S gene, common to all IBV QX genes. No mutations can currently be associated with the attenuation process. Field vac- cination strategies would greatly bene t by such comparative sequence data being mandatorily submitted to regulators prior to vaccine release following a successful registration process.