All IBV stocks were propagated in 10-day-old specific pathogen-free (SPF) Rhode Island Red (RIR) embryonated hens’ eggs. M41-CK (GenBank accession number MK728875.1) is a pathogenic IBV belonging to the GI-1 genotype and Massachusetts serotype that has been adapted for propagation in primary chicken kidney (CK) cells [40, 42, 43 (link)] through serial passage in CK cells. Beau-R [41 (link)] is a molecular clone of Beau-CK, the CK cell-adapted Beaudette strain (GenBank accession number AJ311317) also belonging to the GI-1 genotype and Massachusetts serotype. Unlike M41-CK, Beau-R exhibits an extended host tropism, allowing propagation in DF-1 cells [6, 44 (link)].
CK cells were prepared using kidneys from 2- to 3-week-old SPF RIR chickens by the central services unit at The Pirbright Institute [45 (link)]. DF-1 cells were obtained from Central Services Unit at The Pirbright Institute and maintained in Dulbecco’s modified essential medium (DMEM, Sigma-Aldrich, St Louis, MO, USA) with 10 % foetal bovine serum (FBS, Sigma-Aldrich, St Louis, MO, USA). All cells were maintained at 37 °C in 5 % CO2.
CK cells were prepared using kidneys from 2- to 3-week-old SPF RIR chickens by the central services unit at The Pirbright Institute [45 (link)]. DF-1 cells were obtained from Central Services Unit at The Pirbright Institute and maintained in Dulbecco’s modified essential medium (DMEM, Sigma-Aldrich, St Louis, MO, USA) with 10 % foetal bovine serum (FBS, Sigma-Aldrich, St Louis, MO, USA). All cells were maintained at 37 °C in 5 % CO2.
