Strain S1133 was grown serially 235 times in the chorioallantoic membrane (CAM) at 37° C. and then 65 times in chicken embryo fibroblast (CEF) at 32° C. An additional 135 passages were carried out at 37° C. in CEF [van der Heide et al., Avian Dis., 27:698-706 (1983)].
The 2177 is a non-pathogenic reovirus strain. Strain 2177 was isolated from chickens exhibiting reovirus disease by inoculating tissue samples into embryonated eggs and collecting the yolk fluid. This yolk fluid was then inoculated into CEF and passed 14 times until the cytopathology was observed at which time the virus was plaque purified. This yolk fluid was then propagated in embryonated eggs to produce a stock of virus. The stock was found to be non-pathogenic and was titled strain 2177.
Analysis of the sigma C amino acid sequences of reovirus vaccine strains S1133, 1733, 2408 and 2177 reveals a >99% similarity among vaccine strains (Sellers, 2013).
The use of live reovirus vaccine used in combination with Marek's vaccine is not recommended. This interference is not seen when vaccination is done at seven days post Marek's vaccination.