Restriction endonuclease analysis of Marek's disease virus DNA: differentiation of viral strains and determination of passage history.

The restriction endonuclease (RE) patterns of DNA from serotype 1 Marek's disease viruses (MDVs) are unique to serotype 1 viruses and can also be used to differentiate between low and high cell-culture-passaged viruses. We compared the RE patterns of DNA from seven serotype 2 and 3 MDVs before and after serial in vitro passage. Passage of four serotype 2 strains resulted in a variety of changes in the RE pattern. Individual strains within a serotype exhibited unique restriction patterns that allowed individual isolates to be differentiated. In a similar manner, the serotype 3 virus strains displayed RE pattern variations that were unique to each strain, as well as differences between low and high cell-culture passage. Our findings, together with earlier reports, suggest that the RE patterns of MDV DNA provide a simple and accurate method to: 1) differentiate between the three MDV serotypes, 2) differentiate between virus strains within a serotype, and 3) determine whether the viruses have been passaged extensively in cell culture.