Restriction endonuclease analysis of Marek's disease virus DNA and homology between strains.

The restriction endonuclease patterns of viral DNA obtained from serotypes 1 and 2 strains of Marek's disease virus have been compared and homology between the strains examined by hybridization. The results have shown that HPRS 16 (serotype 1) DNA has a structure similar to its attenuated variant HPRS 16/att except for a few fragments that are present only in the virulent strain. Evidence was obtained which suggested that these restriction fragments contained repeat sequences and that insertion of heterogeneous DNA occurred at these sites during attenuation of HPRS 16. The restriction enzyme patterns of HPRS 24 (serotype 2) differed substantially from those of HPRS 16 and HPRS 16/att and reassociation experiments showed that HPRS 24 shares less than 10% homology with either HPRS 16 or herpesvirus of turkeys (serotype 3).