Progressive multifocal leucoencephalopathy: analysis of JC virus DNA from brain and kidney tissue.

JC virus-specific DNA from both brain and kidney of the PML case G.S. was analysed by restriction mapping and Southern blot analysis. The genome of JCV DNA from brain (JCV GS-B) was full length, whereas JCV DNA GS from kidney (JCV GS-K) was 120 bp smaller. Restriction maps, constructed from JCV GS-B using various enzymes showed that most cleavage sites were consistent with standard map sites. Comparison of virus DNA from brain and kidney revealed that JCV GS-specific cleavage sites were identical, and that the DNAs were therefore of the same subtype. The deletion in kidney DNA was situated in the area of the origin of replication which is known to be hypervariable in the JCV genome. Restriction maps revealed that the DNA from each organ was homogeneous in length but a proportion of the DNA molecules were heterogeneous in restriction sites. It is concluded from these data that initial infection with one JCV subtype was followed by the development of heterogeneous DNA molecules.