Replication of human herpesvirus type 6 (strain AJ) in JJHan cells grown in protein-free medium.

The human T-cell line JJHan, commonly used as a substrate for human herpesvirus type 6 (HHV-6) replication, was established in a protein-free 1:1 mixture of Ham's F12 and Iscove's modified Dulbecco's medium. After 250 passages (4 years) in protein-free medium, the cells, designated JJHan-PF, were cocultured with JJHan cells chronically infected with strain AJ of HHV-6 conventionally grown in serum-supplemented medium. The production of viral antigen was monitored by indirect immunofluorescent antibody staining. The infectivity of the virus in JJHan-PF cells was similar to that in JJHan cultures as shown by HHV-6 antigen detection using a convalescent phase serum. The results show that JJHan-PF cells provide a sensitive substrate for HHV-6 replication without the interference of serum or other proteins usually added to the culture medium.