IMPORTANCE OF AMINO-ACID-101 WITHIN CAPSID PROTEIN VP1 FOR MODULATIONOF THEILERS VIRUS-INDUCED DISEASE

We constructed a Theiler's virus mutant designated DA3304, in which th e amino acid at position 101 of VP1 was changed from a threonine to an alanine. Because of this single amino acid change, DA3304 could still produce a biphasic central nervous system disease similar to that pro duced by the wild-type DA virus. However, DA3304 was significantly att enuated in both the acute and the chronic phases and induced smaller d emyelinating lesions than the wild-type DA virus. The data are most co mpatible with the attenuated phenotype in DA3304 being due to the chan ge of binding efficiency between the virus and receptor resulting from the physical alteration at the mutation site.