THE MAJOR HOMOLOGY REGION OF BOVINE LEUKEMIA-VIRUS P24(GAG) IS REQUIRED FOR VIRUS INFECTIVITY IN-VIVO

In order to gain insight into the role of the major homology region (M HR) in the infectious potential of bovine leukaemia virus (BLV), mutat ions were introduced into the capsid gene of an infectious molecular c lone. A provirus that was designed to contain only a slightly modified version of the MHR (substitution of phenylalanine 147 with a tyrosine ) was still infectious in vivo. Furthermore, the provirus loads were n ot significantly different from those obtained with a wild-type virus. A second mutant was designed to analyse a mild modification of the MH R at the level of arginine 150. The substitution of this residue with a lysine completely destroyed the infectious potential of the recombin ant virus. Finally, a third mutant that was deleted in the MHR region was unable to infect the host. Thus it appears that the integrity of t he MHR domain is essential for BLV infectivity in vivo.