Ka. Schat et al., OPEN READING FRAME L1 OF MAREKS-DISEASE HERPESVIRUS IS NOT ESSENTIAL FOR IN-VITRO AND IN-VIVO VIRUS-REPLICATION AND ESTABLISHMENT OF LATENCY, Journal of General Virology, 79, 1998, pp. 841-849
Two mutant CV1988 Marek's disease virus (MDV) strains were developed i
n which a part of ORF L1 was replaced by lacZ with the SV40 early prom
oter. These mutant strains, CVIL(1)LacZ-A and -B, were inoculated into
chickens to test the hypothesis that ORF L1 is involved in the induct
ion and/or maintenance of latency. Mutant virus could be reisolated fr
om lymphocytes obtained from chickens during both the lytic and latent
phase of infection, indicating that ORF L1 is not essential for the i
nduction and/or maintenance of latency or the reactivation from latenc
y. beta-Galactosidase-positive lymphocytes were detected during the la
tent infection demonstrating that the SV40 early promoter can be activ
e in recombinant MDV strains during latent infection, Although the ins
ertion of lacZ was stable in cell culture, recombination within lacZ a
nd the BamHI-L fragment was observed during in vivo infection.