title: Differential importance of highly conserved residues in UL24 for herpes simplex virus 1 replication in vivo and reactivation.
abstract: The UL24 gene of herpes simplex virus 1 (HSV-1) is widely conserved among all subfamilies of the Herpesviridae. It is one of only four HSV-1 genes for which mutations have been mapped that confer a syncytial plaque phenotype. In a mouse model of infection, UL24-deficient viruses exhibit reduced titres, particularly in neurons, and an apparent defect in reactivation from latency. There are several highly conserved residues in UL24; however, their importance in the role of UL24 in vivo is unknown. In this study, we compared virus strains with substitution mutations corresponding to the PD-(D/E)XK endonuclease motif of UL24 (vUL24-E99A/K101A) or a substitution of another highly conserved residue (vUL24-G121A). Both mutant viruses cause the formation of syncytial plaques at 39 degrees C; however, we found that the viruses differed dramatically when tested in a mouse model of infection. vUL24-E99A/K101A exhibited titres in the eye that were 10-fold lower than those of the wild-type virus KOS, and titres in trigeminal ganglia (TG) that were more than 2 log10 lower. Clinical signs were barely detectable with vUL24-E99A/K101A. Furthermore, the percentage of TG from which virus reactivated was also significantly lower for this mutant than for KOS. In contrast, vUL24-G121A behaved similarly to the wild-type virus in mice. These results are consistent with the endonuclease motif being important for the role of UL24 in vivo and also imply that the UL24 temperature-dependent syncytial plaque phenotype can be separated genetically from several in vivo phenotypes.
authors.affiliation: INRS-Institut Armand-Frappier, Université du Québec, 531 boul. des Prairies, Laval, Quebec, Canada.
authors.forename: Gabriel André
authors.initials: GA
authors.lastname: Leiva-Torres
authors.forename: Pierre-Alexandre
authors.initials: PA
authors.lastname: Rochette
authors.forename: Angela
authors.initials: A
authors.lastname: Pearson
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D004195:Disease Models, Animal; D005123:Eye / Q000821:virology; D006561:Herpes Simplex / Q000473:pathology / Q000821:virology; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000502:physiology; D012720:Severity of Illness Index; D012668:Trigeminal Ganglion / Q000821:virology; D014709:Vero Cells; D019562:Viral Load; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D014775:Virus Activation; D014779:Virus Replication
chemical_list: D050505:Mutant Proteins; C086267:UL24 protein, Human herpesvirus 1; D014764:Viral Proteins