The non-essential UL50 gene of avian infectious laryngotracheitis virus encodes a functional dUTPase which is not a virulence factor.
The DNA sequence of the infectious laryngotracheitis virus (ILTV) UL50, UL51 and UL52 gene homologues was determined. Although the deduced UL50 protein lacks the first of five conserved domains of the corresponding proteins of mammalian alphaherpesviruses, the ILTV gene product was also shown to possess dUTPase activity. The generation of UL50-negative ILTV mutants was facilitated by recombination plasmids encoding green fluorescent protein (GFP), and expression constructs of predicted transactivator proteins of ILTV (alphaTIF, ICP4) were successfully used to increase the infectivity of viral genomic DNA. A GFP-expressing UL50-deletion mutant of ILTV showed reduced cell-to-cell spread in vitro, and was attenuated in vivo. A similar deletion mutant without the foreign gene, however, propagated like wild-type ILTV in cell culture and was pathogenic in chickens. We conclude that the viral dUTPase is not required for efficient replication of ILTV in the respiratory tract of infected animals. The replication defect of the GFP-expressing ILTV recombinant is most likely caused by toxic effects of the reporter gene product, since spontaneously occurring inactivation mutants exhibited wild-type-like growth.
Fuchs
W
W
Institute of Molecular Biology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17498 Insel Riems, Germany. walter.fuchs@rie.bfav.de
Ziemann
K
K
Teifke
J P
JP
Werner
O
O
Mettenleiter
T C
TC
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D004279:DNA, Viral / Q000235:genetics; D017353:Gene Deletion; D017930:Genes, Reporter; D005814:Genes, Viral; D049452:Green Fluorescent Proteins; D006566:Herpesviridae Infections / Q000473:pathology / Q000662:veterinary / Q000821:virology; D001352:Herpesvirus 1, Gallid / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D020161:Physical Chromosome Mapping; D011201:Poultry Diseases / Q000473:pathology / Q000821:virology; D011755:Pyrophosphatases / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014774:Virulence / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
D004279:DNA, Viral; D008164:Luminescent Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D011755:Pyrophosphatases; C020020:dUTP pyrophosphatase