AN EQUINE HERPESVIRUS-1 MUTANT WITH A LACZ INSERTION BETWEEN OPEN READING FRAMES 62 AND 63 IS REPLICATION COMPETENT AND CAUSES DISEASE IN THE MURINE RESPIRATORY MODEL
H. Csellner et al., AN EQUINE HERPESVIRUS-1 MUTANT WITH A LACZ INSERTION BETWEEN OPEN READING FRAMES 62 AND 63 IS REPLICATION COMPETENT AND CAUSES DISEASE IN THE MURINE RESPIRATORY MODEL, Archives of virology, 143(11), 1998, pp. 2215-2231
An equine herpesvirus 1 (EHV-1) mutant was constructed by inserting a
lacZ expression cassette into the intergenic region upstream of gene 6
2 (glycoprotein L; gL) and downstream of gene 63 (a homologue of the h
erpes simplex virus transcriptional activator ICP0). The recombinant l
acZ62/63-EHV-1 had similar growth kinetics in cell culture to those of
the parental wild type (wt) virus, with indistinguishable cytopathic
effects and plaque morphology. Reverse transcriptase PCR confirmed tha
t the lacZ insertion did not interfere with transcription of gL and im
munoblot analysis indicated there was no modification to late gene exp
ression as monitored by synthesis of EHV-1 glycoproteins C and D. The
parental EHV-1 isolate HVS25A used here had almost identical nucleotid
e sequence to that published for isolate Ab4, in a 1200 bp region surr
ounding the insert, but lacked a HindIII site corresponding to Ab4 pos
ition 109,048. The lacZ62/63-EHV-1 caused respiratory disease in BALB/
c mice with clinical signs, histopathology and virus titres in lungs t
hroughout days 1-5 post infection similar to those induced by wt EHV-1
. X-gal staining for beta-galactosidase expression in murine lungs cle
arly demonstrated EHV-1 infection in cells of the bronchiolar epitheli
um and pulmonary parenchyma, with a peak of infection evident at day 2
post infection, when up to 50% of bronchioles demonstrated blue-stain
ing and thus virus-infected epithelial cells. The construction of this
replication competent virus carrying a reporter gene identifies a sit
e for insertion of foreign genes and will facilitate studies on the pa
thogenesis of EHV-1.