Journal of General Virology, Vol 80, 1799-1805, Copyright © 1999 by Society for General Microbiology
Complementation of a gI-deficient feline herpesvirus recombinant by allotopic expression of truncated gI derivatives
JDF Mijnes, C Vlot, JB Buntjer, J van den Broek, MC Horzinek, PJM Rottier and RJ de Groot
Virology Unit, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, 3584 CL Utrecht, The Netherlands
The alphaherpesvirus glycoproteins gE and gI form a hetero-oligomeric
complex involved in cell-to-cell transmission. The gI-deficient recombinant
feline herpesvirus (FHV), FHVDeltagI-LZ, produces plaques that are only 15%
the size of those of wild-type FHV. Here, we have complemented
FHVDeltagI-LZ allotopically by expressing intact gI and C-terminally
truncated gI derivatives from the thymidine kinase locus. The effect on
gE--gI-mediated cell-to-cell spread was assessed by plaque assay employing
computer-assisted image analysis (software available at
http://www.androclus.vet.uu.nl/ spotter/spotter.htm). Allotopic
complementation with intact gI fully restored plaque size. Deletion of the
C-terminal 11 residues of gI did not affect cell-to-cell spread, whereas
deletion of the complete cytoplasmic tail reduced plaque size by only 35%.
Mutants expressing gI(166), roughly corresponding to the N-terminal half of
the ectodomain, displayed a small-plaque phenotype. Nevertheless, their
plaques were reproducibly larger than those of matched gI-deficient
controls, indicating that the gE--gI(166) hetero-oligomer, though crippled,
is still able to mediate cell-to-cell spread. Our data demonstrate that
plaque analysis provides a reliable and convenient tool to measure and
quantitate gE--gI function in vitro.
