Mt. Huber et al., Herpes simplex virus with highly reduced gD levels can efficiently enter and spread between human keratinocytes, J VIROLOGY, 75(21), 2001, pp. 10309-10318
The rapid spread of herpes simplex virus type 1 (HSV-1) in mucosal epitheli
a and neuronal tissue depends primarily on the ability of the virus to navi
gate within polarized cells and the tissues they constitute. To understand
HSV entry and the spread of virus across cell junctions, we have previously
characterized a human keratinocyte cell line, HaCaT. These cells appear to
reflect cells infected in vivo more accurately than many of the cultured c
ells used to propagate HSV. HSV mutants lacking gE/gI are highly compromise
d in spread within epithelial and neuronal tissues and also show defects in
cell-to-cell spread in HaCaT cells, but not in other, nonpolarized cells.
HSV gD is normally considered absolutely essential for entry and cell-to-ce
ll spread, both in cultured cells and in vivo. Here, an HSV-1 gD mutant vir
us, F-US6kan, was found to efficiently enter HaCaT cells and normal human k
eratinocytes and could spread from cell to cell without gD provided by comp
lementing cells. By contrast, entry and spread into other cells, especially
highly transformed cells commonly used to propagate HSV, were extremely in
efficient. Further analyses of F-US6kan indicated that this mutant expresse
d extraordinarily low (1/500 wild-type) levels of gD. Neutralizing anti-gD
monoclonal antibodies inhibited entry of F-US6kan, suggesting F-US6kan util
ized this small amount of gD to enter cells. HaCaT cells expressed high lev
els of an HSV gD receptor, HveC, and entry of F-US6kan into HaCaT cells cou
ld also be inhibited with antibodies specific for HveC. Interestingly, anti
-HveC antibodies were not fully able to inhibit entry of wild-type HSV-1 in
to HaCaT cells. These results help to uncover important properties of HSV a
nd human keratinocytes. HSV, with exceedingly low levels of a crucial recep
tor-binding glycoprotein, can enter cells expressing high levels of recepto
r. In this case, surplus gD may be useful to avoid neutralization by anti-g
D antibodies.