Glycoprotein C-independent binding of herpes simplex virus to cells requires cell surface heparan sulphate and glycoprotein B.

Previous studies have shown that the initial interaction of herpes simplex virus (HSV) with cells is binding to heparan sulphate and that HSV-1 glycoprotein C (gC) is principally responsible for this binding. Although gC-negative viral mutants are impaired for binding and entry, they retain significant infectivity. The purpose of the studies reported here was to explore the requirements for infectivity of gC-negative HSV-1 mutants. We found that absence or alteration of cell surface heparan sulphate significantly reduced the binding of gC-negative mutant virus and rendered cells resistant to infection, as shown previously for the wild-type virus. We isolated a recombinant double-mutated HSV strain that produces virions devoid of both of the known heparin-binding glycoproteins, gB and gC. The drastically impaired binding of these mutant virions to cells, relative to gC-negative and wild-type virions, indicates that gB mediates the binding of gC-negative virions to cells. Thus at least two HSV glycoproteins can independently mediate the binding of HSV to cell surface heparan sulphate to start the process of viral entry into cells.

Single amino acid substitutions in gD of herpes simplex virus 1 confer resistance to gD-mediated interference and cause cell-type-dependent alterations in infectivity.

Previous studies have shown that cell-associated herpes simplex virus (HSV) glycoprotein gD can interfere with infection of the cells by HSV and other alphaherpesviruses and that HSV mutants resistant to this gD-mediated interference can be isolated. Here we report that HSV mutants selected for resistance to gD-mediated interference are altered in specific infectivity for cells that do not express gD. Two independently derived mutants were shown to be impaired in ability to infect HEp-2 cells and enhanced in ability to infect Chinese hamster ovary cells, compared with the wild-type parental strain. The mutants were not significantly different from the parental strain in ability to bind to cells but differed in a postbinding step required for infectivity, probably penetration. The two mutants were shown to have different amino acid substitutions (Q27P and Q27R) in gD. Marker transfer experiments demonstrated that the resistance to gD-mediated interference as well as the altered infectivities resulted from these amino acid substitutions. Thus, small changes in gD structure can not only confer resistance to gD-mediated interference but also alter the relative efficiencies with which HSV penetrates into different cell types.