Cell fusion induced by herpes simplex virus glycoproteins gB, gD, and gH-gL requires a gD receptor but not necessarily heparan sulfate.

To characterize cellular factors required for herpes simplex virus type 1 (HSV-1)-induced cell fusion, we used an efficient and quantitative assay relying on expression of HSV-1 glycoproteins in transfected cells. We showed the following: (1) Cell fusion depended not only on expression of four viral glycoproteins (gB, gD, and gH-gL), as previously shown, but also on expression of cell surface entry receptors specific for gD. (2) Cell fusion required expression of all four glycoproteins in the same cell. (3) Heparan sulfate was not required for cell fusion. (4) Coexpression of receptor with the four glycoproteins in the same cell reduced fusion activity, indicating that interaction of gD and receptor can limit polykaryocyte formation. Overall, the viral and cellular determinants of HSV-1-induced cell fusion are similar to those for viral entry, except that HSV-1 entry is significantly enhanced by binding of virus to cell surface heparan sulfate.

The anti-herpes simplex virus activity of n-docosanol includes inhibition of the viral entry process.

n-Docosanol-treated cells resist infection by a variety of lipid-enveloped viruses including the herpesviruses. Previous studies of the mechanism of action demonstrated that n-docosanol inhibits an event prior to the expression of intermediate early gene products but subsequent to HSV attachment. The studies reported here indicate that n-docosanol inhibits fusion of the HSV envelope with the plasma membrane. Evidence suggests that antiviral activity requires a time-dependent metabolic conversion of the compound. Cellular resistance to infection declines after removal of the drug with a t1/2 of approximately 3 h. Reduced expression of viral genes in n-docosanol-treated cells was confirmed by a 70% reduction in expression of a reporter gene regulated by a constitutive promoter inserted into the viral genome. Inhibited release in treated cells of virion-associated regulatory proteins--an immediate post entry event--was indicated by a 75% reduction in the expression of beta-galactosidase in target cells carrying a stably transfected lacZ gene under control of an HSV immediate--early promoter. Finally, the fusion-dependent dequenching of a lipophilic fluorescent probe, octadecyl rhodamine B chloride, inserted into the HSV envelope was significantly inhibited in treated cells. Inhibition of fusion between the plasma membrane and the HSV envelope, and the subsequent lack of replicative events, may be the predominant mechanism for the anti-HSV activity of n-docosanol.

Variability of herpes simplex virus 1 gL and anti-gL antibodies that inhibit cell fusion but not viral infectivity.

Herpes simplex virus type 1 gL lacks a transmembrane domain but stably associates with membranes through its oligomerization with the integral membrane glycoprotein designated gH. The gH-gL oligomers are essential for virion infectivity and virus-induced cell fusion. Monoclonal and polyclonal antibodies were raised against HSV-1(KOS) gL as probes for antigenic structure and functional protein domains. Antigenic determinants recognized by these antibodies were found to be present on gL expressed by many, but not all, strains of HSV-1 and were not detected on gL expressed by HSV-2 strains. These antigenic determinants were localized to the C-terminal region of HSV-1 gL, where amino acid substitutions define at least two classes of HSV-1 gL and where the sequences of HSV-1 and HSV-2 gL diverge considerably. The antibodies were extremely effective at inhibiting virus-induced cell fusion, provided the virus strain expressed the relevant antigenic determinants, but failed to neutralize viral infectivity despite demonstrable binding to virions. These results define strain-dependent differences in the structure and antigenic conformation of HSV-1 forms of gL and suggest that the roles of gL in cell fusion and viral entry are different.

Case study. Abbott Northwestern Hospital.

Abbott Northwestern hopes to continue learning and sharing its lessons as the teams execute their plans. The results of Innovation are expected to include the following: Improved care for patients and their families. Improved working environment for employees. Improved service to other customers' needs. Improved operating costs. The hospital further expects to begin showing tangible results within the next year. Achieving these results requires implementation, and the implementation details are currently uncertain. Like an explorer crossing an uncharted ocean, Abbott Northwestern does not know exactly where and how it will land on the other shore, but it is surely committed to getting there. Having this chance to make a such a journey is frightening for most of those involved. For some, it is fear of the uncertainty of change, while for others, it is the fear of losing the comfort of the present system. And still others of us fear that we may not reach as far as we can.

Potent neutralizing activity associated with anti-glycoprotein D specificity among monoclonal antibodies selected for binding to herpes simplex virions.

Thirty-three monoclonal antibodies were selected for ability to bind to purified virions of herpes simplex virus and were shown by immunoprecipitation to react with one or another of the envelope glycoproteins. Only six of these antibodies exhibited potent neutralizing activity, and all six were specific for glycoprotein D. Two other anti-glycoprotein D antibodies and 25 antibodies specific for four other viral glycoproteins had much less potent, if any, neutralizing activity.

Anti-gD monoclonal antibodies inhibit cell fusion induced by herpes simplex virus type 1.

Monoclonal antibodies directed against glycoprotein D of herpes simplex virus completely inhibited fusion of Vero cells infected with type 1 virus. In contrast, several monoclonal antibodies directed against other viral glycoproteins, including B, were ineffective or were only minimally inhibitory at the highest concentrations tested.