Fusion from Without Induced by Herpes Simplex Virus Type 1

Abstract

Strains ANG and ANG path of herpes simplex virus type 1 (HSV1) produced fusion from without (FFWO) of cells in culture. FFWO required 45min to become complete. In contrast, fusion from within (FFWI) was not detected until 3–4 h after infection, depending on the cell type. FFWO was temperature dependent: at 0° no fusion could be observed, but increase of temperature increased the degree of fusion. The pH optimum for FFWO was 7.8–8.5. The FFWO activity of the virus was found to be slightly more heat stable at 46° than was infectivity. FFWO was produced in Vero, CV-1 and BSCl cells, but not in BHK clone 13 or in primary or secondary rabbit kidney cells. FFWO was linked to the presence of virus particles and perhaps to other sedimentable, infected-cell material but not to soluble factors. Actinomycin D, cycloheximide, and UV irradiation did not block this activity, indicating no direct activity of the HSV1 genome for FFWO.

Differentiation of herpes simplex virus-induced fusion from without and fusion from within by cyclosporin A and compound 48/80

“…We used the HSV-1 strains ANG (Falke et al, 1985), HFEM (Walev et al, 1991), IES (Falke & Kahl, 1971), MP (Heeg et al, 1986), Len (Heeg et al, 1986), 17 TK 1301 (Sanders et al, 1982), L4-1 and L3-2S (Falke et al, 1985). Strains KOS-804 (syn) and KOS-78R (Little & Schaffer, 1981) were provided by P. Schaffer, Boston, Mass., U.S.A., strains 17 syn and 17 TK 1301 were provided by Professor J. H. SubakSharpe (Glasgow, U.K.) and HSV-2 strains Lux syn and US-A12 by K. E. Schneweis (Bonn, Germany).…”

“…Viruses were grown in Vero cells maintained in roller bottles at 37 °C. Titrations were done as described earlier (Falke et al, 1985).…”

“…This fusion has been named fusion from within (FFWI) because fusion is induced during the course of virus replication. FFWI can be blocked by inhibitors of transcription and translation and can be detected 3 to 4 h after infection (Falke et al, 1985). Up to six loci of HSV may be involved in fusion processes (Tognon et al, 1988;Spear, 1987), and mutations in one of these loci might induce fusion capacity.…”

“…Some time ago, we reported on fusion from without (FFWO) induced by certain strains of HSV-1 (Falke et al, 1985). FFWO is produced by the virus particles themselves 30 to 45 min after infection and cannot be inhibited by inhibitors of transcription or translation (Falke et al, 1985).…”

“…FFWO is produced by the virus particles themselves 30 to 45 min after infection and cannot be inhibited by inhibitors of transcription or translation (Falke et al, 1985). Furthermore, it was possible to show that strains of HSV-I and -2 producing FFWI could be divided into two groups: strains producing FFWI and FFWO, and strains exhibiting FFWI activity only (Walev et al, 1991).…”