Abstract
Low-intensity ultrasound is a useful method to introduce materials into cells due to the transient formation of micropores, called sonoporations, on the cell membrane. Whether oncolytic herpes simplex virus type 1 (HSV-1) can be introduced into oral squamous cell carcinoma (SCC) cells through membrane pores remains undetermined. Human SCC cell line SAS and oncolytic HSV-1 RH2, which was deficient in the γ134.5 gene and fusogenic, were used. Cells were exposed to ultrasound in the presence or absence of microbubbles. The increase of virus entry was estimated by plaque numbers. Viral infection was hardly established without the adsorption step, but plaque number was increased by the exposure of HSV-1-inoculated cells to ultrasound. Plaque number was also increased even if SAS cells were exposed to ultrasound and inoculated with RH2 without the adsorption step. This effect was abolished when the interval from ultrasound exposure to virus inoculation was prolonged. Scanning electron microscopy revealed depressed spots on the cell surface after exposure to ultrasound. These results suggest that oncolytic HSV-1 RH2 can be introduced into SAS cells through ultrasound-mediated pores of the cell membrane that are resealed after an interval.
Highlights
Oncolytic virotherapy with herpes simplex virus type-1 (HSV-1) is under clinical application for the treatment of cancer because the results obtained for the efficiency of oncolytic HSV-1 in advanced malignant melanoma and head and neck cancer in phase I/II studies are promising [1,2,3]
We reported that exposure to ultrasound could increase the efficiency of HSV-1 infection if cells were exposed to ultrasound after an incubation of cells with virus for 30 min [10,11], indicating that ultrasound promotes the entry of HSV-1 when it was applied after an incubation of virus with susceptible cells to facilitate virus binding to their receptors
Adeno-associated virus (AAV) has been used as a vector to carry genomic DNAs into cells through the pore-producing effect of ultrasound [12,13], its ability to facilitate the entry of oncolytic HSV-1 – which is larger than AAV – through pores remains unclarified
Summary
Oncolytic virotherapy with herpes simplex virus type-1 (HSV-1) is under clinical application for the treatment of cancer because the results obtained for the efficiency of oncolytic HSV-1 in advanced malignant melanoma and head and neck cancer in phase I/II studies are promising [1,2,3]. Low-intensity ultrasound does not damage irradiated cells, but transiently produces pores on the cell membrane and allows extracellular materials including DNA, chemicals, and viruses to enter cells [6,7]. This pore-producing effect of ultrasound, called sonoporation, was shown to be elevated in the presence of microbubbles, which were initially used as a contrast agent for ultrasound diagnosis [8,9]. Adeno-associated virus (AAV) has been used as a vector to carry genomic DNAs into cells through the pore-producing effect of ultrasound [12,13], its ability to facilitate the entry of oncolytic HSV-1 – which is larger than AAV – through pores remains unclarified. We investigated whether oncolytic HSV-1 RH2 [14,15] that was deficient in the γ134.5 gene, a neurovirulent gene responsible for encephalitis and exhibiting fusogenic ability, enters into human oral squamous cell carcinoma (SCC) cells thorough ultrasound-mediated membrane pores
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