Transformation of Cells by Photoinactivated Murine Gamma-Herpesvirus 68 during Nonproductive and Quiescent Infection

Abstract

Infection of human MRC-5 cells and mouse NIH-3T3 cells with a murine gamma-herpesvirus (MuHV-4 strain 68; MHV-68) photoinactivated by visible light in the presence of methylene blue (MB) resulted in nonproductive infection and the appearance of morphologically transformed cells. Two stably transformed cell lines were derived from both of these cell types and were confirmed to contain both viral DNA and antigen. Next, a quiescent MHV-68 infection in MRC-5 and NIH-3T3 cells was established after cultivation at 41°C in the presence of phosphonoacetic acid. Following the exposure of quiescently infected cells to visible light for 120 s (5 times daily for 6 days) in the presence of MB, both MRC-5 and NIH-3T3 cells were observed to acquire transformed phenotypes. The cytopathic effect was observed in cells after 4-5 passages, after which the cells degenerated. However, when human interferon (IFN)-α and mouse IFN-β were added to the media of quiescently infected MRC-5 and NIH-3T3 cells during the photoinactivating procedure, 2 stable transformed cell lines containing both viral DNA and the antigen were obtained and resembled those attained following nonproductive infection with photoinactivated virus.

Herpes simplex virus type 1 suppresses the transformed phenotype of cultured cells

“…1f). Similar changes in the structure of actin bundles were obtained in cells infected with UV-irradiated or photoinactivated MHV-68 (5,6). In HaCaT cells infected with UV-irradiated syncytial ANGpath strain, with unchanged phenotype only viral fluorescence antigen similar to that shown in Fig.…”

“…As mentioned above, the ability of HSV-1 and -2 to transform cells after UV irradiation or after photoinactivation has been known for decades (1,2,3,4) and has also been recently demonstrated with MHV-68 (6,7). However, what is new and has been demonstrated in our previous studies (7) and in now presented results is the fact that such inactivated viruses, whether UV-irradiated or photoinactivated in the presence of methylene blue (7) behave completely differently in transformed cells.…”

“…The process of transformation in non-transformed MRC-5 and NIH3T3 cells followed similar pattern as described previously (1,5,6). The transformation of non-transformed cells by inactivated HSV is already well known for years and relatively well understood, so we have not studied it in details now.…”

“…It has been shown decades ago, that herpes simplex viruses type 1 and 2 (HSV-1,-2) after irradiation with UV light or after photoinactivation in the presence of a photosensitizer, e.g. neutral red, are capable of transforming cells in vitro (1,2,3,4), and similar activity was later demonstrated with UV-irradiated and photoinactivated murine gammaherpesvirus 68 (MHV-68) (5,6).…”

Trends and targets in antiviral phototherapy

“…370b, 372 As mentioned above (section 3.7 riboflavin) it was shown that the immunogenicity of hepatitis B is retained after photochemical inactivation of HBV with methylene blue. 29,330 Commercially, methylene blue is used as the active substance in the THERAFLEX MB Plasma system (Macopharma, Tourcoing, France). 18c, 373,374 An older similar method also using methylene blue is referred to as the 'Springe method'.…”