Herpes simplex viruses type 1 and 2 photoinactivated in the presence of methylene blue transform human and mouse cells in vitro

Abstract

Three strains of herpes simplex virus, K17syn- and HSZPsyn+ of type 1 (HSV-1) and USsyn- of type 2 (HSV-2), were photoinactivated in the presence of methylene blue and used to infect 3 cell lines, normal human lung tissue cells (MRC-5), mouse epithelial cells (NIH3T3), and human lung carcinoma cells (A549). The virus titer and phenotype of cells were evaluated to compare the characteristics of normal and carcinoma cells infected with non-syncytial (non-syn) and syncytial (syn) strains of herpes simplex viruses. We found that the cells of both normal cell lines infected with photoinactivated K17syn- and USsyn- but not HSZPsyn+ acquired transformed phenotype accompanied by the presence of virus. Surprisingly, the infection with photoinactivated viruses K17syn- and USsyn- but not HSZPsyn+ resulted in the suppression of the transformed phenotype of A549 cells. Using nested PCR, herpesviral DNA was identified in newly transformed cells and cells that lost the transformed phenotype. The effect of putative herpesvirus-related growth factors (HRGF) produced by cells infected with photoinactivated viruses was quantified and compared. Since methylene blue is currently used in phototherapy of herpetic lesions, these results raise the question of whether such therapy is risky to human health.

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

“…Another interesting finding is that the ability to transform cells or to alter the transformed phenotype of cells is restricted only to synstrains of HSV-1, i. e. the strains causing cell rounding, unable to form polycaryocytes (syncytia). This phenomenon was described in our previous study (7).…”

“…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. They change their transformed phenotype towards the normal one, so that these cells resemble normal, non-transformed, contact inhibited cells (Fig.…”

“…Only UV-irradiated non-syncytial strains KOS and Kupka proved to be able to transform the cells. The cells infected with irradiated syncytial strains HSZP and ANG path remained intact without any morphological changes similar to those infected with photoinactivated syncytial strains (7). The cells infected with both UV-irradiated syncytial and non-syncytial strains contained virus antigen as demonstrated after staining with FITC anti-HSV1,2 goat polyclonal antibody (Invitrogen) (data not shown).…”

“…Recently, Michútová et al (7) continued the studies of these phenomena and obtained interesting original results. Their work suggests that only non-syncytial strains of HSV-1 are capable of transforming cells in vitro after photoinactivation in the presence of methylene blue, such transforming activity has not been demonstrated for photoinactivated syncytial strains.…”

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

“…Quiescent infection of cell cultures may provide an important and amenable means of studying the molecular mechanisms that mimic herpesvirus latency in vivo . Such in vitro models can be established at supraoptimal temperatures [41][42][43] or in the presence of inhibitors of DNA synthesis [34] . Here, we established quiescent infection of MHV-68 in MRC-5 and NIH-3T3 cells by infection with a low dose of virus (0.01 PFU/mL), cultivation in the presence of PAA, and a temperature shift from the usual 37 to 41 ° C. Next, cells were photoinactivated by a procedure previously described, enabling the induction of transformation of the cells infected with treated virus.…”