Inactivation of murine leukaemia virus by exposure to visible light

Prolonged storage of murine leukaemia virus in ambient light leads to a loss of infectivity. Particle integrity and envelope incorporation are unaffected; rather, the defect is functional and intrinsic to the viral core. Light in the violet part of the visible spectrum (wavelength 420-430 nm) is responsible for virus inactivation. Reduced reverse transcriptase-dependent cDNA generation post-entry accounts for the loss in infectivity and is likely due to a polymerase processivity defect. The virion-associated reverse transcription complex is thus photolabile. The phenomenon could be important in certain experimental situations, notably at elevated temperatures or when exposure to light is extensive. Additionally, our study suggests that the reverse transcription complex is a suitable target for an anti-retroviral strategy; identification of the nature of the lesion and the mechanism of its induction may inform the design of novel inhibitors.