Efficacy of 405nm light for inactivation of feline calicivirus : a surrogate for norovirus

Background: Norovirus (NoV) is a leading cause of nosocomial gastroenteritis. With only 10-100 viral particles required for infection, effective decontamination of hospitals is particularly important in preventing the spread of this highly transmissible virus. A technology for continuous environmental decontamination has been developed which utilises 405nm light to inactivate bacteria and fungi, via ROS-generated oxidative damage. Aim(s)/Objectives: To date, the antiviral efficacy of 405nm light has not been fully determined, therefore this study was designed to investigate whether feline calicivirus (FCV), the standard surrogate for NoV, can be inactivated by 405nm light, and how viral susceptibility may be influenced when suspended in biologically-relevant material. Method: FCV was exposed to 405nm light (155.8mW/cm2) whilst suspended in various minimal andnutrient-rich media and inactivation curves were used to establish sensitivity. Viralin activation was measured by assessing infection of a feline embryo cell line (FEA). Results: Antiviral activity of 405nm light against FCV was successfully demonstrated, with a 4-log10(99.99%) reduction in minimal media evident after a dose of 2.8kJ/cm2. However susceptibility was significantly enhanced when exposed in nutrient-rich DMEM and artificial saliva, with an approximate 5-fold reduction in dose required (420J/cm2)for an equivalent level of inactivation. Discussion & Conclusion: The results indicate that FCV can be inactivated using 405nm light, and susceptibility can be significantly enhanced when the virus is present in nutrient-rich, or biologically-relevant material such as saliva. Further research in this area could lead to the development of 405nm light technology for effective NoV decontamination within the hospital environment