Evaluation of Photobiogoverning Role of Blue Light Irradiation on Viral Replication

Analysis of the SARS-CoV-2 inactivation mechanism using violet-blue light (405 nm)

The study evaluated the effects of violet-blue light (VBL) on cell viability and replication, carbonylation of three structural proteins (S, E, and N) and one non-structural protein (NSP13), and direct damage to the RNA of SARS-CoV-2. The virus was exposed to increasing doses of VBL along with influenza A and B viruses to compare their susceptibility. At the highest dose (21.6 J/cm2), SARS-CoV-2 was significantly more susceptible to VBL than the influenza viruses, with a reduction in viral titer of 2.33 log10. Viral RNA did not show significant changes after exposure to VBL, as demonstrated by next-generation sequencing and real-time PCR quantification, suggesting that the inactivation process does not involve direct nucleic acid damage. To exclude the role of the culture suspension in the inactivation process, virus viability experiments were performed using different dilutions of Dulbecco's modified Eagle's medium (DMEM) in phosphate-buffered saline (PBS). The results indicated that the suspension medium played a secondary role in virus inactivation, as viability did not increase with increasing DMEM dilution. Subsequent tests with three different antioxidants (NAC, AsA, and SOD) at different concentrations prevented viral inactivation, from 99.99% to 85.43% (with SOD 0.003 mM). Carbonylation of S and E proteins was more pronounced when viruses were suspended in DMEM rather than PBS, although the tests demonstrated that the intrinsic properties of the viral membrane were a crucial element to consider in relation to its susceptibility to VBL.IMPORTANCELight-based disinfection methods are often used in combination with other cleaning methods due to their non-invasive nature, versatility, and environmental benefits. VBL is an effective approach as it induces the production of reactive oxygen species that reduce microbial viability. In this study, lipid peroxidation was identified as an important factor affecting the structural integrity and function of the viral envelope, reducing its ability to interact with host cells and consequently its ability to be infectious. The lipid envelope of SARS-CoV-2, composed mainly of glycerophospholipids and lacking cholesterol and sphingolipids, appears to be the critical factor in its susceptibility, distinguishing it from influenza viruses, which have a lipid profile richer in components that protect against oxidative stress.

Antiviral and synergistic effects of photo-energy with acyclovir on herpes simplex virus type 1 infection

This experimental study aimed to evaluate the antiviral and synergistic effects of photoenergy irradiation on human herpes simplex virus type I (HSV-1) infection. We assessed viral replication, plaque formation, and relevant viral gene expression to examine the antiviral and synergistic effects of blue light (BL) with acyclovir treatment. Our results showed that daily BL (10 J/cm2) irradiation inhibited plaque-forming ability and decreased viral copy numbers in HSV-1-infected monkey kidney epithelial Vero cells and primary human oral keratinocyte (HOK) cells. Combined treatment with the antiviral agent acyclovir and BL irradiation increased anti-viral activity, reducing viral titers and copy numbers. In particular, accumulated BL irradiation suppressed characteristic viral genes including UL19 and US6, and viral DNA replication-essential genes including UL9, UL30, UL42, and UL52 in HOK cells. Our results suggest that BL irradiation has anti-viral and synergistic properties, making it a promising therapeutic candidate for suppressing viral infections in clinical trials.

The inhibitory and inactivating effects of visible light on SARS-CoV-2: A narrative update

Prior to the coronavirus disease-19 (COVID-19) pandemic, the germicidal effects of visible light (λ = 400 - 700 nm) were well known. This review provides an overview of new findings that suggest there are direct inactivating effects of visible light - particularly blue wavelengths (λ = 400 - 500 nm) - on exposed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions, and inhibitory effects on viral replication in infected cells. These findings complement emerging evidence that there may be clinical benefits of orally administered blue light for limiting the severity of COVID-19. Possible mechanisms of action of blue light (e.g., regulation of reactive oxygen species) and important mediators (e.g., melatonin) are discussed.

Effect of near-infrared and blue laser light on vero E6 cells SARS-CoV-2 infection model

Photobiomodulation therapy (PBMT) employing laser light has been emerging as a safe strategy to challenge viruses. In this study the effect of blue and near-infrared (NIR) laser light was assessed in an in vitro model of SARS-CoV-2 infection. PBMT at blue wavelength inhibited viral amplification when the virus was directly irradiated and then transferred to cell culture and when cells already infected were treated. The NIR wavelength resulted less efficacious showing a minor effect on the reduction of the viral load. The cells receiving the irradiated virus or directly irradiated rescued their viability to level comparable to not treated cells. Virion integrity and antigenicity were preserved after blue and NIR irradiation, suggesting that the PBMT antiviral effect was not correlated to viral lipidic envelope disruption. Our results suggested that PBMT can be considered a valid strategy to counteract SARS-CoV-2 infection, at least in vitro.

Blue light irradiation exerts anti-viral and anti-inflammatory properties against herpes simplex virus type 1 infection

The aim of this study was to investigate the antiviral and anti-inflammatory functions of blue light (BL) in cutaneous viral infections. Previously, we examined the photo-biogoverning role of 450 nm BL in SARS-CoV-2-infected cells, which showed that photo-energy could inhibit viral activation depending on the number of photons. However, the communication network between photo-energy irradiation and immune cells involved in viral infections has not been clarified. We verified viral activation, inflammatory responses, and relevant downstream cascades caused by human simplex virus type I (HSV-1) after BL irradiation. To examine the antiviral effect of BL, we further tested whether BL could disturb viral absorption or entry into host cells. The results showed that BL irradiation, but not green light (GL) exposure, specifically decreased plaque-forming activity and viral copy numbers in HSV-1-infected cells. Accumulated BL irradiation inhibited the localization of viral proteins and the RNA expression of characteristic viral genes such as UL19, UL27, and US6, thus exerting to an anti-viral effect. The results also showed that BL exposure during viral absorption interfered with viral entry or destroyed the virus, as assessed by plaque formation and quantitative PCR assays. The levels of the pro-inflammatory mediators interleukin (IL)-18 and IL-1β in M1-polarized macrophages were increased by HSV-1 infection. However, these increases were attenuated by BL irradiation. Importantly, BL irradiation decreased cGAS and STING expression, as well as downstream NF-κB p65, in M1-polarized HSV-1-infected macrophages, demonstrating anti-viral and anti-inflammatory properties. These findings suggest that BL could serve as an anti-viral and anti-inflammatory therapeutic candidate to treat HSV-1 infections.

Blue Laser Light Counteracts HSV-1 in the SH-SY5Y Neuronal Cell Model of Infection

Herpes simplex virus 1 (HSV-1) is wide-spread virus that triggers painful and recurrent infections, as herpes labialis, causing blister lesions on the lip. HSV-1 infection can be a lifelong condition starting from childhood due to the latency of the virus hidden in the trigeminal ganglia. Despite the use of antiviral treatments, there is not a resolutive cure for herpes. In our study, we tested blue light against HSV-1 in a neuronal cellular model, aimed at mimicking the neuronal tropism of HSV-1. Two laser protocols employing continuous wave and pulse modalities were delivered to infected cell cultures and to the virus alone. A significant reduction of viral replication was observed when the beam was directly applied to the virus, along with an increase in cell survival. Our findings, considering the limitation of the still-unknown mechanisms by which the blue light acts on the virus, suggested a potential use of photobiomodulation therapy for clinical applications against herpes labialis in pediatric patients.