ABSTRACT
Antimicrobial photodynamic therapy (aPDT) [1] has been deployed in tens of thousands of patients in Canada for preoperative intranasal bacterial suppression to reduce the prevalence rate of surgical site infections [2]. This treatment has proven safe and effective, with infection rate reductions of 40-80% in tertiary care systems despite only requiring 4 minutes of therapy [2]. We previously demonstrated that aPDT eliminates the RNA signature of wild-type SARS-CoV-2 in vitro, with reduction of RT-qPCR threshold counts (DELTACt = 22) in a light-dose dependent manner (C = 320 muM, lambda = 664 nm, F = 36 J/cm2) [3]. Photodynamic targets were found to include the receptor binding domain, spike protein and nucleocapsid domain, consistent with a broad spectrum peroxidative effect on anionic moieties throughout the virion [3]. This work describes the benefits of using regular aPDT treatments in the industrial workplace for the purpose of employee COVID-19 prevention. From July 2020 to August 2021, aPDT was deployed at a large Canadian food processing plant. Meat processing facilities face distinctive challenges in control of infectious diseases, including SARS-CoV-2. Factors that increase processing workers' risk for exposure to SARS-CoV-2 include close contact for 8-12 hour shifts, shared transportation, and congregate housing [4,5]. The presence of a slaughtering plant in a community is associated with a 51 to 75% increase in COVID-19 cases per thousand over the baseline community rate, and a 37 to 50% increase in death rate over the baseline community rate [5]. Methylene blue-mediated aPDT (SteriwaveTM Nasal Photodisinfection System, Ondine Biomedical Inc., Vancouver, BC) was added to the standard infection control bundle at the plant, along with employee education. Treatments were administered free of charge to approximately 1,500 employees on a voluntary basis during paid work hours. Compliance levels of employees requesting aPDT were 85%. To determine intervention efficacy, the rate of qPCR-positive COVID-19 tests over the treatment time period was compared to the same rate in the surrounding province. Results demonstrated a reduction of COVID-19 rate of over 3 times (p<.0001, Fisher's Exact Test) in the treated population compared to the untreated population, with the largest adverse event being mild (self-limiting) rhinorrhea in < 1% of cases. The plant continued production and distribution of products without disruption. Important outcomes from this quality improvement initiative included (a) aPDT proved to be a rapid, lightweight intervention that could be deployed at high compliance levels in a commercial high-throughput food processing operation, (b) significant impact (>3X reduction) on the COVID-19 rates was observed and (c) COVID-19-related comorbidities including acute and long-term illness, disability, and death were proportionately avoided.Copyright © 2023
ABSTRACT
Introduction: We previously reported on the elimination of the RNA signature of laboratory strains as well as wild-type SARS-CoV-2 using a photodynamic disinfection technique. This report extends the work to destruction of receptor binding domains, spike protein and nucleocapsid protein of major SARS-CoV-2 variants including the dominant Delta variant. Objectives: The objective of this work was to evaluate effect of a 2-min cycle of aPDT on receptor binding domains, spike protein and nucleocapsid protein of SARS-CoV-2. Methods: Spike glycoprotein receptor binding domain proteins from SARS-Related Coronavirus 2 included recombinant NR-54004 (United Kingdom Variant), NR-54005 (South African Variant), and NR-52366 (Wuhun-Hu-1 Variant) (BEI Resources, NIAID, ATCC). Recombinant spike proteins included B.1.1.7 Spike Protein, United Kingdom Variant (10748-CV-100), B.1.617 Spike Protein, Indian (Delta) Variant (10861-CV-100), B.1.351 Spike Protein, South African Variant (10777-CV-100), P.1 Spike Protein, Brazilian Variant (10795-CV-100) (all from R&D Systems, Inc.), and the stabilized spike glycoprotein, Wuhun-Hu-1 Variant (NR-52397). The SARS-CoV-2 nucleocapsid protein (NR55344, Avi-Histag, Biotin-Labeled, BEI Resources, NIAID, ATCC) was also tested for susceptibility to damage. aPDT was carried out by exposing each viral component to a photosensitizer formulation containing 320 uM methylene blue in an aqueous adjuvant, immediately followed by 36 J/cm2 (120 s) of non-thermal laser light at 664 nm (Steriwave® aPDT system, Ondine Biomedical Inc., Vancouver, B.C.). Illumination was conducted in a custom thin-film cell replicating the anterior nasal architecture. Control solutions were identically treated but without light exposure. 50 ul samples of treated and control solutions were evaluated by SDSPAGE using SYPRO Ruby Protein Gel Stain. Results: SDS-PAGE evaluation of all treated RBD, spike and SARSCoV-2 nucleocapsid protein samples showed no detectable protein remaining after 2 min exposure to photodynamic disinfection treatment. All no-light control samples remained unaffected. Conclusion: A 2-min photodynamic disinfection procedure was demonstrated to destroy RBD's, spike protein and nucleocapsid protein of major SARS-CoV-2 viral variants in circulation, expanding on previous work evaluating RNA damage in this virus. This outcome supports the use of aPDT as a potential SARS-CoV-2 suppression technique.
ABSTRACT
Introduction: SARS-CoV-2 infection initiates in the upper respiratory tract with viral shedding prior to onset of symptoms. Asymptomatic carriers are associated with the majority of COVID-19 transmissions, complicating prophylaxis. Up to half of all clinical cases of COVID-19 develop secondary bacterial infections, primarily secondary bacterial pneumonia which may prove lethal. Effective intranasal antiviral treatment options for SARS-CoV-2 carriers are limited. Objectives: Higher viral titer is associated with increased severity of symptoms and mortality risk. Targeting SARS-CoV-2 colonization sites in the upper airway with a potent, safe, antiviral modality may mitigate the severity of lower tract respiratory disease as well as reduce hospitalization and mortality rates. Intranasal APDT has been deployed for 10 years in Canadian hospitals as an effective, broad-spectrum nasal antimicrobial for reduction of post-surgical infections. The objective of this work was to evaluate effectiveness of APDT against SARS-CoV-2 in vitro. Methods: Studies were carried out using wild-type virus (SARSRelated Coronavirus 2, Isolate USA-WA1/2020, Cat# NR-52286, heat-inactivated, US Centers for Disease Control and Prevention/BEI Resources, NIAID, NIH). APDT was carried out by exposing the viral culture to a photosensitizer formulation containing 320 uM methylene blue in an aqueous carrier, immediately followed by 36 J/cm2 of non-thermal laser light at 664 nm. Illumination was conducted in a custom thin-film cell replicating the anterior nasal architecture. Studies were repeated at 72 J/cm2 for comparison purposes. RNA quantitation was carried out using RT-qPCR with N1/N2 primers and probes and bacteriophage controls. All experiments were repeated in triplicate. Results: Results demonstrated APDT was capable of completely eliminating the RNA signature of SARS-CoV-2. Reduction of threshold count ΔCt = 22 was accomplished in a linear light-dose-dependent manner (starting Ct = 23, ending Ct > 45 nondetectable) with light doses up to 8 min (p < 0.001). Conclusion: Using standard clinical parameters for intranasal pathogen reduction, APDT proved capable of eliminating the RNA signature of wild-type SARS-CoV-2 in vitro. This work supports further development of APDT as a potent, antiviral modality for inhibition of SARS-CoV-2 transmission.