20200509u Santa Cruz, CA: As I searched for what happened today, I came across a church shooting in Texas. For some reason, I took a picture on my phone of the video:
The thought I had when remembering this church shooting was how the COVID-19 pandemic has affected religious services across the world.
I then searched for something else happening on this date and the first thing to catch my eye was this research paper published in the 2019-12-29 edition of Transfus Med: Amotosalen and ultraviolet A light efficiently inactivate MERS-coronavirus in human platelet concentrates. I see now that it was actually published online 2019-11-06, 11 days before the first known COVID-19 case.
Most of the paper authors are from King Abdulaziz University in Jeddah Saudi Arabia. Key quotes from the paper summary:
OBJECTIVE: This study aimed to assess the efficacy of the INTERCEPT™ Blood System [amotosalen/ultraviolet A (UVA) light] to reduce the risk of Middle East respiratory syndrome‐Coronavirus (MERS‐CoV) transmission by human platelet concentrates.
RESULTS: Complete inactivation of MERS‐CoV in spiked platelet units was achieved by treatment with Amotosalen/UVA light with a mean log reduction of 4·48 ± 0·3. Passaging of the inactivated samples in Vero E6 showed no viral replication even after nine days of incubation and three passages. Viral genomic RNA titration in inactivated samples showed titres comparable to those in pre‐treatment samples.
CONCLUSION: Amotosalen and UVA light treatment of MERS‐CoV‐spiked platelet concentrates efficiently and completely inactivated MERS‐CoV infectivity (>4 logs), suggesting that such treatment could minimise the risk of transfusion‐related MERS‐CoV transmission.
Keywords: amotosalen, MERS‐CoV, pathogen inactivation, platelets, UV
This paper is interesting because it looks at using UVA light as an antiviral, as opposed to the shorter wavelength UVC light.
Before going into the paper, I found it helpful to review UV light and where it fits into the electromagnetic spectrum. From the FDA: Ultraviolet (UV) Radiation.
Ultraviolet (UV) light has a frequency just a bit higher than visible light. If you remember the colors of the rainbow in order of low to high frequency using the ROYGBIV acronym, then you know the visible colors Red, Orange, Yellow, Green, Blue, Indigo, Violet. The next colors are Ultraviolet A, Ultraviolet B, and Ultraviolet C.
The longer the UV light wavelength, the more penetration light has into the Earth’s atmosphere, our skin, and our eyes. Light with wavelengths in the range 300-400 nm are blocked by the lens of our eyes. For this reason, we use 400 nm as the cut off point for defining UV light. Light with wavelengths shorter than 300 nm are blocked by the cornea or our eyes.
Ultraviolet A (UVA) is light with an ISO-recommended wavelength of 400-315 nm. Other names for UVA are “Black Light”, “Long-Wave”, or “Soft UV”. UVA light is not absorbed by the Earth’s ozone layer and passes through the atmosphere, the outer layer of our skin (epidermis), and into the middle layer of our skin (dermis).
Ultraviolet B (UVB) is light with an ISO-recommended wavelength of 315-280 nm. This medium-wave UV light is mostly absorbed by the Earth’s ozone layer. The UVB light that does pass through is absorbed by our epidermis and does not make it to our dermis. UVB light is necessary to help the epidermis produce vitamin D3.
Ultraviolet C (UVC) is light with an ISO-recommended wavelength of 280-200 nm. This short-wave UV light, also called “Hard UV”, is completely absorbed by the Earth’s ozone layer and atmosphere. Some UVC lamps operate at a wavelength of 253.7 nm, as this wavelength as been shown effective at killing or inactivating microorganisms. “Far-UVC” light, at a wavelength of 222-207 nm, is being researched as a possible light range that will efficiently kill pathogens without harm to humans. (REF: UVC research at columbia.edu, Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases)
Vacuum UV (in another universe, it’s called UVD) is light with an ISO-recommended wavelength of 200nm-100nm.
Going back to the paper, it focuses on a need to be able to efficiently inactivate pathogens in the blood of blood banks as an alternative to testing. It specifically mentions the problem of blood carrying the MERS virus:
Underreporting of asymptomatic cases is presumed, and thus, the real number of infected patients is likely to be much higher than the number of reported and confirmed cases (Lessler et al., 2016), which together with mild cases may facilitate the spread of the virus and pose a possible risk for blood safety. Higher seropositivity in camel workers compared to the general population has been reported (Müller et al., 2015; Alshukairi et al., 2018). Therefore, asymptomatic donors may donate blood while they potentially carry the virus.
The authors go on to say:
The INTERCEPT™ Blood System technology inactivates a broad spectrum of pathogens, including bacteria, viruses and protozoa, in platelet concentrates prepared for transfusion (Schlenke, 2014). Using amotosalen (a photoactive compound) and UVA light, pathogens’ genomes are modified in a targeted and specific manner by cross‐linking the genomic strands, preventing transcription and replication without affecting the platelet efficacy and patient safety as demonstrated in clinical evaluations (Cid et al., 2012), national routine observations (Jutzi et al., 2018) and by haemovigilance data from multiple countries (Benjamin et al., 2017). As an additional effect, residual white blood cells of the donor are inactivated more efficiently than by gamma irradiation (Castro et al., 2018), reducing the risk of immunological transfusion reactions and transfusion‐associated graft‐versus‐host disease (TA‐GvHD). The INTERCEPT Blood System is currently the only FDA‐approved pathogen reduction system for platelets.
After reading through the paper, my main take-away is that MERS is still circulating in the middle east and the opportunity for a MERS pandemic is real. My second take-away is that UVA is not likely to assist with killing pathogens in the same way as far-UVC and that I’d like to investigate far-UVC more.