Pathogen reduction of monkeypox virus in plasma and whole blood using riboflavin and UV light

Abstract

Background: Monkeypox virus has recently emerged from endemic foci in Africa and, since October 20, 2022, more than 73,000 human infections have been reported by the CDC from over 100 countries that historically have not reported monkeypox cases. The detection of virus in skin lesions, blood, semen, and saliva of infected patients with monkeypox infections raises the potential for disease transmission via routes that have not been previously documented, including by blood and plasma transfusions. Methods for protecting the blood supply against the threats of newly emerging disease agents exist and include Pathogen Reduction Technologies (PRT) which utilize photochemical treatment processes to inactivate pathogens in blood while preserving the integrity of plasma and cellular components. Such methods have been employed broadly for over 15 years, but effectiveness of these methods under routine use conditions against monkeypox virus has not been reported.

Study design and methods: Monkeypox virus (strain USA_2003) was used to inoculate plasma and whole blood units that were then treated with riboflavin and UV light (Mirasol Pathogen Reduction Technology System, Terumo BCT, Lakewood, CO). The infectious titers of monkeypox virus in the samples before and after riboflavin + UV treatment were determined by plaque assay on Vero cells.

Results: The levels of spiked virus present in whole blood and plasma samples exceeded 103 infectious particles per dose, corresponding to greater than 105 DNA copies per mL. Treatment of whole blood and plasma units under standard operating procedures for the Mirasol PRT System resulted in complete inactivation of infectivity to the limits of detection. This is equivalent to a reduction of ≥ 2.86 +/- 0.73 log10 pfu/mL of infectivity in whole blood and ≥ 3.47 +/-0.19 log10 pfu/mL of infectivity in plasma under standard operating conditions for those products.

Conclusion: Based on this data and corresponding studies on infectivity in patients with monkeypox infections, use of Mirasol PRT would be expected to significantly reduce the risk of transfusion transmission of monkeypox.

Fig 1. Monkeypox viral titers in whole blood products pre- and post- treatment with Mirasol.

Plaque assay results from monkeypox virus pre- and post- inactivation with UV light and riboflavin. Assay performed on 6-well cell culture plates and cells stained with crystal violet for plaque visualization. A) Virus stock. B) Virus with riboflavin prior to inactivation. C) Post- inactivation.

Fig 2. Monkeypox viral titers in plasma products pre- and post- treatment with Mirasol.

Plaque assay results from monkeypox virus pre- and post- inactivation with UV light and riboflavin. Assay performed on 6-well cell culture plates and cell monolayer stained with crystal violet for plaque visualization. A) Virus stock. B) Virus with riboflavin prior to inactivation. C) Post- inactivation.