Inactivation of Human Leukocytes in Platelet Products After Pathogen Reduction Technology Treatment in the Presence of Platelet Additive Solution.

Abstract 2116

Poster Board II-93

During the transfusion of blood or blood products, a recipient can receive a large number of allogeneic leukocytes. This can lead to leukocyte-mediated adverse reactions in the recipient and include donor anti-recipient responses such as the life-threatening transfusion-associated graft versus host disease (TA-GVHD) and cytokine production; or recipient anti-donor responses that are induced by direct presentation of foreign antigen by donor leukocytes or indirectly after processing of the donor cells by recipient antigen-presenting cells. To avoid or minimize leukocyte mediated reactions, the leukocytes present in blood products are inactivated or depleted prior to administration. Nucleic acid targeted pathogen reduction processes (PRT) are well suited for leukocyte inactivation. The Mirasol^® PRT System uses riboflavin (Vitamin B2) and ultraviolet (UV) light to reduce the active pathogen load and inactivate residual leukocytes in blood products used for transfusion. To make the PRT System more widely applicable, the effect of treating leukocytes in the presence of platelet additive solution (PAS) was tested. Human peripheral blood mononuclear cells (PBMNC) were purified by Ficoll-Hypaque discontinuous centrifugation and placed in 350 ml of storage solution consisting of 65% PAS (SSP+) and 35% plasma. An untreated control sample was removed before addition of 35 ml of riboflavin (500 μM) and exposure to UV light (9.1 J/ml). PBMNC were recovered after treatment and tested for their ability to proliferate in response to polyclonal stimulators such as phytohemagglutinin, and anti-CD3/CD28 or to allogeneic stimulator cells in a mixed lymphocyte culture (MLC). Treatment was found to inhibit proliferation as well as T cell activation as measured by the upregulation of CD69 expression when incubated with phorbol 12-myristate 13-acetate. Treated PBMNC were unable to produce inflammatory or TH1/TH2 cytokines when stimulated with lipopolysaccharide for 24 hours or anti-CD3/CD28 for 72 hours. Levels of cytokines that are released in the absence of activation, such as IL-6, IL-8 and IL1β, were reduced below levels of detection of the assay after PRT-treatment. Quantitation of the degree of inactivation using limiting dilution assays showed that 5.2 log inactivation could be achieved at the specified energy doses. These treatment conditions resulted in acceptable platelet cell quality over 8 days in storage. In summary, PRT treatment was able to functionally inactivate leukocytes in the presence of PAS to the levels seen with gamma-irradiation without adversely affecting the quality of the platelets.