Inactivation of Infectious CMV in Platelet Products: Comparison of INTERCEPT Blood System™ and Leukofiltration.

Background: While many severely immunocompromised patients require cytomegalovirus (CMV)-safe blood components, the standard approach of providing CMV-seronegative and/or leukoreduced components is still associated with breakthrough cases of CMV transmission. The INTERCEPT Blood System™ is a pathogen-inactivation methodology for platelets and plasma which may be a superior approach for providing CMV-safe transfusions. In this study, we compared the efficacy of INTERCEPT with leukoreduction for inactivating and/or removing infectious CMV experimentally introduced at high levels into platelet components.

Methods: Pooled buffy-coat platelet concentrates (n=6) were prepared from volunteer whole blood donations at a blood center using standard methods. A high titer stock (>10⁸ pfu/mL) containing both cell-associated and cell-free human CMV (AD169) was then spiked into each unit. After collection of pre-treatment samples, the CMV-spiked components were divided into 2 bags of equal volumes (2.5–6.0 ×10¹¹ platelets in ∼350 mL of 35% plasma and 65% InterSol™). One platelet unit was treated with INTERCEPT using methods in routine daily use at the blood center; the other unit was leukoreduced by filtration using commercial leukofilters (e.g., Asahi PLX5). Post-treatment samples were then collected. Total DNA prepared from each sample was subjected to nested PCR amplification. Plasma samples were added to confluent MRC5 monolayers, and the cultures were examined daily over the course of 6 weeks for the appearance of viral cytopathic effect.

Results: Prior to viral spiking, all 6 pooled BC platelet components were CMV-seronegative and had no detectable CMV by either nested PCR or viral culture. After spiking with CMV, all units had readily detectable CMV DNA by PCR; 5 of the 6 units showed replication-competent virus as determined by CMV culture. INTERCEPT uniformly eliminated amplification of the 2,039 bp fragment of CMV UL93 open reading frame, while CMV DNA could be amplified from some filtered units. Using viral culture as a sensitive indicator of replication-competent CMV, INTERCEPT completely prevented CMV replication in all samples. In contrast, each of the 5 components that displayed infectious CMV after spiking still had detectable replication-competent virus after leukoreduction.

Discussion: We found that INTERCEPT treatment could completely inactivate CMV in platelet components treated under standard blood center conditions even when CMV was inoculated into the components at artificially high viral loads (final concentration ∼ 10⁶ pfu/mL). In contrast, leukoreduction was ineffective under these conditions since all inoculated units demonstrated replicating CMV after filtration. These data are consistent with PCR results showing that INTERCEPT also eliminated amplifiable CMV DNA from the platelet components. Thus, INTERCEPT treatment greatly reduces, if not eliminates, the risks of CMV transmission by transfusion, suggesting that INTERCEPT-treated platelets may be optimally CMV safe as compared to leukoreduced units.