Platelets retain function and can be stored following disruption of human leucocyte antigens

BACKGROUND AND OBJECTIVES

Antibodies to human leucocyte antigen (HLA) Class-I antigens can lead to refractoriness to platelet transfusion. Although this can be overcome by transfusion of HLA-compatible platelets, they are not always available. Disruption of HLA antigens on platelets by acid treatment may be a suitable alternative when no other components are available. The aim of this study was to assess the effect of HLA disruption and subsequent storage of platelet components.

MATERIALS AND METHODS

Platelet components were treated with 0.9% saline or citric acid solution (pH 3.0), and then stored until expiry (Day 7). HLA and platelet glycoprotein expression, platelet viability, activation and sialylation were measured by flow cytometry. Release of soluble factors was measured by ELISA and metabolism by biochemistry analyser. Reactivity to patient anti-sera containing anti-HLA antibodies was measured using platelet immunofluorescence tests (PIFTs) and monoclonal antibody immobilization of platelet antigen (MAIPA) assays. Platelet function was measured using aggregometry and thromboelastography (TEG).

RESULTS

Acid treatment reduced detection of HLA Class-I on platelets by 75%, with significant reductions in reactivity to patient anti-sera. Acid treatment reduced platelet content and viability, increased platelet activation and accelerated metabolism. Glycan cleavage was increased by acid treatment. Treatment reduced platelet activation following agonist stimulation by ADP and TRAP-6, but platelets remained functional, displaying increased aggregation response and reduced time to clot formation by TEG.

CONCLUSION

Although HLA disruption had some detrimental effects, acid-treated platelets remained functional, retaining their capacity to respond to agonists and form clots, and with further development could be used to support refractory patients.

Platelets for cancer treatment and drug delivery

Extensive research is currently being conducted into a variety of bio-inspired biomimetic nanoparticles (NPs) with new cell simulation functions across the fields of materials science, chemistry, biology, physics, and engineering. Cells such as erythrocytes, platelets, and stem cells have been engineered as new drug carriers. The platelet-derived drug delivery system, which is a new targeted drug delivery system (TDDS), can effectively navigate the blood circulatory system and interact with the complex tumor microenvironment; it appears to outperform traditional anticancer drugs; hence, it has attracted considerable research interest. In this review, we describe innovative studies and outline the latest progress regarding the use of platelets as tumor targeting and drug delivery vehicles; we also highlight opportunities and challenges relevant to the manufacture of tumor-related platelet TDDSs.

Dual preparation of plasma and platelet concentrates in platelet additive solution from platelet concentrates in plasma using a novel filtration system

BACKGROUND AND OBJECTIVES

Platelet concentrates suspended in a platelet additive solution (PAS-PC) are associated with a reduction in allergic response and are suitable for preparing pathogen-inactivated PC. We aimed to develop an efficient platform for the dual preparation of PAS-PC and platelet-poor plasma.

MATERIALS AND METHODS

PAS-PC was prepared in six steps by using a hollow-fibre system based on cross-flow filtration: priming, loading PC, loading PAS, collection of filtered liquid (flow-through) and collection of platelets by washing with PAS followed by washing with air. In this study, the efficacy of platelet and plasma protein recovery and characteristics of recovered PAS-PC and flow-through plasma were analysed in detail.

RESULTS

Recoveries of platelet in PAS-PC and plasma protein in the flow-through were 95.4% ± 3.7% and 61.6% ± 5.0%, respectively. The residual plasma protein in PAS-PC was 34.1% ± 2.8%. Although the expression level of CD62P, a platelet activation marker, in recovered platelets was approximately 1.2-fold of that in original platelets, swirling patterns were well retained, and aggregation in PAS-PC was not visible. Agonist-induced aggregabilities, platelet morphology and hypotonic shock recovery were conserved. The patterns of plasma protein and lipoprotein in the flow-through were comparable with those in the original PCs. The multimeric pattern analysis of VWF remained unaltered.

CONCLUSION

We propose a highly efficient preparation system that enables the simultaneous production of PAS-PC and platelet-poor plasma. It also achieves a high recovery of functionally well-retained platelets with very low activation.

UV light-emitting diode (UV-LED) at 265 nm as a potential light source for disinfecting human platelet concentrates

The risk of sepsis through bacterial transmission is one of the most serious problems in platelet transfusion. In processing platelet concentrates (PCs), several methods have been put into practice to minimize the risk of bacterial transmission, such as stringent monitoring by cultivation assays and inactivation treatment by photoirradiation with or without chemical agents. As another potential option, we applied a light-emitting diode (LED) with a peak emission wavelength of 265 nm, which has been shown to be effective for water, to disinfect PCs. In a bench-scale UV-LED exposure setup, a 10-min irradiation, corresponding to an average fluence of 9.2 mJ/cm2, resulted in >2.0 log, 1.0 log, and 0.6 log inactivation (mean, n = 6) of Escherichia coli, Staphylococcus aureus, and Bacillus cereus, respectively, in non-diluted plasma PCs. After a 30-min exposure, platelet counts decreased slightly (18 ± 7%: mean ± SD, n = 7); however, platelet surface expressions of CD42b, CD61, CD62P, and PAC-1 binding did not change significantly (P>0.005), and agonist-induced aggregation and adhesion/aggregation under flow conditions were well maintained. Our findings indicated that the 265 nm UV-LED has high potential as a novel disinfection method to ensure the microbial safety of platelet transfusion.