HLA-universal platelet transfusions prevent platelet refractoriness in a mouse model

Area of Science:

• Immunology
• Hematology
• Cellular and Molecular Medicine

Background:

• Platelet (PLT) transfusion refractoriness due to human leukocyte antigen (HLA) alloimmunization is a significant clinical challenge.
• Developing universally compatible PLTs lacking HLA antigens is crucial for managing refractory patients.

Purpose of the Study:

• To assess the efficacy of HLA class I-silenced (HLA-universal) platelets in evading HLA antibody-mediated cytotoxicity in vitro and in vivo.
• To evaluate the potential of HLA-silenced platelets to overcome PLT transfusion refractoriness.

Main Methods:

• Generation of HLA-silenced megakaryocytes (MKs) and PLTs from CD34(+) cells using short hairpin RNA (shRNA) targeting β2-microglobulin (β2m).
• In vitro assessment using lymphocytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) reporter assays with anti-HLA antibodies.
• In vivo evaluation in a mouse model of PLT refractoriness, involving antibody injection and infusion of HLA-silenced MKs.

Main Results:

• HLA silencing significantly protected MKs and PLTs against HLA antibody-mediated cytotoxicity, with only 3% of silenced MKs lysed compared to 80-90% of control MKs.
• In vivo, HLA-silenced MKs escaped rapid clearance in the presence of anti-HLA antibodies, unlike HLA-expressing MKs.
• HLA-silenced MKs successfully produced detectable platelets in mice for up to 11 days, even under immune challenge.

Conclusions:

• HLA-silenced platelets demonstrate robust protection against HLA antibody-mediated cytotoxicity, effectively preventing PLT refractoriness.
• These HLA-universal PLTs represent a promising therapeutic strategy for patients refractory to conventional platelet transfusions.