Sickle cells produce functional immune modulators and cytotoxics

Abstract

Sickle erythrocytes’ (SSRBCs) unique physical adaptation to hypoxic conditions renders them able to home to hypoxic tumor niches in vivo, shut down tumor blood flow and induce tumoricidal responses. SSRBCs are also useful vehicles for transport of encapsulated drugs and oncolytic virus into hypoxic tumors with enhanced anti-tumor effects. In search of additional modes for arming sickle cells with cytotoxics, we turned to a lentiviral β-globin vector with optimized Locus Control Region/β-globin coding region/promoter/enhancers. We partially replaced the β-globin coding region of this vector with genes from the T cell cytolytics, perforin and granzyme or immune modulating superantigens SEG and SEI. These modified vectors efficiently transduced Sca+ckit−Lin− HSCs from humanized sickle cell knockin mice. Irradiated mice reconstituted with these HSCs displayed robust expression of transgenic RNAs and proteins in host sickle cells that was sustained for more than 10 months. SSRBCs from reconstituted mice harboring SEG/SEI transgenes induced robust proliferation and prototypical superantigen-induced cytokine reaction when exposed to human CD4+/CD8+ cells. The β-globin lentiviral vector therefore produces a high level of functional, erythroid-specific immune modulators and cytotoxics that circulate without toxicity. Coupled with their unique ability to target and occlude hypoxic tumor vessels these armed SSRBCs constitute a potentially useful tool for treatment of solid tumors.

Engineered red blood cells as therapeutic agents

“…A significant step forward was realized by Harvey Lodish et al 7 by the introduction of genes encoding surface proteins that can be covalently and specifically modified to became useful sites for the genera- These erythrocytes were also shown to be able to induce protection in animal models of autoimmune diseases. 8 The article by Sun et al 9 In conclusion, after many years of research on the physiology and pathology of RBC, and many attempts in extending the use of erythrocytes over the conventional transfusion practice, we are finally at the clinical staged with some mature applications and a large platform that need to be fully exploited. 10 During these years we have learned that RBC are natural carriers, abundantly available, amenable to a wide range of reproducible modifications, and with an immense potential for serving as therapeutic agents in a number of conditions with high medical needs.…”

“…The article by Sun et al that appears in this issue of The American Journal of Hematology combines the biological peculiarities of sickle erythrocytes with a genetic method consisting in the transduction of sickle hematopoietic stem cells with a lentiviral vector with optimized Locus Control Region/promoters and enhancers of β‐globin and armed with autologous cytotoxics (perforin and granzyme) or with immune modulating superantigens. In fact, sickle erythrocytes under hypoxic conditions are able to home into tumor niches, to shut down blood flow and induce tumoricidal response.…”

“…These erythrocytes were also shown to be able to induce protection in animal models of autoimmune diseases. 8 The article by Sun et al 9 that appears in this issue of The American Journal of Hematology combines the biological peculiarities of sickle erythrocytes with a genetic method consisting in the transduction of sickle hematopoietic stem cells with a lentiviral vector with optimized Locus Control Region/promoters and enhancers of b-globin and armed with autologous cytotoxics (perforin and granzyme) or with immune modulating superantigens. In fact, sickle erythrocytes under hypoxic In conclusion, after many years of research on the physiology and pathology of RBC, and many attempts in extending the use of erythrocytes over the conventional transfusion practice, we are finally at the clinical staged with some mature applications and a large platform that need to be fully exploited.…”