Table 1 Protocols for immune tolerance... | American Society of Hematology

Table 1

Protocols for immune tolerance induction to factor VIII

Tolerance protocol	Model systems	Outcome/Interpretation
Immunosuppression
Cyclophosphamide	AAV gene transfer in HemA mice and dogs; Lentiviral gene transfer into neonatal HemA mice; naked plasmid transfer in HemA mice	Immune responses were suppressed^42-44
RAP + FVIII; MMF + CSA + RAP	FVIII protein or naked plasmid therapy in HemA mice	Prevented or delayed inhibitory antibody^42,50
Costimulatory blockade
IDO + FVIII	Delivery by transposon system in HemA mice	Long-term therapeutic FVIII expression and reduced anti-FVIII titer⁵⁴
CTLA4-Ig ^+/− anti-CD40L or anti-ICOS	Naked plasmid transfer or FVIII protein therapy in HemA mice	Prevented inhibitor formation²⁰ and induced long-term tolerance to FVIII^42,51; blocked differentiation of FVIII-specific memory B cells^11,55
T-cell depletion
Anti-CD3 + FVIII	FVIII protein or naked plasmid transfer therapy in HemA mice	Induced tolerance to FVIII^56,57
B-cell depletion
Anti-CD20 IgG1	FVIII protein therapy in HemA mice	Prevented the increase of inhibitors in FVIII-primed mice⁶
Anti-CD20 IgG2a	FVIII protein therapy or naked plasmid transfer in HemA mice	Prevented primary antibody production but fail to induce long-term tolerance⁵⁹; significantly reduced anti-FVIII inhibitor titers in naive and FVIII primed HemA mice⁵³
Oral tolerance
Oral delivery of FVIII peptide or FVIII C2 domain; feeding of extracts of FVIII-engineered plants	FVIII protein therapy in HemA mice	Reduced C2-speicific antibody titers⁶³; reduced anti-FVIII titers in HemA mice⁶⁴ and prevented anti-FIX antibody in HemB mice^65,66
Gene and cell therapy
Bone marrow gene therapy
Retroviral HSC gene therapy + ATS or CTLA4 + anti-CD40L	Ex vivo gene therapy in HemA mice	Achieved sustained FVIII gene expression and no significant immune responses in naive and FVIII-primed HemA mice^73,74
Transplantation of normal MSCs in utero or postnatally	MSC cell therapy pre- or postnatally in HemA sheep model	Widespread cell engraftment; however, FVIII gene expression was very low⁷⁵; preexisting hemarthroses resolved, spontaneous bleeds ceased, but inhibitors appeared after treatment⁷⁶
Tolerogenic cell therapy
Foamy virus vector transduced iDC expressing FVIII and IL-10 or FVIII-pulsed dendritic cells; cFVIII-pulsed iDC	Recipient HemA mice; FVIII-deficient dogs	Inhibitor titers were reduced⁷⁷; inhibited anti-FVIII antibody response⁷⁹; achieved hyporesponsiveness to FVIII⁷⁸
B cells expressing FVIII domains	Recipient HemA mice	Produced significant suppression of inhibitor titers in naive and FVIII-primed HemA mice⁸¹
Platelet expression of FVIII by gene therapy	Ex vivo gene therapy; intraosseous delivery of lentiviral vectors in HemA mice	Achieved long-term FVIII expression in naive and FVIII-primed HemA mice^85-88
Improving gene therapy for tolerance
Lentiviral gene therapy incorporating microRNA in the vector	Ex vivo gene therapy in HemA mice using lentiviral vectors	Prevented anti-FVIII antibody production⁹¹ (achieved long-term and therapeutic FIX expression^89,90)
Delivery of AAV carrying a codon-optimized FVIII cDNA; naked plasmid transfer + immunomodulation	AAV or naked plasmid transfer in HemA mice	Enhanced tolerance to FVIII^39,46-48,59
Treg immunotherapy
Tregitope administration with antigen	FVIII protein therapy in HemA mice	Not reported yet (promoted tolerance to other antigens⁹²)
In vivo expansion of Tregs by IL2/anti-IL2 mAb complexes; adoptive transfer of Tregs from transgenic mice	Naked plasmid transfer in HemA mice; protein therapy in HemA mice	Prevented antibody production and induced long-term tolerance to FVIII^52,115,116
Additional novel tolerogenic fusion proteins
FVIII-Fc fusions	FVIII protein therapy in HemA mice	Achieved lower immunogenicity¹⁰¹ (and also for FIX¹⁰²)
Crosslinking of antigens to peripheral blood or spleen cells	Protein therapy in HemA mice	Induced tolerance to FVIII¹⁰⁵

Tolerance protocol	Model systems	Outcome/Interpretation
Immunosuppression
Cyclophosphamide	AAV gene transfer in HemA mice and dogs; Lentiviral gene transfer into neonatal HemA mice; naked plasmid transfer in HemA mice	Immune responses were suppressed^42-44
RAP + FVIII; MMF + CSA + RAP	FVIII protein or naked plasmid therapy in HemA mice	Prevented or delayed inhibitory antibody^42,50
Costimulatory blockade
IDO + FVIII	Delivery by transposon system in HemA mice	Long-term therapeutic FVIII expression and reduced anti-FVIII titer⁵⁴
CTLA4-Ig ^+/− anti-CD40L or anti-ICOS	Naked plasmid transfer or FVIII protein therapy in HemA mice	Prevented inhibitor formation²⁰ and induced long-term tolerance to FVIII^42,51; blocked differentiation of FVIII-specific memory B cells^11,55
T-cell depletion
Anti-CD3 + FVIII	FVIII protein or naked plasmid transfer therapy in HemA mice	Induced tolerance to FVIII^56,57
B-cell depletion
Anti-CD20 IgG1	FVIII protein therapy in HemA mice	Prevented the increase of inhibitors in FVIII-primed mice⁶
Anti-CD20 IgG2a	FVIII protein therapy or naked plasmid transfer in HemA mice	Prevented primary antibody production but fail to induce long-term tolerance⁵⁹; significantly reduced anti-FVIII inhibitor titers in naive and FVIII primed HemA mice⁵³
Oral tolerance
Oral delivery of FVIII peptide or FVIII C2 domain; feeding of extracts of FVIII-engineered plants	FVIII protein therapy in HemA mice	Reduced C2-speicific antibody titers⁶³; reduced anti-FVIII titers in HemA mice⁶⁴ and prevented anti-FIX antibody in HemB mice^65,66
Gene and cell therapy
Bone marrow gene therapy
Retroviral HSC gene therapy + ATS or CTLA4 + anti-CD40L	Ex vivo gene therapy in HemA mice	Achieved sustained FVIII gene expression and no significant immune responses in naive and FVIII-primed HemA mice^73,74
Transplantation of normal MSCs in utero or postnatally	MSC cell therapy pre- or postnatally in HemA sheep model	Widespread cell engraftment; however, FVIII gene expression was very low⁷⁵; preexisting hemarthroses resolved, spontaneous bleeds ceased, but inhibitors appeared after treatment⁷⁶
Tolerogenic cell therapy
Foamy virus vector transduced iDC expressing FVIII and IL-10 or FVIII-pulsed dendritic cells; cFVIII-pulsed iDC	Recipient HemA mice; FVIII-deficient dogs	Inhibitor titers were reduced⁷⁷; inhibited anti-FVIII antibody response⁷⁹; achieved hyporesponsiveness to FVIII⁷⁸
B cells expressing FVIII domains	Recipient HemA mice	Produced significant suppression of inhibitor titers in naive and FVIII-primed HemA mice⁸¹
Platelet expression of FVIII by gene therapy	Ex vivo gene therapy; intraosseous delivery of lentiviral vectors in HemA mice	Achieved long-term FVIII expression in naive and FVIII-primed HemA mice^85-88
Improving gene therapy for tolerance
Lentiviral gene therapy incorporating microRNA in the vector	Ex vivo gene therapy in HemA mice using lentiviral vectors	Prevented anti-FVIII antibody production⁹¹ (achieved long-term and therapeutic FIX expression^89,90)
Delivery of AAV carrying a codon-optimized FVIII cDNA; naked plasmid transfer + immunomodulation	AAV or naked plasmid transfer in HemA mice	Enhanced tolerance to FVIII^39,46-48,59
Treg immunotherapy
Tregitope administration with antigen	FVIII protein therapy in HemA mice	Not reported yet (promoted tolerance to other antigens⁹²)
In vivo expansion of Tregs by IL2/anti-IL2 mAb complexes; adoptive transfer of Tregs from transgenic mice	Naked plasmid transfer in HemA mice; protein therapy in HemA mice	Prevented antibody production and induced long-term tolerance to FVIII^52,115,116
Additional novel tolerogenic fusion proteins
FVIII-Fc fusions	FVIII protein therapy in HemA mice	Achieved lower immunogenicity¹⁰¹ (and also for FIX¹⁰²)
Crosslinking of antigens to peripheral blood or spleen cells	Protein therapy in HemA mice	Induced tolerance to FVIII¹⁰⁵

ATS, anti-thymocyte serum; cFVIII, canine factor VIII; CSA, cyclosporin A; HemA, hemophilia A; HemB, hemophilia B; HSC, hematopoeitic stem cell; ICOS, inducible co-stimulatory molecule; IDO, indoleamine 2,3-dioxygenase.

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