Immunoresponse against the transgene limits hematopoietic engraftment of mice transplanted in utero with virally transduced fetal liver

Abstract

In utero cell and gene therapies constitute alternative strategies to the postnatal treatment of inherited diseases. Fetal hematopoietic progenitors could be a potential source of donor cells for these strategies. In this study, hematopoietic lineage-negative fetal liver cells from 14.5-day-old fetuses were transduced under different cytokine and culture combinations using a lentiviral vector expressing the enhanced green fluorescent protein (EGFP). When cells were transduced for 6 h in the presence of mSCF, hTPO and FLT3-L in retronectin-coated dishes at a multiplicity of infection of 10 transduction units/cell, up to 70% of granulo-macrophage colony-forming cells expressed the EGFP reporter gene. In utero transplantation experiments revealed that conditions leading to high transduction efficiencies were associated with poor engraftments of syngeneic recipients. Significantly, this effect was associated with the detection of a humoral and cellular immunoresponse against the transgenic protein. Moreover, the humoral response against EGFP was detected not only in in utero transplanted recipients but also in the operated mothers, suggesting the maternal origin of the anti-EGFP immunoresponse. These observations reinforce the necessity of carefully studying the potential immunoresponses in future prenatal gene therapy protocols.

Fetal gene therapy

“…74 More recently, fetal gene delivery has been shown to induce postnatal immune tolerance to the transgenic protein in sheep receiving AAV6.2-and AAV8-GFP 75 and macaques receiving AAV5-factor X. 76 Interestingly, there have been publications reporting immune response following fetal gene delivery of vector in mice, 77 gene-modified hematopoietic stem cells in mice 78 and vector delivery in rats, 79 sheep, 80 and monkeys. 81 Possible explanations may be that certain gene products are less tolerogenic than others (considering that most genes in preclinical experiments are human and not conspecific to the preclinical model) and that some modes of delivery may be more tolerogenic or less pro-inflammatory.…”