In vivo engineered B cells secrete high titers of broadly neutralizing anti-HIV antibodies in mice

Transplantation of B cells engineered ex vivo to secrete broadly neutralizing antibodies (bNAbs) has shown efficacy in disease models. However, clinical translation of this approach would require specialized medical centers, technically demanding protocols and MHC compatibility of donor cells and recipients. Here, we report in vivo B cell engineering using two adeno-associated viral vectors, with one coding for saCas9 and the other for 3BNC117, an anti-HIV bNAb. After intravenously injecting the vectors into mice, we observe successful editing of B cells leading to memory retention and bNAb secretion at neutralizing titers of up to 6.8 μg/mL. We observed minimal CRISPR-Cas9 off-target cleavage as detected by unbiased CHANGE-Seq analysis, whereas on-target cleavage in undesired tissues is reduced by expressing saCas9 from a B cell-specific promoter. In vivo B cell engineering to express therapeutic antibodies is a safe, potent and scalable method, which may be applicable not only to infectious diseases but also in the treatment of non-communicable conditions, such as cancer and autoimmune disease.