Engineering B Cells as an Evolving Drug to Fight HIV

HIV viremia can be controlled by chronic antiretroviral therapy. However, treatment tolerability and adherence remain a challenge. Combination therapies of broadly neutralizing antibodies (bNAbs) can suppress viremia, but they may have to be chronically administered at a higher cost. bNAbs may be constitutively expressed from muscle, liver or mucosa following AAV transduction, but the antibody is of a single isotype, emergence of resistant strains is probable in lack of affinity maturation, and anti-drug antibodies (ADA) may develop due in part to improper glycosylation. In contrast, bNAbs integrated at the IgH locus in transgenic mice and human B cells were shown capable of undergoing class switch recombination (CSR) and somatic hyper mutation (SHM) and may be less prone to ADA.

Here, we develop IgH engineering in B cells as a therapeutic approach for fighting HIV infections. We use CRISPR/Cas9 and AAV to introduce the anti-HIV bNAb 3BNC117. In particular, we target the intronic sequence downstream to the variable region and upstream to the IgM switch region. In an immunocompetent mouse model, we demonstrate antigen-induced B cell activation leading to germinal center occupancy and differentiation into memory B cells and plasma cells. Antibody secretion is further increased upon boost immunization and is accompanied by class switch recombination. By recoding 3BNC117 to reconstitute hotspots for AID, we allow increased rates of somatic hypermutation (SHM) that are concentrated at the CDR2, demonstrating affinity maturation. Importantly, we have also efficiently engineered PBMC-derived human B cells which also show high rates of antigen-induced activation.

Finally, we demonstrate how B cell genome editing could be performed without CRISPR. Instead, we integrate the bNAb coding cassette into the breaks which occur during the natural process of class switch recombination. Obviating the use of nucleases diminishes the associated risks and IP challenges, creating a clear path for a clinical application.

Uniquely, our method enables antigen-induced bNAb secretion that may be further augmented by affinity maturation, class switch recombination, and the retention of immunological memory. B cells could thus be engineered as a living and evolving drug to counteract HIV escape.