ELICITATION OF ENGINEERED ANTIBODY RESPONSES FROM GENOME-MODIFIED B CELLS

Human HIV broadly neutralizing antibodies (bnAbs) can protect from infection and suppress viremia, but their elicitation through vaccination is exceedingly difficult. Genetic limitations of the human B cell antigen receptor (BCR) repertoire, restrict bnAb elicitation from rare precursor cells which must undergo extensive somatic hypermutation. To bypass this barrier, we have developed methods to introduce bnAb genes directly into the repertoire as functional antigen receptors in engineered B cells. In our approach, we site specifically insert a bnAb cassette into the heavy chain locus of primary B cells using CRISPR-cas9, which allows it to be transcribed using cell endogenous heavy chain (HC) constant genes. In this way, the bnAb can be expressed as a functional BCR or as a soluble secreted effector antibody of any isotype depending on the B cell maturation state. Insertion into the HC locus also allows the variable regions of the bnAb to be somatically mutated during affinity maturation, so that the B cell response can rapidly evolve and improve antibody affinity against quickly evolving targets like HIV (1A). We can reprogram 10% of mouse primary B cells to express the mature VRC01 bnAb based on FACS staining using antigen probes specific for this BCR (1B). When we transfer 75K reprogrammed VRC01-B cells (with mouse constant genes), into wild-type black 6 mice and vaccinate them with various HIV immunogens, we can reproducibly generate boostable memory responses that can result in more than 100ug/ml of isotype-switched VRC01in the serum of animals (1C).

These promising results suggest that engineered B cell vaccines could be used as an HIV functional cure if durable bi- or tri-specific HIV bnAB memory responses could be safely elicited in patients.