Broadly Neutralizing Engineered B cells demonstrate antigen induced activation, memory retention and patterns of affinity maturation in immunized mice

Vaccine development for the HIV pandemic has shown only slight promises, mainly due to the breath of diversity of the virus. The effective class of Broadly Neutralizing Antibodies (bNAb) is cross-clade neutralizing and in some cases able to clear infected cells. bNAbs have however a short half-life, may be targeted by anti-drug antibodies and may trigger viral escape.

We developed engineering of B cells to express bNAbs in a seemingly natural manner. The therapeutic cassettes are targeted to the endogenous immunoglobulin heavy chain locus and are expressed under a promoter active only upon on-target integration. The light chain of the antibody is encoded in full whereas the heavy chain, separated by a 2A peptide, encodes only the variable segment. A splice donor allows for the bNAb encoding transgene to ride on the endogenous heavy chain constant segments, thus enabling class-switch recombination (CSR) and secretion of the antibody.

Murine engineered primary B cells adoptively transferred into syngeneic immunocompetent mice were activated upon immunization with HIV Env proteins. The cells would differentiate into plasma or memory B cells, and proliferate in Germinal Centers (GC) only upon antigen injection. A boost effect was demonstrated upon a subsequent immunization, both by tracking the GC donor specific antigen binding cells and by serum titers of the bNAb. Finally, these B cells showed hints of affinity maturation, as seen by antigen binding amino acids undergoing higher rates of SHM.

B cells may thus be engineered as a living drug for a durable protection against HIV