Control of established chronic lymphocytic choriomeningitis virus (LCMV) infection requires the production of neutralizing antibodies, but it remains unknown how the ensemble of antibodies evolves during ongoing infection. Here, we analyze the evolution of antibody responses during acute or chronic LCMV infection, combining quantitative functional assays and time-resolved antibody repertoire sequencing. We establish that antibody responses initially converge in both infection types on a functional and repertoire level, but diverge later during chronic infection, showing increased clonal diversity, the appearance of mouse-specific persistent clones, and distinct phylogenetic signatures. Chronic infection is characterized by a longer-lasting germinal center reaction and a continuous differentiation of plasma cells, resulting in the emergence of higher-affinity plasma cells exhibiting increased antibody secretion rates. Taken together, our findings reveal the emergence of a personalized antibody response in chronic infection and support the concept that maintaining B cell diversity throughout chronic LCMV infection correlates with the development of infection-resolving antibodies.

Exosomes are nanosized membranous vesicles secreted by a variety of cells. Due to their unique and pharmacologically important properties, cell-derived exosome nanoparticles have drawn significant interest for drug development. By genetically modifying exosomes with two distinct types of surface-displayed monoclonal antibodies, we have developed an exosome platform termed synthetic multivalent antibodies retargeted exosome (SMART-Exo) for controlling cellular immunity. Here, we apply this approach to human epidermal growth factor receptor 2 (HER2)-expressing breast cancer by engineering exosomes through genetic display of both anti-human CD3 and anti-human HER2 antibodies, resulting in SMART-Exos dually targeting T cell CD3 and breast cancer-associated HER2 receptors. By redirecting and activating cytotoxic T cells toward attacking HER2-expressing breast cancer cells, the designed SMART-Exos exhibited highly potent and specific anti-tumor activity both in vitro and in vivo. This work demonstrates preclinical feasibility of utilizing endogenous exosomes for targeted breast cancer immunotherapy and the SMART-Exos as a broadly applicable platform technology for the development of next-generation immuno-nanomedicines.

The design of immunogens that elicit broadly reactive neutralizing antibodies (bnAbs) has been a major obstacle to HIV-1 vaccine development. One approach to assess potential immunogens is to use mice expressing precursors of human bnAbs as vaccination models. The bnAbs of the VRC01-class derive from the IGHV1-2 immunoglobulin heavy chain and neutralize a wide spectrum of HIV-1 strains via targeting the CD4 binding site of the envelope glycoprotein gp120. We now describe a mouse vaccination model that allows a germline human IGHV1-2(∗)02 segment to undergo normal V(D)J recombination and, thereby, leads to the generation of peripheral B cells that express a highly diverse repertoire of VRC01-related receptors. When sequentially immunized with modified gp120 glycoproteins designed to engage VRC01 germline and intermediate antibodies, IGHV1-2(∗)02-rearranging mice, which also express a VRC01-antibody precursor light chain, can support the affinity maturation of VRC01 precursor antibodies into HIV-neutralizing antibody lineages.