PROJECT SUMMARY/ ABSTRACT Infectious diseases are serious and recurrent health threats. Particularly concerning are viruses with the capacity to mutate and generate de novo diversity in short periods of time. These viruses adapt to new hosts and environments, and continuously escape from the host anti-viral immune response. Preventative vaccines are highly desirable; however, no defined guidelines exist for the design of efficacious vaccines against rapidly mutating viruses such as HIV-1, influenza, or the current SARS-CoV2, with multiple different circulating variants. Despite their high diversity, viral variants present conserved regions that are essential for viral fitness and infectivity. These conserved epitopes are their Achilles heels, and the focus of antibody-based vaccine design efforts. A vaccine against a highly mutating virus should elicit an antibody response that specifically targets the conserved regions of the virus, as it would recognize and neutralize the broad diversity of its variants. Significant efforts in the field have focused on engineering viral immunogens to make their conserved epitopes more available for antibody recognition. Unfortunately, targeting antibody responses to specific conserved epitopes of interest is incredibly challenging. Complex antigens, such as viral spike proteins, elicit polyclonal responses dominated by antibodies to non-conserved epitopes. These antibodies have no potential to broadly neutralize the virus, and also interfere with the maturation of broadly protective antibodies in the germinal centers. Aiming to elicit broadly neutralizing antibodies (bNAbs) against a conserved epitope of HIV-1, we recently designed and evaluated a new HIV-1 Envelope (Env)-based priming immunogen, which elicited bNAb-like antibodies against a conserved epitope of Env in wild type mice and macaques; despite this achievement, these antibodies showed no neutralization activity against HIV-1, suggesting that additional immunization would be required to induce bNAbs. Nevertheless, further immunization in macaques elicited a polyclonal antibody response of only limited potency and breadth, dominated by antibodies to non-conserved epitopes of Env. Based on these observations, I hypothesize that reducing interfering antibody responses to non-conserved viral epitopes, and tracking the antibody responses with potential to become bNAbs, will pave the path towards bNAb development and inform vaccine design efforts. In this proposal, we will design and evaluate a novel strategy to modulate epitope immunodominance, which in addition, will allow us to record and track the history of antigen-B-cell interactions in vivo. The proposed technology will be used to customize the immunodominance properties of complex antigens in order to direct the antibody response to the epitopes of interest. In addition, we will use our new technology to barcode B cells responding to multiple immunizations, track their fates and record their history of antigen encounters. This groundbreaking technology will provide very valuable information to elucidate the mechanisms governing the B cell responses to vaccination and infection, and will significantly contribute to establish guidelines for vaccine design.

PROJECT NARRATIVE The design of preventative vaccines to control the spread of infectious diseases is a subject of public health interest, however, no guidelines to develop efficacious vaccines against highly mutating pathogens are available. The proposed research will aim to develop a new technology to specifically target antibody responses to neutralization sensitive epitopes of highly mutating viruses upon vaccination, which in addition, will allow to track the history of B cell-antigen interactions upon repeated immunization. The results of this research will provide novel strategies to design efficacious vaccines against pathogens and harmful molecules that mutate over time such as viruses, bacteria or tumor neo-antigens, and will contribute to elucidate the mechanisms governing the B cell responses to vaccination and infection, which will ultimately be used for rational vaccine design.