Germline targeting for neuraminidase broadly neutralizing antibodies

The development of a broad-spectrum influenza vaccine remains a significant challenge. One promising target for vaccine design is neuraminidase (NA), which is engaged by broadly neutralizing antibodies (bnAbs) that mimic the sialic acid receptor and bind to the conserved active site. These NA bnAbs use long heavy chain complementarity determining region 3 (HCDR3) loops to access the recessed active site. However, antibodies with long HCDR3s are rare in the naive human antibody repertoire, making it unlikely for them to be consistently elicited through standard vaccination strategies. To address this, a strategy called germline targeting vaccine design aims to prime the rare precursor B cells with the potential to develop into bnAbs by giving them an affinity advantage over more common strain-specific competitors. In this proposal, recently discovered NA bnAbs will be evaluated to assess their potential for germline targeting. Factors such as precursor frequency in the human antibody repertoire, somatic hypermutation levels, and structural characteristics will be considered. Once the most promising bnAb candidates have been identified, mammalian display directed evolution will be employed to design NA immunogens that can engage diverse bnAb precursors from those NA bnAb classes. This protein engineering effort will pave the way for future preclinical animal studies and other immunogen validation studies. If successful, a demonstration that NA germline targeting immunogens can engage diverse NA bnAb precursors would open up a new pathway towards a universal influenza vaccine.