Date of Award
Doctor of Philosophy (PhD)
The immunologic obstacles to develop a broadly neutralizing antibody (bNAb) against HIV by vaccine mandate for methodical testing in order to understand and direct the immune response. A mouse model with the predicted human heavy chain variable domain of a bNAb precursor or mature version introduced into the mouse heavy chain immunoglobulin locus proved to be very useful. The immunoglobulin heavy-chain of the predicted germline (GLVH) or mature mutated (MuVH) version of 3BNC60 was knocked into the JH4 locus in mice. 3BNC60 is a bNAb that targets the CD4 binding site (CD4bs) of HIV-11,2 and belongs to the IgHV1-2 class of broadly neutralizing CD4bs antibodies3. In the first part of my thesis I will describe the evolution of the HIV-1 antibody response in GLVH and MuVH mice upon immunization. We immunized the mice with antigens designed to bind to the predicted unmutated precursor of 3BNC60 or with BG505 SOSIP trimers that resemble the native HIV-1 Env. Immunogens specifically designed to activate B cells bearing germline antibodies initiate immune responses, but they do not elicit bNAbs. In contrast, native-like Env trimers fail to activate B cells expressing germline antibodies but elicit bNAbs by selecting for a restricted group of light chains bearing specific somatic mutations that enhance neutralizing activity. The data suggest that vaccination to elicit broad anti-HIV-1 antibodies will require immunization with a succession of related immunogens. Although CD4bs bNAbs are attractive candidates for immunogen design, their features, such as a high degree of somatic hypermutation and a short CDRL3 in combination with our data in 3BNC60 knock-in mice suggest that they might be difficult to elicit through vaccination. In the second part I will describe IOMA, a new class of CD4-mimetic bNAb derived from the VH1-2 germline but with a normal-length CDRL3 and fewer somatic hypermutations than other bNAbs of its class. We defined IOMA’s complete epitope, by using crystal structures of a natively glycosylated Env trimer. Analysis of the native glycan shield on HIV-1 Env allowed us to provide what is, to our knowledge, the first full description of the interplay between heterogeneous untrimmed high-mannose and complex-type N-glycans within the CD4bs and of a natively glycosylated trimer.
von Boehmer, Lotta, "Targeting the CD4 Binding Site of HIV" (2018). Student Theses and Dissertations. 433.