1 Influence of Novel CD4 binding-defective HIV-1 Envelope Glycoprotein Immunogens on Neutralizing Antibody and T Cell Responses in Non-

2 The high affinity in vivo interaction between soluble HIV-1 envelope glycoprotein (Env) immunogens and primate CD4 results in conformational changes that alter the immunogenicity of the gp120 subunit. Because the conserved binding site on gp120 that directly interacts with CD4 is a major vaccine target, we sought to better understand the impact of in vivo Env-CD4 interactions during vaccination. Rhesus macaques were immunized with soluble wildtype (Wt) Env trimers and two trimer immunogens rendered CD4 binding-defective through distinct mechanisms. In one variant, we introduced a mutation that directly disrupts CD4 binding (368D/R). In the second variant, we introduced three mutations (423I/M, 425N/K, 431G/E) that disrupt CD4 binding indirectly by altering a gp120 sub-domain known as the bridging sheet, which is required for locking Env into a stable interaction with CD4. Following immunization, Env-specific binding antibody titers and frequencies of Env-specific memory B cells were comparable between the groups. However, the quality of neutralizing antibody responses induced by the variants was distinctly different