High-resolution mapping of the neutralizing and binding specificities of polyclonal sera post-HIV Env trimer vaccination

Abstract

Mapping polyclonal serum responses is critical to rational vaccine design. However, most high-resolution mapping approaches involve isolating and characterizing individual antibodies, which incompletely defines the polyclonal response. Here we use two complementary approaches to directly map the specificities of the neutralizing and binding antibodies of polyclonal anti-HIV-1 sera from rabbits immunized with BG505 Env SOSIP trimers. We used mutational antigenic profiling to determine how all mutations in Env affected viral neutralization and electron microscopy polyclonal epitope mapping (EMPEM) to directly visualize serum Fabs bound to Env trimers. The dominant neutralizing specificities were generally only a subset of the more diverse binding specificities. Additional differences between binding and neutralization reflected antigenicity differences between virus and soluble Env trimer. Furthermore, we refined residue-level epitope specificity directly from sera, revealing subtle differences across sera. Together, mutational antigenic profiling and EMPEM yield a holistic view of the binding and neutralizing specificity of polyclonal sera.

The Glycan Hole Area of HIV-1 Envelope Trimers Contributes Prominently to the Induction of Autologous Neutralization

“…5C ). They are also consistent with observations that the N130 site and the nearby region are not immunogenic on B41 and BG505 trimers ( 17 , 18 , 26 , 32 ). However, as the autologous NAb titers were analyzed in detail only for the B41 and BG505 trimers, it is possible that the N130 glycan hole may be immunogenic on other trimers.…”

Improved epitope resolution of the prefusion trimer-specific antibody AM14 bound to the RSV F glycoprotein

“…For this, recent advances in polyclonal epitope mapping methods, which allow to structurally characterize human antibody responses, might play a critical role. [48][49][50][51][52] In summary, we report improved resolution structures of RSV prefusion F in its engineered stabilized version, known as DS-Cav1, in complex with Fab AM14, enabling comprehensive interpretation of important antibody-antigen interactions that were previously unappreciated at the available lower resolution. These structures serve as useful tools in understanding the molecular basis for trimer specificity, as well as in guiding the engineering of novel trimer-specific molecular probes or therapeutics to treat RSV infections.…”

A neutralizing antibody target in early HIV-1 infection was recapitulated in rhesus macaques immunized with the transmitted/founder envelope sequence

“…Convergence of neutralizing antibody targeting in HIV-1 infection and vaccination results do suggest that Z1800M T/F Env gp120-based regimens can reproducibly elicit V5 targeted nAb. Indeed, other studies including our own have described V5 loop targeting on other HIV-1 strains by autologous nAb following vaccination, HIV-1 infection, and SHIV infection of RM, including in settings involving the CD4bs and development of breadth [6,8,12,13,58,61,[65][66][67][68][69][70]. The predictability of nAb targeting against this Env, in the vicinity of the CD4bs, the eventual development of heterologous neutralization breadth, and the availability of longitudinal samples and sequences, makes this T/F Env and its longitudinal variants a strong candidate for further immunogen design.…”