Characterization of heterologous HIV-1 Tier 2 neutralizing mAbs cloned from a macaque immunized with viral quasispecies present in a human subject with neutralization breadth

Abstract

Abstract Eliciting Abs that efficiently neutralize multi-clade HIV strains will likely be necessary for an effective HIV-1 vaccine. Such broadly neutralizing Abs have been cloned from a minority of chronically infected patients but have yet to be generated through pre-clinical vaccine regimens in NHPs. Here we characterize the Env-specific mAb response in an NHP with autologous Tier 2 neutralizing activity after co-immunization with plasmid gp160 DNA(x6) + gp140 trimeric protein(x2), using viral quasispecies present in a human subject immediately prior to and concurrent with the development of neutralizing breadth. In brief, 46 mAbs were cloned from single IgG+, antigen-specific, memory B cells, 12 of which neutralized heterologous Tier 1 and Tier 2 virus at IC50s < 4.2 mg/ml in a TZM-bl assay. These mAbs bound SHIVSF162P3-infected rhesus PBMCs significantly more than non-neutralizers (p < 0.001). Octet measurements and peptide mapping revealed the strongest neutralizers bound autologous F8 SOSIP with high affinity (KD ≤ 1.32×10−9), and 10 of these mAbs targeted the viral V3 region in the VH5.51 “cradle” orientation. Interestingly, non-neutralizing mAbs demonstrated high in vitroEnv binding (EC50s < 0.001 mg/ml) via ELISA, and several mediated ADCP against HIVSF162gp120 coated beads. Additionally, ADCC activity was observed with select neutralizing and non-neutralizing mAbs via KHYG-1/NKR24 SHIV-infected reporter assay. Collectively, these results suggest this immunization strategy recapitulated in part the clonal neutralization expansion and Env targeting observed in the patient and provide insights into effector functions of both neutralizing and non-neutralizing HIV-1 Env-specific mAbs elicited during vaccination.