Comprehensive Characterization of Reference Standard Lots of HIV-1 Subtype C Gp120 Proteins for Clinical Trials in Southern African Regions

Abstract

Two HIV-1 subtype C gp120 protein candidates were the selected antigens for several experimental vaccine regimens now under evaluation in HVTN 100 Phase I/II clinical trial aiming to support the start of the HVTN 702 Phase IIb/III trial in southern Africa, which is designed to confirm and extend the partial protection seen against HIV-1 infection in the RV144 Thai trial. Here, we report the comprehensive physicochemical characterization of the gp120 reference materials that are representative of the clinical trial materials. Gp120 proteins were stably expressed in Chinese Hamster Ovary (CHO) cells and subsequently purified and formulated. A panel of analytical techniques was used to characterize the physicochemical properties of the two protein molecules. When formulated in the AS01 Adjuvant System, the bivalent subtype C gp120 antigens elicited 1086.C- and TV1.C-specific binding antibody and CD4+ T cell responses in mice. All the characteristics were highly representative of the Clinical Trial Materials (CTM). Data from this report demonstrate the immunogenicity of the gp120 antigens, provide comprehensive characterization of the molecules, set the benchmark for assessment of current and future CTM lots, and lay the physicochemical groundwork for interpretation of future clinical trial data.