Antibody gene features associated with binding and functional activity in malaria vaccine-derived human mAbs

Abstract

The impact of adjuvants on malaria vaccine-induced antibody repertoire is poorly understood. Here, we characterize the impact of two adjuvants, Alhydrogel® and AS01, on antibody clonotype diversity, binding and function, post malaria vaccination. We expressed 132 recombinant anti-Pfs230D1 human monoclonal antibodies (mAbs) from participants immunized with malaria transmission-blocking vaccine Pfs230D1, formulated with either Alhydrogel® or AS01. Anti-Pfs230D1 mAbs generated by Alhydrogel® formulation showed higher binding frequency to Pfs230D1 compared to AS01 formulation, although the frequency of functional mAbs was similar between adjuvant groups. Overall, the AS01 formulation induced anti-Pfs230D1 functional antibodies from a broader array of germline sequences versus the Alhydrogel® formulation. All mAbs using IGHV1-69 gene from the Alhydrogel® cohort bound to recombinant Pfs230D1, but did not block parasite transmission to mosquitoes, similar to the IGHV1-69 mAbs isolated from the AS01 cohort. These findings may help inform vaccine design and adjuvant selection for immunization with Plasmodium antigens.

Fig. 1. Binding and functional activity of Pfs230D1 mAbs and their relationship with heavy chain V gene usage.

a Human IgG1 mAbs obtained from Pfs230D1-sorted single B cells were expressed in mammalian cells and tested for binding to Pfs230D1 (ELISA). Functional activity was determined as Transmission Reducing Activity (TRA), assessed by Standard Membrane Feeding Assay using NF54 strain P. falciparum parasites fed to Anopheles mosquitoes. Figure was created using Biorender.com. b Percentage of human mAbs obtained from Alhydrogel® and c AS01 vaccinees that bound to recombinant Pfs230D1 and were functional in vivo (TRA > 75% at 100 μg/mL). d–g Alhydrogel® and AS01 mAbs were grouped as d, f binding and non-binding and e, g functional and non-functional, and then are shown according to their V gene classification.

Fig. 2. Association between heavy chain CDR3 length and binding or function of Pfs230D1 mAbs.

a Binding was assessed by ELISA and compared between binding vs. non-binding mAbs in the two trials. b, c Functional activity was determined by Standard Membrane Feeding Assay (SMFA) and compared between functional and non-functional mAbs among b all mAbs, or c only those mAbs that bound antigen. P values were considered significant when <0.05, and statistical analyses were performed using unpaired t tests. Means and standard deviation are shown.