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

Abstract

Adjuvants have been essential to malaria vaccine development, but their impact on the vaccine-induced antibody repertoire is poorly understood. Here, we used cDNA sequences from antigen-specific single memory B cells to express 132 recombinant human anti-Pfs230 monoclonal antibodies (mAbs). Alhydrogel^®-induced mAbs demonstrated higher binding to Pfs230D1, although functional activity was similar between adjuvants. All Alhydrogel^® mAbs using IGHV1-69 gene bound to recombinant Pfs230D1, but none blocked parasite transmission to mosquitoes; similarly, no AS01 mAb using IGHV1-69 blocked transmission. Functional mAbs from both Alhydrogel^® and AS01 vaccines used IGHV3-21 and IGHV3-30 genes. Antibodies with the longest CDR3 sequences were associated with binding but not functional activity. This study assesses adjuvant effects on antibody clonotype diversity during malaria vaccination.

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

(a) Human IgG1 mAbs obtained from Pfs230D1-single B cells were expressed in mammalian cells and tested for binding to domain 1 of Pfs230 (ELISA). Functional activity was determined as Transmission Reducing Activity (TRA), assessed by Standard Membrane Feeding Assay using NF54 Plasmodium falciparum 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, presenting TRA higher than 75% at 100μg/mL. (d,e) Alhydrogel and AS01 mAbs were grouped into binding and nonbinding and (f,g) functional and non-functional and then visualized according to their heavy chain V gene.

Figure 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 less than 0.05 and statistical analyses was performed using unpaired t test. Mean and standard deviation are shown.