Differential gene expression in W614A-3S peptide-specific B cell populations following W614A-3S peptide-KLH vaccination using Squalene emulsion and Alum formulation

W614A-3S peptide is a modified 3S motif of the HIV-gp41 (mutation W614A). We previously detected the presence of natural neutralizing antibodies directed against W614A-3S peptide (NAbs) in long-term non-progressor HIV+ patients. Here, we compared the efficacy of W614A-3S peptide formulated in either squalene emulsion (SQE) or in aluminum hydroxide (Alum) in inducing broadly-NAbs (bNAbs). Rabbit and mouse models were used to screen the induction of bNAbs following 4 immunizations. SQE was more efficient than Alum formulation in inducing W614A-3S-specific bNAbs with up to 67-93% of HIV strains neutralized. We then analyzed the quality of peptide-specific murine B cells by single-cell gene expression by quantitative Reverse Transcription-PCR and single-cell V(D)J sequencing. We found more frequent germinal center B cells in SQE than in Alum, albeit with a different gene expression profile. The V(D)J sequencing of W614A-3S-specific BCR showed significant differences in BCR sequences and validates the dichotomy between adjuvant formulations. All sixteen BCR sequences which were cloned were specific of peptide. Adjuvant formulations of W614A-3S-peptide-conjugated immunogen impact the quantity and quality of B cell immune responses at both the gene expression level and BCR sequence. We used a single-cell quantitative Reverse Transcription-PCR (qRT-PCR) approach to compare between the two formulations the quality of W614A-3S-specific B cell populations isolated from draining lymph nodes, one week after 2nd and 3rd immunizations (W3 and W5, respectively). Draining lymph nodes (dLNs; n=pool of 5 mice/condition - two independent experiments) were harvested at W3 and W5 after immunization, and used to isolate peptide-specific B cells and to perform single-cell gene expression analysis.