Dendritic cell targeting anti-CD40 antibody-CD40L-HIV-1 vaccines are adjuvant intrinsic

Abstract

Abstract Soluble CD40L and agonistic anti-CD40 monoclonal antibody are adjuvants used in vaccination settings. Vaccines based on anti-CD40 antibodies fused to HIV-1 antigens are in clinical development. Studies with current anti-CD40-based dendritic cell (DC) targeting vaccines show that co-administration of an adjuvant is needed for maximal immune responses. We show that by fusing CD40L to CD40-targeting antibodies, activation of DCs concomitant with antigen uptake and processing is maximized, and this provides a context CD40-targeting vaccines with intrinsic adjuvant activity. Direct fusion of CD40L to L or H chain C-termini results in CD40 agonists with ‘superagonist’ properties. Especially on DCs, both potency and efficacy for induction of cytokine secretion and activation markers is greatly enhanced compared to known strong agonists like Pfizer’s anti-CD40 CP-870-89 antibody. This potency was maintained by anti-CD40-CD40L constructs fused to HIV-1 antigens from Gag, Nef, and Pol regions (HIV5pep). Anti-CD40-CD40L-HIV5pep preferentially expanded CD8+ T cells from HIV-1+ donor PBMCs compared to the same antibody-antigen fusions without attached CD40L. Anti-CD40-CD40L-TEα and anti-CD40-TEα both evoked robust proliferation of TEα-specific CD4+ T cells in human CD40 transgenic mice, but only anti-CD40-CD40L-TEα vaccine elicited TEα-specific CD4+ T cells producing IFNγ. Also, anti-CD40-CD40L-Env gp140 vaccine without adjuvant in human CD40 transgenic mice elicited stronger anti-Env gp140 antibody responses than anti-CD40-Env gp140 vaccine. Thus superagonist anti-CD40 antibodies directly fused to the natural ligand show great advantage in inducing immune responses without the use of an extrinsic adjuvant.