HIV vaccine candidate efficacy in female macaques mediated by cAMP-dependent efferocytosis and V2-specific ADCC

Abstract

The development of an effective vaccine to protect against HIV acquisition will be greatly bolstered by in-depth understanding of the innate and adaptive responses to vaccination. We report here that the efficacy of DNA/ALVAC/gp120/alum vaccines, based on V2-specific antibodies mediating apoptosis of infected cells (V2-ADCC), is complemented by efferocytosis, a cyclic AMP (cAMP)-dependent antiphlogistic engulfment of apoptotic cells by CD14+ monocytes. Central to vaccine efficacy is the engagement of the CCL2/CCR2 axis and tolerogenic dendritic cells producing IL-10 (DC-10). Epigenetic reprogramming in CD14+ cells of the cyclic AMP/CREB pathway and increased systemic levels of miRNA-139-5p, a negative regulator of expression of the cAMP-specific phosphodiesterase PDE4D, correlated with vaccine efficacy. These data posit that efferocytosis, through the prompt and effective removal of apoptotic infected cells, contributes to vaccine efficacy by decreasing inflammation and maintaining tissue homeostasis.

Cholera toxin B scaffolded, focused SIV V2 epitope elicits antibodies that influence the risk of SIVmac251 acquisition in macaques

“…Macaques were randomized into groups based on age and weight. Immunological data from an additional twenty-four male and female historical macaques were also used in this study (27,31).…”

“…Ten female macaques were immunized as previously described [Study 1 (31)]. Briefly, macaques were immunized twice intramuscularly at weeks 0 and 4 with DNA-SIV expressing gag and M766 gp160.…”

“…Cells incubated without F(ab') 2 were also used to determine total ADCC killing. These target cells were subsequently used in the ADCC assay as described above (27,29,31). V2 specific ADCC killing was determined by subtracting the ADCC killing in the presence of F(ab')2 from total ADCC killing of the respective samples.…”

“…CD14 + cells were used as effector cells, whereas apoptotic neutrophils were used as target cells. The protocol was readapted in order to use CD14 + monocyte cells rather than differentiated macrophages due to the low cell availability (29,31). CD14 + cells were isolated from cryopreserved PBMCs (10x10 6 cells) collected following pre-immunization and 2 weeks post last immunization (week 14) or 5 weeks post last immunization (week 17) by using non-human primate CD14 MicroBeads (#130-091-097, Miltenyi Biotec Inc.) and following manufacturer instructions.…”

“…In these same studies, anti-V2 polyclonal responses to SIV peptide probes encompassing position 169 and 181 of V2 were also associated with a transient decrease in virus burden in plasma and mucosal tissues in vaccinated animals that became infected. The decreased risk of SIV mac251 acquisition was not only associated with V2-specific antibodies and V2-specific ADCC, but also with mucosal envelope specific NKp44 + cells producing IL-17, CD14 + monocytes mediating efferocytosis, and Th1/Th2 cells expressing no or low levels of CCR5 (21,(27)(28)(29)(30)(31) Here, we generated a novel vaccine platform, CTB-V2c, by scaffolding a mucosal-targeting, pentameric particle approaching the size of a typical virus-like particle (VLP) from cholera toxin B (CTB) onto the SIV V2c B-cell epitope, favoring an a-helical conformation of V2. We investigated the preliminary immunogenicity of CTB-V2c in rabbits and generated two immunization regimens to test in macaques.…”