Vaccine priming is restricted to draining lymph nodes and controlled by adjuvant-mediated antigen uptake.

The innate immune mechanisms by which adjuvants enhance the potency and protection of vaccine-induced adaptive immunity are largely unknown. We introduce a model to delineate the steps of how adjuvant-driven innate immune activation leads to priming of vaccine responses using rhesus macaques. Fluorescently labeled HIV-1 envelope glycoprotein (Env) was administered together with the conventional aluminum salt (alum) adjuvant. This was compared to Env given with alum with preabsorbed Toll-like receptor 7 (TLR7) ligand (alum-TLR7) or the emulsion MF59 because they show superiority over alum for qualitatively and quantitatively improved vaccine responses. All adjuvants induced rapid and robust immune cell infiltration to the injection site in the muscle. This resulted in substantial uptake of Env by neutrophils, monocytes, and myeloid and plasmacytoid dendritic cells (DCs) and migration exclusively to the vaccine-draining lymph nodes (LNs). Although less proficient than monocytes and DCs, neutrophils were capable of presenting Env to memory CD4+ T cells. MF59 and alum-TLR7 showed more pronounced cell activation and overall higher numbers of Env+ cells compared to alum. This resulted in priming of higher numbers of Env-specific CD4+ T cells in the vaccine-draining LNs, which directly correlated with increased T follicular helper cell differentiation and germinal center formation. Thus, strong innate immune activation promoting efficient vaccine antigen delivery to infiltrating antigen-presenting cells in draining LNs is an important mechanism by which superior adjuvants enhance vaccine responses.

Liang F ，Lindgren G ，Sandgren KJ ，Thompson EA ，Francica JR ，Seubert A ，De Gregorio E ，Barnett S ，O'Hagan DT ，Sullivan NJ ，Koup RA ，Seder RA ，Loré K ... -  《-》

Vaccine adjuvants alum and MF59 induce rapid recruitment of neutrophils and monocytes that participate in antigen transport to draining lymph nodes.

Vaccine adjuvants such as alum and the oil-in-water emulsion MF59 are used to enhance immune responses towards pure soluble antigens, but their mechanism of action is still largely unclear. Since most adjuvanted vaccines are administered intramuscularly, we studied immune responses in the mouse muscle and found that both adjuvants were potent inducers of chemokine production and promoted rapid recruitment of CD11b(+) cells. The earliest and most abundantly recruited cell type are neutrophils, followed by monocytes, eosinophils and later dendritic cells (DCs) and macrophages. Using fluorescent forms of MF59 and ovalbumin (OVA) antigen, we show that all recruited cell types take up both adjuvant and antigen to transport them to the draining lymph nodes (LNs). There, we found antigen-positive neutrophils and monocytes within hours of injection, later followed by B cells and DCs. Compared to alum, MF59-injection lead to a more prominent neutrophil recruitment and a more efficient antigen re-localization from the injection site to the LN. As antigen-transporting neutrophils were observed in draining LNs, we asked whether these cells play an essential role in MF59-mediated adjuvanticity. However, antibody-mediated neutrophil ablation left MF59-adjuvanticity unaltered. Further studies will reveal whether other single cell types are crucial or whether the different recruited cell populations are redundant with overlapping functions.

Calabro S ，Tortoli M ，Baudner BC ，Pacitto A ，Cortese M ，O'Hagan DT ，De Gregorio E ，Seubert A ，Wack A ... -  《-》

Adjuvant-Dependent Enhancement of HIV Env-Specific Antibody Responses in Infant Rhesus Macaques.

Toward the goal of developing an effective HIV vaccine that can be administered in infancy to protect against postnatal and lifelong sexual HIV transmission risks, the current pilot study was designed to compare the effect of novel adjuvants on the induction of HIV Env-specific antibody responses in infant macaques. Aligning our studies with the adjuvanted proteins evaluated in a prime-boost schedule with ALVAC in the ongoing HVTN (HIV Vaccine Trials Network) 702 efficacy trial, we selected the bivalent clade C Env immunogens gp120 C.1086 and gp120 TV1 in combination with the MF59 adjuvant. However, we hypothesized that the adjuvant system AS01, that is included in the pediatric RTS,S malaria vaccine, would promote Env-specific antibody responses superior to those of the oil-in-water MF59 emulsion adjuvant. In a second study arm, we compared two emulsions, glucopyranosyl lipid adjuvant formulated in a stable emulsion (GLA-SE) and 3M-052-SE, containing Toll-like receptor 4 (TLR4) and TLR7/TLR8 (TLR7/8) ligand, respectively. The latter adjuvant had been previously demonstrated to be especially effective in activating neonatal antigen-presenting cells. Our results demonstrate that different adjuvants drive quantitatively or qualitatively distinct responses to the bivalent Env vaccine. AS01 induced higher Env-specific plasma IgG antibody levels than the antigen in MF59 and promoted improved antibody function in infants, and 3M-052-SE outperformed GLA-SE by inducing the highest breadth and functionality of antibody responses. Thus, distinct adjuvants are likely to be required for maximizing vaccine-elicited immune responses in infants, particularly when immunization in infancy aims to elicit both perinatal and lifelong immunity against challenging pathogens such as HIV.IMPORTANCE Alum remains the adjuvant of choice for pediatric vaccines. Yet the distinct nature of the developing immune system in infants likely requires novel adjuvants targeted specifically at the pediatric population to reach maximal vaccine efficacy with an acceptable safety profile. The current study supports the idea that additional adjuvants for pediatric vaccines should be, and need to be, tested in infants for their potential to enhance immune responses. Using an infant macaque model, our results suggest that both AS01 and 3M-052-SE can significantly improve and better sustain HIV Env-specific antibody responses than alum. Despite the limited number of animals, the results revealed interesting differences that warrant further testing of promising novel adjuvant candidates in larger preclinical and clinical studies to define the mechanisms leading to adjuvant-improved antibody responses and to identify targets for adjuvant and vaccine optimization.

Phillips B ，Van Rompay KKA ，Rodriguez-Nieves J ，Lorin C ，Koutsoukos M ，Tomai M ，Fox CB ，Eudailey J ，Dennis M ，Alam SM ，Hudgens M ，Fouda G ，Pollara J ，Moody A ，Shen X ，Ferrari G ，Permar S ，De Paris K ... -  《-》

The adjuvants aluminum hydroxide and MF59 induce monocyte and granulocyte chemoattractants and enhance monocyte differentiation toward dendritic cells.

Seubert A ，Monaci E ，Pizza M ，O'Hagan DT ，Wack A ... -  《JOURNAL OF IMMUNOLOGY》

Vaccine adjuvant MF59 promotes the intranodal differentiation of antigen-loaded and activated monocyte-derived dendritic cells.

Cioncada R ，Maddaluno M ，Vo HTM ，Woodruff M ，Tavarini S ，Sammicheli C ，Tortoli M ，Pezzicoli A ，De Gregorio E ，Carroll MC ，D'Oro U ，Piccioli D ... -  《PLoS One》