Identification of QS-21 as an Inflammasome-activating Molecular Component of Saponin Adjuvants.

Many immunostimulants act as vaccine adjuvants via activation of the innate immune system, although in many cases it is unclear which specific molecules contribute to the stimulatory activity. QS-21 is a defined, highly purified, and soluble saponin adjuvant currently used in licensed and exploratory vaccines, including vaccines against malaria, cancer, and HIV-1. However, little is known about the mechanisms of cellular activation induced by QS-21. We observed QS-21 to elicit caspase-1-dependent IL-1ß and IL-18 release in antigen-presenting cells such as macrophages and dendritic cells when co-stimulated with the TLR4-agonist adjuvant monophosphoryl lipid A. Furthermore, our data suggest that the ASC-NLRP3 inflammasome is responsible for QS-21-induced IL-1ß/IL-18 release. At higher concentrations, QS-21 induced macrophage and dendritic cell death in a caspase-1-, ASC-, and NLRP3-independent manner, whereas the presence of cholesterol rescued cell viability. A nanoparticulate adjuvant that contains QS-21 as part of a heterogeneous mixture of saponins also induced IL-1ß in an NLRP3-dependent manner. Interestingly, despite the role NLRP3 plays for cellular activation in vitro, NLRP3-deficient mice immunized with HIV-1 gp120 and QS-21 showed significantly higher levels of Th1 and Th2 antigen-specific T cell responses and increased IgG1 and IgG2c compared with wild type controls. Thus, we have identified QS-21 as a nonparticulate single molecular saponin that activates the NLRP3 inflammasome, but this signaling pathway may contribute to decreased antigen-specific responses in vivo.

Contribution of TLR4 and MyD88 for adjuvant monophosphoryl lipid A (MPLA) activity in a DNA prime-protein boost HIV-1 vaccine.

Recombinant protein vaccines are commonly formulated with an immune-stimulatory compound, or adjuvant, to boost immune responses to a particular antigen. Recent studies have shown that, through recognition of molecular motifs, receptors of the innate immune system are involved in the functions of adjuvants to generate and direct adaptive immune responses. However, it is not clear to which degree those receptors are also important when the adjuvant is used as part of a novel heterologous prime-boost immunization process in which the priming and boosting components are not the same type of vaccines. In the current study, we compared the immune responses elicited by a pentavalent HIV-1 DNA prime-protein boost vaccine in mice deficient in either Toll-like receptor 4 (TLR4) or myeloid differentiation primary response gene 88 (MyD88) to wildtype mice. HIV gp120 protein administered in the boost phase was formulated with either monophosphoryl lipid A (MPLA), QS-21, or Al(OH)3. Endpoint antibody titer, serum cytokine response and T-cell memory response were assessed. Neither TLR4 nor MyD88 deficiency had a significant effect on the immune response of mice given vaccine formulated with QS-21 or Al(OH)3. However, TLR4- and MyD88-deficiency decreased both the antibody and T-cell responses in mice administered HIV gp120 formulated with MPLA. These results further our understanding of the activation of TLR4 and MyD88 by MPLA in the context of a DNA prime/protein boost immunization strategy.

Reduced MyD88 dependency of ISCOMATRIX™ adjuvant in a DNA prime-protein boost HIV vaccine.

ISCOMATRIX™ adjuvant is an integrated adjuvant system due to its ability to both facilitate antigen delivery and immunomodulate the innate and adaptive immune responses to vaccination. ISCOMATRIX™ adjuvant strongly induces both humoral and cell-mediated immunity in formulation with a range of antigens in pre-clinical and clinical evaluations. In this study, we describe the adaptive and innate immune responses associated with ISCOMATRIX™ adjuvant in the context of a previously described HIV-1 vaccine, DP6-001. The DP6-001 vaccine consists of a unique pentavalent HIV-1 Env DNA prime-protein boost regimen. This study demonstrates the potent induction of vaccine-specific antibodies in a mouse model, as well as broadly neutralizing antibodies in immunized rabbits. In addition, we identify a potentially critical role for DNA priming in the induction of the vaccine-specific immune response as well as the serum cytokine profiles associated with ISCOMATRIX™ adjuvant. Most interestingly, DNA prime immunizations made ISCOMATRIX™ adjuvant less dependent on the central innate immune adaptor MyD88, revealing a previously unknown mechanism that may expand our knowledge on the use of adjuvants.

Serum cytokine profiles associated with specific adjuvants used in a DNA prime-protein boost vaccination strategy.

In recent years, heterologous prime-boost vaccines have been demonstrated to be an effective strategy for generating protective immunity, consisting of both humoral and cell-mediated immune responses against a variety of pathogens including HIV-1. Previous reports of preclinical and clinical studies have shown the enhanced immunogenicity of viral vector or DNA vaccination followed by heterologous protein boost, compared to using either prime or boost components alone. With such approaches, the selection of an adjuvant for inclusion in the protein boost component is expected to impact the immunogenicity and safety of a vaccine. In this study, we examined in a mouse model the serum cytokine and chemokine profiles for several candidate adjuvants: QS-21, Al(OH)3, monophosphoryl lipid A (MPLA) and ISCOMATRIX™ adjuvant, in the context of a previously tested pentavalent HIV-1 Env DNA prime-protein boost formulation, DP6-001. Our data revealed that the candidate adjuvants in the context of the DP6-001 formulation are characterized by unique serum cytokine and chemokine profiles. Such information will provide valuable guidance in the selection of an adjuvant for future AIDS vaccine development, with the ultimate goal of enhancing immunogenicity while minimizing reactogenicity associated with the use of an adjuvant. More significantly, results reported here will add to the knowledge on how to include an adjuvant in the context of a heterologous prime-protein boost vaccination strategy in general.

Cytokine markers as predictors of type of respiratory infection in patients during the influenza season.

OBJECTIVE: The objective of this study is to characterize the cytokine response among patients presenting with an influenza-like illness who are infected with the influenza virus, a bacterial pneumonia, or another viral infection. We hypothesize that there are differences in proinflammatory and anti-inflammatory cytokines in relation to cytokines associated with the humoral response during viral and bacterial respiratory infections. METHODS: We enrolled adults who presented to an urban academic emergency department during the 2008 to 2011 influenza seasons with symptoms of fever and a cough. Subjects had nasal aspirates tested by viral culture, and peripheral blood drawn to quantify cytokine concentrations. Cytokine concentrations were compared between groups using the Wilcoxon rank sum test, and receiver operating characteristic curves were calculated. RESULTS: A total of 80 patients were enrolled: 40 with influenza infection, 14 patients with a bacterial pneumonia as determined by infiltrate on chest x-ray, and 26 patients negative for influenza infection and infiltrate. There were differences between the bacterial pneumonia group, and all other viral infections grouped together with regard to interleukin (IL) 4 (2.66 vs 16.77 pg/mL, P < .001), IL-5 (20.57 vs 57.57 pg/mL, P = .006), IL-6 (403.06 vs 52.69 pg/mL, P < .001), granulocyte macrophage colony-stimulating factor (18.26 vs 66.80 pg/mL, P < .001), and interferon γ (0.0 vs 830.36 pg/mL, P < .001). Interleukin 10 concentrations were elevated in patients with influenza (88.69 pg/mL) compared with all other groups combined (39.19 pg/mL; P = .003). CONCLUSION: Cytokines IL-4, IL-5, IL-6, granulocyte macrophage colony-stimulating factor, and interferon γ may serve as distinct markers of bacterial infection in patients with an influenza-like illness, whereas IL-10 is uniquely elevated in influenza patients.