Synthetic adjuvants for vaccine formulations: Evaluation of new phytol derivatives in induction and persistence of specific immune response

Improvement influenza vaccine immune responses with traditional Chinese medicine and its active ingredients

The current influenza vaccines are unable to provide effective protection in many cases, like influenza viruses strain antigenic drift or shift, and the influenza continues to cause significant annual morbidity and mortality. Improving the immune response to influenza vaccination is an unmet need. Traditional Chinese medicine (TCM) and its active ingredients are commonly known to have immunomodulatory properties. We therefore compared influenza vaccination alone or formulated with Astragali Radix (Huangqi in Chinese), and several representative ingredients of TCM, including lentinan (polysaccharide), panax notoginseng saponins (saponin), breviscapine (flavone), andrographolide (terpenoid), and a Chinese herbal compound (kangai) for their potential to enhance immune responses to influenza vaccine in mice. We found that all these TCM-adjuvants were able to increase hemagglutination inhibition (HAI) antibody titers, splenocyte proliferation, splenic T cell differentiation, bone marrow dendritic cell maturity, and both Th1 and Th2 cytokine secretion of influenza vaccine to varying degrees, and that had the characteristics of no excessive inflammatory responses and bidirectional regulation simultaneously. Taken together, our findings show that Astragali Radix exerts a more comprehensive effect on vaccine immunity, on both innate and adaptive immunity. The effects of lentinan and andrographolide on adaptive immunity were more significant, while the effects of breviscapine on innate immunity were stronger, and the other two TCM adjuvants were weaker. As the first report of a comprehensive evaluation of TCM adjuvants in influenza vaccines, the results suggest that TCM and their active ingredients are good candidates for enhancing the immune response of influenza vaccines, and that suitable TCMs can be selected based on the adjuvant requirements of different vaccines.

Purification and immobilization of the recombinant Brassica oleracea Chlorophyllase 1 (BoCLH1) on DIAION®CR11 as potential biocatalyst for the production of chlorophyllide and phytol

Recombinant Brassica oleracea chlorophyllase 1 (BoCLH1) with a protein molecular weight of 38.63 kDa was successfully expressed in E. coli and could catalyze chlorophyll (Chl) hydrolysis to chlorophyllide and phytol in vitro. In this study, we used DIAION^®CR11, a highly porous cross-linked polystyrene divinylbenzene-based metal chelator, for purifying and immobilizing the poly (His)-tagged enzyme. The Cu(II) showed the highest protein adsorption (9.2 ± 0.43 mg/g gel) and enzyme activity (46.3 ± 3.14 U/g gel) for the immobilization of the poly (His)-tagged recombinant BoCLH1 compared with other metal chelators. Biochemical analysis of the immobilized enzyme showed higher chlorophyllase activity for Chl a hydrolysis in a weak base environment (pH 8.0), and activity above 70% was in a high-temperature environment, compared with the free enzyme. In addition, compared with free BoCLH1, the enzyme half-life (t_1/2) of the immobilized BoCLH1 increased from 25.42 to 54.35 min (approximately two-fold) at 60 °C. The immobilized enzyme retained a residual activity of approximately 60% after 17 cycles in a repeated-batch operation. Therefore, DIAION^®CR11Cu(II)-immobilized recombinant BoCLH1 can be repeatedly used to lower the cost and is potentially useful for the industrial production of chlorophyllide and phytol.

Immobilization of Brassica oleracea chlorophyllase 1 (BoCLH1) and Candida rugosa lipase (CRL) in magnetic alginate beads: an enzymatic evaluation in the corresponding proteins

Enzymes have a wide variety of applications in diverse biotechnological fields, and the immobilization of enzymes plays a key role in academic research or industrialization due to the stabilization and recyclability it confers. In this study, we immobilized the Brassica oleracea chlorophyllase 1 (BoCLH1) or Candida rugosa lipase (CRL) in magnetic iron oxide nanoparticles-loaded alginate composite beads. The catalytic activity and specific activity of the BoCLH1 and CRL entrapped in magnetic alginate composite beads were evaluated. Results show that the activity of immobilized BoCLH1 in magnetic alginate composite beads (3.36±0.469 U/g gel) was higher than that of immobilized BoCLH1 in alginate beads (2.96±0.264 U/g gel). In addition, the specific activity of BoCLH1 beads (10.90±1.521 U/mg protein) was higher than that immobilized BoCLH1 in alginate beads (8.52±0.758 U/mg protein). In contrast, the immobilized CRL in magnetic alginate composite beads exhibited a lower enzyme activity (11.81±0.618) than CRL immobilized in alginate beads (94.83±7.929), and the specific activity of immobilized CRL entrapped in magnetic alginate composite beads (1.99±0.104) was lower than immobilized lipase in alginate beads (15.01±1.255). A study of the degradation of magnetic alginate composite beads immersed in acidic solution (pH 3) shows that the magnetic alginate composite beads remain intact in acidic solution for at least 6 h, indicating the maintenance of the enzyme catalytic effect in low-pH environment. Finally, the enzyme immobilized magnetic alginate composite beads could be collected by an external magnet and reused for at least six cycles.

Adjuvants in the Driver's Seat: How Magnitude, Type, Fine Specificity and Longevity of Immune Responses Are Driven by Distinct Classes of Immune Potentiators

The mechanism by which vaccine adjuvants enhance immune responses has historically been considered to be the creation of an antigen depot. From here, the antigen is slowly released and provided to immune cells over an extended period of time. This "depot" was formed by associating the antigen with substances able to persist at the injection site, such as aluminum salts or emulsions. The identification of Pathogen-Associated Molecular Patterns (PAMPs) has greatly advanced our understanding of how adjuvants work beyond the simple concept of extended antigen release and has accelerated the development of novel adjuvants. This review focuses on the mode of action of different adjuvant classes in regards to the stimulation of specific immune cell subsets, the biasing of immune responses towards cellular or humoral immune response, the ability to mediate epitope spreading and the induction of persistent immunological memory. A better understanding of how particular adjuvants mediate their biological effects will eventually allow them to be selected for specific vaccines in a targeted and rational manner.

Synthetic adjuvants for vaccine formulations: phytol derivatives

INTRODUCTION

The development of vaccines is considered a key milestone in preventive medicine. There is no comparable cost-effective means for controlling or eradicating infectious diseases. Yet, a persistent societal problem is the concern about vaccine's safety and long-term effects, and this caters to detractors of vaccination. Pathogen-derived antigen(s) as well as adjuvants/immunostimulants are essential for vaccine efficacy. Currently, adjuvant selection is largely empirical, but the mechanism underlying adjuvanticity is beginning to unravel. This should help develop more defined or targeted adjuvants.

AREAS COVERED

This review provides a brief account and analysis of the host immune parameters modulated by some commonly used as well as new adjuvants, including phytol-based diterpenoids. The major efforts are directed toward evaluating their relative safety and immunomodulatory efficiency, compared to known synthetic and natural adjuvants. Concerns for adverse pathological inflammation and autoimmunity are also addressed.

EXPERT OPINION

The phytol-based adjuvants hold great promise for improving vaccine efficacy, as they cause little or no persistent inflammation, but are highly effective in stimulating a multifaceted immune response, characterized by proficient recruitment of immune cells, generation of antibody and immunological memory, and activation of both Th1 and Th2 responses. Future focus will be on developing cocktail adjuvants to activate the complement system, mobilize follicular T helper cells as well as NKT and γδ T cells and activate cross-presenting dendritic cells to stimulate CD8(+) effector T cells.

Phytol-derived novel isoprenoid immunostimulants

This review describes the adjuvanticity of novel diterpenoids (synthetic phytol derivatives) compared to some commercially available adjuvants. The efficacy of the phytol-derived immunostimulants was evaluated in terms of their ability to activate innate immunity, amplify various antigen-specific immune responses, and engender immunological memory with no discernible adverse effects in both competent and immune-deficient mice. The profile that emerges out of these studies reveals that the phytol derivatives are excellent immunostimulants, superior to a number of commercial adjuvants in terms of long-term memory induction and activation of both innate and acquired immunity. Additionally, the phytol-derived compounds have no cumulative inflammatory or toxic effects even in immuno-compromised mice.

Immune enhancement by novel vaccine adjuvants in autoimmune-prone NZB/W F1 mice: relative efficacy and safety

Background

Vaccines have profoundly impacted global health although concerns persist about their potential role in autoimmune or other adverse reactions. To address these concerns, vaccine components like immunogens and adjuvants require critical evaluation not only in healthy subjects but also in those genetically averse to vaccine constituents. Evaluation in autoimmune-prone animal models of adjuvants is therefore important in vaccine development. The objective here was to assess the effectiveness of experimental adjuvants: two phytol-derived immunostimulants PHIS-01 (phytanol) and PHIS-03 (phytanyl mannose), and a new commercial adjuvant from porcine small intestinal submucosa (SIS-H), relative to a standard adjuvant alum. Phytol derivatives are hydrophobic, oil-in water diterpenoids, while alum is hydrophilic, and SIS is essentially a biodegradable and collagenous protein cocktail derived from extracellular matrices.

Results

We studied phthalate -specific and cross-reactive anti-DNA antibody responses, and parameters associated with the onset of autoimmune disorders. We determined antibody isotype and cytokine/chemokine milieu induced by the above experimental adjuvants relative to alum. Our results indicated that the phytol-derived adjuvant PHIS-01 exceeded alum in enhancing anti-phthalate antibody without much cross reactivity with ds-DNA. Relatively, SIS and PHIS-03 proved less robust, but they were also less inflammatory. Interestingly, these adjuvants facilitated isotype switching of anti-hapten, but not of anti-DNA response. The current study reaffirms our earlier reports on adjuvanticity of phytol compounds and SIS-H in non autoimmune-prone BALB/c and C57BL/6 mice. These adjuvants are as effective as alum also in autoimmune-prone NZB/WF1 mice, and they have little deleterious effects.

Conclusion

Although all adjuvants tested impacted cytokine/chemokine milieu in favor of Th1/Th2 balance, the phytol compounds fared better in reducing the onset of autoimmune syndromes. However, SIS is least inflammatory among the adjuvants evaluated.