Optimizing manufacturing and composition of a TLR4 nanosuspension: physicochemical stability and vaccine adjuvant activity

Preclinical optimization of an enterotoxigenic Escherichia coli adjuvanted subunit vaccine using response surface design of experiments

Enterotoxigenic E. coli (ETEC) is a leading cause of moderate-to-severe diarrhoea. ETEC colonizes the intestine through fimbrial tip adhesin colonization factors and produces heat-stable and/or heat-labile (LT) toxins, stimulating fluid and electrolyte release leading to watery diarrhoea. We reported that a vaccine containing recombinant colonization factor antigen (CfaEB) targeting fimbrial tip adhesin of the colonization factor antigen I (CFA/I) and an attenuated LT toxoid (dmLT) elicited mucosal and systemic immune responses against both targets. Additionally, the toll-like receptor 4 ligand second-generation lipid adjuvant (TLR4-SLA) induced a potent mucosal response, dependent on adjuvant formulation. However, a combination of vaccine components at their respective individual optimal doses may not achieve the optimal immune profile. We studied a subunit ETEC vaccine prototype in mice using a response surface design of experiments (DoE), consisting of 64 vaccine dose-combinations of CfaEB, dmLT and SLA in four formulations (aqueous, aluminium oxyhydroxide, squalene-in-water stable nanoemulsion [SE] or liposomes containing the saponin Quillaja saponaria-21 [LSQ]). Nine readouts focusing on antibody functionality and plasma cell response were selected to profile the immune response of parenterally administered ETEC vaccine prototype. The data were integrated in a model to identify the optimal dosage of each vaccine component and best formulation. Compared to maximal doses used in mouse models (10 µg CfaEB, 1 µg dmLT and 5 µg SLA), a reduction in the vaccine components up to 37%, 60% and 88% for CfaEB, dmLT and SLA, respectively, maintained or even maximized immune responses, with SE and LSQ the best formulations. The DoE approach can help determine the best vaccine composition with a limited number of experiments and may accelerate development of multi-antigen/component ETEC vaccines.

Synthetic Toll-like receptor agonists for the development of powerful malaria vaccines: a patent review

INTRODUCTION

Currently, there is no efficient vaccine available against clinical malaria. However, continuous efforts have been committed to develop powerful antimalarial vaccine by discovery of novel antigens with in-depth understanding of its nature, immunogenicity, and presentation (delivery adjuvants). Moreover, another important part of vaccine development includes discovery of better immunostimulatory formulation components (immunostimulants). A protective vaccine against malaria requires antigen-specific B and T helper cell responses as well as cytotoxic T lymphocyte (CTL) responses. A long-lasting B and T memory cell production is also required for effective malaria vaccine. Since activation of Toll-like receptors (TLRs) promotes both innate inflammatory responses as well as the induction of adaptive immunity, several initiatives have been mounted during the last few years for the use of TLR agonists as malaria vaccine adjuvants.

AREAS COVERED

The review summarizes reports related to the use and development of TLR agonists as malaria vaccine adjuvants and describes various strategies involved for the selection of specific antigens and TLR agonists.

EXPERT OPINION

TLR agonists are promising adjuvants for the development of effective malaria vaccine, allowing for both innate inflammatory responses as well as the induction of adaptive immunity.

Microfluidization trends in the development of nanodelivery systems and applications in chronic disease treatments

Plant bioactive compounds are known for their extensive health benefits and therefore have been used for generations in traditional and modern medicine to improve the health of humans. Processing and storage instabilities of the plant bioactive compounds, however, limit their bioavailability and bioaccessibility and thus lead researchers in search of novel encapsulation systems with enhanced stability, bioavailability, and bioaccessibility of encapsulated plant bioactive compounds. Recently many varieties of encapsulation methods have been used; among them, microfluidization has emerged as a novel method used for the development of delivery systems including solid lipid nanocarriers, nanoemulsions, liposomes, and so on with enhanced stability and bioavailability of encapsulated plant bioactive compounds. Therefore, the nanodelivery systems developed using microfluidization techniques have received much attention from the medical industry for their ability to facilitate controlled delivery with enhanced health benefits in the treatment of various chronic diseases. Many researchers have focused on plant bioactive compound-based delivery systems using microfluidization to enhance the bioavailability and bioaccessibility of encapsulated bioactive compounds in the treatment of various chronic diseases. This review focuses on various nanodelivery systems developed using microfluidization techniques and applications in various chronic disease treatments.

Adsorption of a synthetic TLR7/8 ligand to aluminum oxyhydroxide for enhanced vaccine adjuvant activity: A formulation approach

For nearly a century, aluminum salts have been the most widely used vaccine adjuvant formulation, and have thus established a history of safety and efficacy. Nevertheless, for extremely challenging disease targets such as tuberculosis or HIV, the adjuvant activity of aluminum salts may not be potent enough to achieve protective efficacy. Adsorption of TLR ligands to aluminum salts facilitates enhanced adjuvant activity, such as in the human papilloma virus vaccine Cervarix®. However, some TLR ligands such as TLR7/8 agonist imidazoquinolines do not efficiently adsorb to aluminum salts. The present report describes a formulation approach to solving this challenge by developing a lipid-based nanosuspension of a synthetic TLR7/8 ligand (3M-052) that facilitates adsorption to aluminum oxyhydroxide via the structural properties of the helper lipid employed. In immunized mice, the aluminum oxyhydroxide-adsorbed formulation of 3M-052 enhanced antibody and TH1-type cellular immune responses to vaccine antigens for tuberculosis and HIV.

Saquinavir Loaded Acetalated Dextran Microconfetti - a Long Acting Protease Inhibitor Injectable

PURPOSE

Since the adoption of highly active antiretroviral therapy, HIV disease progression has slowed across the world; however, patients are often required to take multiple medications daily of poorly bioavailable drugs via the oral route, leading to gastrointestinal irritation. Recently, long acting antiretroviral injectables that deliver drug for months at a time have moved into late phase clinical trials. Unfortunately, these solid phase crystal formulations have inherent drawbacks in potential dose dumping and a greater likelihood for burst release of drug compared to polymeric formulations.

METHODS

Using electrospinning, acetalated dextran scaffolds containing the protease inhibitor saquinavir were created. Grinding techniques were then used to process these scaffolds into injectables which are termed saquinavir microconfetti. Microconfetti was analyzed for in vitro and in vivo release kinetics.

RESULTS

Highly saquinavir loaded acetalated dextran electrospun fibers were able to be formed and processed into saquinavir microconfetti while other polymers such as poly lactic-co-glycolic acid and polycaprolactone were unable to do so. Saquinavir microconfetti release kinetics were able to be tuned via drug loading and polymer degradation rates. In vivo, a single subcutaneous injection of saquinavir microconfetti released drug for greater than a week with large tissue retention.

CONCLUSIONS

Microconfetti is a uniquely tunable long acting injectable that would reduce the formation of adherence related HIV resistance. Our findings suggest that the injectable microconfetti delivery system could be used for long acting controlled release of saquinavir and other hydrophobic small molecule drugs.

Identification of GLA/SE as an effective adjuvant for the induction of robust humoral and cell-mediated immune responses to EBV-gp350 in mice and rabbits

Childhood infection with Epstein-Barr virus (EBV) is often asymptomatic and may result in mild flu-like symptoms, but exposure during adolescence and young adulthood can lead to acute infectious mononucleosis (AIM) with a pathology characterized by swollen lymph nodes, sore throat, and severe fatigue lasting weeks or months. A vaccine targeting the envelope glycoprotein gp350 adjuvanted with aluminum hydroxide complexed with the TLR4 agonist monophosphoryl lipid A (MPLA) achieved a 78% reduction in AIM incidence in a small phase II trial of college-age individuals, but development of this vaccine was halted by the manufacturer. Here, we report the evaluation in mice and rabbits of an EBV-gp350 vaccine combined with an adjuvant composed of the synthetic TLR4 agonist glucopyranosyl lipid A (GLA) integrated into stable emulsion (SE). In mice, GLA/SE-adjuvanted gp350 generated high IgG titers (both IgG1 and IgG2a/c subtypes), elevated EBV-neutralizing antibody titers, and robust poly-functional anti-gp350 CD4(+) T cell responses. In addition, GLA/SE routinely demonstrated superior performance over aluminum hydroxide in all immunological readouts, including induction of durable neutralizing antibody titers out to at least 1 year post-vaccination. Both components of the GLA/SE adjuvant were found to be required to get optimal responses in both arms of the immune response: specifically, SE for neutralizing antibodies and GLA for induction of T cell responses. Furthermore, this vaccine also elicited high neutralizing antibody titers in a second species, rabbit. These promising results suggest that clinical development of a vaccine comprised of EBV-gp350 plus GLA/SE has the potential to prevent AIM in post-adolescents.