Development of Next-Generation COVID-19 Vaccines: BARDA Supported Phase 2b Study Designs.

In response to the COVID-19 pandemic, vaccines were quickly and successfully developed and deployed, saving millions of lives globally. While first generation vaccines are safe and effective in preventing disease caused by SARSCoV-2, next-generation vaccines have the potential to improve efficacy and safety. Vaccines delivered by a mucosal route may elicit greater protective immunity at respiratory surfaces thereby reducing transmission. Inclusion of viral antigens in addition to the spike protein may enhance protection against emerging variants of concern. Next-generation vaccine platforms with a new mechanism of action may necessitate efficacy trials to fulfill regulatory requirements. The Biomedical Advanced Research and Development Authority (BARDA) will be supporting Phase 2b clinical trials of candidate next-generation vaccines. The primary endpoint will be improved efficacy in terms of symptomatic disease relative to a currently approved COVID-19 vaccine. In this paper, we discuss the planned endpoints and potential challenges to this complex program.

The Influence of Social Determinants on Receiving Outpatient Treatment with Monoclonal Antibodies, Disease Risk, and Effectiveness for COVID-19.

BACKGROUND: Limited research has studied the influence of social determinants of health (SDoH) on the receipt, disease risk, and subsequent effectiveness of neutralizing monoclonal antibodies (nMAbs) for outpatient treatment of COVID-19. OBJECTIVE: To examine the influence of SDoH variables on receiving nMAb treatments and the risk of a poor COVID-19 outcome, as well as nMAb treatment effectiveness across SDoH subgroups. DESIGN: Retrospective observational study utilizing electronic health record data from four health systems. SDoH variables analyzed included race, ethnicity, insurance, marital status, Area Deprivation Index, and population density. PARTICIPANTS: COVID-19 patients who met at least one emergency use authorization criterion for nMAb treatment. MAIN MEASURE: We used binary logistic regression to examine the influence of SDoH variables on receiving nMAb treatments and risk of a poor outcome from COVID-19 and marginal structural models to study treatment effectiveness. RESULTS: The study population included 25,241 (15.1%) nMAb-treated and 141,942 (84.9%) non-treated patients. Black or African American patients were less likely to receive treatment than white non-Hispanic patients (adjusted odds ratio (OR) = 0.86; 95% CI = 0.82-0.91). Patients who were on Medicaid, divorced or widowed, living in rural areas, or living in areas with the highest Area Deprivation Index (most vulnerable) had lower odds of receiving nMAb treatment, but a higher risk of a poor outcome. For example, compared to patients on private insurance, Medicaid patients had 0.89 (95% CI = 0.84-0.93) times the odds of receiving nMAb treatment, but 1.18 (95% CI = 1.13-1.24) times the odds of a poor COVID-19 outcome. Age, comorbidities, and COVID-19 vaccination status had a stronger influence on risk of a poor outcome than SDoH variables. nMAb treatment benefited all SDoH subgroups with lower rates of 14-day hospitalization and 30-day mortality. CONCLUSION: Disparities existed in receiving nMAbs within SDoH subgroups despite the benefit of treatment across subgroups.

COVID-19 vaccine development during pandemic: gap analysis, opportunities, and impact on future emerging infectious disease development strategies.

The world remains cautiously optimistic about a COVID-19 vaccine that is relatively safe and efficacious and that offers sufficient long-lasting protection/immunity by neutralizing the virus infectivity. However, key technical hurdles pertaining to antigen-adjuvant formulation, delivery, and manufacturing challenges of lipid nanoparticles (LNPs) for mRNA vaccines and stability of formulations need to be addressed for successful product development and stockpiling. In addition, the dosage form, the dosage level and regimen for eliciting a protective immune response remain to be established. The high dependence of global supply chains and demand-supply to sourcing quality raw materials, glassware and other supplies, along with the stress on existing production capacities and platform-specific manufacturing challenges could impede vaccine development and access. This article provides critical analysis of vaccine development processes and unit operations that can derail the pandemic response, and also extends to other emerging infectious disease development efforts - issues that take on added significance given the global mandate for an accelerated and at-risk development path to tackle the COVID-19 pandemic.

Engineering immunity for next generation HIV vaccines: The intersection of bioengineering and immunology.

Bioengineering approaches grounded in immunology have the potential for the discovery and development of a successful HIV vaccine. The overarching goal is to engineer immunity through a fusion of immunology with bioengineering to create novel strategies for the design, development and delivery of vaccines based on the controlled modulation of the immune system. To foster these collaborations, the National Institute of Allergy and Infectious Diseases (NIAID) and National Institute of Biomedical Imaging and Bioengineering (NIBIB) brought together a group of experts (see Table 1) from these diverse fields for a workshop in September 2018 to: (1) engage the engineering, immunology, and HIV vaccinology communities to dialogue on the topic of an HIV vaccine and; (2) generate a framework of new and innovative research avenues to explore in HIV vaccinology between knowledge stakeholders and problem solvers.

D-periodic collagen-mimetic microfibers.

Self-assembling peptides have been previously designed that assemble into macroscopic membranes, nanotapes, and filaments through electrostatic interactions. However, the formation of highly ordered collagen-like fibrils, which display D-periodic features, has yet to be achieved. In this report, we describe for the first time a synthetic peptide system that self-assembles into a fibrous structure with well-defined periodicity that can be visualized by transmission electron microscopy (TEM). Specifically, we designed and synthesized a peptide that utilizes charged amino acids within the ubiquitous Xaa-Yaa-Gly triad sequence to bias the self-assembly into collagen-like homotrimeric helices that are capable of fibrillogenesis with the production of D-periodic microfibers. Potential molecular mechanisms for peptide assembly into triple-helical protomers and their subsequent organization into structurally defined, linear assemblies were explored through molecular dynamics (MD) simulations. The formation of thermodynamically stable complexes was attributed to the presence of strong electrostatic and hydrogen bond interactions at staggered positions along the linear assembly. This unexpected mimicry of native collagen structure using a relatively simple oligopeptide sequence establishes new opportunities for engineering linear assemblies with highly ordered nano- and microscale periodic features. In turn, the capacity to precisely design periodic elements into an assembly that faithfully reproduces these features over large length scales may facilitate the fabrication of ordered two- and three-dimensional fiber networks containing oriented biologically, chemically, or optically active elements.

Hyaluronan-based Glycoclusters as Probes for Chemical Glycobiology.

A strategy is described for the synthesis of ß-(1,3)-GlcA-GlcNAc dimeric and tetrameric glycoclusters through the conjugation of disaccharide groups onto a diaminodiamide aromatic scaffold by reductive amination.

Fabrication and characterization of heparin functionalized membrane-mimetic assemblies.

A membrane-mimetic assembly incorporating surface bound heparin was fabricated as a system to improve the hemocompatibility of blood-contacting devices. As a model system, heparin was chemically modified by end-point conjugation to biotin and immobilized onto membrane-mimetic thin films via biotin-streptavidin interactions. Heparin surface density, determined by radiochemical titration, confirmed that surface density was directly related to the molar concentration of biotinylated lipid within the assembled membrane-mimetic film. The capacity of surface bound heparin to promote ATIII-mediated thrombin inactivation was investigated in a parallel plate flow chamber under simulated venous and arterial wall shear rates of 50 and 500 s(-1), respectively. Significantly, we observed that the rate of thrombin inactivation approached a maximum at a heparin surface concentration greater than 4.4 pmol/cm(2) (61 ng/cm(2)). In the process, mass transport limited regimes were identified for heparin potentiated thrombin inactivation under both simulated venous and arterial conditions.

Membrane-mimetic films containing thrombomodulin and heparin inhibit tissue factor-induced thrombin generation in a flow model.

Membrane-mimetic thin films containing thrombomodulin (TM) and/or heparin were produced and their capacity to inhibit thrombin generation evaluated in a continuous flow system. Tissue factor (TF) along with TM and heparin were immobilized in spatially restricted zones as components of a membrane-mimetic film. Specifically, TF was positioned as an upstream trigger for thrombin generation and TM and/or heparin positioned over the remaining downstream portion of test films. Peak and steady-state levels of thrombin were decreased by antithrombin III (ATIII), as well as by surface bound heparin and TM. Although physiologic concentrations of ATIII have the capacity to significantly inhibit thrombin activity, surface bound TM and heparin nearly abolished steady-state thrombin responses. In particular, surface bound TM appears to be superior to heparin in reducing local thrombin concentrations. These studies are the first to demonstrate the additive effect of surface bound heparin and TM as a combined interactive strategy to limit TF-induced thrombin formation.

Fabrication of a phospholipid membrane-mimetic film on the luminal surface of an ePTFE vascular graft.

A stabilized, membrane-mimetic film was produced on the luminal surface of an ePTFE vascular graft by in situ photopolymerization of an acrylate functonalized phospholipid using a fiber optic diffusing probe. The phospholipid monomer was synthesized, prepared as unilamellar vesicles, and fused onto close-packed octadecyl chains that were components of an amphiphilic terpolymer anchored onto the polyelectrolyte multilayer (PEM) by electrostatic interactions. Scanning electron microscopy (SEM) confirmed that gelatin impregnation of the graft followed by the subsequent biomimetic film coating filled in the fibril and node structure of the luminal surface of the ePTFE graft and was smooth. The lipid film displayed an initial advancing contact angle of 44 degrees , which increased to 55 degrees after being subjected to a wall shear rate of 500s(-1) for 24h at 37 degrees C in phosphate buffered saline (PBS). Fourier transform (FT-IR) spectroscopy was used to characterize the stages of biomimetic film assembly and confirmed the stability of the film under shear flow conditions. In vivo assessment using a baboon femoral arteriovenous shunt model demonstrated minimal platelet and fibrinogen deposition over a 1-h blood-contacting period. The results of this study confirm the versatility of a biomimetic film coating system by successfully transferring the methodology previously developed for planar substrates to the luminal surface of an ePTFE vascular graft.

Photomediated crosslinking of C6-cinnamate derivatized type I collagen.

Synthesis and characterization of cinnamated Type I collagen and its related mechanical properties after photomediated crosslinking were investigated in detail. Using an EDC/NHS conjugation method, collagen was chemically modified to incorporate a photosensitive cinnamate moiety. The cinnamated collagen was fully characterized by 1H NMR, UV-vis, and circular dichroism (CD) spectroscopy, as well as by rheological and mechanical analyses. Cinnamated collagens with varying degrees of derivatization retained collagen triple helical structure. The rheological spectra of collagen solutions demonstrate that the storage modulus decreases with increasing cinnamate content, owing to a decrease in physical crosslinking. The kinetics of the crosslinking process in both hydrated gels and dry films were monitored by UV-vis spectroscopy and confirmed that crosslinking was complete within 60 min of irradiation. The uniaxial stress-strain behavior of crosslinked collagen films, including Young's modulus and ultimate tensile strength, was comparable to values reported for glutaraldehyde-crosslinked monomeric collagen films. These data demonstrate that derivatization of collagen with photosensitive cinnamate moieties provides a facile route for solid-state crosslinking, thereby improving the mechanical properties of collagen and enhancing the potential applicability of collagen-based materials in tissue engineering and drug delivery.

Synthesis of a hyaluronan neoglycopolymer by ring-opening metathesis polymerization.

A hyaluronan (HA)-derived disaccharide was synthesized bearing an n-pentenyl spacer arm, which facilitated disaccharide derivatization with a norbornene template. Subsequent ring opening metathesis polymerization of the monomer produced an HA-mimetic neoglycopolymer of low polydispersity.

A new conformer of 20-hydroxyecdysone from Sesuvium portulacastrum: an x-ray crystallographic study.

X-ray single crystal analysis of 20-hydroxyecdysone (20E, 2), an important insect moulting hormone, isolated from Sesuvium portulacastrum Linn. was found to exhibit a unique stereochemical configuration revealing it to be a different conformer (polymorph) possessing the aliphatic chain atoms in a trans configuration. Moreover, the analysis also revealed the presence of three molecules of water of crystallisation thereby restricting the freedom of the aliphatic side chain.

Engineered PRINT(®) nanoparticles for controlled delivery of antigens and immunostimulants.

Particle replication in non-wetting templates (PRINT) is a novel nanoparticle platform that provides compositional flexibility with the ability to specify size and shape in formulating vaccines. The PRINT platform also offers manufacturing and cost advantages over traditional particle technologies. Across multiple antigen and adjuvant formulations, robust antibody and cellular responses have been achieved using PRINT particles in mouse models. Preclinical studies applying PRINT technology in the disease areas of influenza, malaria, and pneumonia are described in this commentary. The proof of principle studies pave the way toward significant cost-effective solutions to global vaccine supply needs.

Administration in non-human primates of escalating intravenous doses of targeted nanoparticles containing ribonucleotide reductase subunit M2 siRNA.

The results of administering escalating, i.v. doses of targeted nanoparticles containing a siRNA targeting the M2 subunit of ribonucleotide reductase to non-human primates are reported. The nanoparticles consist of a synthetic delivery system that uses a linear, cyclodextrin-containing polycation, transferrin (Tf) protein targeting ligand, and siRNA. When administered to cynomolgus monkeys at doses of 3 and 9 mg siRNA/kg, the nanoparticles are well tolerated. At 27 mg siRNA/kg, elevated levels of blood urea nitrogen and creatinine are observed that are indicative of kidney toxicity. Mild elevations in alanine amino transferase and aspartate transaminase at this dose level indicate that the liver is also affected to some extent. Analysis of complement factors does not reveal any changes that are clearly attributable to dosing with the nanoparticle formulation. Detection of increased IL-6 levels in all animals at 27 mg siRNA/kg and increased IFN-gamma in one animal indicate that this high dose level produces a mild immune response. Overall, no clinical signs of toxicity clearly attributable to treatment are observed. The multiple administrations spanning a period of 17-18 days enable assessment of antibody formation against the human Tf component of the formulation. Low titers of anti-Tf antibodies are detected, but this response is not associated with any manifestations of a hypersensitivity reaction upon readministration of the targeted nanoparticle. Taken together, the data presented show that multiple, systemic doses of targeted nanoparticles containing nonchemically modified siRNA can safely be administered to non-human primates.

Dendrimer-like PEO glycopolymers exhibit anti-inflammatory properties.

A new class of high molecular weight polysulfated PEO dendrimer-like glycopolymer has been synthesized by a combination of arm-first and core-first methodologies followed by trichloroacetimidate glycosidation as a facile bioconjugation strategy. An L-selectin antagonist was identified that exhibits 103-fold greater activity than other multivalent sLex glycopolymers and 20-50 times greater potency than other linear heparinoids. A significant reduction in inflammatory cell recruitment was observed in vivo.

Design and synthesis of dimeric heparinoid mimetics.

Synthetic oligosaccharide constructs exhibiting tailored and well-defined heparan sulfate (HS) like sequences offer the potential to modulate dynamic HS-dependent biomolecular recognition processes. We report an efficient strategy for the generation of HS-like fragments [GlcA-beta-(1,4)-GlcNAc] and related dimerized (gemini) disaccharides (4a and 4b) via n-pentenyl glycoside formation. When a convergent synthetic approach was utilized, construction of target molecules was achieved through a combination of chemoselective protection/deprotection protocols, imidate and n-pentenyl glycosylations, and functional group manipulations followed by ozonolysis and reductive amination. For example, glycosylation of a 2-azido glycoside (25) with a trichloroacetimidate glucuronic acid donor (13), using a catalytic amount of TMSOTf, furnished heparin-like disaccharides (28a and 28b) that were equipped with an n-pentenyl tether at the anomeric end. In turn, heparinoid-like gemini disaccharides (4a and 4b) were produced by selective transformation of the olefinic unit in the n-pentenyl glycoside to the four-carbon aldehyde followed by reductive amination with ethylenediamine. The described synthetic approach provides access to structural variants of small heparinoid oligomers as versatile building blocks for generating novel HS mimetic pharmacotherapeutics, diagnostic reagents, and biomaterials.

Protective activities of some phenolic 1,3-diketones against lipid peroxidation: possible involvement of the 1,3-diketone moiety.

The protective activities of four ginger-derived phenolic 1,3-diketones (1-4) and curcumin (5) against lipid peroxidation was studied by using different biologically relevant model systems and pulse radiolysis. The extraordinary activity of 5 vis-à-vis 1-4 against Fe(2+)-mediated peroxidation may be attributed to the additional phenolic hydroxy group in the former, which lends it better iron-chelating and radical-scavenging properties. In iron-independent peroxidation, however, the ginger constituent [6]-dehydrogingerdione (1) showed activity comparable to that of 5; this indicates its higher affinity for the lipid peroxide radical (LOO(.)), due to its higher hydrophobicity. A very high rate constant for the reaction between 1 and Cl(3)COO(.), measured by pulse radiolysis, not only confirmed this, but also established the superior antioxidant efficacy of 1 in comparison to vitamins E and C. This was also evident from the results obtained from a liposomal peroxidation study with 1 and vitamin C. This study also established a synergistic effect of the latter on the antioxidant activity of 1. HPLC analysis of the products of the reaction between 1 and Cl(3)COO(.) revealed the formation of higher concentrations of ferulic acid (7), along with vanillin (6). The presence of ascorbate affected the generation of 7 more than it did that of 6. On this basis, a mechanism for the antioxidant action of 1 has been proposed, which suggests the contribution of the phenolic group as well as the active methylene group of the 1,3-diketones.