Site-Specific and Stable Conjugation of the SARS-CoV-2 Receptor-Binding Domain to Liposomes in the Absence of Any Other Adjuvants Elicits Potent Neutralizing Antibodies in BALB/c Mice

Understanding immune responses toward viral infection will be useful for potential therapeutic intervention and offer insights into the design of prophylactic vaccines. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the COVID-19 pandemic. To understand the complex immune responses toward SARS-CoV-2 infection, here we developed a method to express and purify the recombinant and engineered viral receptor-binding domain (RBD) to more than 95% purity. We could encapsulate RNA molecules into the interior of a virion-sized liposome. We conjugated the purified RBD proteins onto the surface of the liposome in an orientation-specific manner with defined spatial densities. Both the encapsulation of RNAs and the chemical conjugation of the RBD protein on liposome surfaces were stable under physiologically relevant conditions. In contrast to soluble RBD proteins, a single injection of RBD-conjugated liposomes alone, in the absence of any other adjuvants, elicited RBD-specific B cell responses in BALB/c mice, and the resulting animal sera could potently neutralize HIV-1 pseudovirions that displayed the SARS-CoV-2 spike proteins. These results validate these supramolecular structures as a novel and effective tool to mimic the structure of enveloped viruses, the use of which will allow systematic dissection of the complex B cell responses to SARS-CoV-2 infection.

Streamlining Peptide Mapping LC-MS Approach for Studying Fusion Peptide-Conjugated Vaccine Immunogens

A newly introduced HIV-1 vaccination utilizes a fusion peptide (FP)-based immunogen-carrier conjugate system, where the FP is coupled to a protein carrier via a bifunctional linker. Such heterogeneous materials present a challenge for the routine product quality assessment. Peptide mapping LC-MS analysis has become an indispensable tool for assessing the site-specific conjugation ratio, estimating site occupancy, monitoring conjugation profiles, and analyzing post-translational modifications (PTMs) and disulfide bonds as well as high-order protein structures. To streamline the peptide mapping approach to match the needs of a fast-paced conjugate vaccine product characterization, a selection of signature fragment ions generated by MS^E fragmentation was successfully applied to assess the product quality at the different stages of a conjugates' manufacturing process with an emphasis on monitoring the amount of a reactive linker. This technique was employed in different conjugation studies of the protein carriers, linkers, and FP compositions as well as the cross-linked species formed during stress-degradation studies. Multiple derivatives of the intermediate and final conjugated products formed during a multistaged synthesis were monitored by means of the sensitive extracted-ion chromatogram (XIC) profiling and were included in the estimation of the site-specific conjugation loads. Differentiation of the conjugates with various FP compositions was demonstrated. The conjugation site occupancy was evaluated with respect to the solvent exposure of Lys residues. The findings of these LC-MS studies greatly aided in choosing the best conjugation strategy to ensure that the final recombinant tetanus toxoid heavy chain (rTTHc) product is chemically inert and represents a safe vaccine candidate for clinical evaluation.

Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers

Targeted and efficient delivery of nucleic acids with viral and synthetic vectors is the key step of genetic nanomedicine. The four-component lipid nanoparticle synthetic delivery systems consisting of ionizable lipids, phospholipids, cholesterol, and a PEG-conjugated lipid, assembled by microfluidic or T-tube technology, have been extraordinarily successful for delivery of mRNA to provide Covid-19 vaccines. Recently, we reported a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) synthetic delivery system for mRNA relying on amphiphilic Janus dendrimers and glycodendrimers developed in our laboratory. Amphiphilic Janus dendrimers consist of functional hydrophilic dendrons conjugated to hydrophobic dendrons. Co-assembly of IAJDs with mRNA into dendrimersome nanoparticles (DNPs) occurs by simple injection in acetate buffer, rather than by microfluidic devices, and provides a very efficient system for delivery of mRNA to lung. Here we report the replacement of most of the hydrophilic fragment of the dendron from IAJDs, maintaining only its ionizable amine, while changing its interconnecting group to the hydrophobic dendron from amide to ester. The resulting IAJDs demonstrated that protonated ionizable amines play dual roles of hydrophilic fragment and binding ligand for mRNA, changing delivery from lung to spleen and/or liver. Replacing the interconnecting ester with the amide switched the delivery back to lung. Delivery predominantly to liver is favored by pairs of odd and even alkyl groups in the hydrophobic dendron. This simple structural change transformed the targeted delivery of mRNA mediated with IAJDs, from lung to liver and spleen, and expands the utility of DNPs from therapeutics to vaccines.

The self-assembled nanoparticle-based trimeric RBD mRNA vaccine elicits robust and durable protective immunity against SARS-CoV-2 in mice

As COVID-19 continues to spread rapidly worldwide and variants continue to emerge, the development and deployment of safe and effective vaccines are urgently needed. Here, we developed an mRNA vaccine based on the trimeric receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein fused to ferritin-formed nanoparticles (TF-RBD). Compared to the trimeric form of the RBD mRNA vaccine (T-RBD), TF-RBD delivered intramuscularly elicited robust and durable humoral immunity as well as a Th1-biased cellular response. After further challenge with live SARS-CoV-2, immunization with a two-shot low-dose regimen of TF-RBD provided adequate protection in hACE2-transduced mice. In addition, the mRNA template of TF-RBD was easily and quickly engineered into a variant vaccine to address SARS-CoV-2 mutations. The TF-RBD multivalent vaccine produced broad-spectrum neutralizing antibodies against Alpha (B.1.1.7) and Beta (B.1.351) variants. This mRNA vaccine based on the encoded self-assembled nanoparticle-based trimer RBD provides a reference for the design of mRNA vaccines targeting SARS-CoV-2.

An Epitope Platform for Safe and Effective HTLV-1-Immunization: Potential Applications for mRNA and Peptide-Based Vaccines

Human T-cell lymphotropic virus type 1 (HTLV-1) infection affects millions of individuals worldwide and can lead to severe leukemia, myelopathy/tropical spastic paraparesis, and numerous other disorders. Pursuing a safe and effective immunotherapeutic approach, we compared the viral polyprotein and the human proteome with a sliding window approach in order to identify oligopeptide sequences unique to the virus. The immunological relevance of the viral unique oligopeptides was assessed by searching them in the immune epitope database (IEDB). We found that HTLV-1 has 15 peptide stretches each consisting of uniquely viral non-human pentapeptides which are ideal candidate for a safe and effective anti-HTLV-1 vaccine. Indeed, experimentally validated HTLV-1 epitopes, as retrieved from the IEDB, contain peptide sequences also present in a vast number of human proteins, thus potentially instituting the basis for cross-reactions. We found a potential for cross-reactivity between the virus and the human proteome and described an epitope platform to be used in order to avoid it, thus obtaining effective, specific, and safe immunization. Potential advantages for mRNA and peptide-based vaccine formulations are discussed.

Simultaneous Evaluation of a Vaccine Component Microheterogeneity and Conformational Integrity Using Native Mass Spectrometry and Limited Charge Reduction

Analytical characterization of extensively modified proteins (such as haptenated carrier proteins in synthetic vaccines) remains a challenging task due to the high degree of structural heterogeneity. Native mass spectrometry (MS) combined with limited charge reduction allows these obstacles to be overcome and enables meaningful characterization of a heavily haptenated carrier protein CRM197 (inactivated diphtheria toxin conjugated with nicotine), a major component of a smoking cessation vaccine. The extensive conjugation results in a near-continuum distribution of ionic signal in electrospray ionization (ESI) mass spectra of haptenated CRM197 even after size-exclusion chromatographic fractionation. However, supplementing the ESI MS measurements with limited charge reduction of ionic populations selected within narrow m/z windows gives rise to well-resolved charge ladders, from which both masses and charge states of the ionic species can be readily deduced. Application of this technique to a research-grade material of CRM197/H7 conjugate not only reveals its marginal conformational stability (manifested by the appearance of high charge-density ions in ESI MS) but also establishes a role of the extent of haptenation as a major factor driving the loss of the higher order structure integrity. The unique information provided by native MS used in combination with limited charge reduction provides a strong argument for this technique to become a standard/required tool in the analytical arsenal in the field of biotechnology and biopharmaceutical analysis, where protein conjugates are becoming increasingly common.

Discovery of Oligosaccharide Antigens for Semi-Synthetic Glycoconjugate Vaccine Leads against Streptococcus suis Serotypes 2, 3, 9 and 14*

Streptococcus suis bacteria are one of the most serious health problems for pigs and an emerging zoonotic agent in humans working in the swine industry. S. suis bacteria express capsular polysaccharides (CPS) a major bacterial virulence factor that define the serotypes. Oligosaccharides resembling the CPS of S. suis serotypes 2, 3, 9, and 14 have been synthesized, glycans related to serotypes 2 and 9 were placed on glycan array surfaces to screen blood from infected pigs. Lead antigens for the development of semi-synthetic S. suis serotypes 2 and 9 glycoconjugate veterinary vaccines were identified in this way.

An Engineered Receptor-Binding Domain Improves the Immunogenicity of Multivalent SARS-CoV-2 Vaccines

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein mediates viral entry into cells expressing angiotensin-converting enzyme 2 (ACE2). The S protein engages ACE2 through its receptor-binding domain (RBD), an independently folded 197-amino-acid fragment of the 1,273-amino-acid S-protein protomer. The RBD is the primary SARS-CoV-2 neutralizing epitope and a critical target of any SARS-CoV-2 vaccine. Here, we show that this RBD conjugated to each of two carrier proteins elicited more potent neutralizing responses in immunized rodents than did a similarly conjugated proline-stabilized S-protein ectodomain. Nonetheless, the native RBD is expressed inefficiently, limiting its usefulness as a vaccine antigen. However, we show that an RBD engineered with four novel glycosylation sites (gRBD) is expressed markedly more efficiently and generates a more potent neutralizing responses as a DNA vaccine antigen than the wild-type RBD or the full-length S protein, especially when fused to multivalent carriers, such as a Helicobacter pylori ferritin 24-mer. Further, gRBD is more immunogenic than the wild-type RBD when administered as a subunit protein vaccine. Our data suggest that multivalent gRBD antigens can reduce costs and doses, and improve the immunogenicity, of all major classes of SARS-CoV-2 vaccines.IMPORTANCE All available vaccines for coronavirus disease 2019 (COVID-19) express or deliver the full-length SARS-CoV-2 spike (S) protein. We show that this antigen is not optimal, consistent with observations that the vast majority of the neutralizing response to the virus is focused on the S-protein receptor-binding domain (RBD). However, this RBD is not expressed well as an independent domain, especially when expressed as a fusion protein with a multivalent scaffold. We therefore engineered a more highly expressed form of the SARS-CoV-2 RBD by introducing four glycosylation sites into a face of the RBD normally occluded in the full S protein. We show that this engineered protein, gRBD, is more immunogenic than the wild-type RBD or the full-length S protein in both genetic and protein-delivered vaccines.

Discovery of Semi- and Fully-Synthetic Carbohydrate Vaccines Against Bacterial Infections Using a Medicinal Chemistry Approach

The glycocalyx, a thick layer of carbohydrates, surrounds the cell wall of most bacterial and parasitic pathogens. Recognition of these unique glycans by the human immune system results in destruction of the invaders. To elicit a protective immune response, polysaccharides either isolated from the bacterial cell surface or conjugated with a carrier protein, for T-cell help, are administered. Conjugate vaccines based on isolated carbohydrates currently protect millions of people against Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitides infections. Active pharmaceutical ingredients (APIs) are increasingly discovered by medicinal chemistry and synthetic in origin, rather than isolated from natural sources. Converting vaccines from biologicals to pharmaceuticals requires a fundamental understanding of how the human immune system recognizes carbohydrates and could now be realized. To illustrate the chemistry-based approach to vaccine discovery, I summarize efforts focusing on synthetic glycan-based medicinal chemistry to understand the mammalian antiglycan immune response and define glycan epitopes for novel synthetic glycoconjugate vaccines against Streptococcus pneumoniae, Clostridium difficile, Klebsiella pneumoniae, and other bacteria. The chemical tools described here help us gain fundamental insights into how the human system recognizes carbohydrates and drive the discovery of carbohydrate vaccines.

BNT162b vaccines protect rhesus macaques from SARS-CoV-2

A safe and effective vaccine against COVID-19 is urgently needed in quantities that are sufficient to immunize large populations. Here we report the preclinical development of two vaccine candidates (BNT162b1 and BNT162b2) that contain nucleoside-modified messenger RNA that encodes immunogens derived from the spike glycoprotein (S) of SARS-CoV-2, formulated in lipid nanoparticles. BNT162b1 encodes a soluble, secreted trimerized receptor-binding domain (known as the RBD-foldon). BNT162b2 encodes the full-length transmembrane S glycoprotein, locked in its prefusion conformation by the substitution of two residues with proline (S(K986P/V987P); hereafter, S(P2) (also known as P2 S)). The flexibly tethered RBDs of the RBD-foldon bind to human ACE2 with high avidity. Approximately 20% of the S(P2) trimers are in the two-RBD 'down', one-RBD 'up' state. In mice, one intramuscular dose of either candidate vaccine elicits a dose-dependent antibody response with high virus-entry inhibition titres and strong T-helper-1 CD4+ and IFNγ+CD8+ T cell responses. Prime-boost vaccination of rhesus macaques (Macaca mulatta) with the BNT162b candidates elicits SARS-CoV-2-neutralizing geometric mean titres that are 8.2-18.2× that of a panel of SARS-CoV-2-convalescent human sera. The vaccine candidates protect macaques against challenge with SARS-CoV-2; in particular, BNT162b2 protects the lower respiratory tract against the presence of viral RNA and shows no evidence of disease enhancement. Both candidates are being evaluated in phase I trials in Germany and the USA1-3, and BNT162b2 is being evaluated in an ongoing global phase II/III trial (NCT04380701 and NCT04368728).

Addressing the Cold Reality of mRNA Vaccine Stability

As mRNA vaccines became the frontrunners in late-stage clinical trials to fight the COVID-19 pandemic, challenges surrounding their formulation and stability became readily apparent. In this commentary, we first describe company proposals, based on available public information, for the (frozen) storage of mRNA vaccine drug products across the vaccine supply chain. We then review the literature on the pharmaceutical stability of mRNA vaccine candidates, including attempts to improve their stability, analytical techniques to monitor their stability, and regulatory guidelines covering product characterization and storage stability. We conclude that systematic approaches to identify the key physicochemical degradation mechanism(s) of formulated mRNA vaccine candidates are currently lacking. Rational design of optimally stabilized mRNA vaccine formulations during storage, transport, and administration at refrigerated or ambient temperatures should thus have top priority in the pharmaceutical development community. In addition to evidence of human immunogenicity against multiple viral pathogens, including compelling efficacy results against COVID-19, another key strength of the mRNA vaccine approach is that it is readily adaptable to rapidly address future outbreaks of new emerging infectious diseases. Consequently, we should not wait for the next pandemic to address and solve the challenges associated with the stability and storage of formulated mRNA vaccines.

Nanoparticle-Mediated Cytoplasmic Delivery of Messenger RNA Vaccines: Challenges and Future Perspectives

The COVID-19 pandemic has left scientists and clinicians no choice but a race to find solutions to save lives while controlling the rapid spreading. Messenger RNA (mRNA)-based vaccines have become the front-runners because of their safety profiles, precise and reproducible immune response with more cost-effective and faster production than other types of vaccines. However, the physicochemical properties of naked mRNA necessitate innovative delivery technologies to ferry these 'messengers' to ribosomes inside cells by crossing various barriers and subsequently induce an immune response. Intracellular delivery followed by endosomal escape represents the key strategies for cytoplasmic delivery of mRNA vaccines to the target. This Perspective provides insights into how state-of-the-art nanotechnology helps break the delivery barriers and advance the development of mRNA vaccines. The challenges remaining and future perspectives are outlined.

Design and Synthesis of HCV-E2 Glycoprotein Epitope Mimics in Molecular Construction of Potential Synthetic Vaccines

Hepatitis C virus remains a global threat, despite the availability of highly effective direct-acting antiviral (DAA) drugs. With thousands of new infections annually, the need for a prophylactic vaccine is evident. However, traditional vaccine design has been unable to provide effective vaccines so far. Therefore, alternative strategies need to be investigated. In this work, a chemistry-based approach is explored towards fully synthetic peptide-based vaccines using epitope mimicry, by focusing on highly effective and conserved amino acid sequences in HCV, which, upon antibody binding, inhibit its bio-activity. Continuous and discontinuous epitope mimics were both chemically synthesized based on the HCV-E2 glycoprotein while using designed fully synthetic cyclic peptides. These cyclic epitope mimics were assembled on an orthogonally protected scaffold. The scaffolded epitope mimics have been assessed in immunization experiments to investigate the elicitation of anti-HCV-E2 glycoprotein antibodies. The neutralizing potential of the elicited antibodies was investigated, representing a first step in employing chemically synthesized epitope mimics as a novel strategy towards vaccine design.

FRETing over SARS-CoV-2: Conformational Dynamics of the Spike Glycoprotein

In this issue of Cell Host & Microbe, Lu et al. utilize single-molecule FRET to reveal the conformation dynamics of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, showing transitions from a closed ground state to the open receptor-accessible conformation via an on-path intermediate. These insights into spike conformations will facilitate rational immunogen design.

Structure-based glycoconjugate vaccine design: The example of Group B Streptococcus type III capsular polysaccharide

Microbial surface polysaccharides are important virulence factors and targets for vaccine development. Glycoconjugate vaccines, obtained by covalently linking carbohydrates and proteins, are well established tools for prevention of bacterial infections. Elucidation of the minimal portion involved in the interactions with functional antibodies is of utmost importance for the understanding of their mechanism of induction of protective immune responses and the design of synthetic glycan based vaccines. Typically, this is achieved by combination of different techniques, which include ELISA, glycoarray, Surface Plasmon Resonance in conjunction with approaches for mapping at atomic level the position involved in binding, such as Saturation Transfer NMR and X-ray crystallography. This review provides an overview of the structural studies performed to map glycan epitopes (glycotopes), with focus on the highly complex structure of Group B Streptococcus type III (GBSIII) capsular polysaccharide. Furthermore, it describes the rational process followed to translate the obtained information into the design of a protective glycoconjugate vaccine based on a well-defined synthetic glycan epitope.

Injectable, Ribbon-Like Microconfetti Biopolymer Platform for Vaccine Applications

Previously, high-aspect- ratio ribbon-like microconfetti (MC) composed of acetalated dextran (Ace-DEX) have been shown to form a subcutaneous depot for sustained drug release. In this study, MC were explored as an injectable vaccine platform. Production of MC by electrospinning followed by high-shear homogenization allowed for precise control over MC fabrication. Three distinct sizes of MC, small (0.67 × 10.2 μm²), medium (1.28 × 20.7 μm²), and large (5.67 × 90.2 μm²), were fabricated and loaded with the adjuvant, resiquimod. Steady release rates of resiquimod were observed from MC, indicating their ability to create an immunostimulatory depot in vivo. Resiquimod-loaded MC stimulated inflammatory cytokine production in bone marrow-derived dendritic cells without incurring additional cytotoxicity in vitro. Interestingly, even medium and large MC were able to be internalized by antigen-presenting cells and facilitate antigen presentation when ovalbumin was adsorbed onto their surface. After subcutaneous injection in vivo with adsorbed ovalbumin, blank MC of all sizes were found to stimulate a humoral response. Adjuvant activity of resiquimod was enhanced by loading it into MC and small- and medium-sized MC effectively induced a Th1-skewed immune response. Antigen co-delivered with adjuvant-loaded MC of various sizes illustrates a new potential vaccine platform.

A Multi-Targeting, Nucleoside-Modified mRNA Influenza Virus Vaccine Provides Broad Protection in Mice

Influenza viruses are respiratory pathogens of public health concern worldwide with up to 650,000 deaths occurring each year. Seasonal influenza virus vaccines are employed to prevent disease, but with limited effectiveness. Development of a universal influenza virus vaccine with the potential to elicit long-lasting, broadly cross-reactive immune responses is necessary for reducing influenza virus prevalence. In this study, we have utilized lipid nanoparticle-encapsulated, nucleoside-modified mRNA vaccines to intradermally deliver a combination of conserved influenza virus antigens (hemagglutinin stalk, neuraminidase, matrix-2 ion channel, and nucleoprotein) and induce strong immune responses with substantial breadth and potency in a murine model. The immunity conferred by nucleoside-modified mRNA-lipid nanoparticle vaccines provided protection from challenge with pandemic H1N1 virus at 500 times the median lethal dose after administration of a single immunization, and the combination vaccine protected from morbidity at a dose of 50 ng per antigen. The broad protective potential of a single dose of combination vaccine was confirmed by challenge with a panel of group 1 influenza A viruses. These findings support the advancement of nucleoside-modified mRNA-lipid nanoparticle vaccines expressing multiple conserved antigens as universal influenza virus vaccine candidates.

Optimization of an mRNA vaccine assisted with cyclodextrin-polyethyleneimine conjugates

Messenger RNA (mRNA) vaccines have attracted great interest in recent years due to their high potency, safety profile, and potential of rapid development. Although a number of mRNA vaccines have entered clinical trials, there remain several challenges. Inefficient in vivo delivery of mRNA is the foremost one. Here we synthesized a conjugate composed of β-cyclodextrin (β-CD) and branched polyethyleneimine (molecular weight 2 kDa, bPEI2k) to deliver an mRNA vaccine. The CD-PEI (CP) conjugate helped the encapsulated mRNA molecules pass through the plasma membranes and escape from the endosomes, which consequently ensured high transfection efficiency. On this basis, we optimized several structural elements of mRNA molecules via synthesizing an advanced cap structure and incorporating untranslated regions (UTRs) and an extended poly(A) tail into the sequence. These modifications led to a higher expression level of encoded proteins, which was expected to induce potent immune responses with a relatively low dosage. We also investigated the relevance of the administration route to the immune responses induced by CP-assisted mRNA vaccines with in vivo evidence, providing a basis for the selection of optimum administration route in specific cases. This CP-based mRNA vaccine platform, with an optimized mRNA structure and administrated in a most appropriate route, holds a promise to be applied to specific antigens in the future. Graphical abstract.

Improving the aqueous solubility of HCV-E2 glycoprotein epitope mimics by cyclization using POLAR hinges

In this research we describe the improvement of the water-solubility of cyclic epitope mimics based on the HCV E2 glycoprotein by incorporation of suitable polar hinges. The poor solubility of epitope mimics based on peptide sequences in the envelope (E2) protein hampered their synthesis and purification and made it very difficult to prepare the molecular constructs for evaluation of their bioactivity. Since changes in the amino acid composition are hardly possible in these epitope mimics in order to increase water-solubility, a polar cyclization hinge may offer a remedy leading to a significant increase of polarity and therefore water solubility. These polar hinges were applied in the synthesis of better water-soluble HCV-E2 epitopes. An azide functionality in the polar hinges allowed attachment of a tetraethylene glycol linker by Cu-catalyzed azide-alkyne cyclo-addition (CuAAC) for a convenient conjugation to ELISA plates in order to evaluate the bio-activity of the epitope mimics. The immunoassays showed that the use of more polar cyclization hinges still supported anti-HCV antibody recognition and did not negatively influence their binding. This significantly increased solubility induced by polar hinges should therefore allow for the molecular construction and ultimate evaluation of synthetic vaccine molecules.

Stabilization and formulation of a recombinant Human Cytomegalovirus vector for use as a candidate HIV-1 vaccine

Live attenuated viral vaccine/vector candidates are inherently unstable and infectivity titer losses can readily occur without defining appropriate formulations, storage conditions and clinical handling practices. During initial process development of a candidate vaccine against HIV-1 using a recombinant Human Cytomegalovirus vector (rHCMV-1), large vector titer losses were observed after storage at 4 °C and after undergoing freeze-thaw. Thus, the goal of this work was to develop candidate frozen liquid formulations of rHCMV-1 with improved freeze-thaw and short-term liquid stability for potential use in early clinical trials. To this end, a virus stability screening protocol was developed including use of a rapid, in vitro cell-based immunofluorescence focus assay to quantitate viral titers. A library of ∼50 pharmaceutical excipients (from various known classes of additives) were evaluated for their effect on vector stability after freeze-thaw cycling or incubation at 4 °C for several days. Certain additives including sugars and polymers (e.g., trehalose, sucrose, sorbitol, hydrolyzed gelatin, dextran 40) as well as removal of NaCl (lower ionic strength) protected rHCMV-1 against freeze-thaw mediated losses in viral titers. Optimized solution conditions (e.g., solution pH, buffers and sugar type) slowed the rate of rHCMV-1 titer losses in the liquid state at 4 °C. After evaluating various excipient combinations, three new candidate formulations were designed and rHCMV-1 stability was benchmarked against both the currently-used and a previously reported formulation. The new candidate formulations were significantly more stable in terms of reducing rHCMV-1 titer losses after 5 freeze-thaw cycles or incubation at 4 °C for 30 days. This case study highlights the utility of semi-empirical design of frozen liquid formulations of a live viral vaccine candidate, where protection against infectivity titer losses due to freeze-thaw and short-term liquid storage are sufficient to enable more rapid initiation of early clinical trials.

Assessment of the impact of manufacturing changes on the physicochemical properties of the recombinant vaccine carrier ExoProtein A

Efforts to develop a vaccine for the elimination of malaria include the use of carrier proteins to assemble monomeric antigens into nanoparticles to maximize immunogenicity. Recombinant ExoProtein A (EPA) is a detoxified form of Pseudomonas aeruginosa Exotoxin A which has been used as a carrier in the conjugate vaccine field. A pilot-scale process developed for purification of EPA yielded product that consistently approached a preset upper limit for host cell protein (HCP) content per human dose. To minimize the risk of bulk material exceeding the specification, the purification process was redeveloped using mixed-mode chromatography resins. Purified EPA derived from the primary and redeveloped processes were comparable following full biochemical and biophysical characterization. However, using a process specific immunoassay, the HCP content was shown to decrease from a range of 0.14-0.24% w/w of total protein to below the level of detection with the revised process. The improved process reproducibly yields EPA with highly similar quality characteristics as the original process but with an improved profile for the HCP content.

Development of an imaged capillary isoelectric focusing method for characterizing the surface charge of mRNA lipid nanoparticle vaccines

Lipid nanoparticles (LNPs) have been employed for drug delivery in small molecules, siRNA, mRNA, and pDNA for both therapeutics and vaccines. Characterization of LNPs is challenging because they are heterogeneous mixtures of large complex particles. Many tools for particle size characterization, such as dynamic and static light scattering, have been applied as well as morphology analysis using electron microscopy. CE has been applied for the characterization of many different large particles such as liposomes, polymer, and viruses. However, there have been limited efforts to characterize the surface charge of LNPs and CIEF has not been explored for this type of particle. Typically, LNPs for delivery of oligonucleotides contain at least four different lipids, with at least one being an ionizable cationic lipid. Here, we describe the development of an imaged capillary isoelectric focusing method used to measure the surface charge (i.e., pI) of an LNP-based mRNA vaccine. This method is capable of distinguishing the pI of LNPs manufactured with one or more different ionizable lipids for the purpose of confirming LNP identity in a manufacturing setting. Additionally, the method is quantitative and stability-indicating making it suitable for both process and formulation development.

Recombinant vector vaccine evolution

Replicating recombinant vector vaccines consist of a fully competent viral vector backbone engineered to express an antigen from a foreign transgene. From the perspective of viral replication, the transgene is not only dispensable but may even be detrimental. Thus vaccine revertants that delete or inactivate the transgene may evolve to dominate the vaccine virus population both during the process of manufacture of the vaccine as well as during the course of host infection. A particular concern is that this vaccine evolution could reduce its antigenicity—the immunity elicited to the transgene. We use mathematical and computational models to study vaccine evolution and immunity. These models include evolution arising during the process of manufacture, the dynamics of vaccine and revertant growth, plus innate and adaptive immunity elicited during the course of infection. Although the selective basis of vaccine evolution is easy to comprehend, the immunological consequences are not. One complication is that the opportunity for vaccine evolution is limited by the short period of within-host growth before the viral population is cleared. Even less obvious, revertant growth may only weakly interfere with vaccine growth in the host and thus have a limited effect on immunity to vaccine. Overall, we find that within-host vaccine evolution can sometimes compromise vaccine immunity, but only when the extent of evolution during vaccine manufacture is severe, and this evolution can be easily avoided or mitigated.

Recombinant vector vaccines are live replicating viruses that are engineered to carry extra genes derived from a pathogen—and these extra genes produce proteins against which we want to generate immunity. These vaccine genomes may evolve to lose the extra genes during the process of manufacture of the vaccine or during replication within an individual, and there is a concern that this evolution might severely limit the vaccine’s efficacy. The dynamics of this process are studied here with mathematical models. The potential for vaccine evolution within the host is somewhat limited by the short-term growth of the vaccine population before it is suppressed by the immune response. We find that evolution is a problem only when the process of manufacture results in the majority of the vaccine virus being revertant. We show that increasing the vaccine inoculum size or reducing the level of revertant in the vaccine inoculum can largely avoid the loss of immunity arising from evolution.

A novel application of ion exchange chromatography in recombinant hepatitis B vaccine downstream processing: Improving recombinant HBsAg homogeneity by removing associated aggregates

Production of recombinant HBsAg as a main component of the hepatitis B vaccine has already been established in commercial scale. So far, many studies have been performed to optimize the production process of this recombinant vaccine. However, still aggregation and dissociation of rHBsAg virus-like particles (VLPs) are major challenges in downstream processing of this biomedicine. The structural diversity of rHBsAg is dependent on many factors including cell types, molecular characteristics of the expressed recombinant rHBsAg, buffer composition as well as operation condition and specific characteristics of each downstream processing unit. Hence, it is not relatively easy to implement a single strategy to prevent aggregation formation in already established rHBsAg production processes. In this study, we examined the efficacy of weak anion exchange chromatography (IEC)- packed with DEAE Sepharose Fast Flow medium- on isolation of rHBsAg VLPs from aggregated structures. For this purpose, the influence of ionic strength of elution buffer as a key factor was investigated in isolation and recovery of rHBsAg VLPs. The elution buffer with electrical conductivity between 27 and 31 mS/cm showed the best results for removing aggregated rHBsAg based on SEC-HPLC analysis. The results showed that in the selected conductivity range, about 79% of rHBsAg was recovered with purity above 95%. The percentage of rHBsAg VLPs in the recovered sample was between 94% and 97.5% indicating that we could obtain highly homogeneous rHBsAg within the acceptable quality level. The TEM, SDS-PAGE and western blot analysis were also in agreement with our quantitative measurements.

Injectable Biodegradable Chitosan-Alginate 3D Porous Gel Scaffold for mRNA Vaccine Delivery

mRNA vaccines have proven to be more stable, effective, and specific than protein/peptide-based vaccines in stimulating both humoral and cellular immune response. However, mRNA's fast degradation rate and low-transfection efficiency in vivo impede its potential in vaccination. Recent research in gene delivery has focused on nonviral vaccine carriers and either implantable or injectable delivery systems to improve transgene expression in vivo. Here, an injectable chitosan-alginate gel scaffold for the local delivery of mRNA vaccines is reported. Gel scaffold biodegradation rates and biocompatibility are quantified. Scaffold-mediated mRNA in vivo transgene expression as well as ovalbumin antigen specific cellular and humoral immune responses are evaluated in vivo. Luciferase reporter protein expression resulting from mRNA lipoplex-loaded gel scaffolds is five times higher than systemic injection. Compared to systemic injections of naked mRNA or mRNA:lipoplexes, elevated levels of T cell proliferation and IFN-γ secretion are seen with in vivo scaffold-mediated mRNA lipoplex delivery. Furthermore, a humoral response (ovalbumin antigen specific IgG levels) is observed as early as week 1 for scaffold-mediated mRNA lipoplex delivery, while protein-based immunization did not elicit IgG production until 2 weeks post-injection. Results suggest that injectable scaffold mRNA vaccine delivery maybe a viable alternative to traditional nucleic acid immunization methods.

Development of a novel multiepitope chimeric vaccine against anthrax

Bacillus anthracis (BA), the etiological agent of anthrax, secretes protective antigen (PA), lethal factor (LF), and edema factor (EF) as major virulence mediators. Amongst these, PA-based vaccines are most effective for providing immunity against BA, but their low shelf life limits their usage. Previous studies showed that B-cell epitopes, ID II and ID III present in PA domain IV possess higher toxin neutralization activity and elicit higher antibody titer than ID I. Moreover, N-terminal region of both LF and EF harbors PA-binding sites which share 100% identity with each other. Here, in this study, we have developed an epitope-based chimeric vaccine (ID-LFn) comprising ID II-ID III region of PA and N-terminal region of LF. We have also evaluated its protective efficacy as well as stability and found it to be more stable than PA-based vaccine. Binding reactivities of ID-LFn with anti-PA/LF/EF antibodies were determined by ELISA. The stability of chimeric vaccine was assessed using circular dichroism spectroscopy. ID-LFn response was characterized by toxin neutralization, lymphocyte proliferation isotyping and cytokine profiling. The protective efficacy was analyzed by challenging ID-LFn-immunized mice with B. anthracis (pXO1⁺ and pXO2⁺). ID-LFn was found to be significantly stable as compared to PA. Anti-ID-LFn antibodies recognized PA, LF as well as EF. The T-cell response and the protective efficacy of ID-LFn were found to be almost similar to PA. ID-LFn exhibits equal protective efficacy in mice and possesses more stability as compared to PA along with the capability of recognizing PA, LF and EF at the same time. Thus, it can be considered as an improved vaccine against anthrax with better shelf life. ID-LFn, a novel multiepitope chimeric anthrax vaccine: ID-LFn comprises of immunodominant epitopes of domain 4 of PA and N-terminal homologous stretch of LF and EF. The administration of this protein as a vaccine provides protection against anthrax.

Recent Advances in Toll Like Receptor-Targeting Glycoconjugate Vaccines

Many malignant cell surface carbohydrates resulting from abnormal glycosylation patterns of certain diseases can serve as antigens for the development of vaccines against these diseases. However, carbohydrate antigens are usually poorly immunogenic by themselves, thus they need to be covalently coupled with immunologically active carrier molecules to be functional. The most well established and commonly used carriers are proteins. In recent years, the use of toll-like receptor (TLR) ligands to formulate glycoconjugate vaccines has gained significant attention because TLR ligands can serve not only as carrier molecules but also as built-in adjuvants to form fully synthetic and self-adjuvanting conjugate vaccines, which have several advantages over carbohydrate-protein conjugates and formulated mixtures with external adjuvants. This article reviews recent progresses in the development of conjugate vaccines based on TLR ligands. Two major classes of TLR ligands, lipopeptides and lipid A derivatives will be covered with more focus on monophosohoryl lipid A (MPLA) and related analogs, which are TLR4 ligands demonstrated to be able to provoke T cell-dependent, adaptive immune responses. Corresponding conjugate vaccines have shown promising application potentials to multiple diseases including cancer.

Structural and immunologic correlates of chemically stabilized HIV-1 envelope glycoproteins

Inducing broad spectrum neutralizing antibodies against challenging pathogens such as HIV-1 is a major vaccine design goal, but may be hindered by conformational instability within viral envelope glycoproteins (Env). Chemical cross-linking is widely used for vaccine antigen stabilization, but how this process affects structure, antigenicity and immunogenicity is poorly understood and its use remains entirely empirical. We have solved the first cryo-EM structure of a cross-linked vaccine antigen. The 4.2 Å structure of HIV-1 BG505 SOSIP soluble recombinant Env in complex with a CD4 binding site-specific broadly neutralizing antibody (bNAb) Fab fragment reveals how cross-linking affects key properties of the trimer. We observed density corresponding to highly specific glutaraldehyde (GLA) cross-links between gp120 monomers at the trimer apex and between gp120 and gp41 at the trimer interface that had strikingly little impact on overall trimer conformation, but critically enhanced trimer stability and improved Env antigenicity. Cross-links were also observed within gp120 at sites associated with the N241/N289 glycan hole that locally modified trimer antigenicity. In immunogenicity studies, the neutralizing antibody response to cross-linked trimers showed modest but significantly greater breadth against a global panel of difficult-to-neutralize Tier-2 heterologous viruses. Moreover, the specificity of autologous Tier-2 neutralization was modified away from the N241/N289 glycan hole, implying a novel specificity. Finally, we have investigated for the first time T helper cell responses to next-generation soluble trimers, and report on vaccine-relevant immunodominant responses to epitopes within BG505 that are modified by cross-linking. Elucidation of the structural correlates of a cross-linked viral glycoprotein will allow more rational use of this methodology for vaccine design, and reveals a strategy with promise for eliciting neutralizing antibodies needed for an effective HIV-1 vaccine.

Toll-like Receptor Agonist Conjugation: A Chemical Perspective

Toll-like receptors (TLRs) are vital elements of the mammalian immune system that function by recognizing pathogen-associated molecular patterns (PAMPs), bridging innate and adaptive immunity. They have become a prominent therapeutic target for the treatment of infectious diseases, cancer, and allergies, with many TLR agonists currently in clinical trials or approved as immunostimulants. Numerous studies have shown that conjugation of TLR agonists to other molecules can beneficially influence their potency, toxicity, pharmacokinetics, or function. The functional properties of TLR agonist conjugates, however, are highly dependent on the ligation strategy employed. Here, we review the chemical structural requirements for effective functional TLR agonist conjugation. In addition, we provide similar analysis for those that have yet to be conjugated. Moreover, we discuss applications of covalent TLR agonist conjugation and their implications for clinical use.

Synthesis and Immunological Evaluation of a Multicomponent Cancer Vaccine Candidate Containing a Long MUC1 Glycopeptide

A fully synthetic MUC1-based cancer vaccine was designed and chemically synthesized containing an endogenous helper T-epitope (MHC class II epitope). The vaccine elicited robust IgG titers that could neutralize cancer cells by antibody-dependent cell-mediated cytotoxicity (ADCC). It also activated cytotoxic T-lymphocytes. Collectively, the immunological data demonstrate engagement of helper T-cells in immune activation. A synthetic methodology was developed for a penta-glycosylated MUC1 glycopeptide, and antisera of mice immunized by the new vaccine recognized such a structure. Previously reported fully synthetic MUC1-based cancer vaccines that elicited potent immune responses employed exogenous helper T-epitopes derived from microbes. It is the expectation that the use of the newly identified endogenous helper T-epitope will be more attractive, because it will activate cognate CD4+ T-cells that will provide critical tumor-specific help intratumorally during the effector stage of tumor rejection and will aid in the generation of sustained immunological memory.

Development of a synthetic Vi polysaccharide vaccine for typhoid fever

Typhoid fever remains a serious public health problem with a high impact on toddlers and young children. Vaccines against the Vi capsular polysaccharide are efficacious against typhoid fever demonstrating that antibodies against Vi confer protection. The currently licensed Vi typhoid vaccines have however limited efficacy and are manufactured by a complex process from wild-type bacteria. Due to these inherent issues with the current vaccines, an alternative vaccine based on an O-acetylated high molecular weight (HMW) polygalacturonic acid (GelSite-OAc™) was generated. The HMW polygalacturonic acid shares the same backbone as the Vi polysaccharide of Salmonella Typhi. The GelSite-OAc™ has a high molecular weight (>1 × 106 Da) and a high degree of O-acetylation (DOAc) (>5 μmole/mg), both exceeding the potency specifications of the current Vi vaccine. Studies in Balb/c mice demonstrated that GelSite-OAc™ was highly immunogenic, inducing a strong antigen-specific antibody response in a DOAc- and dose-dependent manner which was comparable to or higher than those induced by the licensed Vi vaccine. Importantly, the GelSite-OAc™ was shown to be fully protective in mice against lethal challenge with Salmonella Typhi. Furthermore, the GelSite-OAc™ demonstrated a boosting effect or memory response, exhibiting a >2-fold increase in antibody levels upon the second immunization with either GelSite-OAc™ or the Vi vaccine. This novel boosting effect is unique among polysaccharide antigens and potentially makes GelSite-OAc™ effective in people under 2 years old. Together these results suggest that the GelSite-OAc™ could be a highly effective vaccine against Salmonella Typhi.

Heterovalent Glycodendrimers as Epitope Carriers for Antitumor Synthetic Vaccines

The large majority of TACA-based (TACA=Tumor-Associated Carbohydrate Antigens) antitumor vaccines target only one carbohydrate antigen, thereby often resulting in the incomplete destruction of cancer cells. However, the morphological heterogeneity of the tumor glycocalix, which is in constant evolution during malignant transformation, is a crucial point to consider in the design of vaccine candidates. In this paper, an efficient synthetic strategy based on orthogonal chemoselective ligations to prepare fully synthetic glycosylated cyclopeptide scaffolds grafted with both Tn and TF antigen analogues is reported. To evaluate their ability to be recognized as tumor antigens, direct interaction ELISA assays have been performed with the anti-Tn monoclonal antibody 9A7. Although both heterovalent structures showed binding capacities with 9A7, the presence of the second TF epitope did not interfere with the recognition of Tn except in one epitope arrangement. This heterovalent glycosylated structure thus represents an attractive epitope carrier to be further functionalized with T-cell peptide epitopes.

A glycosylated recombinant subunit candidate vaccine consisting of Ehrlichia ruminantium major antigenic protein1 induces specific humoral and Th1 type cell responses in sheep

Heartwater, or cowdriosis, is a tick-borne disease of domestic and wild ruminants that is endemic in the Caribbean and sub-Saharan Africa. The disease is caused by an intracellular pathogen, Ehrlichia ruminantium and may be fatal within days of the onset of clinical signs with mortality rates of up to 90% in susceptible hosts. Due to the presence of competent tick vectors in North America, there is substantial risk of introduction of heartwater with potentially devastating consequences to the domestic livestock industry. There is currently no reliable or safe vaccine for use globally. To develop a protective DIVA (differentiate infected from vaccinated animals) subunit vaccine for heartwater, we targeted the E. ruminantium immunodominant major antigenic protein1 (MAP1) with the hypothesis that MAP1 is a glycosylated protein and glycans contained in the antigenic protein are important epitope determinants. Using a eukaryotic recombinant baculovirus expression system, we expressed and characterized, for the first time, a glycoform profile of MAP1 of two Caribbean E. ruminantium isolates, Antigua and Gardel. We have shown that the 37–38 kDa protein corresponded to a glycosylated form of the MAP1 protein, whereas the 31–32 kDa molecular weight band represented the non-glycosylated form of the protein frequently reported in scientific literature. Three groups of sheep (n = 3–6) were vaccinated with increasing doses of a bivalent (Antigua and Gardel MAP1) rMAP1 vaccine cocktail formulation with montanide ISA25 as an adjuvant. The glycosylated recombinant subunit vaccine induced E. ruminantium-specific humoral and Th1 type T cell responses, which are critical for controlling intracellular pathogens, including E. ruminantium, in infected hosts. These results provide an important basis for development of a subunit vaccine as a novel strategy to protect susceptible livestock against heartwater in non-endemic and endemic areas.

Recombinant Botulinum Neurotoxin Hc Subunit (BoNT Hc) and Catalytically Inactive Clostridium botulinum Holoproteins (ciBoNT HPs) as Vaccine Candidates for the Prevention of Botulism

There are few available medical countermeasures against botulism and the discontinuation of the pentavalent botulinum toxoid vaccine by the Centers for Disease Control and Prevention in 2011 has resulted in the need for a safe and effective prophylactic alternative. Advances in genetic engineering have resulted in subsequent vaccine efforts being primarily focused on the production of highly purified recombinant protein antigens representing one or more domains of the botulinum neurotoxin. Recombinant subunit vaccines based on the carboxy one-third of the toxin (Hc) developed in our lab against serotypes A-F have been shown to be safe and effective. However, in response to the identification of an ever increasing number of BoNT subtypes with significant amino acid heterogeneity, we have developed catalytically inactive BoNT holoproteins (ciBoNT HPs) in an attempt to elicit greater protective immunity to address these toxin variants. Here we report the production of ciBoNT/B1 HP, ciBoNT/C1 HP, ciBoNT/E1 HP and ciBoNT/F1 HP and compare the immunological and protective abilities of ciBoNT HPs and BoNT/A Hc, BoNT/B Hc, BoNT/C Hc, BoNT/E Hc and BoNT/F Hc vaccines when challenged with homologous and heterologous toxins. Our results suggest the ciBoNT HP vaccines exhibit superior potency after single vaccinations but multiple vaccinations with BoNT/Hc antigens resulted in increased survival rates at the toxin challenge levels used.

Addition of αGal HyperAcute™ technology to recombinant avian influenza vaccines induces strong low-dose antibody responses

Highly pathogenic avian influenza represents a severe public health threat. Over the last decade, the demand for highly efficacious vaccines against avian influenza viruses has grown, especially after the 2013 H7N9 outbreak in China that resulted in over 600 human cases with over 200 deaths. Currently, there are several H5N1 and H7N9 influenza vaccines in clinical trials, all of which employ traditional oil-in-water adjuvants due to the poor immunogenicity of avian influenza virus antigens. In this study, we developed potent recombinant avian influenza vaccine candidates using HyperAcute^™ Technology, which takes advantage of naturally-acquired anti-αGal immunity in humans. We successfully generated αGal-positive recombinant protein and virus-like particle vaccine candidates of H5N1 and H7N9 influenza strains using either biological or our novel CarboLink chemical αGal modification techniques. Strikingly, two doses of 100 ng αGal-modified vaccine, with no traditional adjuvant, was able to induce a much stronger humoral response in αGT BALB/c knockout mice (the only experimental system readily available for testing αGal in vivo) than unmodified vaccines even at 10-fold higher dose (1000 ng/dose). Our data strongly suggest that αGal modification significantly enhances the humoral immunogenicity of the recombinant influenza vaccine candidates. Use of αGal HyperAcute^™ technology allows significant dose-sparing while retaining desired immunogenicity. Our success in the development of highly potent H5N1 and H7N9 vaccine candidates demonstrated the potential of αGal HyperAcute^™ technology for the development of vaccines against other infectious diseases.

Vaccine technologies: From whole organisms to rationally designed protein assemblies

Vaccines have been the single most significant advancement in public health, preventing morbidity and mortality in millions of people annually. Vaccine development has traditionally focused on whole organism vaccines, either live attenuated or inactivated vaccines. While successful for many different infectious diseases whole organisms are expensive to produce, require culture of the infectious agent, and have the potential to cause vaccine associated disease in hosts. With advancing technology and a desire to develop safe, cost effective vaccine candidates, the field began to focus on the development of recombinantly expressed antigens known as subunit vaccines. While more tolerable, subunit vaccines tend to be less immunogenic. Attempts have been made to increase immunogenicity with the addition of adjuvants, either immunostimulatory molecules or an antigen delivery system that increases immune responses to vaccines. An area of extreme interest has been the application of nanotechnology to vaccine development, which allows for antigens to be expressed on a particulate delivery system. One of the most exciting examples of nanovaccines are rationally designed protein nanoparticles. These nanoparticles use some of the basic tenants of structural biology, biophysical chemistry, and vaccinology to develop protective, safe, and easily manufactured vaccines. Rationally developed nanoparticle vaccines are one of the most promising candidates for the future of vaccine development.

Thermoresponsive Polymer Nanoparticles Co-deliver RSV F Trimers with a TLR-7/8 Adjuvant

Structure-based vaccine design has been used to develop immunogens that display conserved neutralization sites on pathogens such as HIV-1, respiratory syncytial virus (RSV), and influenza. Improving the immunogenicity of these designed immunogens with adjuvants will require formulations that do not alter protein antigenicity. Here, we show that nanoparticle-forming thermoresponsive polymers (TRP) allow for co-delivery of RSV fusion (F) protein trimers with Toll-like receptor 7 and 8 agonists (TLR-7/8a) to enhance protective immunity. Although primary amine conjugation of TLR-7/8a to F trimers severely disrupted the recognition of critical neutralizing epitopes, F trimers site-selectively coupled to TRP nanoparticles retained appropriate antigenicity and elicited high titers of prefusion-specific, TH1 isotype anti-RSV F antibodies following vaccination. Moreover, coupling F trimers to TRP delivering TLR-7/8a resulted in ∼3-fold higher binding and neutralizing antibody titers than soluble F trimers admixed with TLR-7/8a and conferred protection from intranasal RSV challenge. Overall, these data show that TRP nanoparticles may provide a broadly applicable platform for eliciting neutralizing antibodies to structure-dependent epitopes on RSV, influenza, HIV-1, or other pathogens.

Vaccine manufacturing and technology: from biotechnological platforms to syntethic epitopes, current viepoint

THE PURPOSES

The Purposes: the review take into account short history of vaccination practice and development of vaccine technology.

METHODS

In the review we include data from several monographs about manufacturing of vaccines published by authors from such companies as Merck & Co; Sanofi Pasteur; Dynavax Europe/Rhein Biotech GmbH; Latham Biopharm Group; Aridis Pharmaceuticals LLC; Genentech; Amgen; Shamir Biologics LLC; Biopharm Services US; Novartis Pharma AG, аnd several research centers: Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research; Purdue University, West Lafayette, IN, US; Department of Pharmaceutical Chemistry, Univ. Of Kansas; Max Planck Institute for dynamics of Complex Technical Systems; Fraunhofer USA Center for Molecular Biotechnology; US Dep. of Agriculture Animal and Plant Health Inspection Service, etc.

RESULTS

In historic literature there are data about inoculation practices in antique China, Persia, India, Byzantium, native Americans, some African population. In modern immunology since the end of XIX century the vaccines were produced at the in vivo platforms - in animals (rabbits, mice, cows). Since 1931 due to E. Goodpasture' elaboration most virus vaccines were and are produced at the in ovo platform. In 1949 J.F. Enders elaborated large-scale polio virus production in the primary culture of monkey kidney cells in vitro. Up to day primary culture of chiken embrio fibroblasts are used to large-scale production of vaccine viruses of measles, mumps, rabies. Since 2000-th in Western countries most part of virus vaccines were began to produced via a cultivation in continuous tumor cell lines. The last technology is the most low cost for large-scale production of vaccines. We review several new biotechnological platforms for the production of the recombinant protein or virus-like particles as subunit vaccines: plant system, algae, mushrooms, insect cells, etc.

CONCLUSION

Beside of good purpose of vaccination - prophylactic of several infectious deseases, doctors must take into account possibility of inter-species transmission of unknown pathogens (retroviruses, prions, etc) from biotechnological platforms - animals, cell cultures - into human population, and don't ignore L.A. Zilber' theory of virus' etiology of cancer diseases.

Synthetic B-Cell Epitopes Eliciting Cross-Neutralizing Antibodies: Strategies for Future Dengue Vaccine

Dengue virus (DENV) is a major public health threat worldwide. A key element in protection from dengue fever is the neutralising antibody response. Anti-dengue IgG purified from DENV-2 infected human sera showed reactivity against several peptides when evaluated by ELISA and epitope extraction techniques. A multi-step computational approach predicted six antigenic regions within the E protein of DENV-2 that concur with the 6 epitopes identified by the combined ELISA and epitope extraction approach. The selected peptides representing B-cell epitopes were attached to a known dengue T-helper epitope and evaluated for their vaccine potency. Immunization of mice revealed two novel synthetic vaccine constructs that elicited good humoral immune responses and produced cross-reactive neutralising antibodies against DENV-1, 2 and 3. The findings indicate new directions for epitope mapping and contribute towards the future development of multi-epitope based synthetic peptide vaccine.

B Cells Loaded with Synthetic Particulate Antigens: A Versatile Platform To Generate Antigen-Specific Helper T Cells for Cell Therapy

Adoptive cell therapy represents a promising approach for several chronic diseases. This study describes an innovative strategy for biofunctionalization of nanoparticles, allowing the generation of synthetic particulate antigens (SPAg). SPAg activate polyclonal B cells and vectorize noncognate proteins into their endosomes, generating highly efficient stimulators for ex vivo expansion of antigen-specific CD4+ T cells. This method also allows harnessing the ability of B cells to polarize CD4+ T cells into effectors or regulators.

Head-to-Head Comparison of Soluble vs. Qβ VLP Circumsporozoite Protein Vaccines Reveals Selective Enhancement of NANP Repeat Responses

Circumsporozoite protein (CSP) of Plasmodium falciparum is a promising malaria vaccine target. RTS,S, the most advanced malaria vaccine candidate consists of the central NANP repeat and carboxy-terminal region of CSP displayed on a hepatitis B virus-like particle (VLP). To build upon the success of RTS,S, we produced a near full-length Plasmodium falciparum CSP that also includes the conserved amino-terminal region of CSP. We recently showed that this soluble CSP, combined with a synthetic Toll-like-receptor-4 (TLR4) agonist in stable oil-in-water emulsion (GLA/SE), induces a potent and protective immune response in mice against transgenic parasite challenge. Here we have investigated whether the immunogenicity of soluble CSP could be further augmented by presentation on a VLP. Bacteriophage Qβ VLPs can be readily produced in E.coli, they have a diameter of 25 nm and contain packaged E. coli RNA which serves as a built in adjuvant through the activation of TLR7/8. CSP was chemically conjugated to Qβ and the CSP-Qβ vaccine immunogenicity and efficacy were compared to adjuvanted soluble CSP in the C57Bl/6 mouse model. When formulated with adjuvants lacking a TLR4 agonist (Alum, SE and Montanide) the Qβ-CSP induced higher anti-NANP repeat titers, higher levels of cytophilic IgG2b/c antibodies and a trend towards higher protection against transgenic parasite challenge as compared to soluble CSP formulated in the same adjuvant. The VLP and soluble CSP immunogenicity difference was most pronounced at low antigen dose, and within the CSP molecule, the titers against the NANP repeats were preferentially enhanced by Qβ presentation. While a TLR4 agonist enhanced the immunogenicity of soluble CSP to levels comparable to the VLP vaccine, the TLR4 agonist did not further improve the immunogenicity of the Qβ-CSP vaccine. The data presented here pave the way for further improvement in the Qβ conjugation chemistry and evaluation of both the Qβ-CSP and soluble CSP vaccines in the non-human primate model.

Structural and Functional Characterization of Anti-A33 Antibodies Reveal a Potent Cross-Species Orthopoxviruses Neutralizer

Vaccinia virus A33 is an extracellular enveloped virus (EEV)-specific type II membrane glycoprotein that is essential for efficient EEV formation and long-range viral spread within the host. A33 is a target for neutralizing antibody responses against EEV. In this study, we produced seven murine anti-A33 monoclonal antibodies (MAbs) by immunizing mice with live VACV, followed by boosting with the soluble A33 homodimeric ectodomain. Five A33 specific MAbs were capable of neutralizing EEV in the presence of complement. All MAbs bind to conformational epitopes on A33 but not to linear peptides. To identify the epitopes, we have adetermined the crystal structures of three representative neutralizing MAbs in complex with A33. We have further determined the binding kinetics for each of the three antibodies to wild-type A33, as well as to engineered A33 that contained single alanine substitutions within the epitopes of the three crystallized antibodies. While the Fab of both MAbs A2C7 and A20G2 binds to a single A33 subunit, the Fab from MAb A27D7 binds to both A33 subunits simultaneously. A27D7 binding is resistant to single alanine substitutions within the A33 epitope. A27D7 also demonstrated high-affinity binding with recombinant A33 protein that mimics other orthopoxvirus strains in the A27D7 epitope, such as ectromelia, monkeypox, and cowpox virus, suggesting that A27D7 is a potent cross-neutralizer. Finally, we confirmed that A27D7 protects mice against a lethal challenge with ectromelia virus.

Programming the composition of polymer blend particles for controlled immunity towards individual protein antigens

In order for a more precise control over the quality and quantity of immune responses stimulated by synthetic particle-based vaccines, it is critical to control the colloidal stability of particles and the release of protein antigens in both extracellular space and intracellular compartments. Different proteins exhibit different sizes, charges and solubilities. This study focused on modulating the release and colloidal stability of proteins with varied isoelectric points. A polymer particle delivery platform made from the blend of three polymers, poly(lactic-co-glycolic acid) (PLGA) and two random pH-sensitive copolymers, were developed. Our study demonstrated its programmability with respective to individual proteins. We showed the colloidal stability of particles at neutral environment and the release of each individual protein at different pH environments were dependent on the ratio of two charge polymers. Subsequently, two antigenic proteins, ovalbumin (OVA) and Type 2 Herpes Simplex Virus (HSV-2) glycoprotein D (gD) protein, were incorporated into particles with systematically varied compositions. We demonstrated that the level of in vitro CD8(+) T cell and in vivo immune responses were dependent on the ratio of two charged polymers, which correlated well with the release of proteins. This study provided a promising design framework of pH-responsive synthetic vaccines for protein antigens of interest.

IMPIPS: the immune protection-inducing protein structure concept in the search for steric-electron and topochemical principles for complete fully-protective chemically synthesised vaccine development

Determining immune protection-inducing protein structures (IMPIPS) involves defining the stereo-electron and topochemical characteristics which are essential in MHC-p-TCR complex formation. Modified high activity binding peptides (mHABP) were thus synthesised to produce a large panel of IMPIPS measuring 26.5 ±3.5Å between the farthest atoms fitting into Pockets 1 to 9 of HLA-DRβ1* structures. They displayed a polyproline II-like (PPII_L) structure with their backbone O and N atoms orientated to establish H-bonds with specific residues from HLA-DRβ1*-peptide binding regions (PBR). Residues having specific charge and gauche⁺ orientation regarding p3χ1, p5χ2, and p7χ1 angles determined appropriate rotamer orientation for perfectly fitting into the TCR to induce an appropriate immune response. Immunological assays in Aotus monkeys involving IMPIPS mixtures led to promising results; taken together with the aforementioned physicochemical principles, non-interfering, long-lasting, protection-inducing, multi-epitope, multistage, minimal subunit-based chemically-synthesised peptides can be designed against diseases scourging humankind.

Gold Nanoparticles as Carriers for Synthetic Glycoconjugate Vaccines

Recent advances in the preparation and characterization of metal core-based nanoparticles have opened the way to their exploration as carriers for carbohydrate-based vaccines. Here we describe the protocols for the preparation and characterization of water dispersible gold nanoparticles (1-3 nm gold diameter) as carriers for carbohydrate antigens. We mainly refer to the protocols we used for the preparation of gold glyconanoparticles as carrier for an S. pneumoniae carbohydrate-antigen. The high number of ligands at the gold nanoparticles surface and the easiness of their one-pot preparation make these biocompatible nanomaterials an attractive tool for glyco-scientists.