Mammalian cell expressed recombinant trimeric spike protein is a potent vaccine antigen and confers near-complete protection against SARS-CoV-2 infection in Hamster.

Numerous vaccine candidates have emerged in the fight against SARS-CoV-2, yet the challenges posed by viral evolution and the evasion of vaccine-induced immunity persist. The development of broadly protective vaccines is essential in countering the threat posed by variants of concern (VoC) capable of eluding existing vaccine defenses. Among the diverse SARS-CoV-2 vaccine candidates, detailed characterization of those based on the expression of the entire spike protein in mammalian cells have been limited. In our study, we engineered a recombinant prefusion-stabilized trimeric spike protein antigen, IMT-CVAX, encoded by the IMT-C20 gene. This antigen was expressed utilizing a suspension mammalian cell line (CHO-S). The establishment of a stable cell line expressing IMT-CVAX involved the integration of the gene into the CHO genome, followed by the expression, purification, and characterization of the protein. To gauge the vaccine potential of adjuvanted IMT-CVAX, we conducted assessments in small animals. Analyses of blood collected from immunized animals included measurements of anti-spike IgG, SARS-CoV-2 neutralization, and responses from GC-B and Tfh cells. Furthermore, the protective efficacy of IMT-CVAX was evaluated using a Hamster challenge model. Our findings indicate that adjuvanted IMT-CVAX elicits an excellent immune response in both mice and hamsters. Notably, sera from animals immunized with IMT-CVAX effectively neutralize a diverse range of SARS-CoV-2 variants. Moreover, IMT-CVAX immunization conferred complete protection to hamsters against SARS-CoV-2 infection. In hACE2 transgenic mice, IMT-CVAX vaccination induced a robust response from GC-B and Tfh cells. Based on our preclinical model assessments, adjuvanted IMT-CVAX emerges as a highly efficacious vaccine candidate. This protein-subunit-based vaccine exhibits promise for clinical development, offering an affordable solution for both primary and heterologous immunization against SARS-CoV-2 variants.

Evaluation of physicochemical and functional similarity of a new CHO derived anti-EGFR antibody P-mAb to its reference medicinal product.

Epidermal growth factor receptor (EGFR) is the primary target for the treatment of colorectal cancer, the third most diagnosed cancer worldwide. In recent years, regulatory changes have facilitated the approval of biosimilars aimed to bring more access to biologics to patients. However, it has also expended the requirements of non-clinical characterisation data using state-of-the-art and orthogonal methodologies to demonstrate similarity between proposed biologic and its reference medicinal product (RMP). The current study was aimed to develop a stable CHO-S cell line producing panitumumab biosimilar candidate, P-mAb, a fully human IgG2 anti-EGFR monoclonal antibody and assess its physicochemical and functional similarity with RMP, Vectibix. The single-cell clone from stably transfected CHO-S cell pools was used for the production of P-mAb. This was followed by purification and comparative physicochemical and biological characterisation of P-mAb and RMP using SDS-PAGE, LC/MS, MALDI, MS/MS, CD spectrometry, DSF, SAXS, ITF, MTT assay and binding affinity. SAXS and MST assays are being used for first time in biosimilarity analysis of therapeutic monoclonal antibody. The results of structural and functional analysis of anti-EGFR P-mAb, produced by stable CHO-S cell line revealed high similarity between P-mAb and RMP, vectibix, thus providing the scientific basis of its potential for therapeutic applications.

Translating Treg Therapy for Inflammatory Bowel Disease in Humanized Mice.

Crohn's disease and ulcerative colitis, two major forms of inflammatory bowel disease (IBD) in humans, afflicted in genetically predisposed individuals due to dysregulated immune response directed against constituents of gut flora. The defective immune responses mounted against the regulatory mechanisms amplify and maintain the IBD-induced mucosal inflammation. Therefore, restoring the balance between inflammatory and anti-inflammatory immunepathways in the gut may contribute to halting the IBD-associated tissue-damaging immune response. Phenotypic and functional characterization of various immune-suppressive T cells (regulatory T cells; Tregs) over the last decade has been used to optimize the procedures for in vitro expansion of these cells for developing therapeutic interventional strategies. In this paper, we review the mechanisms of action and functional importance of Tregs during the pathogenesis of IBD and modulating the disease induced inflammation as well as role of mouse models including humanized mice repopulated with the human immune system (HIS) to study the IBD. "Humanized" mouse models provide new tools to analyze human Treg ontogeny, immunobiology, and therapy and the role of Tregs in developing interventional strategies against IBD. Overall, humanized mouse models replicate the human conditions and prove a viable tool to study molecular functions of human Tregs to harness their therapeutic potential.

Structural and immunological characterization of E. coli derived recombinant CRM197 protein used as carrier in conjugate vaccines.

It is established that the immunogenicity of polysaccharides is enhanced by coupling them to carrier proteins. Cross reacting material (CRM197), a nontoxic variant of diphtheria toxin (DT) is widely used carrier protein for polysaccharide conjugate vaccines. Conventionally, CRM197 is isolated by fermentation of Corynebacterium diphtheriae C7 (ß197) cultures, which often suffers from low yield. Recently, several recombinant approaches have been reported with robust processes and higher yields, which will improve the affordability of CRM197-based vaccines. Vaccine manufacturers require detailed analytical information to ensure that the CRM197 meets quality standards and regulatory requirements. In the present manuscript we have described detailed structural characteristics of Escherichia coli based recombinant CRM197 (rCRM197) carrier protein. The crystal structure of the E. coli based rCRM197 was found to be identical with the reported crystal structure of the C7 CRM197 produced in C. diphtheriae C7 strain (Protein Data Bank (PDB) ID: 4EA0). The crystal structure of rCRM197 was determined at 2.3 Å resolution and structure was submitted to the PDB with accession number ID 5I82. This is the first report of a crystal structure of E. coli derived recombinant CRM197 carrier protein. Furthermore, the rCRM197 was conjugated to Vi polysaccharide to generate Typhoid conjugate vaccine (Vi-rCRM197) and its immunogenicity was evaluated in Balb/C Mice. The Vi-rCRM197 conjugate vaccine was found to generate strong primary α-Vi antibody response and also showed a booster response after subsequent vaccination in mice. Overall data suggest that E. coli based recombinant CRM197 exhibits structural and immunological similarity with the C7 CRM197 and can be used as a carrier protein in conjugate vaccine development.

Analytical Comparability Assessments of 5 Recombinant CRM197 Proteins From Different Manufacturers and Expression Systems.

Cross-reacting material 197 (CRM197), a single amino acid mutant of diphtheria toxoid, is a commonly used carrier protein in commercial polysaccharide protein conjugate vaccines. In this study, CRM197 proteins from 3 different expression systems and 5 different manufacturers were obtained for an analytical comparability assessment using a wide variety of physicochemical and in vitro antigenic binding assays. A comprehensive analysis of the 5 CRM197 molecules demonstrate that recombinant CRM197's expressed in heterologous systems (Escherichia coli and Pseudomonas fluorescens) are overall highly similar (if not better in some cases) to those expressed in the traditional system (Corynebacterium diphtheriae) in terms of primary sequence/post-translational modifications, higher order structural integrity, apparent solubility, physical stability profile (vs. pH and temperature), and in vitro antigenicity. These results are an encouraging step to demonstrate that recombinant CRM197 expressed in alternative sources have the potential to replace CRM197 expressed in C diphtheriae as a source of immunogenic carrier protein for lower cost polysaccharide conjugate vaccines. The physicochemical assays established in this work to monitor the key structural attributes of CRM197 should also prove useful as complementary characterization methods (to routine quality control assays) to support future process and formulation development of lower cost CRM197 carrier proteins for use in various conjugate vaccines.

Auto-Assembling Detoxified Staphylococcus aureus Alpha-Hemolysin Mimicking the Wild-Type Cytolytic Toxin.

Staphylococcus aureus alpha-hemolysin (Hla) assembles into heptameric pores on the host cell membrane, causing lysis, apoptosis, and junction disruption. Herein, we present the design of a newly engineered S. aureus alpha-toxin, HlaPSGS, which lacks the predicted membrane-spanning stem domain. This protein is able to form heptamers in aqueous solution in the absence of lipophilic substrata, and its structure, obtained by transmission electron microscopy and single-particle reconstruction analysis, resembles the cap of the wild-type cytolytic Hla pore. HlaPSGS was found to be impaired in binding to host cells and to its receptor ADAM10 and to lack hemolytic and cytotoxic activity. Immunological studies using human sera as well as sera from mice convalescent from S. aureus infection suggested that the heptameric conformation of HlaPSGS mimics epitopes exposed by the cytolytic Hla pore during infection. Finally, immunization with this newly engineered Hla generated high protective immunity against staphylococcal infection in mice. Overall, this study provides unprecedented data on the natural immune response against Hla and suggests that the heptameric HlaPSGS is a highly valuable vaccine candidate against S. aureus.

Vaccine composition formulated with a novel TLR7-dependent adjuvant induces high and broad protection against Staphylococcus aureus.

Both active and passive immunization strategies against Staphylococcus aureus have thus far failed to show efficacy in humans. With the attempt to develop an effective S. aureus vaccine, we selected five conserved antigens known to have different roles in S. aureus pathogenesis. They include the secreted factors α-hemolysin (Hla), ess extracellular A (EsxA), and ess extracellular B (EsxB) and the two surface proteins ferric hydroxamate uptake D2 and conserved staphylococcal antigen 1A. The combined vaccine antigens formulated with aluminum hydroxide induced antibodies with opsonophagocytic and functional activities and provided consistent protection in four mouse models when challenged with a panel of epidemiologically relevant S. aureus strains. The importance of antibodies in protection was demonstrated by passive transfer experiments. Furthermore, when formulated with a toll-like receptor 7-dependent (TLR7) agonist recently designed and developed in our laboratories (SMIP.7-10) adsorbed to alum, the five antigens provided close to 100% protection against four different staphylococcal strains. The new formulation induced not only high antibody titers but also a Th1 skewed immune response as judged by antibody isotype and cytokine profiles. In addition, low frequencies of IL-17-secreting T cells were also observed. Altogether, our data demonstrate that the rational selection of mixtures of conserved antigens combined with Th1/Th17 adjuvants can lead to promising vaccine formulations against S. aureus.

Structural and functional characterization of the Staphylococcus aureus virulence factor and vaccine candidate FhuD2.

Staphylococcus aureus is a human pathogen causing globally significant morbidity and mortality. The development of antibiotic resistance in S. aureus highlights the need for a preventive vaccine. In the present paper we explore the structure and function of FhuD2 (ferric-hydroxamate uptake D2), a staphylococcal surface lipoprotein mediating iron uptake during invasive infection, recently described as a promising vaccine candidate. Differential scanning fluorimetry and calorimetry studies revealed that FhuD2 is stabilized by hydroxamate siderophores. The FhuD2-ferrichrome interaction was of nanomolar affinity in surface plasmon resonance experiments and fully iron(III)-dependent. We determined the X-ray crystallographic structure of ligand-bound FhuD2 at 1.9 Å (1 Å=0.1 nm) resolution, revealing the bilobate fold of class III SBPs (solute-binding proteins). The ligand, ferrichrome, occupies a cleft between the FhuD2 N- and C-terminal lobes. Many FhuD2-siderophore interactions enable the specific recognition of ferrichrome. Biochemical data suggest that FhuD2 does not undergo significant conformational changes upon siderophore binding, supporting the hypothesis that the ligand-bound complex is essential for receptor engagement and uptake. Finally, immunizations with FhuD2 alone or FhuD2 formulated with hydroxamate siderophores were equally protective in a murine staphylococcal infection model, confirming the suitability and efficacy of apo-FhuD2 as a protective antigen, and suggesting that other class III SBPs might also be exploited as vaccine candidates.

Vaccines and antibiotic resistance.

Vaccines and antibiotics have significantly contributed to improve health and also to increase the longevity of human beings. The fast-acting effect of antibiotics makes them indispensable to treat infected patients. Likewise, when the causative agent of the infection is unknown and in cases of superinfections with different species of bacteria, antibiotics appear to be the only therapeutic option. On the contrary, vaccines are usually not efficacious in people already infected and their action is generally limited to a much narrowed range of pathogens. However, vaccines have contributed to the eradication of some of the most deadly infectious agents worldwide, can generate immunity to infections lasting for several years or life-long, and are able to induce herd immunity. Nonetheless, infectious diseases are still among the leading causes of morbidity and mortality worldwide. This is mainly owing to the emergence of bacterial resistance to antibiotics and the lack of efficacious medications to treat several other infectious diseases. Development of new vaccines appears to be a promising solution to these issues. Indeed, with the advent of new discovery approaches and adjuvants, today is possible to make vaccines virtually against every pathogen. In addition, while vaccine-resistant bacteria have never been reported, accumulating literature is providing evidence that vaccination can reduce the raise of antibiotic resistant strains by decreasing their use.

Staphylococcus aureus FhuD2 is involved in the early phase of staphylococcal dissemination and generates protective immunity in mice.

Iron availability plays an essential role in staphylococcal pathogenesis. We selected FhuD2, a lipoprotein involved in iron-hydroxamate uptake, as a novel vaccine candidate against Staphylococcus aureus. Unprecedented for staphylococcal lipoproteins, the protein was demonstrated to have a discrete, punctate localization on the bacterial surface. FhuD2 vaccination generated protective immunity against diverse clinical S. aureus isolates in murine infection models. Protection appeared to be associated with functional antibodies that were shown to mediate opsonophagocytosis, to be effective in passive transfer experiments, and to potentially block FhuD2-mediated siderophore uptake. Furthermore, the protein was found to be up-regulated in infected tissues and was required for staphylococcal dissemination and abscess formation. Herein we show that the staphylococcal iron-hydroxamate uptake system is important in invasive infection and functions as an efficacious vaccine target.

Genetic diversity of Mimosa pudica rhizobial symbionts in soils of French Guiana: investigating the origin and diversity of Burkholderia phymatum and other beta-rhizobia.

The genetic diversity of 221 Mimosa pudica bacterial symbionts trapped from eight soils from diverse environments in French Guiana was assessed by 16S rRNA PCR-RFLP, REP-PCR fingerprints, as well as by phylogenies of their 16S rRNA and recA housekeeping genes, and by their nifH, nodA and nodC symbiotic genes. Interestingly, we found a large diversity of beta-rhizobia, with Burkholderia phymatum and Burkholderia tuberum being the most frequent and diverse symbiotic species. Other species were also found, such as Burkholderia mimosarum, an unnamed Burkholderia species and, for the first time in South America, Cupriavidus taiwanensis. The sampling site had a strong influence on the diversity of the symbionts sampled, and the specific distributions of symbiotic populations between the soils were related to soil composition in some cases. Some alpha-rhizobial strains taxonomically close to Rhizobium endophyticum were also trapped in one soil, and these carried two copies of the nodA gene, a feature not previously reported. Phylogenies of nodA, nodC and nifH genes showed a monophyly of symbiotic genes for beta-rhizobia isolated from Mimosa spp., indicative of a long history of interaction between beta-rhizobia and Mimosa species. Based on their symbiotic gene phylogenies and legume hosts, B. tuberum was shown to contain two large biovars: one specific to the mimosoid genus Mimosa and one to South African papilionoid legumes.

Designing the next generation of vaccines for global public health.

Vaccine research and development are experiencing a renaissance of interest from the global scientific community. There are four major reasons for this: (1) the lack of efficacious treatment for many devastating infections; (2) the emergence of multidrug resistant bacteria; (3) the need for improving the safety of the more traditional licensed vaccines; and finally, (4) the great promise for innovative vaccine design and research with convergence of omics sciences, such as genomics, proteomics, immunomics, and vaccinology. Our first project based on omics was initiated in 2000 and was termed reverse vaccinology. At that time, antigen identification was mainly based on bioinformatic analysis of a singular genome. Since then, omics-guided approaches have been applied to its full potential in several proof-of-concept studies in the industry, with the first reverse vaccinology-derived vaccine now in late stage clinical trials and several vaccines developed by omics in preclinical studies. In the meantime, vaccine discovery and development has been further improved with the support of proteomics, functional genomics, comparative genomics, structural biology, and most recently vaccinomics. We illustrate in this review how omics biotechnologies and integrative biology are expected to accelerate the identification of vaccine candidates against difficult pathogens for which traditional vaccine development has thus far been failing, and how research will provide safer vaccines and improved formulations for immunocompromised patients in the near future. Finally, we present a discussion to situate omics-guided rational vaccine design in the broader context of global public health and how it can benefit citizens in both developed and developing countries.

Rhizobium-mediated induction of phenolics and plant growth promotion in rice (Oryza sativa L.).

Qualitative and quantitative estimation of phenolic compounds was done through reverse phase-high performance liquid chromatography (RP-HPLC) from different parts (leaf, stem, and root) of rice plants after inoculation with two rhizobial strains, RRE6 (Rhizobium leguminosarum bv. phaseoli) and ANU 843 (R. leguminosarum bv. trifolii) and infection by Rhizoctonia solani. On the basis of their retention time, the major phenolic acids detected in HPLC analysis were gallic, tannic, ferulic, and cinnamic acids. Furthermore, in all Rhizobium-inoculated rice plants, synthesis of phenolic compounds was more consistently enhanced than in control (uninoculated plants), where the maximum accumulation of phenolic compounds was observed in plants inoculated with RRE6 and infection with R. solani. Under pathogenic stress, RRE6 performed better because a relatively higher amount of phenolics was induced as compared with plants treated with ANU 843. Phenolic acids mediate induced systemic resistance and provide bioprotection to plants during pathogenic stresses. In addition, both rhizobial strains promote growth and productivity of rice plants in greenhouse conditions. This report on Rhizobium-mediated defense responses and growth promotion of nonlegume (such as rice) provides a novel paradigm of symbiotic plant-microbe interaction.

Isolation and identification of natural endophytic rhizobia from rice (Oryza sativa L.) through rDNA PCR-RFLP and sequence analysis.

Three novel endophytic rhizobial strains (RRE3, RRE5, and RRE6) were isolated from naturally growing surface-sterilized rice roots. These isolates had the ability to nodulate common bean (Phaseolus vulgaris). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing of 16S rDNA of these isolates revealed that RRE3 and RRE5 are phylogenetically very close to Burkholderia cepacia complex, whereas RRE6 has affinity with Rhizobium leguminosarum bv. phaseoli. Plant infection test using gusA reporter gene-tagged construct of these isolates indicated that bacterial cells can go inside and colonize the rice root interiors. A significant increase in biomass and grain yield was also recorded in greenhouse-grown rice plants inoculated with these isolates.

Isolation and identification of natural endophytic rhizobia from rice (Oryza sativa L.) through rDNA PCR-RFLP and sequence analysis.

Three novel endophytic rhizobial strains (RRE3, RRE5, and RRE6) were isolated from naturally growing surface sterilized rice roots. These isolates had the ability to nodulate common bean (Phaseolus vulgaris). Polymerase chain reaction-restriction fragment length polymorphism and sequencing of 16S rDNA of these isolates revealed that RRE3 and RRE5 are phylogenetically very close to Burkholderia cepacia complex, whereas RRE6 has affinity with Rhizobium leguminosarum bv. phaseoli. Plant infection test using gusA reporter gene tagged construct of these isolates indicated that bacterial cells can go inside and colonize the rice root interiors. A significant increase in biomass and grain yield was also recorded in greenhouse-grown rice plants inoculated with these isolates.