Recombinant protein vaccines, a proven approach against coronavirus pandemics

A meta-analysis on the immunogenicity of prototype, monovalent-adapted and bivalent vaccines against SARS-CoV-2 wildtype, Omicron BA.1 and Omicron BA.4/5 in healthy adults

Although COVID-19 is no longer classified as the first public health emergency, nevertheless, it still presents a serious menace to the health of the global population. Consequently, the development of COVID-19 vaccines possessing an optimal composition that can elicit broad-spectrum neutralizing responses against various SARS-CoV-2 variants is crucial. This meta-analysis aimed to compare the immunogenicity of prototype, monovalent-adapted, and bivalent COVID-19 vaccines against prototype SARS-CoV-2, Omicron BA.1 variant, and Omicron BA.4/5 subvariant in healthy adults. We utilized 4 medical databases to retrieve original studies and employed the fixed effect model to estimate pooled neutralization titers. A total of 12 studies concerning 4581 subjects were included in the meta-analysis. We found that participants who received prototype, monovalent-adapted, and bivalent vaccines as a second booster significantly developed neutralizing antibody (nAb) titers against prototype SARS-CoV-2, Omicron BA.1 variant, and Omicron BA.4/5 subvariant, with monovalent-adapted and bivalent vaccines exhibiting a higher increment. Furthermore, the bivalent(Prototype/Omicron BA.1) recombinant protein vaccine exhibited the highest increment in neutralization titers(MD = 1.95; 95 %CI:0.78-3.12; p < 0.01) against the prototype SARS-CoV-2 and Omicron BA.4/5 subvariant compared to the other vaccine regimens. Interestingly, only individuals who received the monovalent (Omicron BA.1)-adapted mRNA vaccine as a second booster showed the highest increase in neutralization titers (MD:1.37; 95 %CI:0.50-2.24; p < 0.01) against the Omicron BA.1 variant compared to the other vaccine regimens. These findings showed that bivalent recombinant protein vaccines seem more immunogenic than bivalent mRNA vaccines, and bivalent vaccines might not be superior immunogens for induced strong protective immune responses compared to monovalent-adapted vaccines.

Synthetic and Biogenic Materials for Oral Delivery of Biologics: From Bench to Bedside

The development of nucleic acid and protein drugs for oral delivery has lagged behind their production for conventional nonoral routes. Over the past decade, the evolution of DNA- and RNA-based technologies combined with the innovation of state-of-the-art delivery vehicles for nucleic acids has brought rapid advancements to the biopharmaceutical field. Nucleic acid therapies have the potential to achieve long-lasting effects, or even cures, by inhibiting or editing genes, which is not possible with conventional small-molecule drugs. However, challenges and limitations must be addressed before these therapies can provide cures for chronic conditions and rare diseases, rather than only offering temporary relief. Nucleic acids and proteins face premature degradation in the acidic, enzyme-rich stomach environment and are rapidly cleared by the liver. To overcome these challenges, various delivery vehicles have been developed to transport therapeutic compounds to the intestines, where the active compounds are released and gut microbiota and mucosal immune system also play an important role. This review provides a comprehensive overview of the promises and pitfalls associated with the oral route of administration of biologics, current delivery systems, applications of orally delivered therapeutics, and the challenges and considerations for translation of nucleic acid and protein therapeutics into clinical practice.

Beyond the Pandemic Era: Recent Advances and Efficacy of SARS-CoV-2 Vaccines Against Emerging Variants of Concern

Vaccination has been instrumental in curbing the transmission of SARS-CoV-2 and mitigating the severity of clinical manifestations associated with COVID-19. Numerous COVID-19 vaccines have been developed to this effect, including BioNTech-Pfizer and Moderna's mRNA vaccines, as well as adenovirus vector-based vaccines such as Oxford-AstraZeneca. However, the emergence of new variants and subvariants of SARS-CoV-2, characterized by enhanced transmissibility and immune evasion, poses significant challenges to the efficacy of current vaccination strategies. In this review, we aim to comprehensively outline the landscape of emerging SARS-CoV-2 variants of concern (VOCs) and sub-lineages that have recently surfaced in the post-pandemic years. We assess the effectiveness of existing vaccines, including their booster doses, against these emerging variants and subvariants, such as BA.2-derived sub-lineages, XBB sub-lineages, and BA.2.86 (Pirola). Furthermore, we discuss the latest advancements in vaccine technology, including multivalent and pan-coronavirus approaches, along with the development of several next-generation coronavirus vaccines, such as exosome-based, virus-like particle (VLP), mucosal, and nanomaterial-based vaccines. Finally, we highlight the key challenges and critical areas for future research to address the evolving threat of SARS-CoV-2 subvariants and to develop strategies for combating the emergence of new viral threats, thereby improving preparedness for future pandemics.

COVID-19 vaccination and pregnancy-induced hypertension risk in women undergoing assisted reproduction

STUDY QUESTION

Does COVID-19 vaccination affect the risk of pregnancy-induced hypertension (PIH) in women undergoing ARTs, and does this risk differ based on vaccine type (inactivated vs recombinant) and timing relative to embryo transfer?

SUMMARY ANSWER

Women who received inactivated COVID-19 vaccines before undergoing ART had a significantly increased risk of developing PIH, particularly when vaccinated with two or more doses or when embryo transfer occurred within 1 month of vaccination.

WHAT IS KNOWN ALREADY

COVID-19 vaccination during pregnancy reduces the risk of severe COVID-19 illness with no significant safety concerns for the mother or fetus. PIH is a common complication in ART pregnancies, particularly in older women and those with higher BMI, but the effects of different COVID-19 vaccine types on PIH risk in ART pregnancies remain unclear.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study analyzing 3911 women undergoing ART after receiving COVID-19 vaccines. The study period spanned from 1 December 2020 to 30 September 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were categorized based on COVID-19 vaccination status, vaccine type (inactivated vs recombinant), and the timing of vaccination relative to embryo transfer. The primary outcome was the development of PIH. Multivariate robust Poisson regression was used to assess the association between vaccination and PIH, while subgroup analyses explored the risk across variables like age, BMI, and embryo transfer type.

MAIN RESULTS AND THE ROLE OF CHANCE

Women vaccinated with an inactivated COVID-19 vaccine prior to embryo transfer had a significantly higher incidence of PIH compared to unvaccinated counterparts (relative risk [RR] = 1.45; 95% CI 1.10-1.92; P = 0.009). In contrast, recombinant vaccines did not show a significant association with increased PIH risk (RR = 1.19; 95% CI 0.69-2.05; P = 0.537). The risk was particularly pronounced among women receiving two or more doses of the inactivated vaccines and those who had embryo transfers within 1 month of vaccination. Subgroup analyses showed elevated PIH risk in women aged ≥30 years old, those with BMI ≥22 kg/m2, individuals with secondary infertility, and those undergoing cleavage-stage or fresh embryo transfers.

LIMITATIONS, REASONS FOR CAUTION

The study's retrospective design limits causal inference. The sample is from a single ethnic background, and familial hypertension history was not available, potentially introducing residual confounding.

WIDER IMPLICATIONS OF THE FINDINGS

The study suggests that the type and timing of COVID-19 vaccination may influence PIH risk in ART pregnancies. These findings underscore the need for careful consideration of vaccination type and timing in ART protocols and highlight the importance of further prospective studies to validate these results before influencing clinical decision-making.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Hunan High-Level Talent Aggregation Project [2022RC4007]; the National Natural Science Foundation of China [72004148]; the Hunan Provincial Enterprise Joint Fund [2024JJ9093]; the Hunan Provincial Grant for Innovative Province Construction [2019SK4012]; the Deutschlandstipendium of the Charite; the non-restricted research grant of Boehringer Ingelheim Ltd.; and the Research Grant of CITIC-Xiangya [YNXM-202304, 202217]. The authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Enhanced Humoral and Cellular Immune Responses Elicited by Salmonella Flagellin-Adjuvanted SARS-CoV-2 S1 Subunit Vaccine

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, has been spreading and changing globally. Adjuvant-based vaccines can improve vaccine protection by enhancing the immune response. Bacterial flagellin is a potent adjuvant and promotes protective immune responses. Here, we successfully expressed and purified the S1 subunit of SARS-CoV-2. The adjuvanticity of flagellin (FliC) of Salmonella Typhimurium in mice was determined by combining it with the recombinant S1 subunit vaccine. FliC-adjuvanted S1 vaccine could induce significantly enhanced S1-specific Immunoglobulin G (IgG), IgG1 and IgG2a titers, SARS-CoV-2-neutralizing antibodies, and levels of Th1 type (TNF-α and IFN-γ) and Th2 type (Interleukin-5 (IL-5), IL-4, IL-10, and IL-13) cytokines in splenocytes compared with the S1 alone group. Additionally, the titers of S1-specific IgG antibodies in the FliC adjuvant group could maintain a high level for at least 2 months. These results indicated that the FliC-adjuvanted S1 subunit vaccine could trigger strong humoral and cellular immune responses, which could promote the ongoing development of COVID-19 vaccines.

Advancement insights in cancer vaccines: mechanisms, types, and clinical applications

Immunotherapy can treat cancer by boosting the immune system to mark and destroy cancer cells. Cancer vaccine is a promising therapeutic strategy in immunotherapy. Cancer vaccines are divided into four groups according to different preparation techniques: cell-based vaccine, virus-based vaccine, peptide-based vaccine, and nucleic acid-based vaccine. Cancer vaccines can be given with traditional treatments or another immunotherapy to give better results and overcome tumor resistance. The cancer vaccine is a promising immunotherapy that could stimulate the immune response to kill cancer cells and create immune surveillance. However, much work is still needed to identify neoantigens, optimize the vaccination platform, and develop combination therapy to improve the efficacy of immunotherapy. This review highlights the mechanism of action of cancer vaccines, the main four groups of cancer vaccines regarding their development, research progress, and clinical applications, and how to assess immune response following cancer vaccination.

A promising mRNA vaccine derived from the JN.1 spike protein confers protective immunity against multiple emerged Omicron variants

Despite the declared end of the COVID-19 pandemic, SARS-CoV-2 continues to evolve, with emerging JN.1-derived subvariants (e.g., KP.2, KP.3) compromising the efficacy of current XBB.1.5-based vaccines. To address this, we developed an mRNA vaccine encoding the full-length spike protein of JN.1, incorporating GSAS and 2P mutations and encapsulated in lipid nanoparticles (LNPs). The JN.1-mRNA vaccine elicited robust humoral and cellular immune responses in mice, including high JN.1-specific IgG titers, cross-neutralizing antibodies, and increased T follicular helper (Tfh) cells, germinal center (GC) B cells, and T cell cytokines. Importantly, immunity persisted for up to six months and induced RBD-specific long-lived plasma cells. We also compared the immune responses induced by homologous and heterologous vaccination regimens, and our results demonstrated that the heterologous regimen-combining JN.1-mRNA with a recombinant protein vaccine (RBDJN.1-HR)-induced stronger responses. These findings highlight the JN.1-mRNA vaccine constitutes an effective prophylactic approach against JN.1-related variants, as it induces potent neutralizing antibody responses across all tested lineages. This enhanced immunogenicity is expected to significantly reduce hospitalization rates and mitigate post-COVID complications associated with JN.1 and KP.3 infections. This study emphasizes the need for timely vaccine updates and the adaptability of mRNA vaccines in addressing emerging pathogens, providing a framework for combating future infectious diseases. Collectively, these results offer critical insights for vaccine design and public health strategies in response to emerging SARS-CoV-2 variants.

Immunogenic evaluation of LptD + LtgC as a bivalent vaccine candidate against Neisseria gonorrhoeae

BACKGROUND

Neisseria gonorrhoeae is an escalating global health threat due to increasing antimicrobial resistance. The emergence of multidrug-resistant (MDR) strains necessitates alternative prevention strategies. This study focused on the development of a bivalent vaccine formulation to address this challenge. Lipopolysaccharide transport protein D (LptD) and lytic transglycosylase C (LtgC) as two promising immunogenic targets were considered in this study.

METHODS

The ltgC and lptD genes of N. gonorrhoeae ATCC 19424 were amplified, then cloned into the pET-28a (+) vector, expressed in Escherichia coli BL21 (DE3), and purified using Ni-NTA affinity chromatography. Antigen-specific total IgG levels in serum of patients with gonorrhea were assessed using enzyme-linked immunosorbent assay (ELISA). Proteins were formulated with monophosphoryl lipid A (MPLA) adjuvant in three groups: LptD, LtgC, and a bivalent LptD + LtgC. One additional group received LptD with liposomal MPLA, along with control groups. Vaccine formulations were administered to BALB/c mice in three doses at two-week intervals. Total IgG, IgG1, IgG2a, and IgA levels in sera and vaginal samples were measured using ELISA. Moreover, serum bactericidal (SBA) and opsonophagocytic (OPA) assays were conducted.

RESULTS

The total IgG levels against both proteins were considerably higher in the patients' sera compared to healthy individuals. All vaccine formulations significantly increased total IgG levels in animal model. The LptD + liposomal MPLA group exhibited the highest specific IgG level, whereas the bivalent formulation group exhibited the highest long-term IgG level until the day 112, which also yielded the strongest total IgG response in the whole-cell ELISA. The IgG2a/ IgG1 ratio was greater than 1 in all vaccine regimens, indicating a Th1-polarized response. The LptD + liposomal MPLA formulation elicited the highest serum IgA levels, followed by the LptD + LtgC combination. In addition, the bivalent formulation achieved the highest SBA and OPA titers.

CONCLUSION

This study successfully developed and evaluated a recombinant bivalent vaccine against N. gonorrhoeae. This formulation exhibited the most potent immunogenicity, as evidenced by higher antibody levels and SBA and OPA titers than single-antigen formulations. The Th1-polarized immune response further highlights the vaccine's potential to elicit a protective immune profile. These findings suggest that this multi-antigen formulation can be a promising vaccine candidate against gonorrhea. However, more investigations are required to confirm the vaccine efficacy.

A SARS-CoV-2 mucosal nanovaccine based on assembly of maltodextrin, STING agonist and polyethyleneimine

SARS-CoV-2 has the characteristics of strong transmission with severe morbidity and mortality. Protein-based vaccines have the properties of specificity, effectiveness and safety against SARS-CoV-2. Receptor-binding domain (RBD) homotrimer affords high protection efficacy against stringent lethal viral challenge. Mucosal immunity could block the infection that first infect and replicate in the upper airway mucosa. Due to the physical barriers of the mucosa, mucosal vaccines necessitated appropriate adjuvants and delivery system. In the present study, maltodextrin, PEI and 2',3'-cGAMP acted as the mucosal adjuvants and RBD trimer as the antigen. A mucosal nanovaccine was prepared by assembly of adjuvants and the antigen to a nanoparticle. The vaccine elicited strong serum RBD-specific IgG and IgA response, and mild mucosal IgA and IgG response in the respiratory tract. It stimulated strong neutralizing antibody response and high ACE2-blocking activity in the sera. It promoted the RBD-specific CD4+ and CD8+ T cells secreting IFN-γ, IL-4 and IL-17 A. Moreover, it elicited durable RBD-specific memory T and B memory cell response, activated the T and B cells, enhanced the cytotoxic T cell killing effect, and promoted the maturation of DCs. These findings suggested the clinical potential of the vaccine to combat against SARS-CoV-2 infection.

Development of a novel bivalent vaccine candidate against hepatitis A virus and rotavirus using reverse vaccinology and immunoinformatics

The hepatitis A virus (HAV) and rotavirus are mainly transmitted through fecal-oral and person-to-person contact, and cause severe gastrointestinal complications and liver disease. This work used reverse vaccinology and immunoinformatic methods to create a novel bivalent vaccine against rotavirus and HAV. The amino acid sequences of HAV-rotavirus proteins (VP1 and VP8∗) were retrieved from the GenBank database. Various computational approaches were employed to predict highly conserved regions and the most immunogenic B-cell and T-cell epitopes of VP8 and VP1 of rotavirus and HAV proteins in both humans and BALB/c. Moreover, the predicted fusion protein was analyzed regarding primary and secondary structures and homology validation. In this study, we used two highly conserved peptide sequences of VP8 and VP1 of rotavirus and HAV that induce T and B cell immunogenicity. According to T-cell epitope prediction, this area comprises 2713 antigenic peptides for HLA class II and 30 HLA class I antigenic peptides, both of which are virtually entirely conserved in the Iranian population. In this study, validation as well as analysis of the secondary and three-dimensional structure of the VP8∗-rotavirus + AAY + HAV-VP1 fusion protein, with the aim of designing a multi-epitope vaccine with different receptors. TLR 3, 4 high immunogenic binding ability with immunological properties and interaction between multi-epitope target and TLR were predicted, and it is expected that the target fusion protein has stable antigenic potency and compatible half-life. The above is suggested as a universal vaccination program.

A Live-Cell Imaging-Based Fluorescent SARS-CoV-2 Neutralization Assay by Antibody-Mediated Blockage of Receptor Binding Domain-ACE2 Interaction

Neutralization assays have become an important tool since the beginning of the COVID-19 pandemic for testing vaccine responses and therapeutic antibodies as well as for monitoring humoral immunity to SARS-CoV-2 in epidemiological studies. The spike glycoprotein (S) present on the viral surface contains a receptor binding domain (RBD) that recognizes the angiotensin-converting enzyme 2 receptor (ACE2) in host cells, allowing virus entry. The gold standard for determining SARS-CoV-2 neutralizing antibodies is the plaque reduction neutralization test (PRNT), which relies on live-virus replication performed exclusively in biosafety level 3 (BSL-3) laboratories. Here, we report the development of a surrogate live-cell imaging-based fluorescent SARS-CoV-2 neutralization assay, applicable to BSL-1 or BSL-2 laboratories, by antibody-mediated blockage of the interaction between recombinant RBD with overexpressed ACE2 receptor in a genetically modified HEK 293T stable cell line. Our approach was able to detect neutralizing antibodies both in COVID-19-positive human serum samples and polyclonal equine formulations against SARS-CoV-2. This new cell-based surrogate neutralization assay represents a virus-free fluorescence imaging alternative to the reported approaches, which can be used to detect antibody-neutralizing capabilities toward SARS-CoV-2. This assay could also be extrapolated in the future to other established and emergent viral agents.

RBD-displaying OMV nanovaccine boosts immunity against SARS-CoV-2

BACKGROUND

Since the emergence of SARS-CoV-2, the causative agent of COVID-19, the global health landscape has confronted an unprecedented and formidable challenge. The SARS-CoV-2 receptor-binding domain (RBD) is a key antigen in vaccine design. However, its low immunogenicity has been a hurdle, resulting in the production of minimal anti-RBD antibodies even when combined with alum adjuvant. Outer membrane vesicles (OMVs), secreted by Gram-negative bacteria, are nanospherical structures that can display or deliver antigens while also providing adjuvant activity through pathogen-associated molecular patterns (PAMPs).

RESULTS

In this study, we utilized the SpyTag (ST)/SpyCatcher (SC) bioconjugation system to couple OMV and SARS-CoV-2 RBD in vitro. We successfully prepared a 'plug-and-display' nanovaccine OMV-RBD, which demonstrated good safety profiles and promoted the uptake of antigens by DCs and the maturation of BMDCs by activating TLR3 and NOD2 signaling pathways. Both intranasal and intramuscular immunization with OMV-RBD vaccine elicited robust antigen-specific humoral and cellular immune responses. Importantly, the induced antibodies effectively inhibited the binding of RBD to human angiotensin-converting enzyme 2 (hACE2) and neutralized SARS-CoV-2 pseudoviruses.

CONCLUSIONS

This vaccine platform offers an alternative strategy for developing recombinant subunit vaccines against SARS-CoV-2, potentially enhancing immune responses and improving vaccine efficacy.

Neutralizing antibody responses to three XBB protein vaccines in older adults

The ongoing COVID-19 pandemic has underscored the importance of strong immune defenses against emerging SARS-CoV-2 variants. While COVID-19 vaccines containing XBB subvariants have proven effective in neutralizing new SARS-CoV-2 variants, a gap remains in knowledge regarding neutralizing antibody responses in older adults aged >65 years against these newly emerged variants. This study was therefore undertaken to investigate and compare neutralizing antibody responses to three XBB-containing protein-based vaccines (trivalent XBB.1.5 vaccine, bivalent Omicron XBB vaccine, and tetravalent XBB.1 vaccine) head-to-head in 90 individuals aged >65 years. The results showed that all three XBB-containing vaccines substantially enhanced the neutralizing antibody response, with 100% of vaccinees having detectable antibody titers against ancestral D614G and variants BA.5, XBB.1.5, JN.1, KP.2, and KP.3 after booster immunization. Subsequent analysis indicated that the trivalent XBB.1.5 and tetravalent XBB.1 vaccines elicited higher levels of neutralizing antibodies compared to the bivalent Omicron XBB vaccine. The KP.2 and KP.3 variants displayed antibody resistance comparable to the JN.1 variant. Older adults produce similar neutralizing antibody responses to the vaccines regardless of their underlying medical conditions. These findings indicate that booster vaccination with XBB-containing vaccines can effectively elicit strong neutralizing responses against a number of SARS-CoV-2 variants in older adults over 65 years, which will help guide vaccine strategies in this elderly population.

Enzymatically Crafted Bacterial Cellulose Nanoparticles Functionalized With Antimicrobial Peptides: Toward Sustainable Antimicrobial Formulations

Although natural antimicrobial peptides (AMPs) are endowed with excellent antimicrobial properties, only a few of them have been successfully translated to the market so far. This is mainly due to their short half-life, to their high susceptibility to protease degradation, and to the lack of appropriate strategies for their efficient targeted delivery. Hence, the development of an effective system to deliver AMPs to the site of infection is urgent. The system here selected is represented by bacterial cellulose nanoparticles (BCNPs). Nanocellulose has recently emerged as one of the most promising "green" materials, attracting great attention due to its unique features, including biodegradability, sustainability, biocompatibility, and special physicochemical properties. To produce BCNPs, Komagataeibacter xylinus has been selected as host producing strain. Once obtained BC macrofibers, the production of BCNPs was set up by enzymatic hydrolysis using a commercial mixture of cellulases from Trichoderma reesei to develop a sustainable green biotechnological process. The storage stability of produced BCNPs has been also evaluated. Obtained BCNPs have been functionalized through non-covalent bindings with an antimicrobial peptide previously identified in human apolipoprotein B and found to be endowed with strong antimicrobial properties in in vitro analyses and with good biocompatibility profiles when analyzed on human skin cells. This opens interesting perspectives to the applicability of the developed system in several biotechnological fields.

Antibody Responses and the Vaccine Efficacy of Recombinant Glycosyltransferase and Nicastrin Against Schistosoma japonicum

Schistosomiasis is a neglected tropical disease and the second most common parasitic disease after malaria. While praziquantel remains the primary treatment, concerns about drug resistance highlight the urgent need for new drugs and effective vaccines to achieve sustainable control. Previous proteomic studies from our group revealed that the expression of Schistosoma japonicum glycosyltransferase and nicastrin as proteins was higher in single-sex males than mated males, suggesting their critical roles in parasite reproduction and their potential as vaccine candidates. In this study, bioinformatic tools were employed to analyze the structural and functional properties of these proteins, including their signal peptide regions, transmembrane domains, tertiary structures, and protein interaction networks. Recombinant forms of glycosyltransferase and nicastrin were expressed and purified, followed by immunization experiments in BALB/c mice. Immunized mice exhibited significantly elevated specific IgG antibody levels after three immunizations compared to adjuvant and PBS controls. Furthermore, immunization with recombinant glycosyltransferase and nicastrin significantly reduced the reproductive capacity of female worms and liver egg burden, though egg hatchability and adult worm survival were unaffected. These findings demonstrate that recombinant glycosyltransferase and nicastrin are immunogenic and reduce female worm fecundity, supporting their potential as vaccine candidates against schistosomiasis.

Advancing novel veterinary vaccines: From comprehensive antigen and adjuvant design to preparation process optimization

Vaccination stands as the paramount and cost-effective strategy for the prevention and management of animal infectious diseases. With the advances in biological technology, materials science and industrial optimization, substantial progress has been made in the development of innovative veterinary vaccines. A majority of the novel vaccines under current investigation tend to stimulate multiple immune pathways and to achieve long-term resistance against infectious diseases, yet it remains imperative to concentrate research efforts on the efficient utilization of vaccines, mitigating toxic side effects, and ensuring safe production processes. This article presents an overview of research progress in veterinary vaccines, encompassing comprehensive antigen design, adjuvant formulation advancements, preparation process optimization, and rigorous immune efficacy evaluation. It summarizes cutting-edge vaccines derived from in vitro synthesis and in vivo application, emphasizing immunogenic components and immune response mechanisms. It also highlights novel biological adjuvants that enhance immune efficacy, diversify raw materials, and possess targeted functions, while comprehensively exploring advancements in production methodologies and compatible vaccine products. By establishing a foundation for the integrated use of these innovative veterinary vaccines, this work facilitates future interdisciplinary cooperation in their advancement, aiming to accelerate the achievement of herd immunity through concerted efforts.

Clinical development of SpikoGen®, an Advax-CpG55.2 adjuvanted recombinant spike protein vaccine

Recombinant protein vaccines represent a well-established, reliable and safe approach for pandemic vaccination. SpikoGen® is a recombinant spike protein trimer manufactured in insect cells and formulated with Advax-CpG55.2 adjuvant. In murine, hamster, ferret and non-human primate studies, SpikoGen® consistently provided protection against a range of SARS-CoV-2 variants. A pivotal Phase 3 placebo-controlled efficacy trial involving 16,876 participants confirmed the ability of SpikoGen® to prevent infection and severe disease caused by the virulent Delta strain. SpikoGen® subsequently received a marketing authorization from the Iranian FDA in early October 2021 for prevention of COVID-19 in adults. Following a successful pediatric study, its approval was extended to children 5 years and older. Eight million doses of SpikoGen® have been delivered, and a next-generation booster version is currently in development. This highlights the benefits of adjuvanted protein-based approaches which should not overlook when vaccine platforms are being selected for future pandemics.

Telomerase-based vaccines: a promising frontier in cancer immunotherapy

Telomerase, an enzyme crucial for maintaining telomere length, plays a critical role in cellular immortality and is overexpressed in most cancers. This ubiquitous presence makes telomerase, and specifically its catalytic subunit, human telomerase reverse transcriptase (hTERT), an attractive target for cancer immunotherapy. This review explores the development and application of telomerase-based vaccines, focusing on DNA and peptide-based approaches. While DNA vaccines demonstrate promising immunogenicity, peptide vaccines, such as UV1, UCPVax, and Vx-001, have shown clinical efficacy in certain cancer types. Recent advancements in vaccine design, including multiple peptides and adjuvants, have enhanced immune responses. However, challenges remain in achieving consistent and durable anti-tumor immunity. Accordingly, we discuss the mechanisms of action, preclinical and clinical data, and the potential of these vaccines to elicit robust and durable anti-tumor immune responses. This review highlights the potential of telomerase-based vaccines as a promising strategy for cancer treatment and identifies areas for future research.

A Supramolecular Protein Assembly Intrinsically Rescues Memory Deficits in an Alzheimer's Disease Mouse Model

Supramolecular protein assemblies have been used as intelligent drug delivery systems that can encapsulate drugs and transport them to specific tissues or cells. However, the known methods for designing supramolecular protein assemblies for transportation across the blood-brain barrier (BBB) remain challenging and inefficient. Herein, we report that the supramolecular recombinant-protein-based strategy enables the biosynthesis and production of a supramolecular protein assembly that is intrinsically capable of crossing the BBB. The recombinant protein constituting the essential part of apolipoprotein A1 can self-assemble into a supramolecular protein assembly known as a nanodisc. The nanodisc could efficiently enter the brain of an Alzheimer's disease mouse model, recognize Aβ1-42, eliminate amyloid plaques, promote neurogenesis, and ameliorate cognitive impairment. This work opens a new field for supramolecular protein assemblies and offers a new avenue for designing versatile and intelligent supramolecular biomaterials.

Malaria vaccines: a new era of prevention and control

Malaria killed over 600,000 people in 2022, a death toll that has not improved since 2015. Additionally, parasites and mosquitoes resistant to existing interventions are spreading across Africa and other regions. Vaccines offer hope to reduce the mortality burden: the first licensed malaria vaccines, RTS,S and R21, will be widely deployed in 2024 and should substantially reduce childhood deaths. In this Review, we provide an overview of the malaria problem and the Plasmodium parasite, then describe the RTS,S and R21 vaccines (the first vaccines for any human parasitic disease), summarizing their benefits and limitations. We explore next-generation vaccines designed using new knowledge of malaria pathogenesis and protective immunity, which incorporate antigens and platforms to elicit effective immune responses against different parasite stages in human or mosquito hosts. We describe a decision-making process that prioritizes malaria vaccine candidates for development in a resource-constrained environment. Future vaccines might improve upon the protective efficacy of RTS,S or R21 for children, or address the wider malaria scourge by preventing pregnancy malaria, reducing the burden of Plasmodium vivax or accelerating malaria elimination.

Leveraging Walnut Somatic Embryos as a Biomanufacturing Platform for Recombinant Proteins and Metabolites

Biomanufacturing enables novel sources of compounds with constant demand, such as food coloring and preservatives, as well as new compounds with peak demand, such as diagnostics and vaccines. The COVID-19 pandemic has highlighted the need for alternative sources of research materials, thrusting research on diversification of biomanufacturing platforms. Here, we show initial results exploring the walnut somatic embryogenic system expressing the recombinant receptor binding domain (RBD) and ectodomain of the spike protein (Spike) from the SARS-CoV-2 virus. Stably transformed walnut embryo lines were selected and propagated in vitro. Both recombinant proteins were detected at 3-14 µg/g dry weight of tissue culture material. Although higher yields of recombinant protein have been obtained using more conventional biomanufacturing platforms, we also report on the production of the red pigment betanin in somatic embryos, reaching yields of 650 mg/g, even higher than red beet Beta vulgaris. This first iteration shows the potential of biomanufacturing using somatic walnut embryos that can now be further optimized for different applications sourcing specialized proteins and metabolites.

Prokaryote- and Eukaryote-Based Expression Systems: Advances in Post-Pandemic Viral Antigen Production for Vaccines

This review addresses the ongoing global challenge posed by emerging and evolving viral diseases, underscoring the need for innovative vaccine development strategies. It focuses on the modern approaches to creating vaccines based on recombinant proteins produced in different expression systems, including bacteria, yeast, plants, insects, and mammals. This review analyses the advantages, limitations, and applications of these expression systems for producing vaccine antigens, as well as strategies for designing safer, more effective, and potentially 'universal' antigens. The review discusses the development of vaccines for a range of viral diseases, excluding SARS-CoV-2, which has already been extensively studied. The authors present these findings with the aim of contributing to ongoing research and advancing the development of antiviral vaccines.

Fluoroamphiphiles for enhancing immune response of subunit vaccine against SARS-CoV-2

In recent decades, protein-based therapy has garnered valid attention for treating infectious diseases, genetic disorders, cancer, and other clinical requirements. However, preserving protein-based drugs against degradation and denaturation during processing, storage, and delivery poses a formidable challenge. Herein, we designed a novel fluoroamphiphiles polymer to deliver protein. Two different formulations of nanoparticles, cross-linked (CNP) and micelle (MNP) polymer, were prepared rationally by disulfide cross-linked and thin-film hydration techniques, respectively. The size, zeta potential, and morphology of both formulations were characterized and the delivery efficacy of both in vitro and in vivo was also assessed. The in vitro findings demonstrated that both formulations effectively facilitated protein delivery into various cell lines. Moreover, in vivo experiments revealed that intramuscular administration of the two formulations loaded with a SARS-CoV-2 recombinant receptor-binding domain (RBD) vaccine induced robust antibody responses in mice without adding another adjuvant. These results highlight the potential use of our carrier system as a safe and effective platform for the in vivo delivery of subunit vaccines.

Basic Properties and Development Status of Aluminum Adjuvants Used for Vaccines

BACKGROUND

Aluminum adjuvants, renowned for their safety and efficacy, act as excellent adsorbents and vaccine immunogen enhancers, significantly contributing to innate, endogenous, and humoral immunity. An ideal adjuvant not only boosts the immune response but also ensures optimal protective immunity. Aluminum adjuvants are the most widely used vaccine adjuvants and have played a crucial role in both the prevention of existing diseases and the development of new vaccines. With the increasing emergence of new vaccines, traditional immune adjuvants are continually being researched and upgraded. The future of vaccine development lies in the exploration and integration of novel adjuvant technologies that surpass the capabilities of traditional aluminum adjuvants. One promising direction is the incorporation of nanoparticles, which offer precise delivery and controlled release of antigens, thereby enhancing the overall immune response.

CONCLUSIONS

This review summarizes the types, mechanisms, manufacturers, patents, advantages, disadvantages, and future prospects of aluminum adjuvants. Although aluminum adjuvants have certain limitations, their contribution to enhancing vaccine immunity is significant and cannot be ignored. Future research should continue to explore their mechanisms of action and address potential adverse reactions to achieve improved vaccine efficacy.

Partial Protection of Goats against Haemonchus contortus Achieved with ADP-Ribosylation Factor 1 Encapsulated in PLGA Nanoparticles

BACKGROUND

Haemonchus contortus (H. contortus), a nematode with global prevalence, poses a major threat to the gastrointestinal health of sheep and goats. In an effort to combat this parasite, a nanovaccine was created using a recombinant ADP-ribosylation factor 1 (ARF1) antigen encapsulated within poly lactic-co-glycolic acid (PLGA). This study aimed to assess the effectiveness of this nanovaccine in providing protection against H. contortus infection.

METHODS

Fifteen goats were randomly divided into three groups. The experimental group received two doses of the PLGA encapsulated rHcARF1 (rHcARF1-PLGA) nanovaccine on days 0 and 14. Fourteen days after the second immunization, both the experimental and positive control groups were challenged with 8000 infective larvae (L3) of H. contortus, while the negative control group remained unvaccinated and unchallenged. At the end of the experiment on the 63rd day, all animals were humanly euthanized.

RESULTS

The results showed that the experimental group had significantly higher levels of sera IgG, IgA, and IgE antibodies, as well as increased concentrations of cytokines, such as IL-4, IL-9, IL-17, and TGF-β, compared to the negative control group after immunization. Following the L3 challenge, the experimental group exhibited a 47.5% reduction in mean eggs per gram of feces (EPG) and a 55.7% reduction in worm burden as compared to the positive control group.

CONCLUSIONS

These findings indicate that the nanovaccine expressing rHcARF1 offers significant protective efficacy against H. contortus infection in goats. The results also suggest the need for more precise optimization of the antigen dose or a reassessment of the vaccination regimen. Additionally, the small sample size limits the statistical rigor and the broader applicability of the findings.

A self-adjuvanted VLPs-based Covid-19 vaccine proven versatile, safe, and highly protective

Vaccination has played a critical role in mitigating COVID-19. Despite the availability of licensed vaccines, there remains a pressing need for improved vaccine platforms that provide high protection, safety, and versatility, while also reducing vaccine costs. In response to these challenges, our aim is to create a self-adjuvanted vaccine against SARS-CoV-2, utilizing Virus-Like Particles (VLPs) as the foundation. To achieve this, we produced bacteriophage (Qβ) VLPs in a prokaryotic system and purified them using a rapid and cost-effective strategy involving organic solvents. This method aims to solubilize lipids and components of the cell membrane to eliminate endotoxins present in bacterial samples. For vaccine formulation, Receptor Binding Domain (RBD) antigens were conjugated using chemical crosslinkers, a process compatible with Good Manufacturing Practice (GMP) standards. Transmission Electron Microscopy (TEM) confirmed the expected folding and spatial configuration of the QβVLPs vaccine. Additionally, vaccine formulation assessment involved SDS-PAGE stained with Coomassie Brilliant Blue, Western blotting, and stereomicroscopic experiments. In vitro and in vivo evaluations of the vaccine formulation were conducted to assess its capacity to induce a protective immune response without causing side effects. Vaccine doses of 20 µg and 50 µg stimulated the production of neutralizing antibodies. In in vivo testing, the group of animals vaccinated with 50 µg of vaccine formulation provided complete protection against virus infection, maintaining stable body weight without showing signs of disease. In conclusion, the QβVLPs-RBD vaccine has proven to be effective and safe, eliminating the necessity for supplementary adjuvants and offering a financially feasible approach. Moreover, this vaccine platform demonstrates flexibility in targeting Variants of Concern (VOCs) via established conjugation protocols with VLPs.

Advancements in monkeypox vaccines development: a critical review of emerging technologies

Monkeypox (mpox) is a zoonotic illness caused by the monkeypox virus (MPXV), with higher health concerns among people who are pregnant, children, and persons who are immunocompromised, including people with untreated and advanced HIV disease. Significant progress has been made in developing vaccines against mpox, yet critical challenges and limitations persist in ensuring their effectiveness, safety, and accessibility. The pertinence of this review is highlighted by the World Health Organization's declaration of a global health emergency on August 14, 2024, due to the recent mpox outbreak, underscoring the critical necessity for effective vaccine solutions in the face of a rapidly evolving virus. Here, we comprehensively analyze various vaccine platforms utilized in mpox prevention, including attenuated and non-replicating virus vaccines, viral vector-based vaccines, recombinant protein vaccines, and DNA and mRNA vaccines. We evaluate the advantages and limitations of each platform, highlighting the urgent need for ongoing research and innovation to enhance vaccine efficacy and safety. Recent advancements, such as incorporating immunostimulatory sequences, improved delivery systems, and developing polyvalent vaccines, are explored for their potential to offer broader protection against diverse orthopoxvirus strains. This work underscores the need to optimize currently available vaccines and investigate novel vaccination strategies to address future public health emergencies effectively. By focusing on these advanced methodologies, we aim to contribute to the development of robust and adaptable vaccine solutions for mpox and other related viral threats.

The heterologous expression of novel recombinant protein composed of HN and F moieties of Newcastle disease virus and immunogenicity evaluation in mouse model

Background and Objectives

The rapid spread of Newcastle disease (ND), driven by extensive commercial exchange in the poultry industry, necessitates urgent preventive measures. Although effective vaccines against the Newcastle disease virus (NDV) have been used since 1940, recent outbreaks and the limitations of current vaccines highlight the need for improved solutions. Advances in synthetic biology, reverse vaccinology, molecular biology, and recombinant DNA technology over the past 20 years have led to the development of recombinant vaccines, which offer enhanced protection and broader immunogenic coverage against NDV. This study aimed to express the immunogenic domains of Hemagglutinin Neuraminidase (HN) and Fusion (F) glycoproteins, linked to the heat-labile enterotoxin B subunit (LTB) bio-adjuvant, to develop an effective and reliable recombinant vaccine for NDV.

Materials and Methods

In this study, the L(HN)2F protein, composed of the LTB bio-adjuvant and the immunogenic regions of the doubled Hemagglutinin Neuraminidase (HN-HN) and Fusion (F) epitope, was expressed in Escherichia coli. Subcutaneous injection was used to evaluate the humoral immune response in mice and the result was compared with B1 vaccine.

Results

The induction of strong humoral immune responses proved the strong immunoreactivity of the recombinant protein.

Conclusion

The IgG elicited by the recombinant proteins was comparable to that of the commercial B1 vaccine against NDV, indicating its potential as a viable candidate for further development and evaluation as a recombinant vaccine against NDV.

Exploring recent progress of molecular farming for therapeutic and recombinant molecules in plant systems

An excellent technique for producing pharmaceuticals called "molecular farming" enables the industrial mass production of useful recombinant proteins in genetically modified organisms. Protein-based pharmaceuticals are rising in significance because of a variety of factors, including their bioreactivity, precision, safety, and efficacy rate. Heterologous expression methods for the manufacturing of pharmaceutical products have been previously employed using yeast, bacteria, and animal cells. However, the high cost of mammalian cell system, and production, the chance for product complexity, and contamination, and the hurdles of scaling up to commercial production are the limitations of these traditional expression methods. Plants have been raised as a hopeful replacement system for the expression of biopharmaceutical products due to their potential benefits, which include low production costs, simplicity in scaling up to commercial manufacturing levels, and a lower threat of mammalian toxin contaminations and virus infections. Since plants are widely utilized as a source of therapeutic chemicals, molecular farming offers a unique way to produce molecular medicines such as recombinant antibodies, enzymes, growth factors, plasma proteins, and vaccines whose molecular basis for use in therapy is well established. Biopharming provides more economical and extensive pharmaceutical drug supplies, including vaccines for contagious diseases and pharmaceutical proteins for the treatment of conditions like heart disease and cancer. To assess its technical viability and the efficacy resulting from the adoption of molecular farming products, the following review explores the various methods and methodologies that are currently employed to create commercially valuable molecules in plant systems.

Reverse Vaccinology and Immunoinformatic Approach for Designing a Bivalent Vaccine Candidate Against Hepatitis A and Hepatitis B Viruses

Hepatitis A and B are two crucial viral infections that still dramatically affect public health worldwide. Hepatitis A Virus (HAV) is the main cause of acute hepatitis, whereas Hepatitis B Virus (HBV) leads to the chronic form of the disease, possibly cirrhosis or liver failure. Therefore, vaccination has always been considered the most effective preventive method against pathogens. At this moment, we aimed at the immunoinformatic analysis of HAV-Viral Protein 1 (VP1) as the major capsid protein to come up with the most conserved immunogenic truncated protein to be fused by HBV surface antigen (HBs Ag) to achieve a bivalent vaccine against HAV and HBV using an AAY linker. Various computational approaches were employed to predict highly conserved regions and the most immunogenic B-cell and T-cell epitopes of HAV-VP1 capsid protein in both humans and BALB/c. Moreover, the predicted fusion protein was analyzed regarding primary and secondary structures and also homology validation. Afterward, the three-dimensional structure of vaccine constructs docked with various toll-like receptors (TLR) 2, 4 and 7. According to the bioinformatics tools, the region of 99-259 amino acids of VP1 was selected with high immunogenicity and conserved epitopes. T-cell epitope prediction showed that this region contains 32 antigenic peptides for Human leukocyte antigen (HLA) class I and 20 antigenic peptides in terms of HLA class II which are almost fully conserved in the Iranian population. The vaccine design includes 5 linear and 4 conformational B-cell lymphocyte (BCL) epitopes to induce humoral immune responses. The designed VP1-AAY-HBsAg fusion protein has the potency to be constructed and expressed to achieve a bivalent vaccine candidate, especially in the Iranian population. These findings led us to claim that the designed vaccine candidate provides potential pathways for creating an exploratory vaccine against Hepatitis A and Hepatitis B Viruses with high confidence for the identified strains.

Preparation and immunological activity evaluation of an intranasal protein subunit vaccine against ancestral and mutant SARS-CoV-2 with curdlan sulfate/O-linked quaternized chitosan nanoparticles as carrier and adjuvant

Chitosan and its derivatives are ideal nasal vaccine adjuvant to deliver antigens to immune cells. Previously, we successfully used a chitosan derivative, O-(2-Hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (O-HTCC), and a β-glucan derivative, curdlan sulfate (CS), to prepare a nanoparticle adjuvant CS/O-HTCC which could deliver ovalbumin to antigen presenting cells (APCs) through nasal inhalation. In this article, we used SARS-CoV-2 spike receptor binding domain (S-RBD) as the antigen and CS/O-HTCC nanoparticles as the adjuvant to develop a nasal mucosal protein subunit vaccine, CS/S-RBD/O-HTCC. The humoral immunity, cell-mediated immunity and mucosal immunity induced by vaccines were evaluated. The results showed that CS/S-RBD/O-HTCC could induce desirable immunization with single or bivalent antigen through nasal inoculation, giving one booster vaccination with mutated S-RBD (beta) could bring about a broad cross reaction with ancestral and different mutated S-RBD, and vaccination of the BALB/c mice with CS/S-RBD/O-HTCC containing S-RBD mix antigens (ancestral and omicron) could induce the production of binding and neutralizing antibodies against both of the two antigens. Our results indicate that CS/O-HTCC is a promising nasal mucosal adjuvant to prepare protein subunit vaccine for both primary and booster immunization, and the adjuvant is suitable for loading more than one antigen for preparing multivalent vaccines.

Aluminum hydroxide and immunostimulatory glycolipid adjuvant combination for enhanced COVID-19 subunit vaccine immunogenicity

Protein-based subunit vaccines like RBD-Fc are promising tools to fight COVID-19. RBD-Fc fuses the receptor-binding domain (RBD) of the SARS-CoV-2 virus spike protein with the Fc region of human IgG1, making it more immunogenic than RBD alone. Earlier work showed that combining RBD-Fc with iNKT cell agonists as adjuvants improved neutralizing antibodies but did not sufficiently enhance T cell responses, a limitation RBD-Fc vaccines share with common adjuvants. Here we demonstrate that aluminum hydroxide combined with α-C-GC, a C-glycoside iNKT cell agonist, significantly improved the RBD-Fc vaccine's induction of RBD-specific T-cell responses. Additionally, aluminum hydroxide with α-GC-CPOEt, a phosphonate diester derivative, synergistically elicited more robust neutralizing antibodies. Remarkably, modifying αGC with phosphate (OPO3H2) or phosphonate (CPO3H2) to potentially enhance aluminum hydroxide interaction did not improve efficacy over unmodified αGC with aluminum hydroxide. These findings underscore the straightforward yet potent potential of this approach in advancing COVID-19 vaccine development and provide insights for iNKT cell-based immunotherapy.

Immunogenicity and Safety of SARS-CoV-2 Protein Subunit Recombinant Vaccine (IndoVac®) as a Heterologous Booster Dose against COVID-19 in Indonesian Adolescents

Adolescents are vulnerable to Coronavirus disease 2019 (COVID-19) infections; thus, their antibodies should be maintained above the protective value. This study aimed to evaluate the immune response and safety to the SARS-CoV-2 protein subunit recombinant vaccine (IndoVac®) as a heterologous booster dose against COVID-19 in Indonesian adolescents. This open-label prospective intervention study enrolled 150 clinically healthy adolescents aged 12-17 years who had received complete primary doses of the CoronaVac® vaccine from Garuda Primary Care Centres in Bandung City. The result of immunogenicity was presented with a 95% confidence interval (CI) and analyzed with t-tests from 14 days and 3, 6, and 12 months. The neutralizing antibody geometric mean titers (GMTs) (IU/mL) at baseline and 14 days after booster dose were 303.26 and 2661.2, respectively. The geometric mean fold rises (GMFR) at 3, 6, and 12 months after booster dose were 6.67 (5.217-8.536), 3.87 (3.068-4.886), and 2.87 (2.232-3.685), respectively. Both the neutralizing antibody and IgG antibody were markedly higher in the adolescents than in the adults at every timepoint. The incidence rate of adverse effects (AEs) until 28 days after booster dose was 82.7%, with a higher number of local events reported. Most reported solicited AEs were local pain followed by myalgia with mild intensity. Unsolicited AEs varied with each of the incidence rates < 10%, mostly with mild intensity. Adverse events of special interest (AESI) were not observed. At the 12-month follow-up after the booster dose, four serious adverse events (SAEs) not related to investigational products and research procedures were noted. This study showed that IndoVac® has a favorable immunogenicity and safety profile as a booster in adolescents and that the antibody titer decreases over time.

Wuhan Sequence-Based Recombinant Antigens Expressed in E. coli Elicit Antibodies Capable of Binding with Omicron S-Protein

The development of cross-reactive vaccines is one of the central aims of modern vaccinology. Continuous mutation and the emergence of new SARS-CoV-2 variants and subvariants create the problem of universal coronavirus vaccine design. Previously, the authors devised three recombinant coronavirus antigens, which were based on the sequence collected in 2019 (the Wuhan variant) and produced in an E. coli bacterial expression system. The present work has shown, for the first time, that these recombinant antigens induce the production of antibodies that clearly interact with produced in CHO full-length S-protein of the Omicron variant. The immunogenicity of these recombinant antigens was studied in formulations with different adjuvants: Freund's adjuvant, Al(OH)3 and an adjuvant based on spherical particles (SPs), which are structurally modified plant virus. All adjuvanted formulations effectively stimulated Omicron-specific IgG production in mice. These universal coronavirus antigens could be considered the main component for the further development of broad-spectrum coronavirus vaccines for the prevention of SARS-CoV-2 infection. The present work also provides evidence that the synthetic biology approach is a promising strategy for the development of highly cross-reactive vaccines. Moreover, it is important to note that the bacterial expression system might be appropriate for the production of antigenically active universal antigens.

Maternal Immunization with Adjuvanted Recombinant Receptor-Binding Domain Protein Provides Immune Protection against SARS-CoV-2 in Infant Monkeys

Maternal vaccinations administered prior to conception or during pregnancy enhance the immune protection of newborn infants against many pathogens. A feasibility experiment was conducted to determine if monkeys can be used to model the placental transfer of maternal antibody against SARS-CoV-2. Six adult rhesus monkeys were immunized with adjuvanted recombinant-protein antigens comprised of receptor-binding domain human IgG1-Fc fusion proteins (RBD-Fc) containing protein sequences from the ancestral-Wuhan or Gamma variants. The female monkeys mounted robust and sustained anti-SARS-CoV-2 antibody responses. Blood samples collected from their infants after delivery verified prenatal transfer of high levels of spike-specific IgG, which were positively correlated with maternal IgG titers at term. In addition, an in vitro test of ACE2 neutralization indicated that the infants' IgG demonstrated antigen specificity, reflecting prior maternal immunization with either Wuhan or Gamma-variant antigens. All sera showed stronger ACE2-RBD binding inhibition when variants in the assay more closely resembled the vaccine RBD sequence than with more distantly related variants (i.e., Delta and Omicron). Monkeys are a valuable animal model for evaluating new vaccines that can promote maternal and infant health. Further, the findings highlight the enduring nature and safety of the immune protection elicited by an adjuvanted recombinant RBD-Fc vaccine.

Dynamics of IgM and IgG Antibody Response Profile against Linear B-Cell Epitopes from Exoerythrocytic (CelTOS and TRAP) and Erythrocytic (CyRPA) Phases of Plasmodium vivax: Follow-Up Study

Malaria is a serious health problem worldwide affecting mainly children and socially vulnerable people. The biological particularities of P. vivax, such as the ability to generate dormant liver stages, the rapid maturation of gametocytes, and the emergence of drug resistance, have contributed to difficulties in disease control. In this context, developing an effective vaccine has been considered a fundamental tool for the efficient control and/or elimination of vivax malaria. Although recombinant proteins have been the main strategy used in designing vaccine prototypes, synthetic immunogenic peptides have emerged as a viable alternative for this purpose. Considering, therefore, that in the Brazilian endemic population, little is known about the profile of the humoral immune response directed to synthetic peptides that represent different P. vivax proteins, the present work aimed to map the epitope-specific antibodies' profiles to synthetic peptides representing the linear portions of the ookinete and sporozoite cell passage protein (CelTOS), thrombospondin-related adhesive protein (TRAP), and cysteine-rich protective antigen (CyRPA) proteins in the acute (AC) and convalescent phases (Conv30 and Conv180 after infection) of vivax malaria. The results showed that the studied subjects responded to all proteins for at least six months following infection. For IgM, a few individuals (3-21%) were positive during the acute phase of the disease; the highest frequencies were observed for IgG (28-57%). Regarding the subclasses, IgG2 and IgG3 stood out as the most prevalent for all peptides. During the follow-up, the stability of IgG was observed for all peptides. Only one significant positive correlation was observed between IgM and exposure time. We conclude that for all the peptides, the immunodominant epitopes are recognized in the exposed population, with similar frequency and magnitude. However, if the antibodies detected in this study are potential protectors, this needs to be investigated.

Crimean Congo hemorrhagic fever virus nucleoprotein and GP38 subunit vaccine combination prevents morbidity in mice

Immunizing mice with Crimean-Congo hemorrhagic fever virus (CCHFV) nucleoprotein (NP), glycoprotein precursor (GPC), or with the GP38 domain of GPC, can be protective when the proteins are delivered with viral vectors or as a DNA or RNA vaccine. Subunit vaccines are a safe and cost-effective alternative to some vaccine platforms, but Gc and Gn glycoprotein subunit vaccines for CCHFV fail to protect despite eliciting high levels of neutralizing antibodies. Here, we investigated humoral and cellular immune responses and the protective efficacy of recombinant NP, GP38, and GP38 forms (GP85 and GP160) associated with the highly glycosylated mucin-like (MLD) domain, as well as the NP + GP38 combination. Vaccination with GP160, GP85, or GP38 did not confer protection, and vaccination with the MLD-associated GP38 forms blunted the humoral immune responses to GP38, worsened clinical chemistry, and increased viral RNA in the blood compared to the GP38 vaccination. In contrast, NP vaccination conferred 100% protection from lethal outcome and was associated with mild clinical disease, while the NP + GP38 combination conferred even more robust protection by reducing morbidity compared to mice receiving NP alone. Thus, recombinant CCHFV NP alone is a promising vaccine candidate conferring 100% survival against heterologous challenge. Moreover, incorporation of GP38 should be considered as it further enhances subunit vaccine efficacy by reducing morbidity in surviving animals.

The Development of Epitope-Based Recombinant Protein Vaccines against SARS-CoV-2

The COVID-19 pandemic continues to cause infections and deaths, which are attributable to the SARS-CoV-2 Omicron variant of concern (VOC). Moderna's response to the declining protective efficacies of current SARS-CoV-2 vaccines against Omicron was to develop a bivalent booster vaccine based on the Spike (S) protein from the Wuhan and Omicron BA.4/BA.5 strains. This approach, while commendable, is unfeasible in light of rapidly emerging mutated viral strains. PubMed and Google Scholar were systematically reviewed for peer-reviewed papers up to January 2024. Articles included focused on specific themes such as the clinical history of recombinant protein vaccine development against different diseases, including COVID-19, the production of recombinant protein vaccines using different host expression systems, aspects to consider in recombinant protein vaccine development, and overcoming problems associated with large-scale recombinant protein vaccine production. In silico approaches to identify conserved and immunogenic epitopes could provide broad protection against SARS-CoV-2 VOCs but require validation in animal models. The recombinant protein vaccine development platform has shown a successful history in clinical development. Recombinant protein vaccines incorporating conserved epitopes may utilize a number of expression systems, such as yeast (Saccharomyces cerevisiae), baculovirus-insect cells (Sf9 cells), and Escherichia coli (E. coli). Current multi-epitope subunit vaccines against SARS-CoV-2 utilizing synthetic peptides are unfeasible for large-scale immunizations. Recombinant protein vaccines based on conserved and immunogenic proteins produced using E. coli offer high production yields, convenient purification, and cost-effective production of large-scale vaccine quantities capable of protecting against the SARS-CoV-2 D614G strain and its VOCs.

Recombinant proteins as promising antigens applied to the immunodiagnosis of Chagas disease: a scoping review

Chagas disease (CD), caused by the protozoan Trypanosoma cruzi, is an important public health problem, occurring mainly in Latin America. The disease has a major social and economical effect, negatively impacting the life of the infected individuals, and bringing great costs to public health. An early and accurate diagnosis is essential for administration of early treatment. In addition, prognostic tests may aid disease management, decreasing hospitalization costs. However, the serological diagnostic scenario for CD still faces several challenges, making the development of new diagnostic kits a pressing matter. Facing this scenario, several researchers have expanded efforts in developing and testing new antigens, such as recombinant proteins and recombinant multiepitope proteins, with promising results. These recombinant antigens offer several advantages, such as improved sensitivity and specificity, in addition to facilitated scaling. Also, it has been possible to observe a rising number of studies using ELISA and point-of-care platforms, employing these antigens in the past few years. Among them, recombinant proteins were the most applied antigens, demonstrating great capacity to discriminate between positive and negative samples. Although fewer in number, recombinant multiepitope proteins also demonstrated an improved diagnostic performance. Indeed, a great number of studies employing these antigens showed sensitivity and specificity values above 90%, greatly impacting diagnostic accuracy. Nevertheless, despite the good results found, it is still possible to observe some bottlenecks in the development of new antigens, such as the scarcity of tests with sera from the acute phase and the variability of results in different geographic areas. In this sense, aiming to contribute to control and health programs, the continuous search for a more accurate serological diagnosis is essential, both for the acute and chronic phases of the disease.

Omicron XBB.1.16-Adapted Vaccine for COVID-19: Interim Immunogenicity and Safety Clinical Trial Results

(1) Background: The global coronavirus disease 2019 vaccination adapts to protect populations from emerging variants. This communication presents interim findings from the new Omicron XBB.1.16-adapted PHH-1V81 protein-based vaccine compared to an XBB.1.5-adapted mRNA vaccine against various acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains. (2) Methods: In a Phase IIb/III pivotal trial, adults previously vaccinated with a primary scheme and at least one booster dose of an EU-approved mRNA vaccine randomly received either the PHH-1V81 or BNT162b2 XBB.1.5 vaccine booster as a single dose. The primary efficacy endpoint assessed neutralization titers against the Omicron XBB.1.16 variant at day 14. Secondary endpoints evaluated neutralization titers and cellular immunity against different variants. Safety endpoints comprised solicited reactions up to day 7 post-vaccination and serious adverse events until the cut-off date of the interim analysis. Changes in humoral responses were assessed by pseudovirion-based or virus neutralization assays. (3) Results: At the cut-off date, immunogenicity assessments included 599 participants. Both boosters elicited neutralizing antibodies against XBB.1.16, XBB.1.5, and JN.1, with PHH-1V81 inducing a higher response for all variants. The PHH-1V8 booster triggers a superior neutralizing antibody response against XBB variants compared to the mRNA vaccine. A subgroup analysis consistently revealed higher neutralizing antibody responses with PHH-1V81 across age groups, SARS-CoV-2 infection history, and the number of prior vaccination shots. A safety analysis (n = 607) at the day 14 visit revealed favorable safety profiles without any serious vaccine-related adverse events. (4) Conclusions: PHH-1V81 demonstrates superiority on humoral immunogenicity compared to the mRNA vaccine against XBB variants and non-inferiority against JN.1 with a favorable safety profile and lower reactogenicity, confirming its potential as a vaccine candidate.

Formulation Development of a COVID-19 Recombinant Spike Protein-Based Vaccine

The purpose of this study was to develop a formulation for a recombinant prefusion spike protein vaccine against SARS-CoV-2. It was found that the spike protein was susceptible to aggregation due to mechanical stress. Therefore, formulation studies were initiated focused on screening pharmaceutical excipients capable of preventing this. The screening of a panel of potential stabilizing conditions found that Tween 20 could inhibit mechanically induced aggregation. A concentration-dependent study indicated that a higher concentration of Tween 20 (0.2% v/v) was required to prevent conformational changes in the trimer. The conformational changes induced by mechanical stress were characterized by size exclusion chromatography (SEC) and hydrogen-deuterium exchange mass spectrometry (HDX-MS), indicating the formation of an extended trimeric conformation that was also unable to bind to antibodies directed to the S2 domain. Long-term stability modeling, using advanced kinetic analysis, indicated that the formulation containing 0.2% (v/v) Tween 20 at a neutral pH was predicted to be stable for at least two years at 2 °C to 8 °C. Additional stabilizer screening conducted by thermal shift assay indicated that sucrose and glycerol were able to significantly increase the spike protein melting temperature (Tm) and improve the overall thermostability of the spike protein in a short-term stability study. Thus, while 0.2% (v/v) Tween 20 was sufficient to prevent aggregation and to maintain spike protein stability under refrigeration, the addition of sucrose further improved vaccine thermostability. Altogether, our study provides a systematic approach to the formulation of protein-based COVID-19 vaccine and highlights the impact of mechanical stress on the conformation of the spike protein and the significance of surfactants and stabilizers in maintaining the structural and functional integrity of the spike protein.

Construction of recombinant Omp25 or EipB protein loaded PLGA nanovaccines for Brucellosis protection

Safe and effective vaccine candidates are needed to address the limitations of existing vaccines against Brucellosis, a disease responsible for substantial economic losses in livestock. The present study aimed to encapsulate recombinant Omp25 and EipB proteins, knowledged antigen properties, into PLGA nanoparticles, characterize synthesized nanoparticles with different methods, and assessed theirin vitro/in vivoimmunostimulatory activities to develop new vaccine candidates. The recombinant Omp25 and EipB proteins produced with recombinant DNA technology were encapsulated into PLGA nanoparticles by double emulsion solvent evaporation technique. The nanoparticles were characterized using FE-SEM, Zeta-sizer, and FT-IR instruments to determine size, morphology, zeta potentials, and polydispersity index values, as well as to analyze functional groups chemically. Additionally, the release profiles and encapsulation efficiencies were assessed using UV-Vis spectroscopy. After loading with recombinant proteins, O-NPs reached sizes of 221.2 ± 5.21 nm, while E-NPs reached sizes of 274.4 ± 9.51 nm. The cumulative release rates of the antigens, monitored until the end of day 14, were determined to be 90.39% for O-NPs and 56.1% for E-NPs. Following the assessment of thein vitrocytotoxicity and immunostimulatory effects of both proteins and nanoparticles on the J774 murine macrophage cells,in vivoimmunization experiments were conducted using concentrations of 16µg ml-1for each protein. Both free antigens and antigen-containing nanoparticles excessively induced humoral immunity by increasing producedBrucella-specific IgG antibody levels for 3 times in contrast to control. Furthermore, it was also demonstrated that vaccine candidates stimulated Th1-mediated cellular immunity as well since they significantly raised IFN-gamma and IL-12 cytokine levels in murine splenocytes rather than IL-4 following to immunization. Additionally, the vaccine candidates conferred higher than 90% protection from the infection according to challenge results. Our findings reveal that PLGA nanoparticles constructed with the encapsulation of recombinant Omp25 or EipB proteins possess great potential to triggerBrucella-specific humoral and cellular immune response.

Functionally Designed Nanovaccines against SARS-CoV-2 and Its Variants

COVID-19, generated by SARS-CoV-2, has significantly affected healthcare systems worldwide. The epidemic has highlighted the urgent need for vaccine development. Besides the conventional vaccination models, which include live-attenuated, recombinant protein, and inactivated vaccines, nanovaccines present a distinct opportunity to progress vaccine research and offer convenient alternatives. This review highlights the many widely used nanoparticle vaccine vectors, outlines their benefits and drawbacks, and examines recent developments in nanoparticle vaccines to prevent SARS-CoV-2. It also offers a thorough overview of the many advantages of nanoparticle vaccines, including an enhanced host immune response, multivalent antigen delivery, and efficient drug delivery. The main objective is to provide a reference for the development of innovative antiviral vaccines.

Vaccine adjuvants for infectious disease in the clinic

Adjuvants, materials added to vaccines to enhance the resulting immune response, are important components of vaccination that are many times overlooked. While vaccines always include an antigen to tell the body what to vaccinate to, of equal importance the adjuvant provides the how, a significant factor in producing a complete response. The adjuvant space has been slow to develop with the first use of an adjuvant in a licensed vaccine occurring in the 1930s, and remaining the only adjuvant in licensed vaccines for the next 80 years. However, with vaccination at the forefront of protection against new and complex pathogens, it is important to consider all components when designing an effective vaccine. Here we summarize the adjuvant space in licensed vaccines as well as the novel adjuvant space in clinical trials with a specific focus on the materials utilized and their resulting impact on the immune response. We discuss five major categories of adjuvant materials: aluminum salts, nanoparticles, viral vectors, TLR agonists, and emulsions. For each category, we delve into the current clinical trials space, the impact of these materials on vaccination, as well as some of the ways in which they could be improved. Adjuvants present an exciting opportunity to improve vaccine responses and stability, this review will help inform about the current progress of this space.

Translational impact statement

In the aftermath of the COVID-19 pandemic, vaccines for infectious diseases have come into the spotlight. While antigens have always been an important focus of vaccine design, the adjuvant is a significant tool for enhancing the immune response to the vaccine that has been largely underdeveloped. This article provides a broad review of the history of adjuvants and, the current vaccine adjuvant space, and the progress seen in adjuvants in clinical trials. There is specific emphasis on the material landscape for adjuvants and their resulting mechanism of action. Looking ahead, while the novel vaccine adjuvant space features exciting new technologies and materials, there is still a need for more to meet the protective needs of new and complex pathogens.

The Key to Increase Immunogenicity of Next-Generation COVID-19 Vaccines Lies in the Inclusion of the SARS-CoV-2 Nucleocapsid Protein

Vaccination is one of the most effective prophylactic public health interventions for the prevention of infectious diseases such as coronavirus disease (COVID-19). Considering the ongoing need for new COVID-19 vaccines, it is crucial to modify our approach and incorporate more conserved regions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to effectively address emerging viral variants. The nucleocapsid protein is a structural protein of SARS-CoV-2 that is involved in replication and immune responses. Furthermore, this protein offers significant advantages owing to the minimal accumulation of mutations over time and the inclusion of key T-cell epitopes critical for SARS-CoV-2 immunity. A novel strategy that may be suitable for the new generation of vaccines against COVID-19 is to use a combination of antigens, including the spike and nucleocapsid proteins, to elicit robust humoral and potent cellular immune responses, along with long-lasting immunity. The strategic use of multiple antigens aims to enhance vaccine efficacy and broaden protection against viruses, including their variants. The immune response against the nucleocapsid protein from other coronavirus is long-lasting, and it can persist up to 11 years post-infection. Thus, the incorporation of nucleocapsids (N) into vaccine design adds an important dimension to vaccination efforts and holds promise for bolstering the ability to combat COVID-19 effectively. In this review, we summarize the preclinical studies that evaluated the use of the nucleocapsid protein as antigen. This study discusses the use of nucleocapsid alone and its combination with spike protein or other proteins of SARS-CoV-2.

Recombinant multiepitope proteins expressed in Escherichia coli cells and their potential for immunodiagnosis

Recombinant multiepitope proteins (RMPs) are a promising alternative for application in diagnostic tests and, given their wide application in the most diverse diseases, this review article aims to survey the use of these antigens for diagnosis, as well as discuss the main points surrounding these antigens. RMPs usually consisting of linear, immunodominant, and phylogenetically conserved epitopes, has been applied in the experimental diagnosis of various human and animal diseases, such as leishmaniasis, brucellosis, cysticercosis, Chagas disease, hepatitis, leptospirosis, leprosy, filariasis, schistosomiasis, dengue, and COVID-19. The synthetic genes for these epitopes are joined to code a single RMP, either with spacers or fused, with different biochemical properties. The epitopes' high density within the RMPs contributes to a high degree of sensitivity and specificity. The RMPs can also sidestep the need for multiple peptide synthesis or multiple recombinant proteins, reducing costs and enhancing the standardization conditions for immunoassays. Methods such as bioinformatics and circular dichroism have been widely applied in the development of new RMPs, helping to guide their construction and better understand their structure. Several RMPs have been expressed, mainly using the Escherichia coli expression system, highlighting the importance of these cells in the biotechnological field. In fact, technological advances in this area, offering a wide range of different strains to be used, make these cells the most widely used expression platform. RMPs have been experimentally used to diagnose a broad range of illnesses in the laboratory, suggesting they could also be useful for accurate diagnoses commercially. On this point, the RMP method offers a tempting substitute for the production of promising antigens used to assemble commercial diagnostic kits.

SARS-CoV-2 Neutralization Assays Used in Clinical Trials: A Narrative Review

Since the emergence of COVID-19, extensive research efforts have been undertaken to accelerate the development of multiple types of vaccines to combat the pandemic. These include inactivated, recombinant subunit, viral vector, and nucleic acid vaccines. In the development of these diverse vaccines, appropriate methods to assess vaccine immunogenicity are essential in both preclinical and clinical studies. Among the biomarkers used in vaccine evaluation, the neutralizing antibody level serves as a pivotal indicator for assessing vaccine efficacy. Neutralizing antibody detection methods can mainly be classified into three types: the conventional virus neutralization test, pseudovirus neutralization test, and surrogate virus neutralization test. Importantly, standardization of these assays is critical for their application to yield results that are comparable across different laboratories. The development and use of international or regional standards would facilitate assay standardization and facilitate comparisons of the immune responses induced by different vaccines. In this comprehensive review, we discuss the principles, advantages, limitations, and application of different SARS-CoV-2 neutralization assays in vaccine clinical trials. This will provide guidance for the development and evaluation of COVID-19 vaccines.

Immunogenicity and Safety of SARS-CoV-2 Protein Subunit Recombinant Vaccine (IndoVac®) as a Booster Dose against COVID-19 in Indonesian Adults

According to the WHO target product profile for COVID-19 vaccines, the vaccine in development should be indicated for active immunisation in all populations. Therefore, PT Bio Farma developed a candidate vaccine in a subunit protein recombinant platform to help overcome the issue. This trial was an observer-blind, randomised, prospective intervention study. This study targeted individuals who had received complete primary doses of the authorised/approved COVID-19 vaccine. The groups were divided into the primary inactivated vaccine (CoronaVac®) group, the primary viral vector vaccine (ChAdOx1) group, and the primary mRNA vaccine (BNT162b2) group that received the recombinant protein (IndoVac®). The groups were compared with the control and primary mRNA vaccine (BNT162b2). The participants enrolled in the study were from two primary care centres in Bandung City and three primary care centres in Denpasar City. A total of 696 participants were enrolled from 1 September to 31 October 2022. The demographic characteristics of the all-vaccine group showed a uniform distribution. The results showed that, compared with the control, the investigational product had inferior effectiveness 14 days after the booster dose was administered. However, 28 days after the booster dose, the investigational product exhibited non-inferior effectiveness compared with the primary groups that received CoronaVac® (GMR 0.76 (0.57-0.99)) and ChAdOx1 (GMR 0.72 (0.56-59.93)), but the BNT162b2 group (GMR 0.61 (0.39-0.94)) was inferior to the control. At 12 months follow-up after the booster dose, three serious adverse events (SAEs) were reported in three participants, with causality not correlated with the investigated products. Neither AEs of special interest nor severe COVID-19 cases were reported throughout the follow-up period; thus, the IndoVac® vaccine as a booster was immunogenic and safe. Until the 6-month follow-up after the booster dose, the IndoVac® vaccine was well tolerated and all reported AEs resolved. This vaccine is registered and can be included in the immunisation programme.

Recent development of oral vaccines (Review)

Oral immunization can elicit an effective immune response and immune tolerance to specific antigens. When compared with the traditional injection route, delivering antigens via the gastrointestinal mucosa offers superior immune effects and compliance, as well as simplicity and convenience, making it a more optimal route for immunization. At present, various oral vaccine delivery systems exist. Certain modified bacteria, such as Salmonella, Escherichia coli and particularly Lactobacillus, are considered promising carriers for oral vaccines. These carriers can significantly enhance immunization efficiency by actively replicating in the intestinal tract following oral administration. The present review provided a discussion of the main mechanisms of oral immunity and the research progress made in the field of oral vaccines. Additionally, it introduced the advantages and disadvantages of the currently more commonly administered injectable COVID-19 vaccines, alongside the latest advancements in this area. Furthermore, recent developments in oral vaccines are summarized, and their potential benefits and side effects are discussed.