Search Results (513)

Severe dengue virus (DENV) infections are associated with circulating non-neutralizing antibodies generated during heterotypic infections. Although antibodies are key mediators of both protection and pathogenesis, the specific dynamics of B cells (Bc) and their antibody responses remain insufficiently characterized due to limited methods of identifying DENV-specific Bc (DENV-Bc) and the absence of animal models resembling the human disease. Here, we developed a spectral flow cytometry assay employing biotinylated virus-like particles (VLPs) to detect DENV-Bc in C57BL/6 mice and children hospitalized with dengue. DENV-1 and DENV-2 VLPs were biotinylated, and the efficiency of biotin incorporation was assessed with an HABA-avidin assay and ELISA. Serotype specificity and optimal binding conditions were confirmed using hybridomas 4G2 (pan-flavivirus) and 3H5-1 (DENV-2 specific). Fluorescent agglutimers were subsequently generated by coupling biotinylated VLPs to streptavidin–fluorochrome complexes. Splenocytes from intraperitoneally DENV-infected mice and peripheral blood mononuclear cells (PBMCs) from naturally infected pediatric patients were stained with these VLPs and Bc-lineage markers. Biotinylated VLPs bound specifically to hybridomas, and this binding was competitively inhibited by unlabeled VLPs. After secondary DENV challenge, VLPs identified DENV-specific class-switched plasmablasts in mice. Circulating DENV-specific plasmablasts were also detected in children, with agglutimers enabling the discrimination of serotype-specific and cross-reactive responses in primary and secondary infections. This VLP-based approach represents a scalable platform to investigate the protective and pathogenic roles of DENV-Bc in infection and vaccination. Full article

Background: The R21 malaria vaccine is a next-generation, WHO-prequalified vaccine that was introduced to reduce the burden of clinical malaria. In alignment with WHO recommendations, multi-dose vaccine presentations are preferred for large-scale immunization and inclusion in the Expanded Programme on Immunization (EPI). Accurate protein quantification is a critical quality control parameter for lot release, but it remains challenging when the antigen is present at low protein concentrations or formulated with complex matrices, including adjuvants, stabilizers, and preservatives. Methods: In this study, multiple protein estimation methods including Micro-BCA, BCA, and Bradford assays were evaluated to determine their suitability for quantifying the R21 antigen formulated with Matrix-M1 adjuvant and 2-PE preservative. The Bradford assay was selected as the most appropriate method, based on a comparative assessment of precision, accuracy, and linearity. Further optimization was undertaken to identify suitable buffer systems, and the method was validated in accordance with ICH Q2(R2) guidelines. Results: Validation results demonstrated that the assay is specific, accurate, precise, and repeatable, with a limit of quantitation (LOQ) of 2 µg/mL. The method demonstrated comparable performance to ELISA and was found to be sensitive enough to detect changes in antigen concentration resulting from unintended adsorption of R21 to vial surfaces. The assay offers a rapid, high-throughput, and cost-effective solution for protein quantitation in commercial manufacturing, lot release, and stability studies. The protein content of the drug product, quantified using the Bradford method, demonstrated robust in vivo immunogenicity in both release and stability studies. Conclusions: The robustness and reproducibility of the assay establish a new benchmark in quality control for virus-like particle (VLP)-based vaccines with complex formulations, thereby supporting the precision and reliability required for global malaria prevention efforts. Full article

Background: Porcine circovirus type 2 (PCV2) remains one of the most important pathogens that infects swine, causing considerable economic losses worldwide. PCV2 vaccines are commercially available, and the development of experimental vaccines that could confer better protection against emerging genotypes is underway. The expression of virus-like particles (VLPs) carrying different PCV2 capsid (Cap) peptides in E. coli was recently reported. These chimeric particles were adjuvated with an oil-in-water emulsion with polymer and induced different titers of serum IgG in BALB/c mice after a single subcutaneous injection. The aim of this study was to assess the immune response and protective efficacy elicited by VLPs carrying the PCV2b Cap carboxy-terminal peptide in the target species. Methods: Domestic pigs (Sus scrofa domesticus) were immunized intramuscularly with 25 μg of adjuvated chimeric VLPs on days 0 and 14 and challenged on day 28 with a PCV2b Mexican isolate. PCV2 peptide-specific IgG seroconversion, serum cytokines, viral load in nasal swabs and organs, and histopathological score were determined. Results: IgG levels peaked 28 days post-immunization. Interleukin-12 and -18 and interferon-gamma increased 21 days after immunization. In addition, genomic material of PCV2 was detected in nasal swabs from one specimen on day 7, two specimens on day 14, and two specimens on day 21 following viral challenge. Finally, histological lesions were not less severe in immunized specimens compared to non-vaccinated/challenged specimens. Conclusions: These results suggest that immunization with chimeric VLPs could contribute to controlling viral shedding in pig herds where a PCV2b genotype is most prevalent. Full article

Shellfish allergy is among the most common food allergies (FAs) worldwide and represents a severe immunoglobulin E (IgE)-mediated FA with tropomyosin functioning as the predominant pan-allergen. Current management of shellfish allergies is strictly palliative with allergen avoidance, underscoring the critical need for disease-modifying therapies. While conventional allergen-specific immunotherapy (AIT) approaches, namely oral and sublingual immunotherapies, demonstrate capacity for desensitization, more clinical applications are needed in the potential safety concerns and prolonged treatment durations. Innovative treatments, such as the design of modified shellfish allergens, DNA vaccine technologies, and nanoparticle-based delivery platforms such as virus-like particles (VLP), show efficacy and potential in inducing protective antibodies while promoting antigen-specific immune tolerance with reduced allergenic risks. These innovative approaches hint at a promising pathway in achieving safe, effective, and long-lasting clinical tolerance for shellfish allergy. This review describes the current perspectives on allergen immunotherapy regarding shellfish allergy and analyzes emerging therapeutic strategies poised to overcome these limitations. Full article

Piscine orthoreovirus genotype 1 (PRV-1) is an emerging viral pathogen in salmon aquaculture that causes Heart and Skeletal Muscle Inflammation (HSMI), with high prevalence in salmon-producing countries such as Chile. A significant obstacle in PRV-1 vaccine development is the inability to culture the virus in vitro, which limits the scalability and production of traditional inactivated or DNA-based vaccine strategies. This study describes the development of a novel virus-like particle (VLP)-based vaccine against PRV-1. Recombinant VLP were produced by co-expressing the six structural proteins of PRV-1 (λ1, λ2, μ1, σ1, σ2, σ3) using a baculovirus-based expression system in insect cells. In addition, to enable differentiating infected from vaccinated animals (DIVA) strategies, the σ1 protein was modified by adding of a cmyc epitope tag. The results demonstrated that the native VLP vaccine (VLP6n) significantly reduced viral loads in Atlantic salmon challenged with PRV-1. Moreover, in rainbow trout, the cmyc-tagged VLP-like vaccine (VLP6c) elicited a specific antibody response against the cmyc epitope, allowing differentiation between vaccinated and naturally infected fish. Overall, this VLP-based vaccine platform represents a promising strategy for controlling PRV-1 prevalence in salmon-producing counties, supporting the implementation of serological surveillance programs. Full article

Seasonal human coronaviruses (HCoVs), including HCoV-229E, HCoV-NL63, HCoV-OC43, and HCoV-HKU1, circulate globally in an epidemic pattern and account for a substantial proportion of common cold cases, particularly in infants, the elderly, and immunocompromised individuals. Although clinical manifestations are typically mild, these HCoVs exhibit ongoing antigenic drift and have demonstrated the potential to cause severe diseases in certain populations, underscoring the importance of developing targeted and broad-spectrum vaccines. This review systematically examines the pathogenesis, epidemiology, genomic architecture, and major antigenic determinants of seasonal HCoVs, highlighting key differences in receptor usage and the roles of structural proteins in modulating viral tropism and host immunity. We summarize recent advances across various vaccine platforms, including inactivated, DNA, mRNA, subunit, viral-vectored, and virus-like particle (VLP) approaches, in the development of seasonal HCoV vaccines. We specifically summarize preclinical and clinical findings demonstrating variable cross-reactivity between SARS-CoV-2 and seasonal HCoV vaccines. Evidence indicates that cross-reactive humoral and cellular immune responses following SARS-CoV-2 infection or vaccination predominantly target conserved epitopes of structural proteins, supporting strategies that incorporate conserved regions to achieve broad-spectrum protection. Finally, we discuss current challenges in pathogenesis research and vaccine development for seasonal HCoVs. We propose future directions for the development of innovative pan-coronavirus vaccines that integrate both humoral and cellular antigens, aiming to protect vulnerable populations and mitigate future zoonotic spillover threats. Full article

Background: The development of an effective HIV-1 vaccine remains a major challenge due to HIV-1’s extraordinary diversity, high mutation rate, and the rarity of broadly neutralizing antibody (bnAb) precursors. To address these challenges, we have previously immunized rabbits with mRNA-LNPs encoding for HIV-1 envelope glycoproteins (Envs), together with mRNA-LNPs encoding for HIV-1 Gag, which likely mediated the generation of virus-like particles presenting HIV-1 Envs to the immune system in vivo. Methods: Here, we investigated whether an escalating dose (ED) immunization using mRNA-LNP priming, followed by boosts with synthetic, protein-based, virus-like particles (synVLPs) displaying HIV-1 SOSIP trimers via SpyTag/SpyCatcher conjugation (group 1), could improve the quality and durability of the antibody responses compared to conventional bolus immunization (group 2). Previous studies have shown that, in contrast to single bolus immunization, the ED priming strategy could enhance B cell activation and prolong affinity maturation, resulting in higher-quality antibody responses. Results: Upon vaccination, rabbits from both groups developed strong homologous anti-Env antibody responses, with an increasing ability of sera from immunized rabbits to bind Envs following subsequent boosts. Antibodies in rabbit sera bound heterologous Envs, but there was no statistically significant difference in binding between the two groups. Overall, antibody responses were comparable across all animals and declined similarly over time in both groups, indicating that neither the adjuvants nor the ED priming led to any marked differences within this small sample size. Neutralization activity against homologous tier-2 HIV-1_AD8 (mRNA prime) and tier-2 HIV-1₁₀₅₉ (protein boost) was generally low across both groups; however, a higher neutralization titer was observed for the ED group against HIV-1_AD8 following the final boost. One of the rabbits from the bolus group exhibited exceptionally high neutralization titers that correlated with elevated Env-specific binding against HIV-1₁₀₅₉. Conclusions: These results highlight the challenges in eliciting broad and potent neutralizing antibody (nAb) responses. Our findings underscore the need for the continued development and refinement of immunogen design and delivery strategies to guide the elicitation of nAb. Full article

Background/Objectives: The dengue virus remains endemic in over 100 countries, transmitted by mosquito bites. Current management relies on supportive care, as no highly effective vaccine or approved antiviral exists. The CYD-TDV (Dengvaxia^®) vaccine, licensed since 2015 with around 60% efficacy, raises the risk of severe dengue in seronegative children. The newer “Qdenga” vaccine offers up to 80% efficacy after a year but provides suboptimal protection against DENV-3 in seronegative individuals. Over the past two decades, virus-like particles (VLPs) have gained attention as safe, replication-incompetent vaccine platforms. This study evaluates the toxicity profile of dengue VLP-based antigens in BALB/c mice. Methods: A total of 80 BALB/C mice were randomly divided into two experimental groups: acute and chronic. Each group consisted of a treatment subgroup (10 males and 10 females) and a control subgroup (10 males and 10 females). In the acute group, the VLP was administered intramuscularly on day 1, while in the chronic group, a second VLP dose was given on day 14. The study was conducted over a 28-day period. Throughout the experiment, body temperature, body weight, mortality, and clinical signs were monitored regularly to assess the functional condition of various organs. Results: The results showed no notable alterations in mortality rates, body temperature, body weight, clinical signs, or histopathological observations of the examined organs across all groups, including in the hematological and blood biochemical parameters. Conclusions: The administration of tetravalent dengue VLP vaccine in BALB/c mice did not result in adverse effects in acute or chronic toxicity evaluations. Therefore, the VLP supports progression toward clinical evaluation, with dendritic cell activation providing additional rationale. Full article

Background: Respiratory syncytial virus (RSV) is a major pathogen of acute lower respiratory tract infection (LRTI) in infants, the elderly, and immunocompromised individuals. This review focuses on the progress of RSV vaccine development, especially subunit vaccines targeting the fusion protein (F) and attachment glycoprotein (G), aiming to summarize key strategies, challenges, and future directions in the field. Methods: The review is based on a comprehensive literature search and analysis of recent studies on RSV vaccine development, with a specific focus on subunit vaccines and related technologies. Results: Approved vaccines such as Abrysvo and Arexvy utilize structural engineering to stabilize the prefusion conformation of the F protein (PreF), thereby exposing neutralizing epitopes. Subunit vaccine candidates such as DS-Cav1 and DT-PreF enhance stability through disulfide bonds and dityrosine linkages, while ADV110 targets the conserved domain of the G protein to elicit cross-strain immunity. Virus-like particle (VLP) vaccines like IVX-A12 combine RSV and human metapneumovirus antigens to provide broad-spectrum immunity. However, challenges exist, including maintaining PreF stability, overcoming immunosenescence in the elderly, and addressing safety concerns like Guillain-Barré syndrome (GBS). Conclusions: Future RSV vaccine development should center on combined PreF-G protein vaccines, VLP technology, and optimizing cold-chain logistics to improve global accessibility and overcome existing challenges, thereby providing more effective prevention and control of RSV infections. Full article

Background: The extracellular domain of the M2 protein (M2e) and the conserved region of the second subunit of the hemagglutinin (HA2, 76–130 а.а.) of the influenza A virus, could be used to develop broad-spectrum influenza vaccines. However, these antigens have low immunogenicity and require the use of special carriers to enhance it. Virus-like particles (VLPs) formed from viral capsid proteins are among the most effective carriers. Methods: In this work, we obtained and characterized VLPs based on capsid proteins (CPs) of single-stranded RNA bacteriophages Beihai32 and PQ465, simultaneously displaying M2e and HA2 peptides. Results: Fusion proteins expressed in Escherichia coli formed spherical VLPs of about 30 nm in size. Subcutaneous immunization of mice with chimeric VLPs elicited a robust humoral immune response against M2e and the whole influenza A virus, and promoted the formation of cytokine-secreting antigen-specific CD4⁺ and CD8⁺ effector memory T cells. Conclusions: VLPs based on CPs of phages Beihai32 and PQ465 carrying conserved peptides M2e and HA2 of the influenza A virus can be used for the development of universal influenza vaccines. Full article

Human norovirus (HuNoV), particularly the GII.4 genotype, is a leading cause of acute gastroenteritis worldwide, posing a significant public health and economic burden due to its low infectious dose. To address the need for rapid and sensitive detection, we developed a colorimetric biosensor utilizing a structure-optimized aptamer and gold nanoparticles (AuNPs). Biotin-modified aptamers could protect AuNPs from aggregation in salt solution. Upon specific binding to GII.4 HuNoV virus-like particles (VLPs), this protective effect is disrupted, leading to AuNP aggregation and a measurable color shift quantified by the A620/A520 absorbance ratio. Under optimized conditions, the assay demonstrated a linear response (y = 0.004597x + 0.3277, R² = 0.9922) to GII.4 HuNoV VLP concentrations ranging from 0.1 to 3.0 μg/mL, with the recovery rates between 91.74% and 106.43%. The biosensor exhibited high specificity for GII.4 HuNoV, showing minimal cross-reactivity with other common diarrheal pathogens, and achieved an exceptional detection limit of 27.2 copies/mL in a fecal matrix. Molecular docking and point mutation confirmed the critical roles of specific nucleotide bases (T20, C22, G31, and G44) in the aptamer and the Asn55 residue in the viral capsid for binding. This work establishes a sensitive, rapid, and cost-effective aptamer-based colorimetric platform suitable for the large-scale monitoring of GII.4 HuNoV. Full article

JC virus (JCV) replicates within the nuclei of glial cells in the human brain and causes progressive multifocal leukoencephalopathy. JCV possesses a small, circular, double-stranded DNA genome, divided into early and late protein-coding regions. The non-coding control region (NCCR) functions bidirectionally for both early and late genes, and the agnogene is located downstream of TCR and upstream of three capsid proteins in the late region. Previously, in cell culture systems, we demonstrated that these capsid proteins accumulate in intranuclear domains known as promyelocytic leukemia nuclear bodies (PML-NBs), where they assemble into virus-like particles (VLPs). To investigate the agnogene’s function, VLPs were formed in its presence or absence, and differential gene expression was analyzed using microarray technology. The results revealed altered expression of histone-modifying enzymes, including methyltransferases (EHMT1, PRMT7) and demethylases (KDM2B, KDM5C, KDM6B), as well as various kinases and phosphatases. Notably, CTDP1, which dephosphorylates the C-terminal domain of an RNA polymerase II subunit, was also differentially expressed. The changes were predominant in the presence of the agnogene. These findings indicate that the agnogene and/or its protein product likely influence epigenetic regulation associated with PML-NBs, which may influence cell cycle control. Consistently, in human brain tissue, JCV-infected glial cells displayed maintenance of a diploid chromosomal complement, likely through G2 arrest. The precise mechanism of this, however, remains to be elucidated. Full article

The recent SARS-CoV-2 pandemic has highlighted the need for quickly adaptable technologies in vaccine manufacturing. This can be achieved through virus-like particles (VLPs) as presentation platforms for target antigens. In this study, we investigated the purification of VLPs of the Hepatitis B Core antigen (HBc) and the SplitCore (SplCo) technology. The outer surface protein C (OspC) of Borrelia burgdorferi was genetically fused to HBc and its N-terminal SplCo protein. Product solubility in E. coli increased from 40% for HBc-OspC to 90% for SplCo-OspC. This could not be reproduced with similar SARS-CoV-2 receptor-binding domain fusions due to inclusion body formation. Hydrophobicity was found to be significantly lowered for the OspC fusions, in particular for the SplCo variant. Pre-purified samples were generated by precipitating soluble cell lysate. Subsequently, solubilized precipitates were subjected to anion exchange chromatography (AEX), and the elution fractions obtained contained VLPs, albeit with low purity. The VLPs were also disassembled prior to AEX for dissociative purification, but a subsequent reassembly could not be achieved for both fusion variants. A novel HBc variant was constructed for post-translational modification via click-chemistry. The solubility and hydrophobicity of this HBc variant remained high, but native AEX resulted in complete product loss. By contrast, a yield of 84% VLPs was obtained for the modified HBc after dissociative AEX. The surface-exposed azide group on the particles, introduced for click-chemistry, enabled coupling to fluorophores without compromising VLP stability. Conjugation efficiencies of up to 59% were obtained. These results suggest the potential of combining HBc and click-chemistry for future applications, e.g., the presentation of immunogenic epitopes or antigens. This underlines that for every antigen, both the optimal scaffold-decoration strategy and the subsequent manufacturing process should be carefully selected. Full article

Virus-like particles (VLPs) formed as a result of self-assembly of viral capsid proteins are widely used as a platform for antigen presentation in vaccine development. However, since the inclusion of a foreign peptide into the capsid protein can alter its spatial structure and interfere with VLP assembly, such insertions are usually limited to short peptides. In this study, we have demonstrated the potential of capsid protein (CP) of single-stranded RNA phage PQ465 to present long peptides using green fluorescent protein (GFP) as a model. GFP was genetically linked to either the N- or C-terminus of PQ465 CP. Hybrid proteins were expressed in Escherichia coli and Nicotiana benthamiana plants. Spherical virus-like particles (~35 nm according to transmission electron microscopy) were successfully formed by both N- and C-terminal fusions expressed in E. coli, and by plant-produced CP with GFP fused to the C-terminus. ELISA revealed that GFP in VLPs was accessible for specific antibodies suggesting that it is exposed on the surface of PQ465-GFP particles. VLPs carrying GFP were recognized by anti-CP antibodies with less efficiency than VLPs formed by empty CP, which indicates shielding of the CP core in PQ465-GFP particles. Therefore, PQ465 CP can be used as a chimeric VLP platform for the display of relatively large protein antigens, which can operate in bacterial and plant expression systems. Full article

Background/Objectives: Virus-like particle (VLP) vaccines based on human papillomavirus (HPV) L1 proteins have high efficacy for preventing cervical cancer and other HPV-associated diseases. The production yields of commercial HPV VLPs remain suboptimal. We aimed to improve HPV VLP production efficiency using a hyper-expression vector system for the expression of L1 proteins of four major HPV serotypes—HPV 6, 11, 16, and 18. Methods: HPV L1 proteins were expressed in Trichoplusia ni (Hi5) insect cells via a hyper-expression baculovirus vector system. Following cell lysis using a microfluidizer, VLPs were purified through a two-step chromatographic process. Particle morphology was characterized using transmission electron microscopy and dynamic light scattering. Immunogenicity was evaluated using a murine model; mice received three intramuscular injections of the purified quadrivalent VLPs. The resulting IgG and neutralizing antibody responses were compared with those elicited by the commercial quadrivalent vaccine, Gardasil. Results: The L1 proteins from HPV 6, 11, 16, and 18 were successfully expressed at high levels in Hi5 cells, forming uniformly sized VLPs with hydrodynamic diameters of 50–60 nm. The average production yield of the quadrivalent VLPs exceeded 40 mg/L, an improvement over conventional yields. The candidate VLPs elicited strong HPV-specific IgG and neutralizing antibody responses in mice, comparable to those induced by Gardasil. Conclusions: The hyper-expression baculovirus vector system enables high-yield production of HPV L1 VLPs with desirable structural and immunogenic properties. This approach holds promise for the cost-effective and scalable manufacturing of next-generation HPV VLP vaccines, facilitating broader global access to HPV immunization. Full article