Search Results (449)

Background: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus transmitted predominantly by Aedes aegypti and Aedes albopictus. Infection is characterized by an acute febrile illness accompanied by debilitating polyarthralgia, myalgia, and cutaneous manifestations. Although the acute syndrome is usually self-limited, a substantial proportion of patients experience persistent musculoskeletal symptoms that may progress to chronic inflammatory arthritis, resulting in prolonged disability and impaired quality of life. Objective: To summarize current evidence on the epidemiology, virology, immunopathogenesis, clinical manifestations, laboratory diagnosis, prevention, and vaccine development of CHIKV, with particular emphasis on its implications for public health policy and immunization strategies in Mexico. Methods: This position paper was developed through a structured narrative review of the scientific literature. Publications indexed in PubMed, Scopus, and Embase, together with documents issued by the World Health Organization (WHO), Pan American Health Organization (PAHO), Centers for Disease Control and Prevention (CDC), U.S. Food and Drug Administration (FDA), and European Medicines Agency (EMA), were critically reviewed. Evidence was selected according to its scientific quality and relevance to Mexico and Latin America. Because this work represents an expert consensus rather than a systematic review, no formal risk-of-bias assessment was performed. Results: CHIKV circulates through both urban and sylvatic transmission cycles and continues to expand into regions where competent mosquito vectors are established. Disease progression is driven by complex innate and adaptive immune responses, with exaggerated inflammatory activation contributing to chronic rheumatologic sequelae. Laboratory confirmation relies primarily on molecular assays during the viremic phase and serological testing thereafter. Recent advances in vaccine development—including live-attenuated and virus-like particle (VLP) platforms—have demonstrated favorable immunogenicity and acceptable safety profiles. However, vaccination should be considered one component of an integrated prevention strategy that also includes vector surveillance, environmental control, and rapid outbreak detection. Conclusions: Chikungunya remains an emerging global public health challenge because of its expanding geographic distribution, epidemic potential, and long-term clinical consequences. Incorporating vaccination into comprehensive arboviral control programs, together with strengthened surveillance and integrated vector management, may substantially reduce disease burden. This position paper provides evidence-based recommendations to support future chikungunya prevention and vaccination policies in Mexico. Full article

Feline bocavirus (FBoV) is an emerging enteric virus associated with gastrointestinal diseases in cats and has attracted increasing attention in feline health. However, no commercial vaccine is currently available for the prevention and control of FBoV infection. VP2 is the major capsid protein of FBoV and represents a promising target for vaccine development. In this study, the FBoV VP2 protein was expressed using the insect baculovirus expression system. The purified VP2 protein self-assembled into virus-like particles (VLPs), which were formulated with Alum, ISA 206, or GEL 02 adjuvants to prepare VP2 VLP vaccines. The immunogenicity, cellular immune responses, antigen uptake, biodistribution, germinal center responses, and safety of the vaccines were evaluated in BALB/c mice. The results showed that all VP2 VLP vaccine formulations induced VP2-specific IgG antibodies and neutralizing antibodies, promoted B- and T-lymphocyte activation, enhanced dendritic cell maturation, and stimulated germinal center-related immune responses. Among the tested formulations, VP2+GEL 02 induced the strongest immune responses and showed favorable safety in mice. These findings demonstrate that FBoV VP2 exhibits favorable immunogenicity and represents a promising vaccine antigen for further development against feline bocavirus. Full article

Background/Objectives: Epstein–Barr virus (EBV) is a ubiquitous pathogen responsible for significant malignancies and autoimmune diseases, yet no prophylactic vaccine is available. The viral entry glycoproteins gL/gH and gB are essential for infection, but soluble forms are poorly immunogenic and fail to elicit durable neutralizing antibodies. Moreover, EBV infects both B cells and epithelial cells, demanding broad neutralization. This study aimed to develop a virus-like particle (VLP) platform that displays gL/gH and gB in a dense, repetitive array to overcome these barriers. Methods: We conjugated recombinant gL/gH and gB to Acinetobacter phage AP205 VLPs using SpyTag/SpyCatcher covalent linkage, generating monovalent and bivalent chimeric nanoparticles (co-displaying both antigens on the same particle). Mice were immunized with these VLP constructs or alum-adjuvanted soluble proteins, and antibody responses, neutralization titres against B-cell and epithelial-cell infection, as well as germinal centre responses and durability, were assessed over a four-month period. Results: AP205-conjugated nanoparticles elicited significantly higher antigen-specific IgG titres than soluble proteins. The chimeric VLP, co-displaying gL/gH and gB, induced the stronger neutralising antibodies, effectively blocking EBV entry into both B cells and epithelial cells. Mechanistically, VLP immunization drove robust and sustained germinal centre reactions, resulting in increased plasma and memory B cells, and maintained neutralising activity for at least four months. Conclusions: Precision nanoscale assembly of EBV entry glycoproteins on a synthetic VLP programs high-magnitude, broad-spectrum, and durable humoral immunity. The AP205-SpyTag platform offers a versatile and promising strategy for developing an effective prophylactic EBV vaccine. Full article

Background/Objectives: Mosquito-borne viruses cause substantial global morbidity and mortality. Mosquito saliva, secreted during biting, facilitates blood feeding and can enhance virus infection. Here, we evaluated whether combining virus-specific antigens with mosquito salivary protein-derived peptides improves protection in Zika virus (ZIKV) and chikungunya virus (CHIKV) mouse models. Methods: Peptides from Aedes and Culex salivary proteins were selected based on conservation, predicted T-cell reactivity, and cellular and humoral immunogenicity in mice. Mice were immunised subcutaneously with a prime and boost two weeks apart using adjuvanted salivary peptides (SAL), commercial ZIKV- or CHIKV-like particles (VLPs), or salivary peptides combined with the relevant VLPs. Vaccine doses contained 0.5 µg VLPs and/or 10 nmol of each salivary peptide, formulated with Montanide ISA-51; when combined, VLPs and SAL were administered on opposite flanks. Two weeks after boosting, mice were challenged with ZIKV or CHIKV plus Aedes aegypti saliva. Challenge teams were blinded to group allocation until data analyses were complete. Results: SAL enhanced the protective effect of VLP vaccination compared with VLPs alone. In the CHIKV model, CHIKV VLP + SAL prevented joint swelling and reduced infectious virus in the inoculated ankle and viral RNA in the contralateral ankle. In the ZIKV model, ZIKV VLP + SAL reduced viral RNA in skin and brain tissue and improved survival. Conclusions: Mosquito salivary peptide antigens improved the protective efficacy of VLP vaccines against ZIKV and CHIKV in mouse models. Salivary antigens may provide a complementary vaccine component for multiple arboviruses transmitted by Aedes and Culex mosquitoes. Full article

Human papillomavirus type 16 (HPV16) is a major etiological agent of cervical and other epithelial cancers, yet the mechanisms underlying host–pathogen interactions remain incompletely understood. In this study, we investigated the responses of human peripheral blood leukocytes to engineered HPV16 L1/L2 chimeric virus-like particles (VLPs), produced in suspension by HEK 293-F cells. These VLPs were designed to mimic native viral structures while incorporating chimeric features that enhance stability and immunogenicity. Through experimental assays, we characterized leukocyte engagement, primarily involving leukocyte phenotyping, VLP internalization, confocal colocalization, and endocytic pathway analyses. We demonstrated that recombinant L1/L2 proteins assembled into structured VLPs capable of interacting with mononuclear cells, including lymphocytes and monocytes, but not with polymorphonuclear cells, such as neutrophils, eosinophils and basophils. Uptake occurred via the CD71 transferrin receptor-mediated pathway, in addition to other endocytic routes analyzed, as confirmed by blockage assays using chlorpromazine, rCTB, filipin, nystatin, liquemine, and sodium azide. Confocal colocalization and endocytic pathway analyses further supported receptor-mediated uptake. These findings demonstrate that HPV16 L1/L2 chimeric VLPs interact with and are internalized by human peripheral blood mononuclear cells through CD71-associated and other endocytic pathways. The study provides new insights into HPV16 VLP–leukocyte interactions and contributes to a better understanding of the cellular mechanisms involved in VLP uptake, which may be relevant for future studies on HPV biology and VLP-based vaccine development. Full article

Virus-like particles (VLPs) based on the capsid protein (CP) of the ssRNA bacteriophage Beihai32 represent a promising nanoscale platform for the presentation of heterologous peptides. Previous studies have shown that the C-terminus of the CP tolerates long insertions without compromising VLP assembly. Here, we demonstrate that the N-terminus is similarly permissive to extended insertions. Hybrid CPs with one to four copies of the influenza A virus M2e peptide fused to the N-terminus were expressed in Escherichia coli. Fusion proteins containing four copies of M2e self-assembled into spherical VLPs, displaying the inserted peptides on the surface. Subcutaneous immunization of mice with chimeric VLPs induced high titers of M2e-specific antibodies. Unlike C-terminal fusions, the N-terminal insertion prevented the induction of anti-carrier antibody response indicting masking of the carrier protein in the chimeric VLP. To evaluate the capacity of the N-terminus for larger inserts, green fluorescent protein (GFP, 238 a.a.) was attached to the N-terminus of CP. The hybrid protein was expressed in Escherichia coli and formed VLPs. GFP was displayed on the particle surface and retained fluorescent activity. Overall, the phage Beihai32 CP is a versatile platform for the presentation of peptide antigens, supporting its potential application in VLP-based vaccine design. Full article

Human noroviruses (HuNoVs) are a leading cause of acute gastroenteritis worldwide, yet no effective antiviral therapeutics are currently available. Although environmentally induced capsid conformational changes associated with infectivity have been reported in murine noroviruses (MNVs), comparable conformational switching has not been demonstrated in HuNoVs. In this study, we generated HuNoV GII.3 virus-like particles (VLPs) using a baculovirus expression system and identified two distinct T = 3 particle populations coexisting within VLP preparations derived from a single strain through cryo-electron microscopy single-particle analysis. Comparative structural analysis revealed that these two T = 3 capsid conformations correspond to the resting and rising states of the protruding (P) domain. Rearrangement of the P domain alters intermolecular interactions between adjacent capsid subunits, resulting in distinct capsid surface architectures. In the resting state, intermolecular contacts were mediated predominantly by the P2 subdomain, with limited contribution from the P1 subdomain. In contrast, the rising state exhibited a shift toward an alternative interaction interface primarily involving the P1 subdomain. The alteration of the capsid surface accompanying this conformational switching can influence biologically relevant intermolecular interactions with viral hosts and antibodies as demonstrated in murine norovirus. These findings demonstrate previously unrecognized structural polymorphism in the HuNoV capsid and provide evidence that conformational switching may occur in HuNoVs. Our results offer new insights into norovirus capsid dynamics and may inform future structure-based vaccine and antiviral drug development. Full article

Identifying antigens that elicit protective immunity is the key step for vaccine development. Here, we describe the use of the MS2 VLP platform to identify epitopes of SARS-CoV-2 structural proteins recognized by antibodies from COVID-19 patients, and to present those epitopes to the immune system as vaccines. We constructed an MS2 virus-like particle (VLP) library covering all four structural proteins of SARS-CoV-2 and affinity-selected vaccine candidates by biopanning on antibodies from infected humans. We focused on the structural proteins, reasoning that they are the most likely targets of a protective antibody response. The epitopes we found map almost entirely to the spike and nucleocapsid proteins. The VLPs displaying such epitopes were produced individually in E. coli and then tested for their potential as vaccines. While none of the affinity-selected spike-specific VLPs elicited neutralizing antibodies, VLPs displaying nucleocapsid epitopes induced protective immunity in a hamster model. This work illustrates the MS2 VLP platform’s capacity for the identification of new vaccine candidates and raises the possibility that VLPs displaying nucleocapsid epitopes could provide long-lasting protection against a range of virus variants. Full article

Feline panleukopenia is a highly contagious and often fatal disease in cats caused by the feline panleukopenia virus (FPV), a member of the Parvoviridae family. Despite the widespread use of vaccination, FPV remains a significant threat to both domestic and wild felid populations worldwide, particularly in young or unvaccinated animals. Effective vaccination strategies are therefore essential for controlling the disease and reducing mortality. Current vaccines, including modified live and inactivated vaccines, have demonstrated substantial efficacy in inducing protective immunity; however, several challenges remain, such as maternal antibody interference, vaccine failure, and safety concerns in certain animal populations. Recent advances in vaccine technology have spurred the development of next-generation FPV vaccines, including recombinant vectors, DNA vaccines, virus-like particle (VLP) vaccines, and novel delivery platforms. Among these, probiotic-based vaccine vectors have garnered growing interest due to their favorable safety profiles, mucosal immunogenicity, and suitability for oral administration. These systems may provide innovative approaches for inducing both systemic and mucosal immune responses against FPV. This review summarizes the current understanding of the immunological mechanisms underlying protection against FPV infection and discusses the progress made in FPV vaccine development. Furthermore, it highlights the major challenges associated with current vaccination strategies and explores emerging vaccine platforms, including probiotic vector-based vaccines, as promising tools for future disease control. Improved vaccine design and optimized immunization strategies will be crucial for enhancing the prevention of feline panleukopenia in the future. Full article

Because hepatitis B virus (HBV) remains a major global health burden, innovative strategies are essential to achieve the World Health Organization’s goal of eliminating viral hepatitis and closing persistent coverage gaps for injectable vaccines. While parenteral administration remains the gold standard for immunization, constraints such as cold-chain dependence and needle-associated barriers limit its reach, particularly in resource-constrained environments. This review summarizes work aimed at a plant-produced orally delivered vaccine as a transformative, scalable step towards global hepatitis B elimination. Early studies demonstrated proof of concept for the oral delivery of plant-produced hepatitis B vaccine candidates, including human trials using lettuce and potato as the host, but they were limited by low antigen yields and instability. In contrast, maize-produced antigens represent a significant advancement, achieving high levels of accumulation and utilizing the seed’s natural desiccation physiology for bioencapsulation to protect the antigen from digestion in the gastrointestinal tract. Mechanistically, this platform enables timed antigen release in the duodenum, promoting M-cell uptake and CD103⁺ (cells expressing CD103 known as integrin alpha E) dendritic cell (DC) presentation, thus encouraging immunogenic programming over oral tolerance. In addition, defatting the grain by supercritical fluid extraction further improves antigen thermostability up to 45 °C for one month and ambient temperatures for one year, maintaining structural integrity under extreme conditions in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) stability guidelines. Current recommendations for immunization are for three parenteral administrations using the hepatitis B surface antigen (HBsAg). The primary dose is usually given shortly after birth as a part of a multivalent vaccine. Therefore, initial studies for the oral plant-based vaccine have focused on using an oral boost after the parenteral prime. Data to support this premise are summarized along with co-administration of an oral and parental administration to elicit a stronger immune response. By overcoming past issues related to dose density and stability, this scalable, needle-free platform offers a practical way to eliminate global hepatitis B virus (HBV) transmission, especially in resource-constrained environments. Full article

Background/Objectives: Post-weaning diarrhea remains a major challenge in pig production worldwide. Enterotoxigenic Escherichia coli (ETEC) encoding fimbriae of the F4 type and producing the heat-stable enterotoxin, STb, are one of the important causes of this disease. The aim of the current study was to evaluate whether vaccination of pregnant sows with a novel capsid virus-like particle (cVLP)-based vaccine against F4 and STb (cVLP-FaeG/cVLP-STb) could enhance performance in piglets born after such vaccinated sows. Methods: A field trial was conducted in a commercial sow-to-finisher pig herd. Thirty-five sows were vaccinated twice with the cVLP-FaeG/cVLP-STb vaccine prior to farrowing, while thirty-five control sows were vaccinated twice with commercial vaccines normally used in the herd. Piglets were followed until eight weeks post-weaning to assess antibody responses, diarrhea and treatment incidences, pathogen shedding, and growth performance. Results: Piglets born from immunized sows receiving the cVLP vaccine showed significantly higher serum antibody levels against ETEC F4 throughout the post-weaning period (p ≤ 0.021). The frequency of pathogen detection was similar between groups, while piglets in the cVLP group exhibited significantly lower diarrhea scores at week 6 (p = 0.047), showed a trend of requiring fewer treatments (p = 0.06) and had significantly higher final body weight (p = 0.048). In addition, the cVLP group showed a significantly greater average daily gain over the study period (p = 0.037). Conclusion: Sow immunization with the cVLP vaccine enhanced passive immune protection of piglets, resulting in reduced antimicrobial treatment 2 weeks post-weaning and improved growth performance. Full article

Background/Objectives: Canine papillomavirus (CPV) is an important viral pathogen associated with papillomatosis in dogs, with canine papillomavirus type 1 (CPV1) and type 2 (CPV2) among the most prevalent and clinically relevant genotypes. The L1 capsid protein is a major immunogenic antigen of papillomaviruses; however, conserved linear B-cell epitopes shared between CPV genotypes remain poorly defined. This study aimed to identify conserved cross-reactive B-cell epitopes within CPV1 and CPV2 L1 proteins and to evaluate their preliminary immunoreactivity. Methods: Conserved linear B-cell epitopes were predicted through integrated bioinformatic and structural analyses based on sequence conservation and surface accessibility. Three candidate epitopes were selected. Recombinant CPV1 and CPV2 L1 proteins were expressed in Escherichia coli (E. coli), purified, used as recombinant L1 antigens, together with BSA-conjugated synthetic epitope peptides for mouse immunization. Antigen-specific IgG responses were assessed by ELISA, antigen-associated IFN-γ responses were evaluated by ELISpot, and cross-reactive antibody recognition was assessed by Western blot. Results: Recombinant L1 proteins induced strong antigen-specific IgG responses in mice. The selected peptides induced detectable but weaker humoral responses compared with the recombinant L1 proteins. Among the three epitopes, TPSGSLV and TVVDNTR elicited antibodies that recognized both CPV1 and CPV2 L1 proteins, while the epitope VIVPKVS showed minimal or no detectable immunoreactivity. ELISpot analysis showed only modest antigen-associated IFN-γ responses, particularly in peptide-immunized groups. Conclusions: This study identified conserved cross-reactive linear B-cell epitope candidates within CPV1 and CPV2 L1 proteins and provided preliminary immunological evidence supporting their potential relevance for CPV antigen design. However, peptide-induced responses were weaker than those induced by recombinant L1 proteins, and VLP formation, antibody neutralizing activity, and protective efficacy were not evaluated. Further studies in dogs, including optimized antigen-display platforms, neutralization assays, and protection studies, are required to determine the practical value of these epitopes for CPV vaccine development. Full article

Porcine circovirus type 3 (PCV3) capsid protein (Cap) is a key antigen for immunological studies and vaccine development. Different optimized PCV3 ORF2 sequences were used to construct six baculovirus transfer plasmids, with the pOET1.1-based design yielding the highest Cap level. Cap expression was confirmed by Western blot, IPMA and IFA. Recombinant baculovirus amplification was optimized, achieving the highest titer at an MOI of 0.1 with a 72 h harvest to 10^7.5TCID₅₀/0.1 mL, while maximal Cap production was obtained at an MOI of 0.1 with a 96 h harvest. PCV3 Cap virus-like particles (VLPs) were purified by sucrose density-gradient ultracentrifugation and cation-exchange chromatography, and TEM revealed spherical particles of approximately 17–20 nm. In mice, VLP immunization induced increasing antigen-specific IgG from day 14. Immunization increased both IgG1 and IgG2a without a significant difference, and post-immunization serum specifically recognized PCV3-positive passaged PK-15 cells in an indirect immunofluorescence assay. In splenic lymphocytes, IFN-γ, TNF-α, IL-4, and IL-10 mRNA levels were significantly upregulated (p < 0.01). Moreover, pig challenge data supported the protective potential of PCV3 Cap VLPs in the natural host. In our study, Cap assembled into VLPs and induced immune responses, providing a basis for PCV3 subunit vaccine development. Full article

Background/Objectives: Recombinant poliovirus (PV) virus-like particle (VLP) antigens mimic the conformation of the surface proteins in native PVs (i.e., serotype-specific D-antigen epitopes). Since they lack genomes and are non-infectious, PV-VLPs offer the promise of a safer, next-generation polio vaccine compared to traditional inactivated (IPV) or attenuated live (OPV) vaccines. Sandwich D-antigen ELISA formats are commonly used to measure the in vitro potency values (relative D-antigen content, DU/mL) of unadjuvanted trivalent IPV antigens. If IPV is formulated with aluminum-salt adjuvants, however, a pretreatment step (i.e., adjuvant dissolution or antigen desorption) is required, which may compromise antigen integrity during sample handling. Methods: This work describes the development of three competitive ELISAs to measure the relative D-antigen content of aluminum-salt adjuvanted PV-VLPs (Types 1, 2, 3) without the need for pretreatment. Results: First, key assay parameters were established, including specificity, accuracy, precision, linearity, limit of quantification, and stability-indication. Next, preformulation characterization studies were performed with these methods including (1) rank-ordering the inherent thermal stability profiles of the PV-VLPs (Types 1 > 3 > 2) in-solution and adsorbed to an aluminum phosphate adjuvant (AdjuPhos™, AP) and (2) determining the effect of formulation variables on the thermal stability profiles of AP-adsorbed PV-VLPs including antimicrobial preservatives (thimerosal, 2-PE) and five different antigens present in pediatric combination vaccines (D, T, wP, Hib, Hep B). Conclusions: The development and application of three competitive D-antigen ELISAs were demonstrated, and future use in formulation and storage stability studies with the AP-adjuvanted, trivalent PV-VLPs (Types 1, 2, 3) is discussed with the long-term goal to develop a stable, efficacious, multi-dose, hexavalent combination vaccine presentation. Full article

Objectives: Membrane-enveloped virus-like particles (VLPs) constitute a versatile vaccine platform allowing for the display of heterologous viral surface antigens. The density of displayed antigens is paramount for the efficient elicitation of a strong cellular and humoral immune response. SARS-CoV-2 spike protein variants with engineered cytoplasmic tails (CTs) were generated to enhance decoration efficiency on the surface of VLPs formed by the HIV core protein Gag. These HIV (SARS-CoV-2) chimeric particles serve as a vaccine component prototype. Methods: Spike variants were first analyzed for cellular and surface expression as well as incorporation into extracellular vesicles (EVs) and VLPs using flow cytometric analysis and Western blot analysis. Receptor binding, fusogenicity, i.e., mediating the fusion of spike-positive with receptor-containing membranes, and the proteins’ potential to mediate lentiviral vector gene transduction into susceptible target cells was examined by employing syncytia-formation assays and vector titration experiments. The display of a neutralization-sensitive epitope was examined utilizing immuno-precipitation using a neutralizing antibody. Results: All four variants were shown to be cell-surface expressed, to recruit the cognate receptor, to mediate membrane fusion and cell entry of lentiviral pseudotype vector particles and to decorate VLPs and EVs. However, the spike variant encompassing a truncated CT derived from the gibbon ape leukemia virus (GaLV) transmembrane (TM) envelope protein was most efficiently incorporated into HIV Gag-formed VLPs. All variants exposed a neutralization-sensitive epitope in the receptor binding domain. Conclusions: Engineering of the CTs of viral surface antigens can enhance VLP decoration, while required functionality of the ecto-domain such as receptor recognition, fusogenicity and neutralization-sensitive epitope presentation are not abrogated. This indicates the preservation of the structural integrity of the antigen required to elicit a neutralizing humoral immunity upon vaccination. The identified truncated CT of GaLV TM may be of utility to improve the incorporation of other viral surface antigens into a variety of membrane-enveloped VLPs derived from a range of different parental viruses. Full article