Search Results (495)

Glioblastoma (GB) remains one of the most therapy-resistant solid tumors, characterized by profound metabolic plasticity, intratumoral heterogeneity, and a highly immunosuppressive microenvironment. While immunotherapies such as chimeric antigen receptor T (CAR-T) cells have shown promise in hematological malignancies, their efficacy in GB has been limited. Emerging evidence suggests that tumor-specific metabolic dependencies and post-translational modifications (PTMs) may represent exploitable vulnerabilities. This review discusses disulfidptosis, a recently described form of regulated cell death driven by disulfide stress under conditions of limited reducing capacity, as a context-dependent metabolic–redox vulnerability in GB. We further discuss how altered protein glycosylation and glycocalyx architecture in glioblastoma regulate cell survival, death signaling, and immune recognition. Particular emphasis is placed on the glycosylation of surface antigens targeted by CAR-T cells, including EGFR/EGFRvIII, IL-13Rα2, mesothelin, B7-H3, HER2, and GD2, and on how glycan-dependent epitope accessibility may limit therapeutic efficacy. Finally, we distinguish disulfidptosis, whose direct relevance to CAR-T-cell responses remains to be established, from glycosylation and glycocalyx remodeling as more direct determinants of target–antigen accessibility and immune recognition. Therapeutic strategies addressing these vulnerabilities may provide rational opportunities to improve CAR-T-based and combinatorial therapies for GB. Full article

Inflammation plays a pivotal role in the pathogenesis of acne vulgaris, with Cutibacterium acnes recognised as a key etiological agent. The global increase in acne prevalence, coupled with the rising incidence of antibiotic-resistant strains, underscores the necessity for alternative therapeutic strategies. Vaccination has emerged as a promising approach, with various candidates targeting live-attenuated strains and specific virulence factors. Nevertheless, the expanding availability of C. acnes genomic data presents an opportunity to identify previously uncharacterized antigens that hold potential as novel targets for the development of next-generation acne vaccines. Therefore, this study aimed to identify core proteins among C. acnes genomes and evaluate their immunogenicity as potential multi-epitope peptide constructs. In addition, IA1-specific proteins of C. acnes were examined to develop the peptide constructs targeting acne-associated isolates. Pan-core analysis of 609 genomes identified 972 core genes. These genes were subsequently analysed for epitope prediction and antigenicity, and the highly antigenic epitopes were selected and combined for further analysis. Multi-epitope peptides were constructed based on predicted MHC-I, MHC-II, and linear B-cell epitopes, yielding four promising candidates derived from C. acnes core proteins and IA1-specific proteins. Molecular docking analysis indicated that both groups showed binding affinity for TLR2 and TLR4 receptors, suggesting possible molecular compatibility with these receptors. Furthermore, in silico immune simulations indicated that both types of multi-epitope peptides were associated with simulated humoral and cellular immune response profiles, although these responses require experimental validation. This computational workflow may help narrow the selection of potential acne vaccine candidates and prioritise multi-epitope peptide constructs for subsequent vaccine design steps and experimental validation. Full article

Highly pathogenic avian influenza (HPAI) is a lethal disease of poultry that has recently spilled over into mammals, including dairy cattle and humans, heightening concerns for livestock health, food security, and pandemic emergence. While vaccines that induce neutralizing antibodies against hemagglutinin and neuraminidase provide strain-specific protection, durable cross-subtype immunity requires T-cell responses targeting conserved internal antigens such as nucleoprotein (NP). To leverage these conserved targets, we utilized a previously engineered mosaic nucleoprotein (MNP) incorporating T-cell epitopes from thousands of influenza A virus (IAV) strains, conferring broad protection against epidemic (H3N2) and pandemic (H1N1) IAV in mice. Here, we tested whether precision adjuvancy could differentially imprint adaptive immunity to MNP in cattle. Combination formulations paired the carbomer-based nano-emulsion Adjuplex (ADJ) with either a STING agonist (cyclic dinucleotides; CdN) or a TLR4 agonist (glucopyranosyl lipid A; GLA) to program distinct inflammatory milieus. Both formulations elicited circulating IFN-γ–producing T cell responses and NP-specific antibodies in serum and milk. However, STING activation via CdN generated more potent and consistent cellular and humoral immunity than TLR4 engagement. These data demonstrate that selective activation of innate sensing pathways functionally imprints adaptive immune magnitude and quality in a large animal host. By advancing a broadly protective, T-cell-focused vaccine strategy in cattle, this work supports a One Health framework to mitigate H5N1 transmission risk at the human–animal interface. 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 epidemic diarrhea (PED), caused by the PED virus (PEDV), remains one of the most devastating diseases in the swine industry, with a mortality rate approaching 90–100% in suckling piglets due to severe dehydration and electrolyte imbalances. Passive immunization with egg yolk antibodies (IgY) represents a promising therapeutic strategy. In this study, we developed a novel recombinant adenovirus, rADM-IFN-G-ped, co-expressing selected antigenic regions of the PEDV S protein and chicken interferon-gamma (ChIFN-γ) as a molecular adjuvant. Laying hens were immunized with this construct to produce PEDV-specific IgY, which was subsequently purified from eggs using a polyethylene glycol (PEG-6000) precipitation method. The induced IgY demonstrated potent neutralizing activity against PEDV in vitro, with a neutralization titer (NT₅₀) of 1:96, which was significantly higher than that of IgY derived from hens immunized with a commercial inactivated PEDV G2b vaccine (NT₅₀ = 1:52). In a passive immunization and challenge trial, piglets treated with the rADM-IFN-G-ped-derived IgY exhibited significantly reduced fecal viral RNA shedding following challenge with the virulent PEDV-NX-2022 strain, compared to control groups. Crucially, while all piglets in the challenge control group succumbed to infection within 72 h, a 50% survival rate was achieved in the IgY-treated group. Histopathological examination of intestinal tissues further confirmed the protective efficacy, showing that IgY treatment markedly alleviated villous atrophy, epithelial necrosis, and inflammatory cell infiltration in the small intestine. These findings demonstrate that vaccination of laying hens with the rADM-IFN-G-ped recombinant adenovirus elicits a robust immune response, enabling the production of protective IgY. This proof-of-concept study establishes the viability of the multi-epitope adenoviral IgY platform as a passive immunization strategy against PEDV. Full article

Background and Objectives: Sjögren’s disease (SjD) is a chronic autoimmune disorder in which the immune system attacks the glands that produce tears and saliva, leading to symptoms such as dry eyes and dry mouth. If left untreated, SjD can also cause inflammation and damage to other parts of the body, including the skin, lungs, kidneys, and nervous system, and increase the risk of developing lymphoma. The human leukocyte antigen (HLA) class II molecule HLA-DR3 is strongly associated with SjD. Materials and Methods: To investigate how post-translational modifications (PTMs) influence the presentation of SjD-associated autoantigens by HLA-DR3, we employed a computational framework to determine the binding of PTM-mimic peptides to HLA-DR3. We further supported the in-silico results with in-vitro experiments. Results: Our analysis revealed that PTM-mimic substitutions at canonical anchor positions rarely improved predicted binding affinity using the Stabilized Matrix Method, with most modifications resulting in reduced affinity. However, a comprehensive analysis of full-length SjD-associated autoantigen sequences (Ro60, Ro52, La) identified discrete regions with high densities of PTM-eligible anchor sites, specifically, the Ro60 HEAT solenoid, Ro52 RING/B-box/PRY-SPRY modules, and the La motif-RRM1 region, suggesting that PTMs may alter epitope presentation in a sequence-dependent manner. Experimental validation of selected PTM-mimic peptides showed enhanced T cell responses, which were associated with increased binding affinity to HLA-DR3. Structural modeling of a representative complex revealed that PTM-mimic peptides adopt a slightly shifted backbone orientation and altered side-chain positioning, leading to a larger peptide–DR3 interaction interface. Conclusions: These findings provide new insights into the role of PTMs in shaping the immunogenicity of SjD-associated autoantigens and highlight the potential for PTM-mimic peptides to modulate T cell responses in SjD. Full article

Background/Objectives: Current prophylactic human papillomavirus (HPV) vaccines rely on major capsid proteins (L1). Although highly immunogenic, L1-based immunity is clade-restricted owing to the hypervariability of HPV strains across different geographic regions. This restricts cross-protection against diverse, localized, and non-vaccine viral strains circulating in specific areas, leaving these populations vulnerable to regional genotypes. Methods: We aimed to design a cross-protective vaccine tailored to local viral diversity through evolutionary and immunoinformatic analyses of circulating HPV strains in Thailand. Both major (L1) and minor (L2) capsid proteins were analyzed to evaluate selective evolutionary pressures, structural sequence conservation, and cross-strain promiscuity of predicted B- and T-cell epitopes using the IEDB database. The predicted immunogenic profile of the combined L1/L2 proteins was further assessed using in silico immune response simulations. Results: Evolutionary analysis confirmed that although the L1 protein is under strict purifying selection, it exhibits high regional interclade variability. L1-only epitopes demonstrated restricted cross-strain conservation, creating structural blind spots against divergent regional variants. The minor capsid protein (L2) harbored highly conserved dual-action core peptides that are evolutionarily conserved across multiple HPV type. Incorporation of conserved L2 regions alongside L1 sequences may broaden the predicted epitope coverage and help address limitations associated with L1 variability. The proposed multi-targeted L1/L2 construct therefore represents a computational framework for the development of candidate cross-reactive HPV vaccines relevant to circulating Thai genotypes. However, experimental validation remains necessary to determine immunogenicity, cross-neutralization potential, and protective efficacy. Conclusion: Our findings highlight these conserved HPV epitopes as potential targets for future development of next-generation cross-subtype prophylactic vaccines with broader population coverage. Full article

Understanding the molecular mechanisms underlying host immune responses to SARS-CoV-2 vaccination remains essential, particularly in populations with a high prevalence of obesity. In this cross-sectional study, we evaluated whether body mass index (BMI) is associated with vaccine-induced humoral immunity in a cohort from northeastern Mexico and discuss the findings within a structural immunology framework of spike antigenicity and antibody–epitope interactions. A total of 138 adults were recruited in Reynosa and Matamoros (June 2021–June 2022) and categorized as healthy weight, overweight, or obese according to BMI criteria. Serum anti-SARS-CoV-2 IgG was assessed using an ELISA-based assay, and differences across BMI groups were tested using the Kruskal–Wallis approach. Among all participants, 33.3% were classified as obese and 99.3% (137/138) were seropositive for anti-SARS-CoV-2 IgG. No significant differences in IgG levels were detected between BMI categories (p = 0.20). These results indicate that, in this Mexican cohort—sampled during a period of heterogeneous and often incomplete vaccination schedules—obesity was not associated with reduced detectable anti-SARS-CoV-2 IgG responses. Our findings support the need to integrate population-level serology with mechanistic studies that interrogate antibody quality (e.g., neutralization potency and epitope specificity) to better connect clinical determinants such as obesity with molecular correlates of protection. Full article

Background/Objectives: The GMZ2.6c malaria vaccine candidate is a multi-stage P. falciparum chimeric protein that contains a fragment of the sexual stage Pfs48/45-6c protein genetically fused to GMZ2, which is an asexual stage vaccine construct consisting of conserved domains of Glutamate-Rich Protein (GLURP) and Merozoite Surface Protein-3 (MSP-3). Previous studies showed that GMZ2.6c is widely recognized by antibodies from individuals living in endemic areas of Brazil and that levels of anti-GMZ2.6c increase with malaria exposure and may contribute to immunity against the parasite. As cell-mediated responses are crucial for parasite control and protection, identifying antigens that elicit antigen-specific T cell recall in naturally exposed populations is the key to vaccine development. This study aimed to evaluate the cellular immune response against GMZ2.6c and its components (MSP-3, GLURP, and Pfs48/45) and to identify promiscuous T cell epitopes in individuals exposed to malaria in the Brazilian Amazon, considering the impact of active P. falciparum infection on antigen-specific T cell recall. Methods: This study was carried out using peripheral blood mononuclear cells (PBMCs) from individuals with active P. falciparum infection (PFI) and non-infected individuals exposed to malaria (NI) from Cruzeiro do Sul and Mâncio Lima, Acre State, and Guajará, Amazonas State. The PBMCs were stimulated with GMZ2.6c and its components, and cellular activation, CD4⁺ and CD8⁺ memory T cell subsets, and cytokine production were evaluated by flow cytometry. IFN-γ-secreting T cells were quantified by ELISpot using predicted T cell epitopes. Results: The individuals infected by P. falciparum displayed more CD8⁺ T cell activation in response to MSP-3 and Pfs48/45 and an increase in CD4⁺ T_CM cells and a reduction in CD4⁺ T_EM cells following stimulation with Pfs48/45 and GMZ2.6c. The PBMCs from both groups showed elevated production of IL-6 and TNF after stimulation with GMZ2.6c, MSP-3, and Pfs48/45, but only the non-infected individuals had high levels of IL-10. T cell epitope prediction identified sequences within MSP-3, GLURP, and Pfs48/45 that elicited IFN-γ responses in both the non-infected and P. falciparum-infected individuals. Conclusions: Individuals exhibit cellular immune responses to MSP-3 and Pfs48/45 that are recalled following GMZ2.6c stimulation. P. falciparum infection may modulate immune response, inducing a prominent pro-inflammatory response. Conversely, in the absence of the parasite, the individuals displayed balanced Th1/Th2 cytokine production. Several promiscuous T cell epitopes were able to recall IFN-γ responses. Further studies are needed to fully ascertain the potential of GMZ2.6c as a protective candidate vaccine against malaria. Full article

Background: Pertussis toxin (Ptx) is a major virulence factor and protective antigen of Bordetella pertussis. Understanding its antigenic landscape is essential for improving vaccine design. This study aimed to compare the linear epitope profiles of Ptx recognized by antibodies from vaccinated children and mice, identifying conserved and species-specific immune targets across subunits S1–S5. Methods: Two libraries of overlapping 14-mer peptides spanning the full-length Ptx sequence were synthesized. Sera from children and mice immunized with the whole-cell pertussis vaccine were analyzed to map antibody-binding regions. Comparative and structural analyses were performed to evaluate epitope distribution and recognition patterns. Results: Murine sera recognized 12 major epitopes, whereas children’s sera identified 24. Eleven epitopes were shared between species, mainly in subunits S1 (Ep3–5, 7, 9, 10), S3 (Ep20, 21, 25, 26), and S5 (Ep32), although minor positional shifts were observed. Eight epitopes were unique to children’s sera, located in S1 (Ep1, 6, 8), S3 (Ep22–24), and S4 (Ep27, 29–30). In the S2 subunit, four distinct epitopes were identified for each species, while only one mouse-specific epitope was detected in S4 (Ep28). Structural analysis revealed non-uniform antibody recognition, with dominant targeting of S3 and conserved antigenic hotspots, as well as selective recognition of the catalytic S1 subunit. Fourteen novel epitopes were identified. Conclusions: These findings highlight both shared and species-specific Ptx epitopes, revealing differences between murine and human immune responses. The identified conserved regions and novel epitopes provide a basis for improved pertussis vaccine design. Full article

Background: Porcine epidemic diarrhea virus (PEDV) remains a major threat to the global swine industry, highlighting the urgent need for safe and effective next-generation vaccines. mRNA vaccines have emerged as a promising platform due to their rapid development and favorable safety profile. Objectives: This study aimed to design and perform the preliminary evaluation of a PEDV multi-epitope mRNA vaccine using an immunoinformatics-guided strategy combined with experimental validation. Methods: Immunoinformatics tools were used to identify B-cell and cytotoxic T lymphocyte (CTL) epitopes from the PEDV spike (S), membrane (M), and nucleocapsid (N) proteins. Selected epitopes were assembled into a multi-epitope antigen (E). mRNA constructs encoding S1, S2, and antigen E were synthesized via in vitro transcription and encapsulated into lipid nanoparticles (LNPs). Expression was evaluated in HEK293T cells, and immunogenicity was assessed in mice measuring antigen-specific antibody responses and cytokine levels following immunization. Results: The mRNA constructs exhibited high structural integrity and efficient intracellular translation. The LNP formulations showed good physicochemical stability and delivery efficiency. Immunization with the antigen E mRNA-LNP formulation induced significantly higher PEDV-specific IgG levels compared with control groups. Elevated cytokine levels further indicated activation of both humoral and cellular immune responses. Conclusions: This study presents a feasible workflow for the development of a PEDV multi-epitope mRNA vaccine. The antigen E construct demonstrated favorable immunogenicity in a mouse model, supporting its potential as a promising construct for further investigation and optimization. Although further studies are required to validate antigen expression at the protein level and to further characterize immune mechanisms, these findings provide preliminary evidence supporting the feasibility of multi-epitope mRNA vaccines for PEDV prevention. Full article

Despite prolonged viral inhibition with combination antiretroviral therapy (ART), HIV-1 survives as genetically intact, replication-capable proviruses within durable CD4+ T-cell fractions, involving central memory, transitional memory, and stem cell-like memory populations, as well as within tissue-resident compartments including lymphoid follicles and gut-associated lymphoid tissue. Reservoir stability is preserved via clonal growth of infected cells and epigenetic processes that impose proviral transcriptional silencing. As a result, current therapeutic approaches seek to either directly alter proviral survival or to improve immune-driven elimination of infected cells. At the molecular level, investigational strategies such as CRISPR–Cas9 and CRISPR–Cas12 gene-editing systems are intended to remove or induce inactivating mutations inside embedded proviral DNA, as well as alter host entrance co-receptors such as CCR5 to provide cellular resistance to infection. In addition, pharmacologic latency regulation is being studied via histone deacetylase inhibitors, protein kinase C agonists, and bromodomain inhibitors to reverse latency, along with Tat inhibitors and other transcriptional repressors aimed to persistently silence proviral expression. Moreover, immunological techniques aim to counteract inefficient endogenous antiviral defenses. Broadly neutralizing antibodies with tailored Fc-driven effector functions are under examination for both neutralization and antibody-dependent cellular cytotoxicity. Therapeutic vaccine approaches seek to elevate polyfunctional HIV-specific CD8+ T-cell responses, while adoptive cellular approaches, involving CAR-T cells aiming HIV envelope epitopes, remain in early clinical research. Immune checkpoint blockade is also being investigated to reverse T-cell depletion inside reservoir-rich tissues. Nevertheless, the key obstacles continue to be the diverse reservoir composition, restricted tissue penetration, viral escape, and safety limitations. The molecular and translational obstacles that characterize attempts toward an HIV cure must be addressed through ongoing multidisciplinary research. Full article

Background/Objectives: Extraintestinal pathogenic Escherichia coli (ExPEC) is a major pathogen that causes septicemia, meningitis, and polyserositis in pigs. The increasing prevalence of antimicrobial resistance and the diverse serotypes of ExPEC highlight the urgent need for broadly protective vaccines. Methods and Results: In this study, an OmpC epitope vaccine based on the T4 phage display system was developed and evaluated. Two B-cell epitopes (OmpC-1 and OmpC-2) were identified by bioinformatic analysis and displayed on recombinant T4 phages. Immunization induced strong antigen-specific IgG responses, with the OmpC-1-T4 group showing significantly higher antibody titers than the OmpC protein group. In the O11 serotype PCN033 challenge model, survival rates reached 100% in the OmpC-1-T4 group, 60% in the OmpC-2-T4 group, and approximately 80% in the OmpC protein group. In the O18 serotype 2103 challenge model, both recombinant phage groups had survival rates of approximately 60%, whereas all the mice in the OmpC protein group died within three days. OmpC-1-T4 immunization also significantly reduced bacterial loads in lung and brain tissues after PCN033 infection and decreased TNF-α and IL-6 expression in lung tissues, accompanied by reduced inflammatory infiltration and tissue damage. Conclusions: Overall, the T4 phage-displayed OmpC epitope vaccine induced strong humoral immunity and provided protection against different ExPEC serotypes. Among the candidates, OmpC-1-T4 showed superior immune protection, bacterial clearance, and inflammation control, supporting its potential as a vaccine candidate against porcine ExPEC infection. Full article

Background: Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants, seniors, and immunocompromised individuals, contributing substantially to the global disease burden. Given the limited preventive options available, developing an effective and safe vaccine remains a public health priority. Methods: An mRNA vaccine encoding the RSV PreF protein was designed and prepared. Antigen properties were evaluated in silico, and the coding sequence was optimized using NLP algorithms. The stability and translational efficiency of the mRNA constructs were verified through in vitro and in vivo assays, followed by immunogenicity evaluation of the formulated mRNA vaccines in a BALB/c mouse model. Results: The optimized mRNA showed predicted improvements in structural stability and a lower free energy state, which were associated with increased translational efficacy in vitro. Correct antigen conformation and retention of key epitopes were confirmed by intracellular staining followed by flow cytometry. A balanced Th1-biased immune response was induced in mice, characterized by high levels of neutralizing antibodies and antigen-specific T-cell immunity, along with enhanced memory T-cell proliferation and differentiation, indicating long-term immunological memory. Conclusions: A novel RSV PreF mRNA vaccine was successfully developed via optimization of protein structure and mRNA sequence. Superior immunogenicity was demonstrated in the BALB/c mouse model, together with promising potential in terms of vaccine safety and immunological persistence. These findings represent a promising step forward in the pursuit of an effective RSV vaccine and suggest the potential of the developed mRNA vaccine to induce substantial immune responses that may correlate with protection in future challenge studies. Full article

Background/Objectives: Klebsiella pneumoniae (K. pneumoniae) is a leading cause of serious hospital-acquired and community-acquired infections, with limited treatment options, especially for immunocompromised and critically ill patients. No licensed vaccine is currently available. The FimA antigen, a key fimbrial subunit essential for bacterial adhesion and invasion, represents a promising vaccine target. However, little is known about the immunodominant antibody responses against invasive K. pneumoniae. This study aimed to evaluate the immunogenicity and protective efficacy of recombinant FimA protein, to fine-map its immunodominant linear B-cell epitopes, and to assess the individual and combined protective capacity of these epitopes against both standard and clinically isolated K. pneumoniae strains. Methods: A murine model of lethal K. pneumoniae challenge was used. Recombinant FimA protein was administered to evaluate immunogenicity and protective efficacy. Immunodominant linear B-cell epitopes were identified by overlapping peptide ELISA using immune antisera. The identified epitopes were synthesized and conjugated to keyhole limpet hemocyanin (KLH). Mice were immunized with individual epitope-KLH conjugates or a mixture of all four, then challenged with the standard strain ATCC700721 or with multiple clinical isolates of distinct multilocus sequence types (MLST). Epitope-specific antibody responses (total IgG and IgG subclasses) and survival rates were measured. Results: Immunization with full-length recombinant FimA conferred 90% protection against lethal challenge with the standard strain ATCC700721 and induced robust IgG1-dominant antibody responses. Four novel immunodominant linear B-cell epitopes were identified: FimA_97–114, FimA_103–120, FimA_109–126, and FimA_145–160. Structural mapping revealed that the first three epitopes reside within the α-helical region, while FimA_145–160 is located in the β-sheet domain. These epitopes are highly conserved, exhibiting 100% sequence identity across 36 diverse K. pneumoniae strains. Among individual epitope-KLH conjugates, FimA_109–126-KLH induced the highest epitope-specific antibody titers, followed by FimA_103–120-KLH. Immunization with a mixture of all four epitope-KLH conjugates elicited significant cross-protection against multiple clinical isolates, achieving survival rates of 60%, 50%, 50%, and 40% against strains 10CYZ, 13LGY, 19ZXQ, and 22CZY, respectively. Protective immunity was primarily associated with IgG1 subtype responses. Conclusions: This study provides the first fine-mapping and protective evaluation of immunodominant linear B-cell epitopes within K. pneumoniae FimA. The identification of highly conserved, functionally relevant B-cell epitopes and the demonstration of cross-protection conferred by a multi-epitope formulation underscore the potential of FimA-based epitope-driven vaccines. These findings offer a promising strategy for the development of broadly protective vaccines against K. pneumoniae infections. Full article