Search Results (415)

Single-domain antibodies (sdAbs) are the smallest antigen-binding antibody (Ab) fragments (12–15 kDa) and have emerged as a versatile therapeutic platform. Their compact size, high solubility, stability, and ability to access cryptic epitopes distinguish them from conventional monoclonal Abs (mAbs) and larger Ab fragments. These properties are particularly attractive in ophthalmology, where molecular size, tissue penetration, and formulation constraints critically influence therapeutic performance. This narrative review summarizes the structural features, engineering strategies, immunogenicity considerations, and production platforms of sdAbs, with a focus on ocular applications. Preclinical studies demonstrate promising efficacy in retinal vascular diseases through targeting of VEGFA, ANG2, TNFα, and complement components, as well as in inflammatory and anterior segment disorders. SdAbs can be formatted as multimeric or Fc-fused constructs to extend intraocular half-life or delivered via gene therapy vectors as a sustained intraocular “biofactory” approach. Notably, recent work demonstrates the feasibility of vector-encoded sdAbs targeting complement C3 in vivo. While challenges remain regarding immunogenicity, pharmacokinetics, and regulatory pathways, the approval of several sdAb-based drugs in other fields underscores their clinical potential. SdAbs represent a promising next-generation modality for ocular therapeutics, enabling innovative strategies beyond conventional antibody formats. Full article

Background: Antigenic drift limits the protective efficacy of influenza vaccine. Glycosylation of hemagglutinin (HA) represents a promising immunofocusing strategy that enhances neutralizing antibody responses by masking immunodominant non-neutralizing epitopes. Methods: B-cell epitopes of influenza viruses were retrieved from the Immune Epitope Database and were mapped onto the HA structure of A/Puerto Rico/8/1934 (H1N1). Structure-guided analysis identified residues 136 and 137 as candidate sites for N-linked glycosylation (NLG). Single-site mutants (136NLG and 137NLG) were generated using reverse genetics and evaluated for stability, receptor binding, viral replication, and immunogenicity in a murine model with inactivated whole-virus vaccines. Results: Both mutants exhibited increased thermostability at 42 °C. Glycosylation reduced the HA–sialic acid affinity, resulting in decreased viral adsorption and internalization efficiency in MDCK cells, and delayed viral replication at low multiplicity of infection (MOI). In vivo, all vaccine groups provided complete protection against lethal challenge; notably, the 136NLG group exhibited reduced weight loss, indicating improved protective efficacy compared with wild-type (WT). Conclusions: Targeted glycosylation at residue 136 in the HA head domain effectively enhances the viral stability and elicits a 1.78-fold increase in hemagglutination inhibition titer (GMT) relative to the WT, thereby improving vaccine performance. These findings establish a rational and structure-based design strategy for developing more stable and effective influenza vaccines. Full article

Background and objectives: The PWWP domain of lens epithelium-derived growth factor p75 (LEDGF/p75) mediates chromatin engagement through recognition of histone H3 lysine 36 di- and trimethylation (H3K36me2/3) and nucleosomal DNA. LEDGF/p75 plays a role in multiple human diseases. In particular, its interaction with HIV-1 integrase enables viral genome integration. However, the LEDGF PWWP domain remains difficult to target with small molecules as it lacks optimally shaped binding pockets. Here, we report the generation of high-affinity nanobodies (Nbs) to investigate the structure and function of this domain. Methods: Camelids were immunized with recombinant LEDGF PWWP domain, and immune phage display libraries were screened for affinity. Selected Nbs were recombinantly expressed in E. coli and purified. Their interaction with the PWWP domain of LEDGF and its close homolog HRP-2 was characterized using size-exclusion chromatography and surface plasmon resonance. Structural characterization of the Nbs was performed using X-ray crystallography. Functional effects on chromatin engagement were evaluated using an AlphaScreen assay. Results: Nine sequence-distinct Nbs were identified, seven of which were confirmed to bind the LEDGF PWWP domain with nanomolar affinities. Five Nbs also bound the HRP-2 domain, consistent with conserved functional surfaces, while two showed reduced affinity. The crystal structures of two Nbs (NbC03 and NbH10) confirmed there were canonical immunoglobulin folds, while the latter additionally revealed a domain-swapped dimer. Moreover, NbH10 dose-dependently inhibited the interaction between full-length LEDGF/p75 and H3K36me3-modified nucleosomes in vitro. Conclusions: This work establishes a validated panel of Nbs targeting the LEDGF PWWP domain and identifies one Nb capable of functionally disrupting the LEDGF–chromatin interaction. These Nbs serve as valuable tools for functional studies and structure-based drug design. Full article

Lymphocyte activation gene-3 (LAG-3) is a pivotal immune checkpoint receptor that exerts a negative regulatory effect on T-cell function. Although LAG-3-blocking antibodies have shown promising clinical potential, the inherent limitations of conventional monoclonal antibodies necessitate the development of novel antibody formats with enhanced biological and pharmacological properties. In this study, a panel of single-domain antibodies (sdAbs) targeting human LAG-3 was generated via phage display technology. Among these candidates, 2H-G7 was identified as a high-affinity sdAb that binds to LAG-3 with an equilibrium dissociation constant (K_D) in the nanomolar range. Notably, 2H-G7 potently blocks the interactions of LAG-3 with both of its key ligands, fibrinogen-like protein 1 (FGL1) and major histocompatibility complex class II (MHC-II). Its capacity to restore impaired T-cell function was validated by quantifying interleukin-2 (IL-2) secretion and CD69 expression in stimulated primary human peripheral blood mononuclear cells (PBMCs). Epitope mapping studies localized the binding site of 2H-G7 to the D1D2 extracellular domains of LAG-3, distinct from relatlimab, a clinically approved LAG-3-blocking antibody serving as the benchmark. In a xenogeneic mouse model of non-small-cell lung cancer (NSCLC), 2H-G7-Fc exhibited superior tumor growth inhibition efficacy compared with relatlimab. These findings demonstrate that 2H-G7 is a promising lead candidate for the development of next-generation LAG-3-targeted tumor immunotherapies. Full article

Background and Objectives: Myopic choroidal neovascularization (mCNV) is a vision-threatening complication of pathologic myopia. While anti-VEGF monotherapy is the current standard of care, recurrence and suboptimal responses remain challenges. Faricimab is a novel bispecific antibody that targets both vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) to improve vascular stability. This study aims to evaluate the short-term efficacy and safety of a single intravitreal faricimab injection in eyes with active mCNV. Materials and Methods: This retrospective, single-center study included 27 eyes from 24 patients with active mCNV, including both treatment-naïve and previously treated cases. All eyes received a single intravitreal injection of faricimab (6.0 mg/0.05 mL). Best-corrected visual acuity (BCVA) in logMAR and central retinal thickness (CRT) via spectral-domain optical coherence tomography were assessed at baseline and one month post injection. Statistical significance was determined using paired and independent t-tests (p < 0.05). Results: The study population (mean age 55.5 ± 13.9 years; mean axial length 29.3 ± 1.6 mm) showed significant improvements at one month. Mean BCVA improved from 0.77 ± 0.71 logMAR to 0.51 ± 0.52 logMAR (p < 0.005). Mean CRT decreased from 290.2 ± 66.0 μm to 242.5 ± 45.7 μm (p < 0.005). No ocular adverse events, such as intraocular inflammation, retinal detachment, or endophthalmitis, were observed. Conclusions: A single intravitreal injection of faricimab provides significant short-term functional and anatomical improvement in this small retrospective series. Dual inhibition of VEGF-A and Ang-2 appears to be a safe and effective approach for stabilizing retinal vasculature in patients with high myopia. Larger, long-term prospective studies are needed to determine optimal treatment intervals for mCNV. Full article

Background/Objectives: Precise intracellular delivery of chemotherapeutics remains a major challenge in HER2-positive breast cancer, where intratumoral heterogeneity and limited tissue penetration constrain efficacy. A key contributor is the tumor-restricted epidermal growth factor receptor variant III (EGFRvIII), a constitutively active, ligand-independent mutant generated by deletion of exons 2–7. Although classically associated with glioblastoma, lung (NSCLC), head/neck, and prostate cancers, EGFRvIII is also present in subsets of HER2-positive breast cancers, where low-abundance subclones drive aggressive phenotypes and attenuate therapeutic responses. HER2–EGFRvIII co-expression amplifies oncogenic signaling, supported by frequent co-expression in ErbB2-positive primary tumors and metastases, and by sustained receptor phosphorylation in the absence of EGFR gene amplification, depicting EGFRvIII as a compelling therapeutic target. Methods: We evaluated the shark-derived single-domain antibody vNAR R426 as a modular theranostic platform for receptor-mediated cisplatin delivery. Conjugation to cisplatin and fluorescein enabled simultaneous intracellular drug transport and immunofluorescence-based detection in EGFRvIII-positive SKBR3 cells and 3D spheroids. The compact vNAR-based immunoconjugates support efficient receptor recognition, internalization, and intracellular trafficking, features rarely achieved by conventional IgG antibodies. Results: vNAR_CDDP elicited robust, receptor-mediated cytotoxicity, achieving an IC₅₀ of 2.68 µM—approximately 50-fold lower than that of free cisplatin—while unconjugated vNAR maintained scaffold biocompatibility. In three-dimensional spheroid models, the theranostic vNAR (vNAR_CDDP+FITC) exhibited deep and uniform penetration throughout tumor-like architectures, with immunofluorescence intensity closely correlating with regions of intracellular drug delivery and the initiation of cytotoxic responses. Notably, cisplatin conjugation did not impair tissue diffusion or receptor engagement, facilitating effective payload delivery to both peripheral and central cell populations. Conclusions: By integrating tumor-restricted targeting and efficient intracellular drug delivery within a modular single-domain scaffold, vNAR R426 represents a next-generation theranostic platform capable of addressing intratumoral heterogeneity. This approach combines potent cytotoxic activity with immunofluorescence-based detection, thereby advancing the rational design of precision therapeutics for HER2-positive breast cancer. Full article

Background/Objectives: The continuous emergence of immune-evasive SARS-CoV-2 variants underscores the need for adaptable and accessible therapeutics that complement vaccination. Single-domain antibodies (sdAbs) offer advantages in size, stability, and production costs compared to conventional monoclonal antibodies, but their clinical utility is limited by rapid clearance. This study aimed to develop a rabbit-derived sdAb with broad SARS-CoV-2 neutralization capacity and improved pharmacokinetic properties. Methods: A rabbit-derived variable light-chain (VL) sdAb library was constructed and subjected to phage display selection to identify high-affinity binders. Candidate sdAbs were characterized for cross-variant binding and neutralization. The lead sdAb, B3, was fused to the albumin-binding domain (ABD) of the Streptococcus zooepidemicus Zag protein to enhance in vivo half-life. Expression, albumin-binding capacity, and in vitro neutralization were assessed, followed by biodistribution studies in mice. Results: The selected sdAb, B3, showed strong binding and cross-variant neutralization against multiple SARS-CoV-2 lineages, including Delta and Omicron. Fusion to ABD(Zag) preserved neutralization potency, increased expression yields ~5-fold, and enabled cross-species albumin binding. In vivo, B3-ABD(Zag) exhibited markedly extended blood retention, showing a 21.2-fold increase at 24 h post-injection (5.30 vs. 0.25% I.A./g), and reduced renal uptake by 40% compared with unmodified B3. Conclusions: Rabbit-derived VL sdAbs fused to ABD(Zag) provide a promising platform for next-generation SARS-CoV-2 biologics. The enhanced pharmacokinetic profile of B3-ABD(Zag) supports its potential as a scalable therapeutic modality and highlights the broader utility of this approach for future emerging infectious threats. Full article

Next-generation sequencing (NGS) and antisense oligonucleotide (ASO) technologies are converging to transform the diagnosis and treatment of rare monogenic disorders. NGS enables comprehensive, single-test molecular diagnoses through targeted panels, whole-exome sequencing, and whole-genome sequencing, which together reveal pathogenic variants across coding, intronic, and structural domains. Integration with transcriptomic analyses, including RNA sequencing, further refines genotype–phenotype correlations and identifies splicing aberrations amenable to correction by ASOs. Therapeutic advances now span RNase H1-dependent gapmers for transcript knockdown, splice-modulating phosphorodiamidate morpholino oligomers (PMOs), and peptide/antibody-conjugated PMOs that enhance muscle and cardiac delivery. These platforms underpin the rise in N-of-1 ASO therapies—customized drugs developed for individual patients with unique pathogenic variants. Landmark cases such as Milasen and Atipeksen illustrate the clinical feasibility and ethical complexities of personalized RNA therapeutics, while updated FDA guidance supports expedited, patient-specific investigational pathways. Despite progress, challenges persist in delivery efficiency, long-term efficacy, and equitable access. Emerging approaches—including long-read sequencing, AI-driven oligo design, and improved delivery—promise to extend ASO precision and reach. This review synthesizes current advances linking genomic diagnosis to individualized RNA-targeted interventions, outlining how integrated NGS-ASO pipelines are reshaping the therapeutic landscape for rare genetic diseases. Full article

Background/Objectives: Childhood-onset Sjögren disease (cSjD) is a rare autoimmune disorder with heterogeneous manifestations and ongoing diagnostic challenges, as there are no validated paediatric criteria. Our study aims to characterise the clinical, laboratory, and imaging features of children diagnosed with cSjD at a single Romanian paediatric rheumatology centre between 2015 and 2025 and contextualise these findings within the most recent literature. Methods: A retrospective review of 15 consecutive cSjD patients was conducted, including clinical features, autoantibodies, imaging, biopsy findings, treatment, and outcomes. Results: Our cohort showed a significant female predominance (80%) and a broad age range at disease onset (3–15 years). Extraglandular manifestations were more common at presentation than glandular phenotypes (53.3% vs. 40%). Lupus-like extraglandular presentations frequently led to initial misdiagnosis as childhood-onset systemic lupus erythematosus (SLE) in our cohort. Sicca symptoms were present at diagnosis in only 3 of 15 patients (20%) and developed later during follow-up in an additional 4 patients (26.7%). Notably, the cohort included novel findings, such as an unprecedented presentation with acute exudative pericarditis complicated by cardiac tamponade. Anti-SSA antibodies and salivary gland ultrasound abnormalities were highly prevalent (86.7% and 100%, respectively). Anti-SSB antibodies were detected in seven patients (46.7%), with titres showing more variability than those of anti-SSA, ranging from just above the positivity threshold to mildly elevated levels. The association with macro-creatine kinase type I was another distinctive feature of this series. Chronic musculoskeletal pain and dryness were our patients’ most frequently reported symptoms at the last assessment, affecting up to 5/15 (33.3%) in each domain. One patient showed irreversible ocular damage during our study. Conclusions: Extraglandular presentations of cSjD are highly heterogeneous and diagnostically challenging, often occurring without glandular symptoms. Lupus-like systemic features—including facial vasculitic purpura, with or without arthralgia, and occasional pericarditis, as observed in our cohort—may contribute to frequent initial diagnostic misattribution to SLE. Early salivary gland ultrasonography, targeted autoantibody testing, and selective biopsy are essential for timely diagnosis, underscoring the urgent need for paediatric-specific validated classification criteria. Full article

Apolipoprotein E4 (apoE4) is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD). Yet the molecular mechanisms underlying its contribution to AD remain to be fully elucidated. Here, we developed and characterized a set of apoE-specific single-domain antibodies (nanobodies) as a molecular toolbox to investigate intracellular apoE4. The nanobodies bind human apoE with nanomolar to sub-nanomolar affinity and recognize both apoE3 and apoE4. Domain-level epitope mapping revealed nanobodies that selectively bind either an N-terminal (residues 1–173) or C-terminal (residues 170–299) apoE4 fragment. Several nanobodies were validated as endoplasmic reticulum-targeted intrabodies that bind apoE4 intracellularly and promote its intracellular retention. These nanobodies constitute a versatile toolbox for probing and manipulating apoE4 in cellular models. As an exploratory application of this nanobody toolbox, we examined cytosolic apoE4, motivated by previous studies suggesting that cytosolic apoE4 fragments may influence AD-related cellular processes. Cytosolic expression of apoE4 resulted in perinuclear protein assemblies and the appearance of a ~25 kDa apoE4 fragment. Using a nanobody-based nuclear relocalization assay, we showed that cytosolic apoE4 remains accessible for nanobody binding but was not relocated to the nucleus by a nuclear localization signal-equipped nanobody. Altogether, this study introduces a nanobody-based toolbox to investigate apoE4 in distinct intracellular contexts, which can be relevant to AD. Full article

Background/Objectives: Developability assessment is a critical step in advancing antibody-based molecules toward clinical application. This evaluation typically begins during clinical candidate selection and continues throughout all modifications of the molecule during development. It is guided by the target product profile, which includes the intended administration route and regimen, formulation parameters, and process conditions encountered during manufacturing, storage, and delivery. While developability testing is well established for conventional therapeutic antibodies, strategies for assessing single-domain antibodies (sdAbs) and their conjugates remain underexplored. Here, we present a strategy to test the developability of sdAbs as a case study for two clinical candidates intended as precursors for the production of diagnostic tracers for clinical imaging. Methods: Assays were developed to evaluate chemical and thermodynamic stability, target binding affinity and capacity, and chelation efficiency (“chelatability”). Accelerated stability studies were conducted for both unconjugated sdAbs and their chelator conjugated forms following incubation at two pH conditions, at multiple time points, and after twelve freeze–thaw cycles to simulate process conditions and long-term storage. Analytical assays were applied stepwise in a hierarchical approach to minimize experimental effort and material consumption. Candidates exhibiting critical developability features were selectively addressed by assays with increasing precision. Results: A tailored panel of analytical assays optimized for low molecular weight proteins was established and applied to the two clinical candidates, identifying instability hotspots as well as potential mitigation strategies. Successful engineering of a candidate with an initially critical developability profile was achieved. Conclusions: This study demonstrates the implementation of a structured developability assessment strategy for sdAb conjugates. The approach integrates physicochemical and functional stability evaluations, supporting robust candidate selection, formulation development, and method optimization for this class of molecules. Full article

Background/Objectives: The SARS-CoV-2 virus frequently undergoes mutations to evade the human immune system. Vaccines for new strains are developed each season, and an identification test confirming the specific strain is essential for vaccine quality control, as stated by the U.S. Food and Drug Administration. However, a shorter timeline of antibody discovery was required to adjust vaccine development schedules. Therefore, anti-SARS-CoV-2 strain-specific, single-domain antibodies (sdAbs) for SARS-CoV-2 vaccines were discovered using alpaca synthetic libraries without animal immunization. Methods: A synthetic sdAb library was developed based on conserved alpaca sdAb frameworks, with a degree of freedom in the three complementarity-determining regions. Specific and high-affinity sdAb clones were selected from the library by one ribosomal display round, followed by two phage display selections using a biotinylated strain-specific SARS-CoV-2 receptor-binding domain (RBD) of the spike protein as bait and non-biotinylated RBD variants to block. The sdAbs clones were applied to the identification test using Western blotting. The binding epitopes were determined by hydrogen–deuterium exchange mass spectrometry. Results: Five clones of XBB.1.5 and two clones of JN.1-specific sdAbs were discovered. Anti-JN.1 sdAb clone 1B9 detected JN.1 vaccine products but no other previously produced vaccine strains, Wuhan, BA.5 and XBB.1.5, by WB for vaccine identification test. Four binding epitopes for anti-JN.1 sdAb clone 1B9 were identified, including the L455S mutation, a critical amino acid to evade neutralizing antibodies for the JN.1 strain. Conclusions: Anti-XBB.1.5 and JN.1-specific sdAbs were discovered from a synthetic single-domain antibody library within 8–9 weeks, and these sdAbs were applied to vaccine identification testing. Full article

Lateral flow assays (LFAs) are among the most successful technologies for point-of-care and at-home testing, but further advances are needed to reduce costs and accelerate development. Alpaca-derived nanobodies (Nbs), single-domain antibody fragments, are promising immunoassay reagents across diverse applications. Their small size and ease of recombinant production make them particularly well suited for diagnostics. Here, we present a paper-based LFA targeting the SARS-CoV-2 nucleocapsid (N) protein that exclusively uses Nbs for direct antigen detection. We also demonstrate in-house synthesis of Nb-coated gold nanoparticles, enabling instrument-free visual readout and detection of N protein down to 40 ng/mL. This design avoids components that require mammalian cell culture and can be produced entirely from in-house reagents, simplifying manufacturing and lowering component costs. Because the assay is read visually without an external reader, it is well suited for deployment in resource-limited settings. Together, these results highlight the speed and practicality of developing Nb-based LFAs and suggest a broadly applicable strategy for detecting other clinically important disease biomarkers. Full article

Background: bacterial pathogens and their toxins present analytical challenges for rapid and specific detection, contributing to over 600 million cases of illness annually and worsening antimicrobial resistance (AMR). Conventional detection methods are useful but limited. Single-domain antibodies (sdAbs) offer alternative recognition elements with unique biochemical and engineering benefits, enabling the development of nanobody-based immunoassays and biosensing platforms that provide fast, highly selective, and reliable detection of bacterial pathogens and toxins in both food and clinical environments. Objectives: this systematic review assesses the analytical and functional performance of nanobody-based immunoassays and sensing formats for detecting bacteria and toxins across food and clinical samples. Methods: following PRISMA guidelines, major scientific databases were used to gather research, resulting in 32 eligible studies published between 2011 and 2025. Results: data collected included assay platforms, target bacteria and toxins, limit of detection, sensitivity, specificity, matrix recovery, and practicality. Risk of bias was evaluated using an adapted QUADAS-2 framework. The review shows that nanobody-based immunoassays have achieved high performance, thermostability, compatibility with genetic engineering, and versatile assay design. When combined with advanced transduction and signal amplification strategies, these systems contribute to the development of highly sensitive and user-friendly bioanalytical platforms for detecting bacteria and toxins. Conclusions: however, most studies relied on spiked samples and lacked large-scale validation, emphasizing the need for standardized benchmarking and real-world testing. Full article

There is a strong need for nanobodies that target novel cancer-associated antigens to advance radioligand imaging and antibody-based therapeutics. In this study, we investigated whether non-targeted llama immunization using tumor cells, combined with non-targeted phage-display panning of human cell lines, could yield nanobodies specific to Prostate-Specific Membrane Antigen (PSMA). Nanobody selection using both classical three-round PSMA negative–positive panning and single-round panning of cell lines (positive or negative) for PSMA showed clear enrichment for PSMA binders in both strategies. Using shRNA knockdown, flow cytometry, cell-ELISA, immunohistochemistry and structural modeling and docking, we confirmed the PSMA-targeting of selected nanobodies. Two distinct epitopes were predicted to be bound by nanobodies PSMANb9 and A7 (JVZ-007), and this was corroborated by epitope competition assays. These findings support the feasibility of non-targeted immunization and panning strategies for isolating antigen-targeting cancer nanobodies. Full article