Cell Proliferation Receptor-Enhanced 3D High-Throughput Screening Model for Optimized Drug Efficacy Evaluation in Breast Cancer Cells.

A higher correlation of epidermal growth factor receptor (EGFR)-targeting drugs has been reported with the use of the cell proliferation receptor-enhanced three-dimensional high-throughput screening model (CPRE 3D-HTS model) compared with two-dimensional (2D) cell-based HTS. A greater expression of differential human EGFR 2 (HER2) protein between HER2-positive and HER2-negative cell lines was observed in breast cancer (BC) cell lines cultured using the CPRE 3D-HTS model compared with 2D-cultured cells. When using 2D-cultured cells, properties such as the expression of the cell proliferation receptor are lost as the cells attach to the bottom of the well plate. In an effort to solve this problem, the CPRE 3D-HTS model expressing high cell proliferation receptors was optimized by the selection of alginate as the extracellular matrix. Results from the use of the CPRE 3D-HTS model showed higher drug resistance with increased expression of drug resistance-related proteins. Of particular interest, a higher correlation of HER2-targeted drugs was observed with the use of the CPRE 3D-HTS model. In order to validate this higher correlation of target drugs observed in the CPRE 3D-HTS model, the results of Western blot analysis and high content imaging analysis were analyzed, which confirmed that 3D-cultured BC cell lines showed a greater difference in the expression of HER2-positive and HER2-negative BC cell lines than 2D-cultured cells. Thus, the use of CPRE 3D-HTS using a 384-pillar plate resulted in increased accuracy when screening HER2-targeted drugs in BC, and it is a very useful platform for analyzing the efficacy of targeted drugs by enhancing the expression of HER2.

Three-Dimensional Aggregated Spheroid Model of Hepatocellular Carcinoma Using a 96-Pillar/Well Plate.

A common method of three-dimensional (3D) cell cultures is embedding single cells in Matrigel. Separated cells in Matrigel migrate or grow to form spheroids but lack cell-to-cell interaction, which causes difficulty or delay in forming mature spheroids. To address this issue, we proposed a 3D aggregated spheroid model (ASM) to create large single spheroids by aggregating cells in Matrigel attached to the surface of 96-pillar plates. Before gelling the Matrigel, we placed the pillar inserts into blank wells where gravity allowed the cells to gather at the curved end. In a drug screening assay, the ASM with Hepatocellular carcinoma (HCC) cell lines showed higher drug resistance compared to both a conventional spheroid model (CSM) and a two-dimensional (2D) cell culture model. With protein expression, cytokine activation, and penetration analysis, the ASM showed higher expression of cancer markers associated with proliferation (p-AKT, p-Erk), tight junction formation (Fibronectin, ZO-1, Occludin), and epithelial cell identity (E-cadherin) in HCC cells. Furthermore, cytokine factors were increased, which were associated with immune cell recruitment/activation (MIF-3α), extracellular matrix regulation (TIMP-2), cancer interaction (IL-8, TGF-ß2), and angiogenesis regulation (VEGF-A). Compared to CSM, the ASM also showed limited drug penetration in doxorubicin, which appears in tissues in vivo. Thus, the proposed ASM better recapitulated the tumor microenvironment and can provide for more instructive data during in vitro drug screening assays of tumor cells and improved prediction of efficacious drugs in HCC patients.

Functional Expression and Characterization of the Recombinant N-Acetyl-Glucosamine/N-Acetyl-Galactosamine-Specific Marine Algal Lectin BPL3.

Lectins, characterized by their carbohydrate-binding ability, have extensive practical applications. However, their industrial use is limited due to impurity. Thus, quality-controlled production of recombinant lectin is necessary. In this study, the algal lectin BPL3 (Bryopsis plumosa lectin 3) was successfully produced using a bacterial expression system, BL21(DE3), with an artificial repeated structure (dimeric construct). Recombinant dimeric BPL3 (rD2BPL3) was confirmed by LC-MS/MS spectrometry. Expression efficiency was greater for the construct with the repeat structure (rD2BPL3) than the monomeric form (rD1BPL3). Optimal conditions for expression were 1 mM IPTG at 20 °C. Recombinant lectin was purified under denaturing conditions and refolded by the flash dilution method. Recombinant BPL3 was solubilized in 1× PBS containing 2 M urea. rD2BPL3 showed strong hemagglutination activity using human erythrocyte. rD2BPL3 had a similar sugar specificity to that of the native protein, i.e., to N-acetyl-glucosamine (GlcNAc) and N-acetyl-galactosamine (GalNAc). Glycan array results showed that recombinant BPL3 and native BPL3 exhibited different binding properties. Both showed weak binding activity to α-Man-Sp. Native BPL3 showed strong binding specificity to the alpha conformation of amino sugars, and rD2BPL3 had binding activity to the beta conformation. The process developed in this study was suitable for the quality-controlled large-scale production of recombinant lectins.

Deep Sequencing of the Medicago truncatula Root Transcriptome Reveals a Massive and Early Interaction between Nodulation Factor and Ethylene Signals.

The legume-rhizobium symbiosis is initiated through the activation of the Nodulation (Nod) factor-signaling cascade, leading to a rapid reprogramming of host cell developmental pathways. In this work, we combine transcriptome sequencing with molecular genetics and network analysis to quantify and categorize the transcriptional changes occurring in roots of Medicago truncatula from minutes to days after inoculation with Sinorhizobium medicae. To identify the nature of the inductive and regulatory cues, we employed mutants with absent or decreased Nod factor sensitivities (i.e. Nodulation factor perception and Lysine motif domain-containing receptor-like kinase3, respectively) and an ethylene (ET)-insensitive, Nod factor-hypersensitive mutant (sickle). This unique data set encompasses nine time points, allowing observation of the symbiotic regulation of diverse biological processes with high temporal resolution. Among the many outputs of the study is the early Nod factor-induced, ET-regulated expression of ET signaling and biosynthesis genes. Coupled with the observation of massive transcriptional derepression in the ET-insensitive background, these results suggest that Nod factor signaling activates ET production to attenuate its own signal. Promoter:ß-glucuronidase fusions report ET biosynthesis both in root hairs responding to rhizobium as well as in meristematic tissue during nodule organogenesis and growth, indicating that ET signaling functions at multiple developmental stages during symbiosis. In addition, we identified thousands of novel candidate genes undergoing Nod factor-dependent, ET-regulated expression. We leveraged the power of this large data set to model Nod factor- and ET-regulated signaling networks using MERLIN, a regulatory network inference algorithm. These analyses predict key nodes regulating the biological process impacted by Nod factor perception. We have made these results available to the research community through a searchable online resource.

The FRIGIDA complex activates transcription of FLC, a strong flowering repressor in Arabidopsis, by recruiting chromatin modification factors.

The flowering of Arabidopsis thaliana winter annuals is delayed until the subsequent spring by the strong floral repressor FLOWERING LOCUS C (FLC). FRIGIDA (FRI) activates the transcription of FLC, but the molecular mechanism remains elusive. The fri mutation causes early flowering with reduced FLC expression similar to frl1, fes1, suf4, and flx, which are mutants of FLC-specific regulators. Here, we report that FRI acts as a scaffold protein interacting with FRL1, FES1, SUF4, and FLX to form a transcription activator complex (FRI-C). Each component of FRI-C has a specialized function. SUF4 binds to a cis-element of the FLC promoter, FLX and FES1 have transcriptional activation potential, and FRL1 and FES1 stabilize the complex. FRI-C recruits a general transcription factor, a TAF14 homolog, and chromatin modification factors, the SWR1 complex and SET2 homolog. Complex formation was confirmed by the immunoprecipitation of FRI-associated proteins followed by mass spectrometric analysis. Our results provide insight into how a specific transcription activator recruits chromatin modifiers to regulate a key flowering gene.

Halamphorahampyeongensis sp. nov. (Amphipleuraceae, Bacillariophyceae), a new marine benthic diatom from a tidal mudflat in Hampyeong Bay, South Korea.

The abundance and variety of benthic diatoms inhabiting tidal flats is widely acknowledged, although it has received relatively less attention than other research areas. In this investigation, we provide a formal description of a benthic diatom found in the tidal mudflat of South Korea, based on morphological and molecular characteristics and the similarities and differences between Halamphorahampyeongensis sp. nov., with morphologically similar Halamphora species are also discussed. Morphological characteristics are described from light and electron microscopy images. H.hampyeongensis is distinguished by its wide ventral sides of the valve, small and rounded areolae present across the whole valve face, and dense dorsal striae biseriate (34-38 in 10 µm). Phylogenetic analysis based on 18S rDNA and rbcL sequence data revealed that H.hampyeongensis is related to H.montana, H.mosensis, and H.specensa. The results (morphometric and molecular) provide sufficient elements to support and propose this taxon as a new species.

Cooperation and functional diversification of two closely related galactolipase genes for jasmonate biosynthesis.

Jasmonic acid (JA) plays pivotal roles in diverse plant biological processes, including wound response. Chloroplast lipid hydrolysis is a critical step for JA biosynthesis, but the mechanism of this process remains elusive. We report here that DONGLE (DGL), a homolog of DEFECTIVE IN ANTHER DEHISCENCE1 (DAD1), encodes a chloroplast-targeted lipase with strong galactolipase and weak phospholipase A(1) activity. DGL is expressed in the leaves and has a specific role in maintaining basal JA content under normal conditions, and this expression regulates vegetative growth and is required for a rapid JA burst after wounding. During wounding, DGL and DAD1 have partially redundant functions for JA production, but they show different induction kinetics, indicating temporally separated roles: DGL plays a role in the early phase of JA production, and DAD1 plays a role in the late phase of JA production. Whereas DGL and DAD1 are necessary and sufficient for JA production, phospholipase D appears to modulate wound response by stimulating DGL and DAD1 expression.

Reduced-intensity conditioning therapy with busulfan, fludarabine, and antithymocyte globulin for HLA-haploidentical hematopoietic cell transplantation in acute leukemia and myelodysplastic syndrome.

Any role for reduced-intensity conditioning (RIC) before hematopoietic cell transplantation (HCT) from a human leukocyte antigen (HLA)-haploidentical donor remains to be defined. We therefore assessed 83 patients (age, 16-70 years): 68 with acute leukemia (including 34 in remission and 34 with refractory disease) and 15 patients with myelodysplastic syndrome, in HCT trials using RIC with busulfan, fludarabine, and antithymocyte globulin. The HLA-haploidentical donors, offspring (n = 38), mothers (n = 24), or siblings (n = 21) of patients, underwent leukapheresis after receiving granulocyte colony-stimulating factor, and donated cells were transplanted without further manipulation. Cyclosporine and methotrexate were given for GVHD prophylaxis. The cumulative incidences of neutrophil engraftment, grade 2 to 4 acute GVHD, chronic GVHD, and transplantation-related mortality after HCT, were 92%, 20%, 34%, and 18%, respectively. After a median follow-up time of 26.6 months (range, 16.8-78.8 months), the event-free and overall survival rates were 56% and 45%, respectively, for patients with acute leukemia in remission; 9% and 9%, respectively, for patients with refractory acute leukemia; and 53% and 53%, respectively, for patients with myelodysplastic syndrome. HCT from an HLA-haploidentical family member resulted in favorable outcomes when RIC containing antithymocyte globulin was performed. This study is registered at www.clinicaltrials.gov as #NCT00521430 and #NCT00732316.

Structure-function studies of a plant tyrosyl-DNA phosphodiesterase provide novel insights into DNA repair mechanisms of Arabidopsis thaliana.

TDP1 (tyrosyl-DNA phosphodiesterase 1), a member of the PLD (phospholipase D) superfamily, catalyses the hydrolysis of a phosphodiester bond between a tyrosine residue and the 3'-phosphate of DNA. We have previously identified and characterized the AtTDP gene in Arabidopsis thaliana, an orthologue of yeast and human TDP1 genes. Sequence alignment of TDP1 orthologues revealed that AtTDP has both a conserved C-terminal TDP domain and, uniquely, an N-terminal SMAD/FHA (forkhead-associated) domain. To help understand the function of this novel enzyme, we analysed the substrate saturation kinetics of full-length AtTDP compared with a truncated AtTDP mutant lacking the N-terminal FHA domain. The recombinant AtTDP protein hydrolysed a single-stranded DNA substrate with Km and kcat/Km values of 703±137 nM and (1.5±0.04)×10(9) M(-1)·min(-1) respectively. The AtTDP-(Δ1-122) protein (TDP domain) showed kinetic parameters that were equivalent to those of the full-length AtTDP protein. A basic amino acid sequence (RKKVKP) within the AtTDP-(Δ123-605) protein (FHA domain) was necessary for nuclear localization of AtTDP. Analysis of active-site mutations showed that a histidine and a lysine residue in each of the HKD motifs were critical for enzyme activity. Vanadates, inhibitors of phosphoryl transfer reactions, inhibited AtTDP enzymatic activity and retarded the growth of an Arabidopsis tdp mutant. Finally, we showed that expression of the AtTDP gene could complement a yeast tdp1Δrad1Δ mutant, rescuing the growth inhibitory effects of vanadate analogues and CPT (camptothecin). Taken together, the results of the present study demonstrate the structure-based function of AtTDP through which AtTDP can repair DNA strand breaks in plants.

In Vitro three-dimensional (3D) cell culture tools for spheroid and organoid models.

Three-dimensional (3D) cell culture technology has been steadily studied since the 1990's due to its superior biocompatibility compared to the conventional two-dimensional (2D) cell culture technology, and has recently developed into an organoid culture technology that further improved biocompatibility. Since the 3D culture of human cell lines in artificial scaffolds was demonstrated in the early 90's, 3D cell culture technology has been actively developed owing to various needs in the areas of disease research, precision medicine, new drug development, and some of these technologies have been commercialized. In particular, 3D cell culture technology is actively being applied and utilized in drug development and cancer-related precision medicine research. Drug development is a long and expensive process that involves multiple steps-from target identification to lead discovery and optimization, preclinical studies, and clinical trials for approval for clinical use. Cancer ranks first among life-threatening diseases owing to intra-tumoral heterogeneity associated with metastasis, recurrence, and treatment resistance, ultimately contributing to treatment failure and adverse prognoses. Therefore, there is an urgent need for the development of efficient drugs using 3D cell culture techniques that can closely mimic in vivo cellular environments and customized tumor models that faithfully represent the tumor heterogeneity of individual patients. This review discusses 3D cell culture technology focusing on research trends, commercialization status, and expected effects developed until recently. We aim to summarize the great potential of 3D cell culture technology and contribute to expanding the base of this technology.

WITHDRAWN: In Vitro three-dimensional (3D) cell culture tools for spheroid and organoid models.

The Publisher regrets that this article is an accidental duplication of an article previously published at http://dx.doi.org/10.1016/j.slasd.2023.03.006. This duplication was due to an error in the publishing workflow and was not the responsibility of the authors or editors. As a result, the duplicate article has been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

3D cell subculturing pillar dish for pharmacogenetic analysis and high-throughput screening.

A pillar dishe for subculture of 3D cultured cells on hydrogel spots (Matrigel and alginate) have been developed. Cells cultured in 3D in an extracellular matrix (ECM) can retain their intrinsic properties, but cells cultured in 2D lose their intrinsic properties as the cells stick to the bottom of the well. Previously, cells and ECM spots were dispensed on a conventional culture dish for 3D cultivation. However, as the spot shape and location depended on user handling, pillars were added to the dish to realize uniform spot shape and stable subculture, supporting 3D cell culture-based high-throughput screening (HTS). Matrigel and alginate were used as ECMs during 6-passage subculture. The growth rate of lung cancer cell (A549) was higher on Matrigel than on alginate. Cancer cell was subcultured in three dimensions in the proposed pillar dish and used for drug screening and differential gene expression analysis. Interestingly, stemness markers, which are unique characteristics of lung cancer cells inducing drug resistance, were upregulated in 3D-subcultured cells compared with those in 2D-subcultured cells. Additionally, the PI3K/Akt/mTOR, VEGFR1/2, and Wnt pathways, which are promising therapeutic targets for lung cancer, were activated, showing high drug sensitivity under 3D-HTS using the 3D-subcultured cells.

Cytotoxicity of Human Hepatic Intrasinusoidal Gamma/Delta T Cells Depends on Phospho-antigen and NK Receptor Signaling.

BACKGROUND/AIM: We previously showed that human hepatic intrasinusoidal (HI) natural killer (NK) T cells selectively eliminate hepatocellular carcinoma (HCC) cell lines. In this study, we investigated the underlying mechanisms on how HI γδ T cells, expanded with zoledronate, exhibit a superior cytotoxic effect on HI NK-resistant Huh7 HCC cells. MATERIALS AND METHODS: γδ T cells were obtained from living liver transplant donors or from peripheral blood mononuclear cells (PBMC) of healthy volunteers and were expanded in the presence of IL-2, IL-15, and zoledronate for 2 weeks. Cytotoxicity was measured using the lactate dehydrogenase (LDH) assay in vitro and by flow cytometry using carboxyfluorescein succinimidyl ester (CFSE) in vivo. RESULTS: The cytotoxicity of expanded HI γδ T cells against Huh7 cells was associated with a higher pyrophosphate expression in Huh7 cells compared to SNU398 cells. In contrast, the cytotoxicity of HI γδ T cells against SNU398 cells depended on NKG2D. HI γδ T cells expressed less PD-1 than PB γδ T cells. The cytotoxicity of HI γδ T cells against Du145 and PC3 prostate cancer cells was also associated with pyrophosphate expression in these cells, as well as NKG2D and DNAM-1. CONCLUSION: The expression levels of phospho-antigen in tumor cells determined the cytotoxicity of HI γδ T cells, although the NK activating receptors, death ligands, and immune checkpoint molecules also contribute to their cytotoxicity. γδ T cells are attractive candidates for cancer immune cell therapy.

Auxin response factor gene family in Brassica rapa: genomic organization, divergence, expression, and evolution.

Completion of the sequencing of the Brassica rapa genome enabled us to undertake a genome-wide identification and functional study of the gene families related to the morphological diversity and agronomic traits of Brassica crops. In this study, we identified the auxin response factor (ARF) gene family, which is one of the key regulators of auxin-mediated plant growth and development in the B. rapa genome. A total of 31 ARF genes were identified in the genome. Phylogenetic and evolutionary analyses suggest that ARF genes fell into four major classes and were amplified in the B. rapa genome as a result of a recent whole genome triplication after speciation from Arabidopsis thaliana. Despite its recent hexaploid ancestry, B. rapa includes a relatively small number of ARF genes compared with the 23 members in A. thaliana, presumably due to a paralog reduction related to repetitive sequence insertion into promoter and non-coding transcribed region of the genes. Comparative genomic and mRNA sequencing analyses demonstrated that 27 of the 31 BrARF genes were transcriptionally active, and their expression was affected by either auxin treatment or floral development stage, although 4 genes were inactive, suggesting that the generation and pseudogenization of ARF members are likely to be an ongoing process. This study will provide a fundamental basis for the modification and evolution of the gene family after a polyploidy event, as well as a functional study of ARF genes in a polyploidy crop species.

Optimization of 3D-aggregated spheroid model (3D-ASM) for selecting high efficacy drugs.

Various three-dimensional (3D) cell culture methods have been developed to implement tumor models similar to in vivo. However, the conventional 3D cell culture method has limitations such as difficulty in using an extracellular matrix (ECM), low experimental reproducibility, complex 3D cell culture protocol, and difficulty in applying to high array plates such as 96- or 384-plates. Therefore, detailed protocols related to robust 3D-aggregated spheroid model (3D-ASM) production were optimized and proposed. A specially designed wet chamber was used to implement 3D-ASM using the hepatocellular carcinoma (HCC) cell lines, and the conditions were established for the icing step to aggregate the cells in one place and optimized ECM gelation step. Immunofluorescence (IF) staining is mainly used to simultaneously analyze drug efficacy and changes in drug-target biomarkers. By applying the IF staining method to the 3D-ASM model, confocal microscopy imaging and 3D deconvolution image analysis were also successfully performed. Through a comparative study of drug response with conventional 2D-high throughput screening (HTS), the 3D-HTS showed a more comprehensive range of drug efficacy analyses for HCC cell lines and enabled selective drug efficacy analysis for the FDA-approved drug sorafenib. This suggests that increased drug resistance under 3D-HTS conditions does not reduce the analytical discrimination of drug efficacy, also drug efficacy can be analyzed more selectively compared to the conventional 2D-HTS assay. Therefore, the 3D-HTS-based drug efficacy analysis method using an automated 3D-cell spotter/scanner, 384-pillar plate/wet chamber, and the proposed 3D-ASM fabrication protocol is a very suitable platform for analyzing target drug efficacy in HCC cells.

Identification of tyrosyl-DNA phosphodiesterase as a novel DNA damage repair enzyme in Arabidopsis.

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a key enzyme that hydrolyzes the phosphodiester bond between tyrosine of topoisomerase and 3'-phosphate of DNA and repairs topoisomerase-mediated DNA damage during chromosome metabolism. However, functional Tdp1 has only been described in yeast and human to date. In human, mutations of the Tdp1 gene are involved in the disease spinocerebellar ataxia with axonal neuropathy. In plants, we have identified the functional nuclear protein AtTDP, homolog to human Tdp1 from Arabidopsis (Arabidopsis thaliana). The recombinant AtTDP protein certainly hydrolyzes the 3'-phosphotyrosyl DNA substrates related to repairing in vivo topoisomerase I-DNA-induced damage. The loss-of-function AtTDP mutation displays developmental defects and dwarf phenotype in Arabidopsis. This phenotype is substantially caused by decreased cell numbers without any change of individual cell sizes. The tdp plants exhibit hypersensitivities to camptothecin, a potent topoisomerase I inhibitor, and show rigorous cell death in cotyledons and rosette leaves, suggesting the failure of DNA damage repair in tdp mutants. These results indicate that AtTDP plays a clear role in the repair of topoisomerase I-DNA complexes in Arabidopsis.

Overexpression of EVE1, a novel ubiquitin family protein, arrests inflorescence stem development in Arabidopsis.

In Arabidopsis, inflorescence stem formation is a critical process in phase transition from the vegetative to the reproductive state. Although inflorescence stem development has been reported to depend on the expression of a variety of genes during floral induction and repression, little is known about the molecular mechanisms involved in the control of inflorescence stem formation. By activation T-DNA tagging mutagenesis of Arabidopsis, a dominant gain-of-function mutation, eve1-D (eternally vegetative phase1-Dominant), which has lost the ability to form an inflorescence stem, was isolated. The eve1-D mutation exhibited a dome-shaped primary shoot apical meristem (SAM) in the early vegetative stage, similar to that seen in the wild-type SAM. However, the SAM in the eve1-D mutation failed to transition into an inflorescence meristem (IM) and eventually reached senescence without ever leaving the vegetative phase. The eve1-D mutation also displayed pleiotropic phenotypes, including lobed and wavy rosette leaves, short petioles, and an increased number of rosette leaves. Genetic analysis indicated that the genomic location of the EVE1 gene in Arabidopsis thaliana corresponded to a bacterial artificial chromosome (BAC) F4C21 from chromosome IV at ∼17cM which encoded a novel ubiquitin family protein (At4g03350), consisting of a single exon. The EVE1 protein is composed of 263 amino acids, contains a 52 amino acid ubiquitin domain, and has no glycine residue related to ubiquitin activity at the C-terminus. The eve1-D mutation provides a way to study the regulatory mechanisms that control phase transition from the vegetative to the reproductive state.

Characteristics of Human Peripheral Blood γδ T Cells Expanded With Zoledronate.

BACKGROUND/AIM: This study aimed to investigate the characteristics of human peripheral blood γδ T cells, which were expanded ex vivo in the presence of zoledronate (ZOL). MATERIALS AND METHODS: Human peripheral blood cells were cultured with IL-2 and IL-15 in the presence or absence of ZOL, which was added as a phospho-antigen, and their phenotypes were assessed by flow cytometry. Expanded γδ T cells were transduced with CD19 CAR vector, and the cytotoxicity was evaluated in vitro and in vivo by flow cytometry. RESULTS: Ex vivo expansion did not hamper the expression of activating receptors. Interestingly, ZOL promoted the expression of CD226 (DNAM-1), TRAIL, and FAS-L in the Vδ1 subset of γδ T cells. Expanded γδ T cells containing CD19 CAR+ γδ T cells removed B cell lymphoma cells effectively in vivo. CONCLUSION: γδ T cells could be a promising immunotherapeutic for cancer.

Characterization of a Novel Mannose-Binding Lectin with Antiviral Activities from Red Alga, Grateloupia chiangii.

Lectins have the ability to bind specific carbohydrates and they have potential applications as medical and pharmacological agents. The unique structure and usefulness of red algal lectin have been reported, but these lectins are limited to a few marine algal groups. In this study, a novel mannose-binding lectin from Grateloupia chiangii (G. chiangii lectin, GCL) was purified using antiviral screens and affinity chromatography. We characterized the molecular weight, agglutination activity, hemagglutination activity, and heat stability of GCL. To determine the carbohydrate specificity, a glycan microarray was performed. GCL showed strong binding affinity for Maltohexaose-ß-Sp1 and Maltoheptaose-ß-Sp1 with weak affinity for other monosaccharides and preferred binding to high-mannan structures. The N-terminal sequence and peptide sequence of GCL were determined using an Edman degradation method and LC-MS/MS, and the cDNA and peptide sequences were deduced. GCL was shown to consist of 231 amino acids (24.9 kDa) and the N-terminus methionine was eliminated after translation. GCL possessed a tandem repeat structure of six domains, similar to the other red algal lectins. The mannose binding properties and tandem repeat structure of GCL may confer it the potential to act as an antiviral agent for protection against viral infection.