Immunotherapeutic Potential of Mollusk Hemocyanins in Murine Model of Melanoma.

The development of antitumor drugs and therapy requires new approaches and molecules, and products of natural origin provide intriguing alternatives for antitumor research. Gastropodan hemocyanins-multimeric copper-containing glycoproteins have been used in therapeutic vaccines and antitumor agents in many cancer models. MATERIALS AND METHODS: We established a murine model of melanoma by challenging C57BL/6 mice with a B16F10 cell line for solid tumor formation in experimental animals. The anticancer properties of hemocyanins isolated from the marine snail Rapana thomasiana (RtH) and the terrestrial snail Helix aspersa (HaH) were evaluated in this melanoma model using various schemes of therapy. Flow cytometry, ELISA, proliferation, and cytotoxicity assays, as well as histology investigations, were also performed. RESULTS: Beneficial effects on tumor growth, tumor incidence, and survival of tumor-bearing C57BL/6 mice after administration of the RtH or HaH were observed. The generation of high titers of melanoma-specific IgM antibodies, pro-inflammatory cytokines, and tumor-specific CTLs, and high levels of tumor-infiltrated M1 macrophages enhanced the immune reaction and tumor suppression. DISCUSSION: Both RtH and HaH exhibited promising properties for applications as antitumor therapeutic agents and future experiments with humans.

Structural insights into a functional unit from an immunogenic mollusk hemocyanin.

Mollusk hemocyanins, among the largest known proteins, are used as immunostimulants in biomedical and clinical applications. The hemocyanin of the Chilean gastropod Concholepas concholepas (CCH) exhibits unique properties, which makes it safe and effective for human immunotherapy, as observed in animal models of bladder cancer and melanoma, and dendritical cell vaccine trials. Despite its potential, the structure and amino acid sequence of CCH remain unknown. This study reports two sequence fragments of CCH, representing three complete functional units (FUs). We also determined the high-resolution (1.5 Å) X-ray crystal structure of an "FU-g type" from the CCHB subunit. This structure enables in-depth analysis of chemical interactions at the copper-binding center and unveils an unusual, truncated N-glycosylation pattern. These features are linked to eliciting more robust immunological responses in animals, offering insights into CCH's enhanced immunostimulatory properties and opening new avenues for its potential applications in biomedical research and therapies.

Selective Cytotoxicity and Changes in Protein Expression of T24 Bladder Carcinoma Permanent Cell Line after Treatment with Hemocyanins.

BACKGROUND: Some molluscan hemocyanins (Hcs) have significant immunological and antitumor potential, enabling their application in oncology. The antitumor activity of Hcs from marine snails Rapana venosa (RvH), giant keyhole limpet Megathura crenulata (KLH) and garden snails Helix lucorum (HlH), as well as their different derivatives, were studied in vitro on a permanent T24 cell line of bladder cancer and normal urothelial cell line HL 10/29 compared to doxorubicin. METHODS: The antiproliferative activity of the tested Hcs was determined using the WST-1 assay and BrdU ELISA assay. Morphological changes in both urothelial cell lines were confirmed by fluorescence microscopy. The proteomic analysis of a bladder cancer cell line before and after treatment with functional unit (FU) ßc-HlH-h using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry revealed differences in the expression of some proteins. RESULTS: Studies prove that the T24 tumor cell line is dose- and time-dependent, sensitive to the action of the tested isoforms, and it glycosylated FU of these hemocyanins. Selective inhibition of T24 cell growth was observed after incubation with structural subunits (ßc-HlH, RvHI and RvHII) and FUs (ßc-HlH-h and RvHII-e). Additionally, fluorescent microphotographs did not show apoptotic or necrotic alterations in the normal urothelial cell line HL 10/29. The FU ßc-HlH-h demonstrated the highest antiproliferative effect (similarly to doxorubicin), in which predominantly apoptotic and less late apoptotic or necrotic changes in the tumor cells were observed. Several downand up-regulated proteins identified by proteome analysis may be associated with the apoptosis pathway. CONCLUSION: The present study illustrated the selectivity of the cytotoxic effect of Hcs against the Т24 cancer cell line. This is the first report of protein expression in T24 human bladder cancer cells under the influence of FU ßc-HlH-h. That is probably due to the specific oligosaccharide structures rich in methylated hexoses exposed on the surface of ßc-HlH-h.

Functional Characterization, Antimicrobial Effects, and Potential Antibacterial Mechanisms of NpHM4, a Derived Peptide of Nautilus pompilius Hemocyanin.

Hemocyanins present in the hemolymph of invertebrates are multifunctional proteins that are responsible for oxygen transport and play crucial roles in the immune system. They have also been identified as a source of antimicrobial peptides during infection in mollusks. Hemocyanin has also been identified in the cephalopod ancestor Nautilus, but antimicrobial peptides derived from the hemocyanin of Nautilus pompilius have not been reported. Here, the bactericidal activity of six predicted peptides from N. pompilius hemocyanin and seven mutant peptides was analyzed. Among those peptides, a mutant peptide with 15 amino acids (1RVFAGFLRHGIKRSR15), NpHM4, showed relatively high antibacterial activity. NpHM4 was determined to have typical antimicrobial peptide characteristics, including a positive charge (+5.25) and a high hydrophobic residue ratio (40%), and it was predicted to form an alpha-helical structure. In addition, NpHM4 exhibited significant antibacterial activity against Gram-negative bacteria (MBC = 30 µM for Vibrio alginolyticus), with no cytotoxicity to mammalian cells even at a high concentration of 180 µM. Upon contact with V. alginolyticus cells, we confirmed that the bactericidal activity of NpHM4 was coupled with membrane permeabilization, which was further confirmed via ultrastructural images using a scanning electron microscope. Therefore, our study provides a rationalization for the development and optimization of antimicrobial peptide from the cephalopod ancestor Nautilus, paving the way for future novel AMP development with broad applications.

Antitumor Properties of Epitope-Specific Engineered Vaccine in Murine Model of Melanoma.

Finding new effective compounds of natural origin for composing anti-tumor vaccines is one of the main goals of antitumor research. Promising anti-cancer agents are the gastropodan hemocyanins-multimeric copper-containing glycoproteins used so far for therapy of different tumors. The properties of hemocyanins isolated from the marine snail Rapana thomasiana (RtH) and the terrestrial snail Helix aspersa (HaH) upon their use as carrier-proteins in conjugated vaccines, containing ganglioside mimotope GD3P4 peptide, were studied in the developed murine melanoma model. Murine melanoma cell line B16F10 was used for solid tumor establishment in C57BL/6 mice using various schemes of therapy. Protein engineering, flow cytometry, and cytotoxicity assays were also performed. The administration of the protein-engineered vaccines RtH-GD3P4 or HaH-GD3P4 under the three different regimens of therapy in the B16F10 murine melanoma model suppressed tumor growth, decreased tumor incidence, and prolonged the survival of treated animals. The immunization of experimental mice induced an infiltration of immunocompetent cells into the tumors and generated cytotoxic tumor-specific T cells in the spleen. The treatment also generates significantly higher levels of tumor-infiltrated M1 macrophages, compared to untreated tumor-bearing control mice. This study demonstrated a promising approach for cancer therapy having potential applications for cancer vaccine research.

Lectin-Like Activity of Hemocyanin in Freshwater Prawn, Macrobrachium rosenbergii.

Lectins are proteins that bind to the carbohydrate moieties on surface of bacteria, erythrocytes and other cells of invertebrates causing agglutination and mediate in recognition of foreign substances. In the present study, we isolated and characterized a lectin molecule present in the hemolymph of Macrobrachium rosenbergii, an important cultured freshwater prawn. Lectin in serum samples of adult prawns was assessed through hemagglutination (HA) test using rabbit RBC that showed a titre ranging from 16 to 64. This serum hemagglutinin was confirmed as a C-type lectin based on its dependency on calcium ions towards binding to rabbit RBCs. The hemagglutinin was also found to be stable at the pH range of 5.0-10.0 and temperature range of 10-40 °C. Of various sugars and glycoproteins tested in hemagglutination inhibition assay, the serum lectin was found specific only to N-acetylneuraminic acid and fetuin with respective minimum inhibitory concentrations at 50 mM and 0.31 mg/ml. Further, the lectin was purified by affinity chromatography on rabbit erythrocyte stroma, which showed hemagglutination with rabbit RBC. In electrophoretic analyses, the purified lectin showed one band with molecular weight of ~ 427 kDa in native gradient PAGE, and its two constituent polypeptide chains of ~ 81 and ~ 73 kDa in SDS-PAGE. These polypeptides were analysed in MALDI-TOF/TOF mass spectrometry and identified as hemocyanins. It was hence, concluded that hemocyanin in M. rosenbergii possesses lectin-like activity.

Myriapod haemocyanin: the first three-dimensional reconstruction of Scolopendra subspinipes and preliminary structural analysis of S. viridicornis.

Haemocyanins (Hcs) are copper-containing, respiratory proteins that occur in the haemolymph of many arthropod species. Here, we report the presence of Hcs in the chilopode Myriapoda, demonstrating that these proteins are more widespread among the Arthropoda than previously thought. The analysis of transcriptome of S. subspinipes subpinipes reveals the presence of two distinct subunits of Hc, where the signal peptide is present, and six of prophenoloxidase (PPO), where the signal peptide is absent, in the 75 kDa range. Size exclusion chromatography profiles indicate different quaternary organization for Hc of both species, which was corroborated by TEM analysis: S. viridicornis Hc is a 6 × 6-mer and S. subspinipes Hc is a 3 × 6-mer, which resembles the half-structure of the 6 × 6-mer but also includes the presence of phenoloxidases, since the 1 × 6-mer quaternary organization is commonly associated with hexamers of PPO. Studies with Chelicerata showed that PPO activity are exclusively associated with the Hcs. This study indicates that Scolopendra may have different proteins playing oxygen transport (Hc) and PO function, both following the hexameric oligomerization observed in Hcs.

Folate-conjugated Helix lucorum hemocyanin - preparation, stability, and cytotoxicity.

This is the first report on the modification of a hemocyanin from Helix lucorum (HlH), a large molluscan respiratory protein, with folic acid (FA). In a two-step synthetic reaction, we prepared samples of HlH conjugated with 20 and 50 FA residues denoted as FA-HlH-1 and FA-HlH-2, respectively. Comparison of the attenuated total reflectance-Fourier transform infrared spectra in the amide I band region showed a structural rearrangement in the HlH that is due to FA conjugation. The changes in the secondary structure were more noticeable for FA-HlH-2. The thermal stability of HlH was not significantly affected by the FA modification, which is consistent with the observed structural similarities with the native protein. Preliminary cytotoxicity assays showed that FA-HlH-1 and FA-HlH-2 stimulate fibroblast proliferation when applied in concentrations of 50 and 100 µg/well. A negligible reduction of fibroblast growth was observed only for FA-HlH-1 and FA-HlH-2, exposed to 200 µg/well for 48 h. We found that FA-HlH-2 exhibits a low to moderate cytotoxic effect on two breast cancer cell lines, which express folate receptors, a hormone-dependent (MCF-7) and a hormone-independent (MDA-MB-231). FA-HlH-2 protects nontransformed cells and affects only neoplastic cells, which could be an advantage, and the protein could have potential in combination with other chemotherapeutics.

Crayfish hemocyanin on chitin bone substitute scaffolds promotes the proliferation and osteogenic differentiation of human mesenchymal stem cells.

Crustacean chitin-hemocyanin-calcium mineral complexes were designed as bone biomimetics, with emphasis on their ability to bind or release calcium ions. Chitin scaffolds were prepared by dissolving chitin flakes in LiCl/dimethylacetamide, followed by gel formation and freeze-drying. Some of these scaffolds were modified by incorporation of CaCO3 . In some of the chitin-CaCO3 scaffolds, macroporosity was introduced by HCl treatment. Hemocyanin from the crayfish Cherax quadricarinatus was used to further modify the chitin scaffolds by dip coating. Cytocompatibility, cellular adherence and proliferation of human mesenchymal stem cells (hMSCs) were evaluated in terms of cell number as reflected in lactate dehydrogenase activity. The chitin, chitin-CaCO3 , and porous chitin-CaCO3 scaffolds were all found to facilitate cell attachment. Hemocyanin dip-coating of these scaffolds led to increased initial cell adhesion, enhanced proliferation, and osteogenic differentiation. Since the hemocyanin loading of the scaffolds was impaired by sterilization by gamma-irradiation (as required for biomedical applications), the hemocyanin loading was performed on previously sterilized scaffolds. All scaffolds facilitated osteogenic differentiation of osteoblasts, with the highest cell ALP-activity being found on hemocyanin-modified porous chitin-CaCO3 scaffolds. Thus, chitin-hemocyanin scaffolds enhanced the initial stages of bone cell development and could serve as promising biomaterials for bone regeneration.

Self-Albumin Camouflage of Carrier Protein Prevents Nontarget Antibody Production for Enhanced LDL-C Immunotherapy.

Elevated low-density lipoprotein cholesterol (LDL-C) increases the risk of atherosclerotic cardiovascular disease. Peptide-based PCSK9 vaccines have shown a promising prospect of reducing LDL-C. In peptide vaccine (pVax) design, the peptide antigens need to conjugate with carrier protein (CP). However, CP incorporation can induce undesirable anti-CP antibodies, which sterically mask peptide epitopes from being recognized by specific B cells and impair subsequent therapeutically antibody production. This epitopic suppression has posed a barrier in clinical translation of conjugate vaccines all along. A model CP (keyhole limpet hemocyanin, KLH) is herein camouflaged with serum albumin (SA) into hybrid nanocarriers (SA@N), with PCSK9 peptide being anchored onto the surface to form nanovaccine (SA@NVax). Such camouflage of KLH via high "self" SA coverage is able to inhibit KLH from extracellular immune recognition and prevent detectable anti-KLH antibody production. Furthermore, the nanovaccine around 70 nm stabilized by intermolecular disulfide network is ideal for internalization and biodegradation by antigen presenting cells as well as better retention in draining lymph nodes and spleen. As expected, the SA@NVax efficiently primes higher anti-PCSK9 IgG antibody titer than PCSK9 pVax.

Intranasal Peptide-Based FpvA-KLH Conjugate Vaccine Protects Mice From Pseudomonas aeruginosa Acute Murine Pneumonia.

Pseudomonas aeruginosa is an opportunistic pathogen causing acute and chronic respiratory infections associated with morbidity and mortality, especially in patients with cystic fibrosis. Vaccination against P. aeruginosa before colonization may be a solution against these infections and improve the quality of life of at-risk patients. To develop a vaccine against P. aeruginosa, we formulated a novel peptide-based P. aeruginosa subunit vaccine based on the extracellular regions of one of its major siderophore receptors, FpvA. We evaluated the effectiveness and immunogenicity of the FpvA peptides conjugated to keyhole limpet hemocyanin (KLH) with the adjuvant curdlan in a murine vaccination and challenge model. Immunization with the FpvA-KLH vaccine decreased the bacterial burden and lung edema after P. aeruginosa challenge. Vaccination with FpvA-KLH lead to antigen-specific IgG and IgM antibodies in sera, and IgA antibodies in lung supernatant. FpvA-KLH immunized mice had an increase in recruitment of CD11b+ dendritic cells as well as resident memory CD4+ T cells in the lungs compared to non-vaccinated challenged mice. Splenocytes isolated from vaccinated animals showed that the FpvA-KLH vaccine with the adjuvant curdlan induces antigen-specific IL-17 production and leads to a Th17 type of immune response. These results indicate that the intranasal FpvA-KLH conjugate vaccine can elicit both mucosal and systemic immune responses. These observations suggest that the intranasal peptide-based FpvA-KLH conjugate vaccine with curdlan is a potential vaccine candidate against P. aeruginosa pneumonia.

N-Glycosylation of mollusk hemocyanins contributes to their structural stability and immunomodulatory properties in mammals.

Hemocyanins are widely used as carriers, adjuvants, and nonspecific immunostimulants in cancer because they promote Th1 immunity in mammals. Hemocyanins also interact with glycan-recognizing innate immune receptors on antigen-presenting cells, such as the C-type lectin immune receptors mannose receptor (MR), macrophage galactose lectin (MGL), and the Toll-like receptors (TLRs), stimulating proinflammatory cytokine secretion. However, the role of N-linked oligosaccharides on the structural and immunological properties of hemocyanin is unclear. Mollusk hemocyanins, such as Concholepas concholepas (CCH), Fissurella latimarginata (FLH), and Megathura crenulata (KLH), are oligomeric glycoproteins with complex dodecameric quaternary structures and heterogeneous glycosylation patterns, primarily consisting of mannose-rich N-glycans. Here, we report that enzyme-catalyzed N-deglycosylation of CCH, FLH, and KLH disrupts their quaternary structure and impairs their immunogenic effects. Biochemical analyses revealed that the deglycosylation does not change hemocyanin secondary structure but alters their refolding mechanism and dodecameric structure. Immunochemical analyses indicated decreased binding of N-deglycosylated hemocyanins to the MR and MGL receptors and TLR4 and reduced endocytosis concomitant with an impaired production of tumor necrosis factor α, and interleukins 6 and 12 (IL-6 and IL-12p40, respectively) in macrophages. Evaluating the function of N-deglycosylated hemocyanins in the humoral immune response and their nonspecific antitumor effects in the B16F10 melanoma model, we found that compared with native hemocyanins N-deglycosylated hemocyanins elicited reduced antibody titers, as well as partially diminished antitumor effects and altered carrier activities. In conclusion, the glycan content of hemocyanins is, among other structural characteristics, critically required for their immunological activities and should be considered in biomedical applications.

A novel approach for preparing disulfide-rich peptide-KLH conjugate applicable to the antibody production.

To produce the antiserum against a small peptide, the target peptide-keyhole limpet hemocyanine (KLH) conjugate is generally used as an antigen, although the disulfide-rich peptide-KLH conjugate is still difficult to prepare. In our previous study, we have developed a preparation method of the disulfide-rich peptide-KLH conjugate, and this method was applied to produce the antiserum against a relaxin-like peptide. However, this method is limited to the synthetic peptide antigen, and is not applicable to a native or a recombinant peptide. In this study, to expand the applicability of this method to wide variety of peptides, we newly designed a novel thiol probe enabling the conjugation between various peptides and KLH, and applied it to produce the antiserum against relaxin-like peptide of a starfish Asterias amurensis. The antiserum obtained here showed high antibody-titer and good specificity, strongly suggesting that the method developed in this study is applicable to various peptides.

Protein encapsulation in the hollow space of hemocyanin crystals containing a covalently conjugated ligand.

Encapsulation of guest molecules into the vacant space of biomacromolecular crystals has been utilized for various purposes including functioning as a protein container to protect against physical stress and structural determination of the guest. Todarodes pacificus hemocyanin (TpHc) is a hollow cylindrical decameric protein complex with an inner space 110 Šin diameter and 160 Šin height. In the crystal, TpHc forms a straw-like bundle and contains one reactive Cys (Cys3246) in the inner domain of each protomer. Here, we conjugated biotin onto Cys3246 of TpHc followed by incubation with streptavidin. The streptavidin was immobilized into the inner space of TpHc due to its interaction with biotin. Moreover, the complex containing TpHc and streptavidin was crystallized under the same conditions used for unmodified TpHc. In order to expand this methodology for a variety of proteins, we conjugated the ligand nitrilotriacetic acid (NTA) chelated to a Ni2+ ion (Ni2+-NTA) to TpHc. We found that His-tagged green fluorescent protein (GFP) was encapsulated into the Ni2+-NTA-conjugated TpHc via the interaction between the His-tag and the Ni2+-NTA group. X-ray crystallography demonstrated that the crystal packing of the complex containing TpHc and GFP was identical to that of the unmodified TpHc. Our guest immobilization method is distinct from previous approaches that are dependent on diffusion of the guest into the host crystal. Thus, our findings may accelerate the development of proteinaceous crystal engineering.

Immunotherapeutic Potential of Mollusk Hemocyanins in Combination with Human Vaccine Adjuvants in Murine Models of Oral Cancer.

Mollusk hemocyanins have been used for decades in immunological and clinical applications as natural, nontoxic, nonpathogenic, and nonspecific immunostimulants for the treatment of superficial bladder cancer, as carriers/adjuvants of tumor-associated antigens in cancer vaccine development and as adjuvants to dendritic cell-based immunotherapy, because these glycoproteins induce a bias towards Th1 immunity. Here, we analyzed the preclinical therapeutic potential of the traditional keyhole limpet hemocyanin (KLH) and two new hemocyanins from Concholepas concholepas (CCH) and Fissurella latimarginata (FLH) in mouse models of oral squamous cell carcinoma. Due to the aggressiveness and deadly malignant potential of this cancer, the hemocyanins were applied in combination with adjuvants, such as alum, AddaVax, and QS-21, which have been shown to be safe and effective in human vaccines, to potentiate their antitumor activity. The immunogenic performance of the hemocyanins in combination with the adjuvants was compared, and the best formulation was evaluated for its antitumor effects in two murine models of oral cancer: MOC7 cells implanted in the flank (heterotopic) and bioluminescent AT-84 E7 Luc cells implanted in the floor of the mouth (orthotopic). The results demonstrated that the hemocyanins in combination with QS-21 showed the greatest immunogenicity, as reflected by a robust, specific humoral response predominantly characterized by IgG2a antibodies and a sustained cellular response manifesting as a delayed hypersensitivity reaction. The KLH- and FLH-QS-21 formulations showed reduced tumor development and greater overall survival. Hemocyanins, as opposed to QS-21, had no cytotoxic effect on either oral cancer cell line cultured in vitro, supporting the idea that the antitumor effects of hemocyanins are associated with their modulation of the immune response. Therefore, hemocyanin utilization would allow a lower QS-21 dosage to achieve therapeutic results. Overall, our study opens a new door to further investigation of the use of hemocyanins plus adjuvants for the development of immunotherapies against oral carcinoma.

Structural and conformational stability of hemocyanin from the garden snail Cornu aspersum.

Various aspects of biomedical applications of molluscan hemocyanins, associated with their immunogenic properties and antitumor activity, promoted us to perform structural studies on these glycoproteins. The stability and reassociation behavior of native Cornu aspersum hemocyanin (CaH) are studied in the presence of different concentrations of Ca2+ and Mg2+ ions and pH values using electron microscopy. Higher concentrations of those ions led to a more rapid reassociation of CaH, resulting in stable multidecamers with different lengths. The conformational changes of native CaH are investigated within a wide pH-temperature range by UV circular dichroism. The relatively small changes of initial [θ]λ indicated that many secondary structural elements are preserved, even at high temperatures above 80°C, especially at neutral pH. The mechanism of thermal unfolding of CaH has a complicated character, and the process is irreversible. The conformational stability of the native didecameric aggregates of CaH toward various denaturants indicates that hydrophilic and polar forces stabilize the quaternary structure. For the first time, the unfolding of native CaH in water solutions in the presence of four different denaturants is investigated. The free energy of stabilization in water, ∆GDH2O, was calculated in the range of 15.48-16.95 kJ mol-1. The presented results will facilitate the further investigation of the properties and potential applications of CaH.

Broad-spectrum Antimicrobial Activity of Purified Hemocyanin Subunit IIIA Isolated from Asian Horseshoe Crab, Tachypleus gigas.

BACKGROUND AND OBJECTIVES: Hemocyanin Subunit IIIA is believed to possess antimicrobial properties, but its efficacy against microbial pathogens is still unclarified. Thus, this study aimed to determine antimicrobial activities of hemocyanin subunit IIIA and to identify the best activator of this protein. MATERIALS AND METHODS: The hemocyanin was partially purified using spin column affinity, its fraction was applied to Hi-Prep Sephacryl Exclusion 26/60 2-200 HR column, followed by Hi-Prep 26/10 Desalting Column on fast protein liquid chromatography. The purity of hemocyanin was validated by Matrix Assisted Laser Desorption Ionization-Time of Flight/Mass Spectrometry. The antimicrobial activity was performed by Disc Diffusion Test. RESULTS: Purified hemocyanin subunit IIIA was identified to have a molecular weight of 72.9 kDa. SDS was found to be the best activator of hemocyanin, as indicated by elevated level of phenoloxidase. As for antimicrobial activity, hemocyanin was minimally inhibited by all bacteria strains tested (Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae), with relatively lower Minimum Inhibitory Concentration (MIC) at 0.005 g mL-1, than recorded MIC for fungal test strains. Two fungal strains (Penicillium sp. and A. niger) show susceptible response to phenoloxidase using MgSO4 as inducer. Whereas, lysate-treated CaCl2 induced susceptibility only to A. niger. CONCLUSION: Hemocyanin shows better antimicrobial activity than phenoloxidase because of its broad-spectrum activity against bacterial and fungal strains tested. Hence, the hemocyanin may potentially become a new antimicrobial candidate to be discovered for a future use in treatment of resistant bacteria.

A Litopenaeus vannamei Hemocyanin-Derived Antimicrobial Peptide (Peptide B11) Attenuates Cancer Cells' Proliferation.

Antimicrobial peptides play important roles in the immune response to pathogens and tumor cells; for this reason, they are being exploited for therapeutic use. In this study, we describe a Litopenaeus vannamei hemocyanin-derived peptide, denoted B11, which shares similar features with other anticancer peptides and attenuates the proliferation of cancer cells. Cell viability assay revealed that B11 significantly inhibited the proliferation of human cervical (HeLa), human hepatocellular carcinoma (HepG2), and human esophageal cancer (EC109) cancer cell lines, but not normal liver cell lines (T-antigen-immortalized human liver epithelial (THLE) cells or THLE-3), by inducing morphological changes, nuclear condensation, and margination, features which are indicative of apoptosis. Besides, peptide B11-induced apoptosis was confirmed by isothiocyanate-labeled Annexin V/propidium iodide (Annexin V-FITC/PI) double staining of HeLa cells. Moreover, cell uptake studies, confocal microscopy, and Western blot analysis revealed that rhodamine-labeled B11 permeated HeLa cells and localized to the mitochondria, causing mitochondria dysfunction through lost mitochondrial membrane potential, which consequently triggered the induction of apoptosis. Increased expression levels of caspase-9, caspase-3, and Bax (Bcl-2-associated X) proteins, coupled with a decrease in Bcl-2 (B-cell lymphoma 2) protein, confirmed that peptide B11 induced apoptosis via the mitochondrial pathway. Thus, the hemocyanin-derived peptide, B11, inhibits the proliferation of cancer cells by causing mitochondrial dysfunction and inducing apoptotic cell death, for which reason it could be explored as an anticancer peptide.

Protective Epitope Discovery and Design of MUC1-based Vaccine for Effective Tumor Protections in Immunotolerant Mice.

Human mucin-1 (MUC1) is a highly attractive antigen for the development of anticancer vaccines. However, in human clinical trials of multiple MUC1 based vaccines, despite the generation of anti-MUC1 antibodies, the antibodies often failed to exhibit much binding to tumor presumably due to the challenges in inducing protective immune responses in the immunotolerant environment. To design effective MUC1 based vaccines functioning in immunotolerant hosts, vaccine constructs were first synthesized by covalently linking the powerful bacteriophage Qß carrier with MUC1 glycopeptides containing 20-22 amino acid residues covering one full length of the tandem repeat region of MUC1. However, IgG antibodies elicited by these first generation constructs in tolerant human MUC1 transgenic (Tg) mice did not bind tumor cells strongly. To overcome this, a peptide array has been synthesized. By profiling binding selectivities of antibodies, the long MUC1 glycopeptide was found to contain immunodominant but nonprotective epitopes. Critical insights were obtained into the identity of the key protective epitope. Redesign of the vaccine focusing on the protective epitope led to a new Qß-MUC1 construct, which was capable of inducing higher levels of anti-MUC1 IgG antibodies in MUC1.Tg mice to react strongly with and kill a wide range of tumor cells compared to the construct containing the gold standard protein carrier, i.e., keyhole limpet hemocyanin. Vaccination with this new Qß-MUC1 conjugate led to significant protection of MUC1.Tg mice in both metastatic and solid tumor models. The antibodies exhibited remarkable selectivities toward human breast cancer tissues, suggesting its high translational potential.

Generation and Characterization of Anti-phenyl Sulfate Monoclonal Antibodies and a Potential Use for Phenyl Sulfate Analysis in Human Blood.

Patients with chronic kidney disease (CKD) have increased blood levels of phenyl sulfate (PS), a circulating uremic toxin. In this study, we produced anti-PS monoclonal antibodies (mAbs) and characterized their cross-reactivity to structural PS analogs. To induce PS-specific mAbs, we synthesized 4-mercaptophenyl sulfate with a sulfhydryl group at the para-position of PS and conjugated it to carrier proteins via bifunctional linkers. Using these PS conjugates as immunogens and as antigens for enzyme-linked immunosorbent assay (ELISA) screening, we produced by a hybridoma method two novel mAbs (YK33.1 and YKS19.2) that react with PS conjugates independent of carrier and linker structures. Although all of the PS analogs tested, with the exception of indoxyl sulfate, were cross-reactive to both mAbs in phosphate buffered saline (PBS), PS specificity for YKS19.2 was enhanced in human plasma and serum. YKS19.2 mAb was cross-reactive only with o-cresyl sulfate, which is absent in human blood. PS sensitivity for YKS19.2 mAb increased to an IC50 of 10.4 µg/mL when 0.1% Tween 20 was added in a primary competitive reaction. To explore potential clinical applications, we determined concentrations of PS in serum samples from 19 CKD patients by inhibition ELISA using YKS19.2 mAb and compared them to those found using an LC-MS/MS method. A good correlation was observed between each value (R2=0.825). Therefore, the unique antigen specificity of YKS19.2 mAb could be useful for prescreening of patients with accumulated PS or for comprehensive analysis of uremic toxins that have a PS-like structure.