Exudate gums: occurrence,production, and applications

This paper presents a review of the industrially most relevant exudate gums: gum arabic, gum karya, and gum tragacanth. Exudate gums are obtained as the natural exudates of different tree species and exhibit unique properties in a wide variety of applications. This review covers the chemical structure, occurrence and production of the different gums. It also deals with the size and relative importance of the various players on the world market. Furthermore, it gives an overview of the main application fields of the different gums, both food and non-food.     

Affinity chromatography of two sets of isomeric antibodies having specificity for different oligosaccharide units of gum arabic

Two sets of antibodies directed against different carbohydrate units of gum arabic were isolated from the sera of rabbits immunized intramuscularly with gum arabic and Freund's complete adjuvant. The isolation was effected by affinity chromatography on two columns attached in series and containing an absorbent of AH-Sepharose 4B with ligands of partially hydrolyzed gun arabic in the first column and an adsorbent of AH-Sepharose 4B with ligands of native gum arabic in the second column. The two populations of anti-gum arabic antibodies were obtained and have been designated as Set 1 and Set 2 on the basis of their mobilities on agar diffusion. The antibodies of Set 1 consisted of 4 isomeric antibodies and those of Set 2 consisted of 11 isomeric antibodies. Native gum arabic samples were oxidized with periodate or reduced with sodium borohydride and carbodiimide under standard conditions and the modified samples were totally inactive in the precipitin test. On the basis of methylation data and immunological results it was concluded that terminal disaccharide moieties of the gum having the structure beta-D-glucosyluronic acid-(1----6)-D-galactose and alpha-L-arabinofuranosyl-(1----4)-D-glucuronic acid were the immunodeterminant groups for Set 1 and Set 2 antibodies, respectively.     

Comparison of two Pithecellobium gum exudates

Pithecellobium saman and Pithecellobium mangense exudate a yellow clear gum. The gums are both dextrorotatory. The acidity of these gums is very similar. Galactose and arabinose are the major neutral sugar constituents. The high content of rhamnose in P. saman gums contrasts with the absence of this methyl pentose in P. mangense gum. ¹³C-NMR spectra of the gums studied showed interesting structural features of these complex polymers.     

The amino acid composition of gum exudates from Prosopis species

The amino acid compositions of the proteinaceous components of the gum exudates from Prosopis alba, P. chilensis, P. glandulosa, P. laevigata, P. torreyana and P. velutina, and for a sample of commercial gum mesquite, are presented. In agreement with data published previously for the polysaccharide components of their gums, only minor differences in composition are shown by these species. The amino acid compositions are characterized by very high proportions of hydroxyproline and by high proportions of proline and serine; these three amino acids account for 62.5% of those present in the gum from Prosopis velutina. The amino acid compositions of these Prosopis gums are remarkably similar to that established recently for the gum from Acacia senegal (gum arabic).     

Immunochemical Properties of Ubiquitin Conjugates in the Paired Helical Filaments of Alzheimer Disease

Immunocytochemical and peptide sequencing studies indicate that the regulatory protein ubiquitin (Ub) is incorporated into the paired helical filaments (PHF) of Alzheimer disease. In this study, we showed that some antibodies raised to PHF recognize epitopes of Ub. Analysis of the Ub sequences recognized by the antibodies raised to PHF, along with the known specificity of several monoclonal antibodies raised to artificial Ub conjugates, indicates the immunochemical representation of Ub residues 34-76 in PHF. The Ub epitopes recognized by antibodies raised to PHF are distinct from those recognized by antibodies raised to artificial Ub conjugates in two respects. First, antibodies that are raised to PHF and that recognize Ub react with PHF equally, whether denatured or not, whereas those raised to artificial Ub conjugates show greater reaction after denaturation. Second, mapping of the epitopes recognized by two monoclonal antibodies to PHF onto Ub indicates a distinction in the Ub residues recognized, compared with monoclonal antibodies raised to artificial Ub conjugates. The proximity of their epitopes to the site of conjugation, as well as their affinity for PHF polypeptides, suggests that the PHF antibodies that recognize Ub may be directed specifically to Ub epitopes defined by the protein conjugated to Ub.     

Tree gum-based renewable materials: Sustainable applications in nanotechnology,biomedical and environmental fields

The prospective uses of tree gum polysaccharides and their nanostructures in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. In addition to extensive applications of tree gums in food, there are substantial non-food applications of these commercial gums, which have gained widespread attention due to their availability, structural diversity and remarkable properties as ‘green’ bio-based renewable materials. Tree gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. This review focuses on non-food applications of several important commercially available gums (arabic, karaya, tragacanth, ghatti and kondagogu) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, environmental bioremediation, bio-catalysis, biosensors, coordination complexes of metal–hydrogels, and for antimicrobial and biomedical applications. Furthermore, polysaccharides acquired from botanical, seaweed, animal, and microbial origins are briefly compared with the characteristics of tree gum exudates.     

Immunological heterogeneity of rat apolipoprotein B epitope expression. A study using monoclonal antibodies to rat apolipoprotein B

Epitope expression of rat apolipoprotein B on lipoproteins was investigated with the help of six monoclonal antibodies produced from mice. Through a variety of techniques, which include cotitrations, ELISAs and quantitative immunoadsorption precipitation, we concluded that the six monoclonal antibodies recognize five different epitopes. LRB 110 and LRB 260 recognize epitopes that may be overlapping. LRB 240 and LRB 250 recognize epitopes that are preferentially expressed in triacylglycerol-rich particles. LRB 220 recognizes an epitope that is expressed by all apolipoprotein-B-containing lipoproteins. We have also determined that apolipoprotein B epitope expression in rat lipoproteins is very similar to its human counterpart. Both rat and human apolipoprotein B epitope expression on lipoproteins showed heterogeneities even in homologous lipoprotein preparations. We concluded that a variety of techniques are necessary to fully characterize monoclonal antibodies to apolipoproteins. The possible implications of epitope expression in pathophysiology are also discussed.     

Identification of neutralizing epitopes within structural domain III of the West Nile virus envelope protein

Using a panel of neutralizing monoclonal antibodies, we have mapped epitopes in domain III of the envelope protein of the New York strain of West Nile virus. The ability of monoclonal antibodies that recognize these epitopes to neutralize virus appeared to differ between lineage I and II West Nile virus strains, and epitopes were located on the upper surface of domain III at residues E307, E330, and E332.     

An Artificial “gum-tree” for marmosets (Callithrix j. jacchus)

Marmosets (Callithrix, Cebuella) in the wild gouge wells in trees and eat the exudates that accumulate there. An artificial gum-tree was made of wooden dowel and filled with Acacia Senegal exudate (gum arabic) dissolved in water. Three families of marmosets avidly gouged and consumed gum from this device, showing all of the behavioral patterns described in nature. The gum-tree cost little and was easy to make.     

Topologic mapping of protective and nonprotective epitopes on the variant surface glycoprotein of the WRATat 1 clone of Trypanosoma brucei rhodesiense

Monoclonal antibodies were used in competitive antibody binding assays to define and map epitopes on the variant surface glycoprotein of the WRATat 1 clone of T. b. rhodesiense. By using a panel of 30 WRATat 1-specific monoclonal antibodies, 16 epitopes were defined that fall into four clusters, having 1, 1, 3, and 11 distinct epitopes respectively. All epitopes were easily classified as being 1) exposed uniformly on the surface of the trypanosome, 2) exposed only in the region of the flagellar pocket, or 3) "buried", based on the ability or inability of the monoclonal antibodies to bind living trypanosomes in a fluid phase immunofluorescence assay. Monoclonal antibodies that bind exposed surface epitopes are protective, whereas only three of seven that bind exclusively to flagellar pocket epitopes are protective. None of the nine monoclonal antibodies that recognize buried epitopes are protective. Also, antibody-mediated immunity to WRATat 1 trypanosomes is not associated with any particular subclass of antibody. The IgM, IgG1, IgG2a, IgG2b, IgG3, and IgA subclasses each contain examples of protective monoclonal antibodies.     

Monoclonal antibodies to bovine UDP-galactosyltransferase. Characterization, cross-reactivity, and utilization as structural probes

A series of mouse monoclonal antibodies has been developed against a soluble form of bovine UDP-galactose:N-acetylglucosamine galactosyltransferase purified to apparent chemical homogeneity by a combination of affinity and immunoadsorption chromatography. The purified enzyme consists of two molecular mass variants of 42 and 48 kDa. Individual monoclonal antibodies were selected for by their ability to recognize immobilized affinity-purified galactosyltransferase and were not reactive against bovine alpha-lactalbumin and bovine immunoglobulins. Based on competitive binding assays and Western blot analysis with either galactosyltransferase or lactose synthetase (covalently cross-linked alpha-lactalbumin galactosyltransferase), these monoclonal antibodies can be subdivided into four groups. Group A (3 clones) recognize an epitope at or near the alpha-lactalbumin binding site. In addition, this group is cross-reactive with soluble galactosyltransferase from human milk and pleural effusion. Group B (6 clones) and D (1 clone) appear to recognize two different epitopes on the 6-kDa fragment which is released when the 48-kDa galactosyltransferase polypeptide is converted to the 42-kDa form, apparently by proteolysis. Groups A and C (1 clone) recognize epitopes found on both the 48- and 42-kDa polypeptide. Interestingly, immunofluorescence studies indicate that only two monoclonal antibody groups (C and D) are able to decorate membrane-bound galactosyltransferase (Golgi-associated) in formalin-fixed, methanol-, or detergent-permeabilized cells. Thus, these groups of monoclonal antibodies appear to identify four separate structural/functional domains on soluble galactosyltransferase, two of which are not readily accessible for binding in situ.     

Molecular changes in carbohydrate antigens associated with cancer.

Oncogenic transformation is often associated with aberrant glycosylation in experimental and human tumors. The carbohydrate epitopes, resulting either from incomplete synthesis or neosynthesis, accumulate in high density, possibly in a novel conformation, at the tumor cell surface. A variety of monoclonal antibodies have been developed that recognize tumor-associated carbohydrate antigens and their aberrant organization at the cell surface. These carbohydrate epitopes and the antibodies specific to these structures are being exploited to develop novel diagnostic tools and therapeutic strategies for cancer.     

Human interferon-gamma receptor. Mapping of epitopes recognized by neutralizing antibodies using native and recombinant receptor proteins.

Monoclonal antibodies produced against native interferon-gamma receptor (IFN gamma-R) have been characterized for their capacity to react with purified receptor and receptor-positive cells, to inhibit the binding of IFN gamma to cellular receptor, to precipitate the receptor protein when cross-linked to IFN-gamma, and to recognize the recombinant interferon-gamma receptor and 19 overlapping fragments of this protein expressed in Escherichia coli. The results of this analysis showed that: (i) the extracellular portion of human IFN gamma-R is located between the N terminus and the transmembrane region (amino acids 18-246). (ii) The intracellular domain is between the transmembrane region and the C terminus (amino acids 269-489). (iii) The monoclonal antibodies that react with the IFN gamma-R intracellular domain recognize small linear epitopes. (iv) The human IFN gamma-R binding site is located between the N terminus and the transmembrane region. (v) The monoclonal antibodies that react with IFN gamma-R extracellular domain and inhibit the binding of IFN gamma recognize two different epitopes. One of these epitopes (included between amino acids 26 and 133) is very close to the binding site for IFN gamma. The second (included between amino acids 70 and 210) is related to the binding site for IFN gamma without including it. (vi) These two functional epitopes are conformational and need S-S bridges to maintain their architecture. (vii) These conformational epitopes are formed in receptor fragments expressed in E. coli.     

Monoclonal antibodies to mitochondrial F1-ATPase and oligomycin sensitivity conferring protein (OSCP). Tools for recognition of well conserved and essential antigenic sites

The preparation of anti-OSCP monoclonal antibodies is described for the first time. One of these antibodies prevents the activating effect of OSCP in reconstitution experiments. These antibodies and antibodies previously obtained against the alpha- and beta-subunits of pig heart mitochondrial F1-ATPase have been used to look for well conserved epitopes in various species. One anti-beta antibody can recognize all species tested while the anti-OSCP antibodies only recognize the pig or beef enzyme. The above anti-beta antibody inhibits ATP synthesis without modifying the rate of ATP hydrolysis. This antibody also prevents the ADP-induced hysteretic inhibition of F1-ATPase.     

Sharing of antigenic epitopes between synaptophysin and granulophysin.

The immunological crossreactivity between the two granule-specific membrane glycoproteins, synaptophysin and granulophysin, was studied using a series of site-specific monoclonal and polyclonal antibodies. The epitope relatedness of six monoclonal antibodies against granulophysin was examined by competitive ELISA. The antibodies are shown to recognize distinct, but overlapping epitopes within a compact region that is constructed by the three-dimensional configuration of the molecule. All these antibody clones also recognize rat neuronal synaptophysin. Two monoclonal antibodies against synaptophysin, of which one is the well-characterized SY38 antibody, directed against the carboxy terminal of the molecule, are also shown to react with granulophysin. Characterized polyclonal antibodies against different peptide antigens of synaptophysin failed to recognize granulophysin. Synaptophysin and granulophysin are distinctly recognized in brain cell (white matter) and the pituitary both qualitatively and quantitatively. Based on these and other observations, it is suggested that the repeat motif in the cytoplasmic tail of synaptophysin represents an immunodominant construct that is the target for the observed crossreactive antibodies and that a similar tertiary construct has been preserved in granulophysin and in other transmembrane proteins.     

Preparation and characterization of monoclonal antibodies against native membrane-bound penicillin-binding protein 1B of Escherichia coli.

We prepared monoclonal antibodies against penicillin-binding protein 1B (PBP 1B) of Escherichia coli to study the membrane topology, spatial organization, and enzyme activities of this protein. The majority of the antibodies derived with PBP 1B as the immunogen reacted against the carboxy terminus. To obtain monoclonal antibodies recognizing other epitopes, we used PBP 1B lacking the immunodominant carboxy-terminal 65 amino acids as the immunogen. Eighteen monoclonal antibodies directed against membrane-bound PBP 1B were isolated and characterized. The epitopes recognized by those monoclonal antibodies were located with various truncated forms of PBP 1B. We could distinguish four different epitope areas located on different parts of the molecule. Interestingly, we could not isolate monoclonal antibodies against the amino terminus, although they were specifically selected for. This is attributed to its predicted extreme hydrophilicity and flexibility, which could make the amino terminus very sensitive to proteolytic degradation. All antibodies reacted against native PBP 1B in a dot-blot immunobinding assay. One monoclonal antibody also recognized PBP 1B in a completely sodium dodecyl sulfate-denatured form. This suggests that all the other monoclonal antibodies recognize conformational epitopes. These properties make the monoclonal antibodies suitable tools for further studies.     

Common epitopes in human isoferritins characterized by murine monoclonal antibodies

Three monoclonal antibodies against human liver ferritin were selected to study antigenic determinants (epitopes) of human isoferritins. These monoclonal antibodies were found to form immunoprecipitin lines with ferritin in double diffusion tests (Ouchterlony), indicating multiple epitopes on a single ferritin molecule. The antibodies revealed high species specificity as well. Monoclonal antibodies MA301 and MA311 appeared to recognize different epitopes, since they did not inhibit each other in competitive enzyme-linked immunosorbent assay (ELISA). However, MA309 recognized both epitopes for MA301 and MA311 with similar competitive inhibition. These epitopes were not detectable when ferritin was treated with 8M urea (pH 2.5) and were detectable upon reconstruction by dialysis against 2 M urea (pH 7.2), suggesting that these monoclonals recognize epitopes in the tertiary structure of the ferritin molecule. As a matter of fact, these monoclonals react preferentially with intact ferritin molecule and only negligibly with subunits. Isoelectric focusing patterns of human ferritins demonstrated that liver, spleen, placenta, and hepatoma cells (Li-7) transplanted in nude mice contained basic isoferritins, whereas HeLa cells (carcinoma), Wa cells (EB virus-transformed B cells), and Raji cells (Burkitt's lymphoma) contained acidic isoferritins. Human heart ferritin displayed a somewhat intermediate pattern between liver and HeLa ferritins. In spite of the heterogeneous population of human isoferritins, the dissociation constants (Kd) of the three monoclonal antibodies to liver, HeLa, and heart isoferritins were quite similar.     

Identification of Intestinal Bacteria Responsible for Fermentation of Gum Arabic in Pig Model

Acacia spp. produce gum exudates, traditionally called gum arabic or gum acacia, which are widely used in the food industry such as emulsifiers, adhesives, and stabilizers. The traditional gum arabic is highly variable with average molecular weights varying from 300,000–800,000. For this reason a standardized sample was used for the present experiments, based on a specific species of gum arabic (Acacia(sen)SUPER GUM^TM EM2). The literature indicates that gum arabic can be fermented by the intestinal bacteria to short chain fatty acid, particularly propionate. However, the bacteria responsible for the fermentation have not been determined. In this study, we used enrichment culture of pig cecal bacteria from the selected high molecular weight specific gum arabic of (M_W 1.77 × 10⁶). We found Prevotella ruminicola-like bacterium as a predominant bacterium that is most likely to be responsible for fermentation of the gum arabic used to propionate.     

Antibodies recognizing a variety of different structural motifs on meningococcal Lip antigen fail to demonstrate bactericidal activity.

The neisserial Lip antigen is a conserved antigen associated with the pathogenic Neisseria species, and is composed of multiple repeats of a consensus pentapeptide. A series of monoclonal antibodies reacting with meningococcal Lip antigen were subjected to epitope mapping, using solid-phase synthetic peptides based on the consensus repeat sequence. The antibodies were found to recognize different continuous epitopes based on the consensus sequence. One monoclonal antibody was utilized in affinity chromatography to obtain purified Lip antigen and the antigen was used for immunization of mice. The resulting antisera did not recognize Lip antigen on Western blots but reacted specifically with Lip antigen in immune precipitation experiments, indicating that the predominant polyclonal immune response was directed against conformational epitopes. Despite the diversity of both continuous and conformational epitopes recognized by the antibodies produced, none of the antibodies demonstrated the ability to promote complement-mediated bactericidal activity. Thus despite its initial apparent promise as a potential vaccine candidate the case for the inclusion of Lip antigen in vaccine formulation cannot be supported at present.     

Cross-neutralization of SARS-CoV-2 by HIV-1 specific broadly neutralizing antibodies and polyclonal plasma

Cross-reactive epitopes (CREs) are similar epitopes on viruses that are recognized or neutralized by same antibodies. The S protein of SARS-CoV-2, similar to type I fusion proteins of viruses such as HIV-1 envelope (Env) and influenza hemagglutinin, is heavily glycosylated. Viral Env glycans, though host derived, are distinctly processed and thereby recognized or accommodated during antibody responses. In recent years, highly potent and/or broadly neutralizing human monoclonal antibodies (bnAbs) that are generated in chronic HIV-1 infections have been defined. These bnAbs exhibit atypical features such as extensive somatic hypermutations, long complementary determining region (CDR) lengths, tyrosine sulfation and presence of insertions/deletions, enabling them to effectively neutralize diverse HIV-1 viruses despite extensive variations within the core epitopes they recognize. As some of the HIV-1 bnAbs have evolved to recognize the dense viral glycans and cross-reactive epitopes (CREs), we assessed if these bnAbs cross-react with SARS-CoV-2. Several HIV-1 bnAbs showed cross-reactivity with SARS-CoV-2 while one HIV-1 CD4 binding site bnAb, N6, neutralized SARS-CoV-2. Furthermore, neutralizing plasma antibodies of chronically HIV-1 infected children showed cross neutralizing activity against SARS-CoV-2 pseudoviruses. Collectively, our observations suggest that human monoclonal antibodies tolerating extensive epitope variability can be leveraged to neutralize pathogens with related antigenic profile.