Interaction of baboon anti-alpha-galactosyl antibody with pig tissues

In-situ and real-time monitoring of two-stage enzymatic preparation of ACE inhibitory peptides from Cordyceps militaris medium residues by ultrasonic-assisted pretreatment

A protocol for the preparation of angiotensin-Ⅰ-converting enzyme (ACE) inhibitory peptides from Cordyceps militaris medium residues (CMMR) was established by two-stage enzymatic hydrolysis (amylase and protease). In a combination (mono-, dual-, and tri-frequency) of five different frequencies (20, 28, 35, 40 and 50 kHz), ultrasound-assisted pretreatment increased ACE inhibition rate in hydrolysate by 63.30 % under the mode of 20/28 kHz. Afterwards, near-infrared (NIR) spectrometer combined with spectral preprocessing methods and multivariate analysis like partial least square (PLS), synergy interval-PLS (Si-PLS), random frog-PLS (RF-PLS) and competitive adaptive reweighted sampling (CARS-PLS) was used to monitor the ACE inhibitory activity. The performance of models was evaluated by the correlation coefficient (R_p) and root mean square error (RMSEP). CARS-PLS models achieved optimal results for both amylase and protease hydrolysis with R_p = 0.9693, RMSEP = 0.01 for the former and R_p = 0.9454, RMSEP = 0.03 for the latter. NIR spectrometer combined with CARS-PLS models may be employed for in-situ and real-time monitoring of the preparation of ACE inhibitory peptides under ultrasonic-assisted pretreatment.

Highly stable, antihypertensive, and antioxidative peptide production from Apostichopus japonicus by integrated enzymatic membrane reactor and nanofilter-purification mechanism

Enzymatic hydrolysis-offline and membrane separation (EH-offline MS), enzymatic membrane reactor (EMR) (various operational modes), and conjoined nanofilter-purification (desalination) were used to produce highly stable antihypertensive and antioxidative peptides from ultrasonic-slurry viscosity reduced sea cucumber (A. japonicus) protein. The adoption of the optimum batch parameters by EMR-gradient diafiltration feeding (GDF), water feeding, and substrate feeding ensured a significant (p < 0.05) enhancement in protein conversion degree (PCD) by 60.39, 46.69, and 23.33%, respectively, over the conventional EH-offline MS. Also, the antihypertensive activity (ACE-inhibitory potency) of the peptides produced was in the order EMR-GDF > substrate feeding > water feeding > batch process > EH-offline MS. The EMR-GDF and nanofilter-purification produced highly digestible peptides with ACE-inhibition activities of 79.44% and 77.57% for gastric and gastrointestinal digests, respectively. Peptides with molecular weights of 1000-500 Da and 500 Da significantly contributed to the antihypertensive potency of desalinated peptides. In vitro simulated peptides showed a significant increase in the hydroxyl radical scavenging activity for gastric (77.27%) and gastrointestinal (85.32%) digests. The antioxidative stability of the produced peptides was least affected by high-temperature storage. The high arginine (Arg) and hydrophobic amino acid (HAA) content of the peptides resulted in their improved digestibility. Therefore, conjoined EMR-GDF and nanofilter-purification in the production of highly stable desalinated bioactive peptides for industrial applications could be a viable alternative.

The necessity of enzymatically hydrolyzing walnut protein to exert antihypertensive activity based on in vitro simulated digestion and in vivo verification

Since not all proteins are suitable for preparing bioactive peptides by enzymatic degradation, the purpose of this study is to evaluate the necessity of walnut protein (WP) enzymolysis to exert its potential antihypertensive activity. Five proteases were used to hydrolyze WP to produce WP hydrolysate (WPH) enzymatically. The angiotensin-I-converting enzyme (ACE) inhibitory activity of WP and WPH before and after simulated digestion in vitro was measured, and the antihypertensive effect was evaluated in vivo. The results showed that after simulated digestion in vitro, the ACE inhibitory activity of WP digests (44.85%) was not significantly different from that of WPH digests (p > 0.05). In vivo experimental results showed that both WP and WPH had significant blood pressure lowering effects in the acute and long-term administrative experiments. The mechanism of its antihypertensive activities was regulating the balance of the renin-angiotensin-aldosterone system and the kallikrein-kinin system by inhibiting ACE activities in tissues and regulating the level of endothelium-derived vasoconstrictor factors and relaxing factors in serum. It seems unnecessary to carry out enzymatic hydrolysis to produce walnut peptides with antihypertensive activity.

In situ monitoring of grape seed protein hydrolysis by Raman spectroscopy

Raman spectroscopy was used to monitor the enzymatic hydrolysis process of grape seed protein. The degree of hydrolysis (DH), IC₅₀ of the ACE inhibitory activity, and peptide content of the digestive products of grape seed protein were analyzed offline. The partial least squares (PLS), interval partial least squares (IPLS), and joint interval partial least squares (Si-PLS) models of DH, IC₅₀ , and peptide content were established and the optimal pretreatment method was selected. In the optimal model, the corrected model r of the grape seed protein hydrolysis degree is 0.997, the Root Mean Square Error of Cross Validation (RMSECV) is 0.507%. The predicted model r value is 0.9932, the Root Mean Square Error of Prediction (RMSEP) is 1.15%. The corrected model r value of the IC₅₀ is 0.9965, the RMSECV is 11.9%. The r value and RMSEP of predicted model are 0.9978 and 9.64%. The corrected model r value of the peptide content is 0.9955, the RMSECV is 12.7%, the predicted model r value is 0.9953, and the RMSEP is 15.4%. These results showed that in situ real-time monitoring of grape seed protein hydrolysis process can be achieved by Raman spectroscopy. PRACTICAL APPLICATIONS: This study uses Raman spectroscopy method to establish the quantification of proteolysis, IC50, and peptide content of the simulated digestive products during grape seed proteolysis. Analyze the model to monitor and evaluate the target parameters during the entire grape seed proteolysis process. In situ real-time monitoring of grape seed proteolysis is of great significance to the entire grape seed active peptide industry.

SARS-CoV-2 replicating in nonprimate mammalian cells probably have critical advantages for COVID-19 vaccines due to anti-Gal antibodies: A minireview and proposals

Glycoproteins of enveloped viruses replicating in nonprimate mammalian cells carry α‐1,3‐galactose (α‐Gal) glycans, and can bind to anti‐Gal antibodies which are abundant in humans. The antibodies have protected humans and their ancestors for millions of years, because they inhibit replication of many kinds of microbes carrying αGal glycans and aid complements and macrophages to destroy them. Therefore, severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) replicating in nonprimate mammalian cells (eg, PK‐15 cells) carry αGal glycans and could be employed as a live vaccine for corona virus 2019 (COVID‐19). The live vaccine safety could be further enhanced through intramuscular inoculation to bypass the fragile lungs, like the live unattenuated adenovirus vaccine safely used in US recruits for decades. Moreover, the immune complexes of SARS‐CoV‐2 and anti‐Gal antibodies could enhance the efficacy of COVID‐19 vaccines, live or inactivated, carrying α‐Gal glycans. Experiments are imperatively desired to examine these novel vaccine strategies which probably have the critical advantages for defeating the pandemic of COVID‐19 and preventing other viral infectious diseases.

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) replicating in nonprimate mammalian cells carries α‐1,3‐galactose (α‐Gal) glycans which can bind to anti‐Gal antibodies abundant in humans.

Anti‐Gal antibodies inhibit replication of various α‐Gal‐carrying pathogens and aid complements and macrophages to destroy them.

α‐Gal‐carrying SARS‐CoV‐2 could be used as a live vaccine for corona virus 2019 (COVID‐19).

The live vaccine safety could be enhanced through intramuscular inoculation to bypass the fragile lungs.

Live and inactivated COVID‐19 vaccines could be more effective if produced using PK‐15 rather than Vero cells.

Human Natural Antibodies to Mammalian Carbohydrate Antigens as Unsung Heroes Protecting against Past, Present, and Future Viral Infections

Human natural antibodies to mammalian carbohydrate antigens (MCA) bind to carbohydrate-antigens synthesized in other mammalian species and protect against zoonotic virus infections. Three such anti-MCA antibodies are: (1) anti-Gal, also produced in Old-World monkeys and apes, binds to α-gal epitopes synthesized in non-primate mammals, lemurs, and New-World monkeys; (2) anti-Neu5Gc binds to Neu5Gc (N-glycolyl-neuraminic acid) synthesized in apes, Old-World monkeys, and many non-primate mammals; and (3) anti-Forssman binds to Forssman-antigen synthesized in various mammals. Anti-viral protection by anti-MCA antibodies is feasible because carbohydrate chains of virus envelopes are synthesized by host glycosylation machinery and thus are similar to those of their mammalian hosts. Analysis of MCA glycosyltransferase genes suggests that anti-Gal appeared in ancestral Old-World primates following catastrophic selection processes in which parental populations synthesizing α-gal epitopes were eliminated in enveloped virus epidemics. However, few mutated offspring in which the α1,3galactosyltransferase gene was accidentally inactivated produced natural anti-Gal that destroyed viruses presenting α-gal epitopes, thereby preventing extinction of mutated offspring. Similarly, few mutated hominin offspring that ceased to synthesize Neu5Gc produced anti-Neu5Gc, which destroyed viruses presenting Neu5Gc synthesized in parental hominin populations. A present-day example for few humans having mutations that prevent synthesis of a common carbohydrate antigen (produced in >99.99% of humans) is blood-group Bombay individuals with mutations inactivating H-transferase; thus, they cannot synthesize blood-group O (H-antigen) but produce anti-H antibody. Anti-MCA antibodies prevented past extinctions mediated by enveloped virus epidemics, presently protect against zoonotic-viruses, and may protect in future epidemics. Travelers to regions with endemic zoonotic viruses may benefit from vaccinations elevating protective anti-MCA antibody titers.

Impact of ultrasound pretreatment on hydrolysate and digestion products of grape seed protein

The effects of ultrasound pretreatment with different working modes, including mono frequency ultrasound (MFU), simultaneous dual frequency ultrasound (SDFU) and alternate dual frequency ultrasound (ADFU) using energy-gather counter flow ultrasound equipment, on the degree of hydrolysis (DH) of grape seed protein (GSP) hydrolysate and IC₅₀ of GSP digestion products were studied. Amino acid composition analysis (AACA), ultraviolet-visible (UV) spectroscopy and atomic force microscopy (AFM) of GSP with different ultrasound pretreatments were measured. The results showed that MFU, SDFU and ADFU pretreatments improved the DH and reduced the IC₅₀ of GSP significantly (P < .05). The MFU of 20 kHz and SDFU of 20/40 kHz showed higher ACE inhibitory activity within the MFU and SDFU groups, respectively. ADFU of 20/35 kHz produced the highest ACE inhibitory activity among the three working modes (MFU, SDFU and ADFU). AACA showed that all the working modes of the ultrasound pretreatment could increase the amount of hydrophobic amino acids and the total amino acids. The changes in UV spectra and amino acid analysis indicated the unfolding of protein structure and exposure of more hydrophobic groups by SDFU and ADFU pretreatments. AFM analysis of the GSP indicated that the microstructures were destroyed and the particle size reduced after dual-frequency ultrasound pretreatments. Therefore, energy-gather counter flow ultrasound pretreatment is an effective method to improve the DH and reducing the IC₅₀ due to the changes of molecular conformation and effects on the microstructure by sonochemistry of GSP. In conclusion, it is necessary to select the frequency and working modes of ultrasound pretreatment for the preparation of ACE inhibitory peptide of GSP.

Mechanism study of multimode ultrasound pretreatment on the enzymolysis of wheat gluten

BACKGROUND

Ultrasound pretreatment could improve the angiotensin-I converting enzyme (ACE) inhibitory activity of hydrolysates of wheat gluten (WG). The working mode of ultrasound has an important effect on the enzymatic hydrolysis of protein.

RESULTS

The results showed that the optimum working mode of ultrasound was alternate dual-frequency mode (20/35 kHz), substrate concentration was 30 g L^-1 , initial temperature of the suspension was 30 °C, ultrasound pretreatment time was 10 min and power density was 150 W L^-1 . Under optimised conditions, ACE inhibitory activity of WG hydrolysates reached to its maximum value in advance. The surface hydrophobicity (H₀ ) of WG and the content of small peptides at the beginning of the enzymolysis were improved by the ultrasound pretreatment. The structure of WG was destroyed by the ultrasound pretreatment. The enzymatic residue of ultrasound pretreated WG were damaged greater than control.

CONCLUSION

It was concluded that alternate dual-frequency ultrasound pretreatment improved the ACE inhibitory activity. Ultrasonic pretreatment may loosen the tissue of WG aggregate, and help the enzyme alcalase to attack the interior of WG aggregate easily, which resulted in the release of low molecular weight peptides from WG aggregate. © 2017 Society of Chemical Industry.

Effects of ultrasound pretreatment with different frequencies and working modes on the enzymolysis and the structure characterization of rice protein

The effects of ultrasound pretreatment with different frequencies and working modes, including mono-frequency ultrasound (MFU), dual-frequency ultrasound (DFU) and tri-frequency ultrasound (TFU), on the degree of hydrolysis (DH) of rice protein (RP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of RP hydrolysate were investigated. Ultraviolet-visible (UV) spectroscopy, fourier transform infrared (FTIR) spectroscopy, surface hydrophobicity and scanning electron microscopy (SEM) of RP pretreated with ultrasound were measured. The results showed that ultrasound pretreatment did not increase DH of RP significantly (p>0.05). However, all the ultrasound pretreatment increased the ACE inhibitory activity of RP hydrolysate significantly (p<0.05). The MFU of 20kHz showed higher ACE inhibitory activity compared to that of other MFU. The ACE inhibitory activity of sequential DFU was higher than that of simultaneous with the same frequency combination. Sequential TFU of 20/35/50kHz produced the highest increase in ACE inhibitory activity in contrast with other ultrasound frequencies and working modes. All the results under ultrasound pretreatment showed that ultrasound frequencies and working modes were of great effect on the ACE inhibitory activity of RP. The changes in UV-Vis spectra and surface hydrophobicity indicated the unfolding of protein and exposure of hydrophobic groups by ultrasound. The FTIR analysis showed that all the ultrasound pretreatment with different frequencies and working modes decreased α-helix, β-turn content and increased β-sheet, random coil content of RP. The SEM results indicated that ultrasound pretreatment resulted in the deformation of RP. In conclusion, the frequency selection of ultrasound pretreatment of RP is essential for the preparation of ACE inhibitory peptide.

Impact of Power Ultrasound on Antihypertensive Activity, Functional Properties, and Thermal Stability of Rapeseed Protein Hydrolysates

The effects of power ultrasound pretreatments on the degree of hydrolysis (DH), angiotensin-I-converting enzyme (ACE) inhibitory activity, amino acid composition, surface hydrophobicity, protein solubility, and thermal stability of ACE inhibition of rapeseed protein hydrolysates were evaluated. Ultrasonic pretreatments before enzymolysis in terms of power and exposure time increased the DH and ACE inhibitory activities over the control (without sonication). In this study, maximum DH 22.07% and ACE inhibitory activity 72.13% were achieved at 600 W and 12 min pretreatment. Compared to the hydrolysates obtained without sonication, the amino acid profile of ultrasound pretreated hydrolysates showed significant changes particularly in the proline content and hydrophobic amino acids with an increased rate of 2.47% and 6.31%, respectively. Ultrasound pretreatment (600 watts, 12 min) improved functional properties of protein hydrolysates over control by enhancing surface hydrophobicity and solubility index with an increased rate of 130.76% and 34.22%. Moreover, the stability test showed that the ACE inhibitory activity remains stable against heat treatments. However, extensive heat, prolonged heating time, and alkaline conditions were not in the favor of stability test, while under mild heat and acidic conditions their ACE inhibitory activities were not significantly different from unheated samples.

Relationships between the structure of wheat gluten and ACE inhibitory activity of hydrolysate: stepwise multiple linear regression analysis

BACKGROUND

Ultrasound pretreatment of wheat gluten (WG) before enzymolysis can improve the angiotensin converting enzyme (ACE) inhibitory activity of the hydrolysates by alerting the structure of substrate proteins. Establishment of a relationship between the structure of WG and ACE inhibitory activity of the hydrolysates to judge the end point of the ultrasonic pretreatment is vital.

RESULTS

The results of stepwise multiple linear regression (MLR) showed that the contents of free sulfhydryl, α-helix, disulfide bond, surface hydrophobicity and random coil were significantly correlated to ACE Inhibitory activity of the hydrolysate, with the standard partial regression coefficients were 3.729, -0.676, -0.252, 0.022 and 0.156, respectively. The R(2) of this model was 0.970. External validation showed that the stepwise MLR model could well predict the ACE inhibitory activity of hydrolysate based on the content of free sulfhydryl, α-helix, disulfide bond, surface hydrophobicity and random coil of WG before hydrolysis.

CONCLUSION

A stepwise multiple linear regression model describing the quantitative relationships between the structure of WG and the ACE Inhibitory activity of the hydrolysates was established. This model can be used to predict the endpoint of the ultrasonic pretreatment. © 2015 Society of Chemical Industry.

Surface topography, nano-mechanics and secondary structure of wheat gluten pretreated by alternate dual-frequency ultrasound and the correlation to enzymolysis

The effects of alternate dual-frequency ultrasound (ADFU) pretreatment on the degree of hydrolysis (DH) of wheat gluten (WG) and angiotensin I-converting enzyme (ACE) inhibitory activity were investigated in this research. The surface topography, nano-mechanics and secondary structure of WG were also determined using atomic force microscope (AFM) and circular dichroism (CD). The correlations of ACE inhibitory activity and DH with surface topography, nano-mechanics and secondary structure of WG were determined using Pearson's correlation analysis. The results showed that with an increase in either pretreatment duration or power, the ACE inhibitory activity of the hydrolysate also increases, reaching maximum at 10 min and 150 W/L, respectively, and then decreases thereafter. Similarly, AFM analysis showed that as the pretreatment duration or power increases, the surface roughness also increase and again a decrease occurs thereafter. As the pretreatment duration or power increased, the Young's modulus and adhesion of WG also increased and then declined. Young's modulus and adhesions average values were compared with ACE inhibitory activity reversely. The result of the CD spectra analysis exhibited losses in the relative percentage of α-helix of WG. Pearson's correlation analysis showed that the average values of Young's modulus and the relative percentage of α-helix correlated with ACE inhibitory activity of the hydrolysates linearly and significantly (P<0.05); the relative percentage of β-sheet correlated linearly with DH of WG significantly (P<0.05). In conclusion, ADFU pretreatment is an efficient method in proteolysis due to its physical and chemical effect on the Young's modulus, α-helix and β-sheet of WG.

Identification of the tetraspanin CD82 as a new barrier to xenotransplantation

Significant immunological obstacles are to be negotiated before xenotransplantation becomes a clinical reality. An initial rejection of transplanted vascularized xenograft is attributed to Galα1,3Galβ1,4GlcNAc-R (Galα1,3-Gal)-dependent and -independent mechanisms. Hitherto, no receptor molecule has been identified that could account for Galα1,3-Gal-independent rejection. In this study, we identify the tetraspanin CD82 as a receptor molecule for the Galα1,3-Gal-independent mechanism. We demonstrate that, in contrast to human undifferentiated myeloid cell lines, differentiated cell lines are capable of recognizing xenogeneic porcine aortic endothelial cells in a calcium-dependent manner. Transcriptome-wide analysis to identify the differentially expressed transcripts in these cells revealed that the most likely candidate of the Galα1,3-Gal-independent recognition moiety is the tetraspanin CD82. Abs to CD82 inhibited the calcium response and the subsequent activation invoked by xenogeneic encounter. Our data identify CD82 on innate immune cells as a major "xenogenicity sensor" and open new avenues of intervention to making xenotransplantation a clinical reality.

The αGal HyperAcute(®) Technology: enhancing immunogenicity of antiviral vaccines by exploiting the natural αGal-mediated zoonotic blockade

The αGal HyperAcute(®) Technology exploits a robust zoonotic blockade to enhance potency of antiviral vaccines. Naturally acquired immunity against the common αGal epitope [galactose-alpha(1,3)-galactose-beta(1,4)N-acetylglucosamine-R (Gal-α(1,3)-Gal-β(1,4)-GlcNAc-R)] is facilitated by the loss of a key enzyme in the epitope's biosynthetic pathway. As human cells are devoid of this epitope, chronic stimulus from gut flora leads to high levels of circulating anti-αGal antibodies and the development of a robust immune pathway. As the αGal epitope is immediately recognized as foreign, the naturally acquired αGal immune pathway in humans serves as a strong barrier to zoonotic infection. The αGal HyperAcute(®) Technology takes advantage of this natural process to facilitate the rapid presentation of modified antigens to antigen-presenting cells, leading to a strong immune response. The evolutionary immunity to αGal ensures that the presence of αGal epitopes on antigens will lead to a robust immune response involving cross-activation of T(H)1 immunity, characterized by cytokine secretion and increased phagocytic activity, and T(H)2 immunity characterized by high antibody titres. αGal epitopes can be applied to antiviral vaccines by biological, enzymatic or chemical means. Several detection methods that directly and indirectly verify αGal addition are discussed. Enhanced immunogenicity (humoral and cellular) of αGal-modified vaccines is shown for several antiviral vaccine candidates. αGal modification of antiviral vaccine components leads to enhanced immunogenicity. The existing body of literature describing the utility of αGal epitopes as a safe and robust immunostimulatory and -modulatory agent in humans supports the basis for applying the αGal HyperAcute(®) Technology to the improvement of antiviral vaccines, both new and currently approved.

Alpha1,3-galactosyltransferase knockout does not alter the properties of porcine extracellular matrix bioscaffolds

Extracellular matrix (ECM) bioscaffolds, such as porcine small intestine submucosa (SIS) and urinary bladder matrix (UBM), have been successfully used to improve soft tissue healing. Yet they contain plenty of galactose α1,3 galactose (αGal) epitopes, which cause rejection responses in pig organ transplantation to human. Recently, ECM bioscaffolds derived from genetically modified pigs that are αGal-deficient (αGal(-)) have become available. To ensure that the ECM bioscaffolds from these pigs can be used as alternatives, we examined their morphological, bioactive and biomechanical properties and compared them with those from the wild-type pigs (n=5 per group). Morphologically, the αGal(-) ECMs were found to be similar to the wild-type ECMs in gross observation and matrix appearance with hematoxylin and eosin staining. Growth factors commonly known to be present in ECM bioscaffolds, including FGF-2, TGF-β1, VEGF, IGF-1 and PDGF-BB, also showed no significant differences in terms of quantity (p>0.05) and distribution in tissue from the results of enzyme-linked immunosorbent assay, Western blot analysis and immunohistochemistry. Furthermore, a bromodeoxyuridine cell proliferation assay confirmed the bioactivity of the extracts from the αGal(-) bioscaffolds to be similar to the wild-type bioscaffolds. Under uniaxial tensile testing, no significant differences were found between the αGal(-) and wild-type bioscaffolds in terms of their viscoelastic and mechanical properties (p>0.05). These multidisciplinary results suggest that genetic modification to eliminate the αGal epitopes in the ECM bioscaffolds had not altered the properties of these ECM bioscaffolds and, as such, they should retain their performance in tissue engineering in humans.

Expression profiling of endogenous secretory receptor for advanced glycation end products in human organs

The receptor for advanced glycation end products (RAGE) is a cell surface multiligand receptor of the immunoglobulin superfamily, which participates in physiological and pathological processes such as neuronal development, diabetes, inflammation, neurodegenerative disorders, and cancer. A novel splice variant of RAGE-endogenous secretory decoy form (esRAGE) was recently identified and is thought to be a prospective candidate to modify these RAGE-associated conditions. Here, we investigated the expression and distribution of esRAGE and RAGE proteins with domain-specific antibodies. We studied a wide variety of adult normal human preparations obtained from surgical and autopsy specimens using a tissue microarray technique. The results revealed that esRAGE was widely distributed and we classified its expression into four patterns. In pattern A, the cytoplasm is stained diffusely in neurons, vascular endothelium, pneumocytes, mesothelium, pancreatic beta cells, and macrophages/monocytes. In pattern B, dot-like granules are stained in the supranuclear regions facing the luminal surface of the bile ducts, salivary glands, digestive tracts, renal tubules, prostate, skin, thyroid, and bronchioles. Pattern C is represented by diffuse staining in the stromal area of the arterial walls. Pattern D shows diffuse and strong staining of secreted materials such as thyroidal colloid, crystals in renal tubular lumen, and glandular lumen in prostate. This study provides, for the first time, a histopathological basis for understanding the physiological roles of esRAGE in humans, and will contribute to elucidating the participation of esRAGE in pathological processes and to exploring novel diagnostic and therapeutic concepts.

Comparison of the binding properties of the mushroom Marasmius oreades lectin and Griffonia simplicifolia I-B isolectin to alphagalactosyl carbohydrate antigens in the surface phase

The binding of two alpha-galactophilic lectins, Marasmius oreades agglutinin (MOA), and Griffonia simplicifolia I isolectin B(4) (GS I-B(4)) to neoglycoproteins and natural glycoproteins were compared in a surface phase assay. Neoglycoproteins carrying various alpha-galactosylated glycans and laminin from basement membrane of mouse sarcoma that contains the xenogenic Galalpha1-3Gal1-4GlcNAc epitope were immobilized in microtiter plate wells and lectin binding determined with an enzyme-linked assay. After 24 h of incubation, MOA had higher affinity for the xenogenic pentasaccharide (Galalpha1-3Gal1-4GlcNAcbeta1-3Galbeta1-4Glc) than for the Galalpha-monosaccharide. The binding properties of MOA and GS I-B(4) to the xenogenic disaccharide (Galalpha1-3Galbeta1) were comparable while the binding of MOA to the xenogenic pentasaccharide was much stronger than the binding of GS I-B(4) to the same epitope. Non-xenogenic disaccharide-coupled neoglycoproteins having galactose end groups linked alpha1-2 or alpha1-4 to Gal or linked alpha1-3 to GalNAc bound very weakly to MOA, whereas GS I-B(4) recognized all of these disaccharides with similarly high affinity. MOA also showed high affinity for laminin. The results indicate that the Marasmius oreades lectin has nearly the same affinities as does GS I-B(4) for the simple xenogenic carbohydrate antigens, but MOA has greater affinity for the pentasaccharide and is far more specific in its binding preferences than the Griffonia lectin.

In vivo gene transfer of endo-beta-galactosidase C removes alphaGal antigen on erythrocytes and endothelial cells of the organs

BACKGROUND

The presence of Galalpha1-3Galbeta1-4GlcNAc (alphaGal) in pigs is a formidable barrier for pig-to-primate xenotransplantation. We have reported that administration of recombinant endo-beta-galactosidase C (EndoGalC) removes alphaGal on porcine erythrocytes and kidneys. The present study examined the effects of EndoGalC gene therapy on alphaGal suppression.

METHODS

Naked plasmid DNA encoding Igkappa-EndoGalC was given to rats by rapid tail vein injection. The expression of alphaGal in the heart and kidney were studied by lectin staining followed by computer-assisted quantitative analyses. alphaGal expression on erythrocytes was determined by flow cytometric analyses. Enzymatic activity of EndoGalC in the serum was also determined by evaluating the capacity of EndoGalC in removing alphaGal epitopes. Elimination of alphaGal was further studied by injecting antibodies against alphaGal to rats 2 days after the gene transfer.

RESULTS

Administration of 1 mg of Igkappa-EndoGalC/pCAGGS plasmid eliminated alphaGal from the vascular endothelium of the heart and kidney on day 1 and day 2. Between days 4 and 7, alphaGal started to reappear, but remained suppressed. No serious adverse effect was observed in rats treated with EndoGalC. Flow cytometric analyses showed that EndoGalC digested 97% of alphaGal on erythrocytes when measured 4 days after the gene transfer. Enzymatic activity of EndoGalC in the serum peaked on day 1, and significant levels were still observed on day 7. When antibodies against alphaGal were given, rats treated with EndoGalC showed no change, while all control rats died within 40 min.

CONCLUSIONS

The present study demonstrates the potential of an EndoGalC gene transfer, using a hydrodynamics-based delivery system, in eliminating alphaGal from endothelial cells in vivo. The results also ensured that EndoGalC is not harmful suggesting that the production of pigs overexpressing EndoGalC would be a reasonable alternative to pigs deficient in alpha1,3galactosyltransferase.

Solid phase measurements of antibody and lectin binding to xenogenic carbohydrate antigens

OBJECTIVES

In future pig-to-man xenotransplantation it is important to master tools that identify potentially xenogenic alphagalactose (Galalpha) antigens in the doner tissue.

DESIGN AND METHODS

We have measured the binding potentials of Galalpha detecting lectins and antibodies, including a naturally occurring subfraction from human serum, to Galalpha containing neoglycoproteins and mouse laminin that were immobilized on microtiter plates.

RESULTS

Galalpha reactive antibodies with similar monosaccharide specificity have distinct structural preference for sugar ligands. Laminin and neoglycoproteins were treated with alpha-galactosidase and subsequently incubated with antibodies and lectins. The enzyme treatment was more deleterious on antibody binding than on lectin binding.

CONCLUSION

Antibodies and lectins may bind to different galactose determinants on the glycoproteins. Two anti-Galalpha1 antibodies that both have been raised against glycans on rabbit red blood cells may recognize Galalpha-antigens with varying specificities. Binding results obtained after digestion with alpha-galactosidase indicate that some xenoreactive Galalpha groups are not directly accessible for removal by the enzyme.

The immunological hurdles to cardiac xenotransplantation

The main hurdle to clinical application of cardiac xenotransplantation is the immune response of the recipient against the graft. Although all xenografts arouse an intense immune response, the effect of that response depends very much on whether the graft consists of isolated cells or an intact organ, such as the heart. Intact organs, which are transplanted by primary vascular anastomosis, are subject to severe vascular injury owing to the reaction of immune elements with the endothelial lining of donor blood vessels. Vascular injury leads to hyperacute rejection, acute vascular rejection, and chronic rejection. The immunological basis for these types of rejection and potential therapies, which might be used to avert them, are discussed.

Recent strategies to overcome the hyperacute rejection in pig to human xenotransplantation

Due to the ever increasing shortage of suitable human donors, alternative strategies are sought to moderate the current discrepancy between the number of executable and required transplantations. Xenotransplantation (i.e., the transplantation of organs [tissues or cells] between different species) appears to be a reasonable solution. However, various problems (immunological, physiological, infectious-microbiological, ethical-juridicial) seem to be associated with xenotransplantation. One of the most formidable barriers to xenotransplantation is the phenomenon of hyperacute rejection that may lead to the destruction of the transplanted vascularized organ in a few minutes to hours. In the pathogenesis of hyperacute rejection, xenoreactive antibodies and the complement system appear to be of primary importance. Various methods can be applied to prevent hyperacute rejection; both the recipient and the donor can be treated. In this brief review, the author attempts to present a synopsis of the possible therapeutical interventions to prevent hyperacute rejection..