An investigation of the specificity of induced anti-pig antibodies in baboons

AIM

To provide information on the specificity of induced anti-pig antibodies (Abs) in baboons after exposure and sensitization to pig antigens.

MATERIALS AND METHODS

Baboons (n=7) received either porcine mobilized peripheral blood progenitor cells (n=3), kidney (n=3) or heart (n=1) transplants. After rejection of these cells or organs, pre- and post-rejection sera were analyzed by enzyme-linked immunosorbent assay (ELISA) and flow cytometry to detect and measure anti-Galactosealpha1,3Galactose (Gal) and anti-non-Gal Abs. To study the anti-non-Gal carbohydrate response, the sera were incubated with pig red blood cells pretreated with alpha-galactosidase (to remove Gal) and three other exoglycosidases to remove other potential oligosaccharide epitopes, and studied by flow cytometry. To study the anti-swine leukocyte antigen (SLA) response, non-Gal Abs from two baboons sensitized with kidneys from inbred miniature swine of dd or aa haplotype, respectively, were adsorbed on cells of aa, cc, or dd haplotypes, and binding to aa, cc or dd cells was measured by flow cytometry. Cytotoxicity of anti-non-Gal Abs was tested in vitro by a complement-mediated cytotoxicity assay, using pig cells as targets.

RESULTS

In pre-transplant and pre-rejection sera, anti-Gal Abs were detected, but anti-non-Gal Abs were either absent or at minimal levels. After exposure to pig antigens, baboons developed induced anti-Gal and anti-non-Gal Abs. No anti-non-Gal Abs directed to the tested carbohydrate epitopes could be detected. Anti-non-Gal Abs showed minor evidence of specific SLA haplotype reactivity, suggesting that the major Ab response was to pan-pig determinants. Anti-non-Gal Abs showed a low level of complement-mediated lysis of pig cells in vitro.

CONCLUSIONS

In this limited study, no Ab response to non-Gal carbohydrates was observed, and anti-SLA specificity was minor, indicating that most induced anti-non-Gal Ab was directed against non-specific pig proteins, including SLA-epitopes.

Study of tea polyphenol as a reversal agent for carcinoma cell lines' multidrug resistance (study of TP as a MDR reversal agent)

The aim of this study was to examine MDR1 expression product P-glycoprotein (Pgp) and study the effect and mechanism of tea polyphenol (TP) in reversion of multidrug resistance (MDR) in carcinoma cell lines. Immunocytochemical method was used for qualitative detection of Pgp. A comparative study of cytotoxicity and multidrug resistance reversion effect was made by MTT assay for tea polyphenol and quinidine in MCF-7 and MCF-7/Adr cell lines. The multidrug resistance reversion effect and mechanism were studied by measuring the uptake of 99mTc-tetrofosmin in the carcinoma cell lines. (1) The Pgp overexpression in MCF-7/Adr cells was found to be strong positive, while the Pgp expression of MCF-7 was negative. (2) Although both tea polyphenol and quinidine could not remarkably change the toxicity of adriamycin to MCF-7, they could improve the sensitivity of MCF-7/Adr to adriamycin. The reversion index of tea polyphenol and quinidine was 3 and 10 respectively. (3) The cellular uptake of 99mTc-tetrofosmin was remarkably lower in MCF-7/Adr than in MCF-7. The uptake of 99mTc-tetrofosmin in MCF-7/Adr exhibited a 4, 13, 16 fold increase in the presence of 200, 400 and 500 microg/ml of tea polyphenol respectively. The uptake of 99mTc-tetrofosmin in MCF-7/Adr exhibited only a 4-fold increase in the presence of 200 microM of quinidine. Immunocytochemistry can detect P-glycoprotein expression level qualitatively. Tea polyphenol is not only an anti-tumor agent, but also a multidrug resistant modulator similar to quinidine. The multidrug resistance reversion mechanism of tea polyphenol seems to be its inhibition of the activity of P-glycoprotein. Tea polyphenol has the advantage of very low toxicity in tumor treatment.

The synthesis, testing and use of 5-fluoro-alpha-D-galactosyl fluoride to trap an intermediate on green coffee bean alpha-galactosidase and identify the catalytic nucleophile

5-Fluoro-alpha-D-galactopyranosyl fluoride was synthesized and its interaction with the active site of an alpha-galactosidase from green coffee bean (Coffea arabica), a retaining glycosidase, characterized kinetically and structurally. The compound behaves as an apparently tight binding (Ki = 600 nM) competitive inhibitor, achieving this high affinity through reaction as a slow substrate that accumulates a high steady-state concentration of the glycosyl-enzyme intermediate, as evidenced by ESiMS. Proteolysis of the trapped enzyme coupled with HPLC/MS analysis allowed the localization of a labeled peptide that was subsequently sequenced. Comparison of this sequence information to that of other members of the same glycosidase family revealed the active site nucleophile to be Asp145 within the sequence LKYDNCNNN. The importance of this residue to catalysis has been confirmed by mutagenesis studies.

Expression of Egr-1 in late stage emphysema

The transcription factor early growth response (Egr)-1 is an immediate-early gene product rapidly and transiently expressed after acute tissue injury. In contrast, in this report we demonstrate that lung tissue from patients undergoing lung reduction surgery for advanced emphysema, without clinical or anatomical evidence of acute infection, displays a selective and apparently sustained increase in Egr-1 transcripts and antigen, compared with a broad survey of other genes, including the transcription factor Sp1, whose levels were not significantly altered. Enhanced Egr-1 expression was especially evident in smooth muscle cells of bronchial and vascular walls, in alveolar macrophages, and some vascular endothelium. Gel shift analysis with (32)P-labeled Egr probe showed a band with nuclear extracts from emphysematous lung which was supershifted with antibody to Egr-1. Egr-1 has the capacity to regulate genes relevant to the pathophysiology of emphysema, namely those related to extracellular matrix formation and remodeling, thrombogenesis, and those encoding cytokines/chemokines and growth factors. Thus, we propose that further analysis of Egr-1, which appears to be up-regulated in a sustained fashion in patients with late stage emphysema, may provide insights into the pathogenesis of this destructive pulmonary disease, as well as a new facet in the biology of Egr-1.

A prospective randomized-controlled trial of ventricular fibrillation detection time in a DDDR ventricular defibrillator. Ventak AV II DR Study Investigators

Implantable cardioverter defibrillators (ICDs) with dual chamber and dual chamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibrillation (VF). The objectives of this study were to compare the VF detection times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory period shortening. Patients receiving an ICD were randomized in a paired comparison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacing) during ICD threshold testing to create a "worst case scenario" for VF detection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allowed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients were tested at both programmed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 +/- 11 years, 78% were men, coronary artery disease was present in 85%, and a mean left ventricular ejection fraction of 0.34 +/- 0.11. Fifty-two episodes of VF were induced in 26 patients. Despite the high pacing rate, all VF episodes were appropriately detected. The mean VF detection time was 2.4 +/- 1.0 seconds during DDD pacing and 2.9 +/- 1.9 seconds during DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the "worst case scenario" tested. Delays in detection may be seen with long programmed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening.

Binding of human natural antibodies to nonalphaGal xenoantigens on porcine erythrocytes

BACKGROUND

Xenotransplantation is considered one of possible solutions for the serious shortage of organs and cells in transplantation. Although the alphaGal epitope (Gal alpha1,3Gal beta1,4GlcNAc-R) has been identified as being a major xenoantigen responsible for hyperacute rejection, the removal of anti-alphaGal antibody alone from human serum is insufficient to circumvent antibody-mediated immune responses.

METHODS AND RESULTS

We report here the characterization of xenoreactive human natural antibodies against antigens without the alphaGal epitope (nonalphaGal xenoantigens) on porcine erythrocytes using flow cytometry and the evidence for their involvement in complement-mediated hemolysis. Furthermore, a novel protein of 45-kDa has been isolated from the porcine erythrocyte membrane as a major protein antigen recognized by human anti-nonalphaGal.

CONCLUSION

The data presented here will add to our knowledge of xenoantigens on porcine red cells and be important for developing strategies to produce modified red cells immunologically compatible to humans.

Receptor-dependent cell stress and amyloid accumulation in systemic amyloidosis

Accumulation of fibrils composed of amyloid A in tissues resulting in displacement of normal structures and cellular dysfunction is the characteristic feature of systemic amyloidoses. Here we show that RAGE, a multiligand immunoglobulin superfamily cell surface molecule, is a receptor for the amyloidogenic form of serum amyloid A. Interactions between RAGE and amyloid A induced cellular perturbation. In a mouse model, amyloid A accumulation, evidence of cell stress and expression of RAGE were closely linked. Antagonizing RAGE suppressed cell stress and amyloid deposition in mouse spleens. These data indicate that RAGE is a potential target for inhibiting accumulation of amyloid A and for limiting cellular dysfunction induced by amyloid A.

Introduction to porcine red blood cells: implications for xenotransfusion

Advances in the field of xenotransplantation raise the intriguing possibility of using porcine red blood cells (pRBCs) as an alternative source for blood transfusion. The domestic pig is considered the most likely donor species for xenotransplantation. However, identification of xenoantigens on porcine erythrocytes and elucidation of their possible roles in antibody-mediated RBC destruction are necessary for developing clinical strategies to circumvent immunological incompatibility between humans and pigs. Although the alphaGal epitope (Galalpha1,3Galbeta1,4GIcNAc-R) is the major xenoantigen on porcine erythrocytes and is responsible for the binding of the majority of human natural antibodies, other non-alphaGal xenoantigens have been identified. The importance of these non-alphaGal xenoantigens in binding human natural antibodies and subsequently triggering immunological responses cannot be underestimated. Our data suggest that non-alphaGal xenoantigen(s) identified on the porcine erythrocyte membrane are not only recognized by xenoreactive human natural antibodies but are also involved in complement-mediated hemolysis.

Assessment of amino-acid substitutions at tryptophan 16 in alpha-galactosidase

The tryptophan residue at position 16 of coffee bean alpha-galactosidase has previously been shown to be essential for enzyme activity. The potential role of this residue in the catalytic mechanism has been further studied by using site-directed mutagenesis to substitute every other amino acid for tryptophan at that site. Mutant enzymes were expressed in Pichia pastoris, a methylotrophic yeast strain, and their kinetic parameters were calculated. Only amino acids containing aromatic rings (phenylalanine and tyrosine) were able to support a significant amount of enzyme activity, but the kinetics and pH profiles of these mutants differed from wild-type. Substitution of arginine, lysine, methionine, or cysteine at position 16 allowed a small amount of enzyme activity with the optimal pH shifted towards more acidic. All other residues abolished enzyme activity. Our data support the hypothesis that tryptophan 16 is affecting the pKa of a carboxyl group at the active site that participates in catalysis. We also describe an assay for continuously measuring enzyme kinetics using fluorogenic 4-methylumbelliferyl substrates. This is useful in screening enzymes from colonies and determining the enzyme kinetics when the enzyme concentration is not known.

Expression of Rh30 and Rh-related glycoproteins during erythroid differentiation in a two-phase liquid culture system

BACKGROUND

To gain insight into the formation of the Rh complex during erythroid differentiation, the ways in which Rh30 and Rh-related glycoproteins, especially Rh50, were produced in a modified two-phase liquid culture system were studied.

STUDY DESIGN AND METHODS

A mononuclear cell fraction from fresh peripheral blood was first cultured in a medium supplemented with conditioned medium collected from the culture of a bladder carcinoma cell line (5637) for 7 days. Nonadherent cells were then collected for culture in a secondary medium containing 2 U per mL of erythropoietin to initiate erythroid differentiation. The expression of Rh30 and Rh50 during secondary culture (16 days) was monitored by flow cytometry.

RESULTS

D+ cells appeared after Day 4 and increased to 70 percent by Day 8. On Day 12, 90 percent of the total cells became D+ and remained so until the end of the culture. A similar expression profile was obtained for Rh50. As determined from mean fluorescence intensities recorded in flow cytometry, the number of both D and Rh50 antigenic sites per cell increased as the differentiation progressed. Rh-related glycoprotein, CD47, had expression patterns significantly different from those of Rh30 and Rh50. In addition, the cultured cells produced partially glycosylated protein (approx. 32 kDa) in Rh50.

CONCLUSION

Expressions of Rh30 and Rh50 occur simultaneously during erythroid differentiation, and both proteins are most actively synthesized at the last stage of the differentiation. In contrast, CD47 may be involved in expression of Rh30 in a different manner from Rh50. The two-phase liquid culture system will be an excellent model for studying the interaction among the components of the Rh complex during protein synthesis and complex assembly on the cell membrane.

The carboxyl terminus of coffee bean alpha-galactosidase is critical for enzyme activity

The role of the carboxyl (C)-terminal region of coffee bean alpha-galactosidase (alpha-GAL) has been studied by expressing C-terminal deletion mutants in the methylotrophic yeast strain Pichia pastoris. A previous study of human alpha-galactosidase determined that enzyme activity increased when up to 10 amino acid residues were deleted. Deleting 11 residues reduced activity, and deleting 12 residues abolished activity. In our studies, alpha-GAL activity is reduced when one or two amino acids are deleted, as is enzyme secretion directed by P. pastoris signal sequences. The pH profile is similar to that of the wild-type enzyme. Deleting 3 or more residues from the C-terminal end results in a complete loss of both enzyme secretion and activity. The C-terminus of alpha-GAL seems to play an important role in overall enzyme conformation and may directly affect the proper conformation of the active site.

Surface expression of Rh-associated glycoprotein (RhAG) in nonerythroid COS-1 cells

In the Rh blood system, RhAG (Rh-associated glycoprotein, or Rh50) is thought to be involved in Rh30 (D, CE) expression by forming a protein complex on the red cell surface. To obtain further insight into the Rh complex, we chose nonerythroid COS-1 cells instead of proerythroblast-like K562 cells, which produce endogenous Rh proteins as cell host, for the expression of both RhAG and RhD. The RhAG cDNA was subcloned into a retroviral vector, and a stable COS-1 cell line was then established via retroviral transduction. Surface expression of RhAG on the COS-1 cells was monitored by flow cytometry using mouse monoclonal anti-RhAG(2D10). Under these conditions, we detected significant expression of RhAG on the cell surface, compared to stable COS-1 cells transduced with the vector alone. To confirm the results, we isolated RhAG by immunoprecipitation from the lysate of the COS-1 cells, which were metabolically labeled with [(35)S]-methionine. A strong band of the 32 kd on SDS-PAGE was obtained, corresponding to the results obtained from other cultured cells (K562 cell and others), which always produce partially glycosylated RhAG with a molecular weight of 32 kd. Thus, RhAG was expressed without Rh30 and other Rh-related glycoproteins (LW, glycophorin B) in nonerythroid cells. Using the same strategy, however, we could not express RhD epitopes on COS-1 cells even in the presence of RhAG cDNA, suggesting that other factors might be required for the surface expression of RhD antigen. (Blood. 2000;95:336-341)

[Cloning of glycoprotein B gene from strain Rispens of Marek's disease virus and construction of recombinant fowlpox virus]

Purified DNAs from Chicken Embryo Fibroblast (CEF) cultures infected with MDV strain Rispens were used as templates. Specific fragment with the size of about 2.9 kb was successfully amplified through Polymerase Chain Reaction(PCR) and identified to be gB gene of MDV by dot blot hybridization with a digoxigenin-labelled MDV gB specific oligonucleotide probe. The gB gene from strain Rispens was cloned into pUC19 and FPV insertion vector pFG1175-1 to construct plasmid pMGB and pFGBR1775-1 respectively. DOSPER liposome-mediated transfection with insertion vector DNA pFGBR1175-1 was performed on CEF monolayers infected with FPV 3-4 h earlier. Recombinant FPV was clone purified. Immunofluorescence Assay(IFA) showed that MDV gB gene had been expressed in FPV.