Selection of T cell clones with restricted TCR-CDR3 lengths during in vitro and in vivo alloresponses

In a model of heart allograft rejection in adult congeneic rats mismatched for both class I and class II MHC molecules, we analyzed the TCR beta chain repertoire of T cells infiltrating rejected allografts [graft-infiltrating T cells (GITC)]. Although all BV families were used by GITC, oligoclonal expansions reflected by an altered distribution of TCR beta chain CDR3 lengths were detected throughout the rejection process. Interestingly, expansions involving TCR beta chains with common length and BV usage were recurrently found within distinct individuals at late stages of rejection in vivo and after in vitro mixed lymphocyte culture between donor and naive recipient cells. Sequence analysis of the CDR3 regions within recurrent TCR beta chains comprising either BV2 or BV13 gene segments demonstrated a complete sequence identity between BV2-BJ2S3 junctions derived from GITC in all individuals tested and the presence of conserved amino acids at constrained CDR3 positions within GITC BV13+ junctions derived from most individuals. These results suggest the existence of several major alloantigens responsible for expansion of T cell clones bearing a 'public' beta chain rearrangement within rejected allografts. The demonstration that such clones are also expanded during in vitro mixed lymphocyte reactions provides an experimental approach which might allow molecular characterization of the above major alloantigens and their possible in vivo targeting.

Study of the in vitro effect on glomerular albumin permselectivity of serum before and after renal transplantation in focal segmental glomerulosclerosis

BACKGROUND

The selective proteinuria observed in patients with focal segmental glomerulosclerosis (FSGS) suggests an abnormal loss of fixed anionic charges on the glomerular capillary wall.

METHODS

In this article, we have studied the putative presence of such factor(s) by using a new in vitro assay to assess glomerular permselectivity by measuring glomerular volume variation (GVV) in isolated glomeruli after hypotonic stress. We randomly tested the serum GVV activity of 10 healthy donors and 143 patients before transplantation. Of the patients, 80 had FSGS, 26 membranous glomerulonephritis, 19 polycystic kidney disease, and 18 malformative uropathies. Moreover, we tested the pre- and posttransplantation serum of 14 patients with recurrence and 14 without recurrence.

RESULTS

Serum GVV was significantly higher in patients with FSGS than in those with the other end-stage renal diseases studied (P<0.01) or in healthy donors (P<0.01). However, a wide distribution of serum GVV activity in patients with and without FSGS was observed. Statistically, pregraft GVV values were not predictive of the recurrence of FSGS after transplantation. Moreover, we observed a significant decrease in serum GVV activity after transplantation in patients without recurrence (P<0.01) compared to those who underwent a recurrence.

CONCLUSIONS

These results reinforce the hypothesis of a circulating factor that alters glomerular albumin permselectivity in FSGS patients. However, the presence of this factor before transplantation did not appear to predict relapse of the disease after transplantation, as recently supported, although its activity seems to be down-regulated after transplantation in patients who do not experience recurrence of the disease.

Disposition of basiliximab, an interleukin-2 receptor monoclonal antibody, in recipients of mismatched cadaver renal allografts

BACKGROUND

Basiliximab is an interleukin-2 receptor (IL-2R; CD25) chimeric monoclonal antibody for immunoprophylaxis against acute rejection in renal transplantation. Its pharmacokinetics were characterized in a multicenter open-label, prospective dose-escalation study to identify a single-dose regimen providing IL-2R-saturating serum concentrations in the critical first posttransplant month.

METHODS

Thirty-two recipients of primary, mismatched cadaver kidneys were enrolled: 20 men and 12 women, who were 47+/-11 years old and weighed 65+/-12 kg. The immunosuppression regimen consisted of steroids and azathioprine from day 0 and cyclosporine from day 10. Basiliximab was infused over 30 min as a single dose preoperatively.

RESULTS

Thirty patients were evaluable for basiliximab pharmacokinetics: 24 received 40 mg and 6 received 60 mg. Basiliximab was well tolerated without evidence of cytokine-release syndrome, hypersensitivity reactions, or anti-idiotype antibody response. Peak concentration and area under the concentration curve increased proportionally with dose. Postinfusion concentrations declined in a biphasic manner with a terminal half-life of 6.5+/-2.1 days. Weak, widely dispersed correlations were noted between body weight versus distribution volume (r=0.29) and versus clearance (r=0.45), suggesting no clinical relevance for weight-adjusted dosing. There were no apparent gender-related differences in basiliximab disposition. Previous phase II data indicated that serum concentrations in excess of 0.2 microg/ml are sufficient to saturate IL-2R epitopes on circulating T lymphocytes. Concentrations were above this threshold for 26+/-8 days (range 16 to 46) at the 40-mg dose level and for 32+/-11 days (range 22 to 51) at the 60-mg dose level.

CONCLUSIONS

Total basiliximab doses of 40-60 mg were well tolerated, nonimmunogenic, and estimated to provide immunoprophylaxis to cover the first posttransplant month.

Immunosuppression by D-isomers of HLA class I heavy chain (amino acid 75 to 84)-derived peptides is independent of binding to HSC70

BACKGROUND

Peptides derived from the class I heavy chain were shown to modulate immune responses in vitro and in vivo. A peptide derived from HLA-B2702 (2702.75-84) inhibited differentiation of cytotoxic T cells as well as T cell and natural killer cell-mediated cytotoxicity in vitro. Peptide-mediated immunomodulation seemed to be independent of the MHC proteins expressed by responder and stimulator cells. In vivo studies in rodents demonstrated prolongation of heart and skin allograft survival after peptide therapy. Here, the correlation between the peptide's biological activity and its amino acid sequence was analyzed using peptides derived from amino acid 75-84 of several mouse, rat, and human MHC class I proteins as well as peptides with single amino acid substitutions in the 2702.75-84 sequence.

METHODS

Peptides consisting of both L- and D-amino acids were tested for inhibition of murine and human T cell-mediated and lymphokine-activated killer cell-mediated cytotoxicity, binding to hsc70, and prolongation of heart allograft survival in vivo.

RESULTS

Replacement of glutamic acid residue (E) at position 75 with valine (V) resulted in a peptide [2702.75-84(E>V)] with increased in vitro and in vivo activity but unchanged affinity for hsc70. Surprisingly, both L- and D-isomers of 2702.75-84 and 2702.75-84(E>V) inhibited cytotoxic cells in vitro and prolonged heart allograft survival in vivo. However, as expected, the peptides consisting of D-amino acids did not bind to hsc70.

CONCLUSION

Assuming that both D- and L-isomers modulate immune responses by similar mechanisms, these results suggest that the peptides' effect is independent of binding to hsc70.

Adenovirus-mediated gene transfer in rat liver of interleukin 4 but not interleukin 10 produces severe acute hepatitis

Several immune responses are either limited to or concentrated in a given organ. Cytokines produced during ongoing immune responses have organ-localized effects that can be only partially mimicked upon their systemic delivery. Recombinant adenoviruses are efficient vectors to induce transient organ-localized cytokine expression. This allows in vivo analysis of the effects of cytokines produced spatially and temporally in a manner comparable to that observed during immune responses. The authors generated recombinant adenovirus for rat IL-4 (AdIL-4) and IL-10 (AdIL-10) to analyse the in vivo effects of these two important immunoregulatory molecules after gene transfer in the liver. It was first established that AdIL-4 and AdIL-10 were able to direct the production of biologically active cytokines by different rat cell types in vitro. Intraportal injection of doses of up to 10(10) pfu of AdIL-10 or control non-coding recombinant adenovirus were well tolerated, and hepatic histology showed only mild alterations. Conversely, animals receiving more than 2.5 x 10(9) pfu of AdIL-4 showed dose-dependent mortality, with clinical signs of hepatic dysfunction. Liver histology in animals receiving 2.5 x 10(9) pfu of AdIL-4 showed severe acute hepatitis with maximal lesions between day 7 and 14 and almost complete normalization by day 28 after gene transfer. The leukocyte infiltrate was composed primarily of mononuclear cells, but eosinophils and mast cells were significantly increased as compared to control animals. Hepatic function was also altered in animals that received AdIL-4, with kinetics similar to that of histological lesions. Our study describes a model for investigating cytokine function in vivo through liver-localized transgene expression mediated by adenoviral vectors and demonstrates that liver production of IL-4 but not IL-10 results in acute severe hepatitis.

Comparative study of target antigens for primate xenoreactive natural antibodies in pig and rat endothelial cells

BACKGROUND

A rat-to-primate cardiac xenograft model has been proposed as an alternative to the clinically relevant but more cumbersome pig-to-primate model for assessing the efficacy of strategies aimed at preventing xenograft hyperacute rejection. As in pig xenografts, the rejection of rat hearts was mediated by the binding of xenoreactive natural antibodies (XNA) and complement activation. The present study was conducted to identify target antigens recognized by cynomolgus and rhesus monkey IgM XNA on rat tissues and cells in comparison with pig cells.

METHODS

The reactivity of rhesus or cynomolgus serum on pig and rat endothelial cells (ECs) was studied by flow cytometry, ELISA, and complement-dependent cytotoxicity, after removal of primate XNA by perfusion of pig livers, immunoadsorption on a Gal alpha(1,3)Gal affinity column, and enzymatic removal of alpha-galactosyl epitopes from the cell surface. Rat and pig EC extracts were also immunoprecipitated with primate serum and resolved in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The expression of the Gal alpha(1,3)Gal epitope was analyzed on rat tissues and ECs by immunohistochemistry, flow cytometry, and Western blot, using the isolectin B4 from Griffonia simplicifolia.

RESULTS

Removal of primate XNA or of alphaGal epitopes resulted in a decrease in XNA binding to pig and rat cells, leaving a similar degree of residual reactivity in the two species. At least five proteins of 260, 210, 110, 56, and 50 kDa were immunoprecipitated on rat ECs, with molecular weight similar to several proteins identified on pig ECs. These results suggest that primate XNA recognize similar antigens on rat and pig ECs. Rat cells expressed lower levels of the Gal alpha(1,3)Gal epitope than pig cells. A large proportion, but not all, of primate XNA react with this epitope on pig and rat ECs.

CONCLUSION

This study suggests that the rat is a valuable species for the evaluation of genetic engineering strategies on the vascular endothelium aimed at preventing hyperacute xenograft rejection.

Randomised trial of basiliximab versus placebo for control of acute cellular rejection in renal allograft recipients. CHIB 201 International Study Group

BACKGROUND

Currently available immunosuppressive regimens for cadaver-kidney recipients are far from ideal because acute-rejection episodes occur in about 30% to 50% of these patients. In the phase III study described here we assessed the ability of basiliximab, a chimeric interleukin (IL)-2 receptor monoclonal antibody, to prevent acute-rejection episodes in renal allograft recipients.

METHODS

380 adult recipients of a primary cadaveric kidney transplant were randomly allocated, in this double-blind trial, to receive a 20 mg infusion of basiliximab on day 0 (day of surgery) and on day 4, to provide IL-2-receptor suppression for 4-6 weeks (n=193), or to receive placebo (n=187). Both groups received baseline dual immunosuppressive therapy with cyclosporin and steroids throughout the study. The primary outcome measure was incidence of acute-rejection episodes during the 6 months after transplantation. Safety and tolerability were monitored over the 12 months of the study.

FINDINGS

376 patients were eligible for intention-to-treat analysis (basiliximab, n=190; placebo, n=186). No significant differences in patient characteristics were apparent. The incidence of biopsy-confirmed acute rejection 6 months after transplantation was 51 (29.8%) of 171 in the basiliximab group compared with 73 (44.0%) of 166 in the placebo group (32% reduction; 14.2% difference [95% Kaplan-Meier CIs 3% to 24%], p=0.012). The incidence of steroid-resistant first rejection episodes that required antibody therapy was significantly lower in the basiliximab group (10% vs 23.1%, 13.1% difference [5.4% to 20.8%], p<0.001). At weeks 2 and 4 post-transplantation, the mean daily dose of steroids was significantly higher in the placebo group (p<0.001 with one-way analysis of variance). The incidence of graft loss at 12 months post-transplantation was 23 (12.1%) of 190 in the basiliximab group and 25 (13.4%) of 186 in the placebo group (1.3% difference [-5% to 9%], p=0.591). The incidence of infection and other adverse events was similar in the two treatment groups. The acute tolerability of basiliximab was excellent, with no evidence of cytokine-release syndrome. 14 deaths (basiliximab n=9; placebo n=5; -2.0% difference [-6% to 2%], p=0.293) occurred during the 12-month study and a further three deaths (basiliximab n=1; placebo n=2) occurred within the 380-day cut-off period. One post-transplantation lymphoproliferative disorder was recorded in each group.

INTERPRETATION

Prophylaxis with 40 mg basiliximab reduces the incidence of acute rejection episodes significantly, with no clinically relevant safety or tolerability concerns.

Adenovirus-mediated gene transfer into isolated mouse adult pancreatic islets: normal beta-cell function despite induction of an anti-adenovirus immune response

The in vitro purification of pancreatic islets offers an opportunity for their modification by ex vivo gene transfer. We investigated the efficiency and functional consequences of adenovirus-mediated gene transfer into adult murine pancreatic islets with a recombinant adenovirus encoding for the beta-galactosidase (beta-Gal) reporter gene. At 10(6) pfu/islet, almost all of the islets were transduced, but maximal transduction was obtained at 10(7) pfu/islet. Histochemical analysis of frozen islet sections showed that transduced cells were only located at the periphery of islets. Transduced islets showed normal insulin secretion in vitro, and were able to normalize in vivo the glycemia of streptozotocin-induced diabetes in syngeneic and allogeneic mice. beta-Gal expression in transduced islets was observed for at least 6 weeks in naive normal recipients and in immunodeficient mice, but was shortened in mice preimmunized to adenovirus. Nevertheless, islets maintained normal control of glycemia in all mice. An early leukocyte infiltrate was observed in syngeneic grafts of transduced islets, but no acceleration in rejection of fully MHC-incompatible islet grafts occurred. In summary, adenovirus-mediated gene transfer in adult mouse islets, although sparing most of the beta-cells, was highly efficient and did not impair insulin secretion by islets. The immune response to the adenovirus and/or to the transgene might be only partially responsible for the decreased expression over time of the transduced gene. Accordingly, adenovirus-mediated gene transfer might allow efficient expression of vectorized sequences with potential immunosuppressive effects in the islet microenvironment.

Rat spleen dendritic cells express natural killer cell receptor protein 1 (NKR-P1) and have cytotoxic activity to select targets via a Ca2+-dependent mechanism

Dendritic cells (DC) are a subset of leukocytes whose major function is antigen presentation. We investigated the phenotype and function of enriched (95-98.5%) rat DC. We show that both spleen and thymus DC express the natural killer cell receptor protein 1 (NKR-P1) as a disulfide linked homodimer of 60 kD. Freshly isolated DC express a low level of NKR-P1, which is strongly upregulated after overnight culture. Spleen, but not thymus DC, were able to kill the NK-sensitive YAC-1 cell line in vitro, and since this killing was Ca2+ dependent, a Fas ligand-Fas interaction was probably not involved. Besides their potent antigen-presenting function, DC can thus be cytotoxic for some tumor targets.

Idiopathic and secondary membranous nephropathy and polymorphism at TAP1 and HLA-DMA loci

In a previous study on the effects of TAP1 and TAP2 gene polymorphism in kidney allograft recipients, we found no association between graft outcome and recipient/donor TAP1 and TAP2 allele polymorphism or compatibility, but we observed a surprising increased frequency of the TAP1*0201 allele among kidney recipients. This increase was restricted to patients with glomerulopathy. We now report on a larger cohort of 178 patients with membranous nephropathy who were typed for their HLA-DPB1, -DRB1, -DMA, -DMB, LMP2, LMP, TAP1 and TAP2 genes compared with 100 random ethnically matched and healthy unrelated individuals used as controls. The results show a significant increased frequency of two markers in membranous nephropathy patients as compared with controls: firstly the previously recognized increase in HLA-DR3 (59% vs 18%: Pc < 1 x 10(-9), RR = 6.6), secondly a new association with two TAP1 amino acid variants displaying respectively a valine in amino acid position 333 (TAP1-Val-333) and consequently a glycine in position 637 (TAP1Gly-637) due to its strong linkage disequilibrium with Val-333. No linkage disequilibrium was found between TAP1-Val-333 and HLA-DR3. Moreover, we also noticed a decrease of the DMA*0102 phenotype in membranous nephropathy patients. The other HLA-DPB, -DMB, LMP2, LMP7 and TAP2 phenotype frequencies were roughly similar between patients and controls. These results show that the TAP1-Val-333 like HLA-DR3 phenotype is positively associated with membranous nephropathy and that these two risk factors are not cumulative in membranous nephropathy pathophysiology.

Predominant Th1 cell infiltration in acute rejection episodes of human kidney grafts

T-cells and their cytokines are thought to play a major role in the genesis of cellular infiltration and rejection in human kidney allografts. Production of Th1 (IFN-gamma) and Th2-type (IL-4 and IL-5) cytokines was assessed in a large series of T-cell clones, derived from core biopsies of kidney grafts in 10 patients with acute interstitial grade I/II rejection (AIR), 6 patients with a histology of "borderline rejection" (BLR) and 3 with cyclosporine A (CsA) toxicity, all receiving standard maintenance immunosuppression. Biopsies were pre-cultured in IL-2 in order to preferentially expand T-cells activated in vivo, and T-cell blasts were cloned with phytohemagglutinin (PHA) and IL-2 using a highly efficient (23 to 98%) cloning technique. A total of 483 T-cell clones obtained from AIR episodes were compared with 346 and 132 clones derived from patients with BLR episodes and CsA toxicity, respectively. In two series of 22 AIR and 77 BLR T-cell clones, alloreactivity against donor cells was shown by 25 and 14% of CD8+ and 21 and 4% of CD4+ clones, respectively. When stimulated by donor-derived EBV B-cells, all these alloreactive clones produced IFN-gamma, but not IL-4 or IL-5 (Th1 clones). Upon stimulation with PHA, the principal qualitative and quantitative differences between AIR- and BLR-derived T-cell clones were that cells derived from AIR patients: (i) showed significantly higher proportions (80 +/- 15 vs. 55 +/- 13%) of Th1 clones in their progeny; (ii) included smaller proportions (3 +/- 4 vs. 20 +/- 17%) of clones incapable of producing IFN-gamma, IL-4 or IL-5 ('null' clones); and (iii) produced significantly higher quantities of IFN-gamma (100 +/- 50 vs. 36 +/- 7 U/10(6) cells/ml), these quantities also being significantly correlated (r = 0.83) with the degree of interstitial graft infiltration (item 'i' in the Banff histological grading). The clones derived from CsA toxicity biopsies exhibited a pattern very similar to that found in BIR cases. These data lead us to conclude that the powerful inflammatory response elicited in acute rejection of a kidney graft recruits and activates both allospecific and non-specific Th1 effector cells, which are primed to high IFN-gamma production. Our results also suggest that IFN-gamma could contribute, at least in part, to the degree of graft infiltration and to the severity of the rejection episode.

Usefulness of DNA viral load quantification for cytomegalovirus disease monitoring in renal and pancreas/renal transplant recipients

BACKGROUND

The purpose of this prospective study was to evaluate the usefulness of quantifying DNA-cytomegalovirus (CMV) load for the diagnosis and monitoring of CMV disease among renal and pancreas transplant patients under immunosuppressive drugs.

METHODS

A longitudinal study was conducted among 34 consecutive, unselected renal and pancreas/renal transplanted patients in our unit. During the first 3 posttransplant months, weekly monitoring of CMV infection and CMV disease was done, involving the determination of viremia by the shell vial assay, qualitative DNAemia by semi-nested polymerase chain reaction (PCR) and quantitative DNAemia by the hybrid capture system (HCS), a new and original hybridization method (337 samples were collected for each test). Qualitative and quantitative DNAemia results were blinded to physicians and three grades of disease were defined according to CMV related symptom occurrence.

RESULTS

PCR was the most sensitive (100%) but the least specific (78%) method for the diagnosis of CMV disease. HCS was specific for CMV genome detection, sensitive and reproducible. Blood DNA levels above 60 pg/ml were predictive of severe or moderate CMV disease (sensitivity, 92%; specificity, 100%). A significant decrease in viral load was observed after ganciclovir administration, and a positive PCR or HCS result at the end of the antiviral treatment was associated with relapse of CMV infection or disease.

CONCLUSIONS

It is concluded that quantitative DNAemia detection, with this new commercially available method, can predict disease and may be useful for a rational evaluation of ganciclovir preemptive therapy in such patients.

Intact pig pancreatic islet function in the presence of human xenoreactive natural antibody binding and complement activation

BACKGROUND

The expression of xenogeneic epitopes and the activation of human complement by adult pig islets after prolonged culture have hitherto not been described.

MATERIALS AND METHODS

Freshly isolated and cultured islets were analyzed by fluorescence-activated cell sorter analysis, fluorescence microscopy, and immunohistology for expression of Gal(alpha1,3)Gal epitopes, binding of human xenoreactive natural antibodies (XNA), and complement deposition.

RESULTS

Freshly isolated and cultured islets showed detectable Gal(alpha1,3)Gal expression and human XNA binding limited to intraislet capillary endothelial cells. No significant modification in Gal(alpha1,3)Gal expression and human XNA binding levels was detected in adult pig islets cultured for up to 4 days compared with freshly isolated islets. Incubation of pig islets with human serum demonstrated the deposition of C3, C4, and membrane attack complex, but not factor B with a similar pattern to XNA. However C3 and C4 showed a more widespread deposition. Despite complement activation, no cytotoxic effect on islets was detected after 4 hr of incubation with human serum capable of killing porcine endothelial cells. Even after 4 days of culture in 50% intact human serum, pig islets retained both their normal morphology and a normal insulin response to glucose stimulation.

CONCLUSIONS

Neither islet cell lysis nor, more importantly, any alteration in beta cell function occurred, which suggests that adult pig islets may not be directly damaged by serum after xenotransplantation in humans. Nevertheless, complement activation in vivo could trigger rapid cellular rejection mechanisms through islet cell opsonization and release of bioactive fragments.

Decreased cytotoxic activity of natural killer cells in kidney allograft recipients treated with human HLA-derived peptide

Peptides derived from a conserved region (aa 75-84) of HLA class I, overlapping the supertypic HLA-BW4/BW6 antigen region, have been shown to exhibit nonallele restricted immunosuppressive properties in rats and mice, prolonging survival of major histocompatibility complex-mismatched allografts. Furthermore, HLA-B7 peptides inhibit alloreactive cytotoxic cells, and both HLA-B7 and HLA-B2702 peptides inhibit natural killer (NK) cytotoxicity in vivo. In this article, we report on a randomized, controlled study of the safety and pharmacokinetics of HLA-B2702-derived peptide in human recipients of a first kidney allograft. Escalating doses of HLA-B2702 were compared with doses of placebo controls. No toxicity and no immunization against the peptide were noted. Although the study was not designed as an efficacy trial, patients who received the high-dose protocol (7 mg/kg) did experience more rejection episodes, but this was not statistically significant when compared with control patients. Interestingly, in human recipients, as previously observed in rodents, administration of the peptide was associated with a statistically significant decrease in the cytotoxicity of NK cells against K562 targets (P<0.001). As these peptides correspond to a region of the HLA class I molecule that interacts with the newly described NK receptors for class I, their mode of action through interaction with such receptors is discussed. As a peptide of the same sequence from HLA-B7 blocks both NK and alloreactive T cell cytotoxicity, it is possible that, in humans too, both types of cytotoxic cells are affected by this peptide. The biological significance of these observations should be confirmed in future controlled studies with a larger patient population.

Porcine alpha1,3-galactosyltransferase: tissue-specific and regulated expression of splicing isoforms

Expression of the Gal alpha1,3 Gal epitope on membrane glycolipids and glycoproteins is known to vary widely from one tissue to another. In the course of studying the mechanisms underlying this variability, we have isolated from pig cDNA four sequences corresponding to four isoforms of alpha1,3-galactosyltransferase (alpha1,3GT), the Golgi enzyme that links galactose in alpha1,3 on the galactose residue of N-acetyllactosamine. The isoforms differ from each other in the alternative presence of two nucleotide stretches of 36 and 63 base pairs in a segment encoding the stem region of the protein. Stable expression experiments show that all four isoenzymes can confer alpha-galactosyltransferase activity to HeLa cells, and that they are all located within the Golgi compartment, indicating that variations in length in the stem region do not affect enzyme activity or cellular localization. Analysis of RNA from different pig organs and cells shows quantitative differences between tissues in levels of alpha1,3GT, as well as qualitative differences, the four isoforms being unequally represented in different tissues.