Influence of HLA-C environment on the spontaneous clearance of hepatitis C in European HIV-HCV co-infected individuals.

Natural killer (NK) cell functions are regulated by diverse inhibitory and activating receptors, including killer cell immunoglobulin-like receptors (KIR), which interact with human leukocyte antigen (HLA) class I molecules. Some KIR/HLA genetic combinations were reported associated with spontaneous clearance (SC) of hepatitis C virus (HCV) but with discordant results, possibly reflecting KIR and/or HLA gene polymorphism according to populations. KIR/HLA genetic combinations associated with both an exhaustive NK and T cell repertoire were investigated in a cohort of HIV-HCV co-infected individuals with either SC (n = 68) or chronic infection (CI, n = 163) compared to uninfected blood donors [controls (Ctrl), n = 100]. Multivariate analysis showed that the HLA C2C2 environment was associated with SC only in European HIV-HCV co-infected individuals [odds ratio (OR) = 4·30, 95% confidence interval = 1·57-12·25, P = 0·005]. KIR2D+ NK cell repertoire and potential of degranulation of KIR2DL1/S1+ NK cells were similar in the SC European cohort compared to uninfected individuals. In contrast, decreased frequencies of KIR2DS1+ and KIR2DL2+ NK cells were detected in the CI group of Europeans compared to SC and a decreased frequency of KIR2DL1/S1+ NK cells compared to controls. Regarding T cells, higher frequencies of DNAX accessory molecule-1 (DNAM-1)+ and CD57+ T cells were observed in SC in comparison to controls. Interestingly, SC subjects emphasized increased frequencies of KIR2DL2/L3/S2+ T cells compared to CI subjects. Our study underlines that the C2 environment may activate efficient KIR2DL1+ NK cells in a viral context and maintain a KIR2DL2/L3/S2+ mature T cell response in the absence of KIR2DL2 engagement with its cognate ligands in SC group of HCV-HIV co-infected European patients.

Failure of Calcineurin Inhibitor (Tacrolimus) Weaning Randomized Trial in Long-Term Stable Kidney Transplant Recipients.

Long-term renal transplant outcome is limited by side effects of immunosuppressive drugs, particularly calcineurin inhibitor (CNI). We assumed that some patients selected for a "low immunological risk of rejection" could be eligible and benefit from a CNI weaning strategy. We designed a prospective, randomized, multicenter, double-blind placebo-controlled clinical study (Eudract: 2010-019574-33) to analyze the benefit-risk ratio of tacrolimus weaning on highly selected patients (≥4 years of transplantation, normal histology, stable graft function, no anti-HLA immunization). The primary endpoint was improvement of renal function. Fifty-two patients were scheduled in each treatment arm, placebo compared to the CNI maintenance arm. Only 10 patients were eligible and randomized. Five patients were assigned to the placebo arm and five were assigned to the tacrolimus maintenance arm. In the tacrolimus maintenance arm, all patients maintained stable graft function and no immunological events occurred. Contrastingly, in the placebo arm, all five patients had to reintroduce a full dose of tacrolimus since three of them presented an acute rejection episode (one humoral, one mixed, and one borderline) and two displayed anti-HLA antibodies without histological lesion (one donor-specific antibodies [DSA] and one non-DSA). Clearly, tacrolimus withdrawal must be avoided even in long-term highly selective stable kidney recipients.

Pretransplant sensitization against angiotensin II type 1 receptor is a risk factor for acute rejection and graft loss.

The angiotensin II type 1 receptor (AT1R) is an emerging target of functional non-HLA antibodies (Ab). We examined the potential of determining the degree of presensitization against AT1R as a risk factor for graft survival and acute rejection (AR). The study included 599 kidney recipients between 1998 and 2007. Serum samples were analyzed in a blinded fashion for anti-AT1R antibodies (AT1R-Abs) using a quantitative solid-phase assay. A threshold of AT1R-Ab levels was statistically determined at 10 U based on the time to graft failure. An extended Cox model determined risk factors for occurrence of graft failure and a first AR episode. AT1R-Abs >10 U were detected in 283 patients (47.2%) before transplantation. Patients who had a level of AT1R-Abs >10 U had a 2.6-fold higher risk of graft failure from 3 years posttransplantation onwards (p = 0.0005) and a 1.9-fold higher risk of experiencing an AR episode within the first 4 months of transplantation (p = 0.0393). Antibody-mediated rejection (AMR) accounted for 1/3 of AR, whereby 71.4% of them were associated with >10 U of pretransplant AT1R-Abs. Pretransplant anti-AT1R-Abs are an independent risk factor for long-term graft loss in association with a higher risk of early AR episodes.

Failure of bortezomib to cure acute antibody-mediated rejection in a non-compliant renal transplant patient.

Bortezomib has appeared recently as a potential active treatment for acute AMR for few years. We reported a patient who received two courses of bortezomib for the treatment of an acute AMR associated with de novo HLA DSA that occurred 18 months after renal transplantation because of non-compliance. Graft biopsy revealed features of acute humoral rejection with plasmocyte infiltration and C4d staining. Bortezomib was associated with corticosteroid pulses, IVIgs, and PP. Despite this rapid management, the patient lost his graft and carried on dialysis. Bortezomib therapy in addition to current therapy of AMR is not always effective in the treatment for late acute AMR in renal transplantation. We discuss on the place of such a treatment and other therapeutic strategies in this indication.

16th IHIW: international histocompatibility working group in hematopoietic cell transplantation.

The International Histocompatibility Working Group is a collaborative international effort to understand the HLA and non-HLA genetics of the transplantation barrier. The Working Group is comprised of experts in the fields of histocompatibility and immunogenetics, hematopoietic cell transplantation and outcomes research. Data for 25 855 unrelated donor transplants were submitted in support of research studies for the 16th International Histocompatibility Workshop. Active investigation is in progress in seven key areas: the impact of HLA matching, role of race and ethnicity, identification of permissible HLA mismatches, haplotype-associated determinants, minor histocompatibility antigens, immune response genes and KIR genetics. New hypotheses for the 16th workshop were developed for immunogenetic studies in cord blood and haploidentical-related donor transplantation.

The natural history of clinical operational tolerance after kidney transplantation through twenty-seven cases.

We report here on a European cohort of 27 kidney transplant recipients displaying operational tolerance, compared to two cohorts of matched kidney transplant recipients under immunosuppression and patients who stopped immunosuppressive drugs and presented with rejection. We report that a lower proportion of operationally tolerant patients received induction therapy (52% without induction therapy vs. 78.3%[p = 0.0455] and 96.7%[p = 0.0001], respectively), a difference likely due to the higher proportion (18.5%) of HLA matched recipients in the tolerant cohort. These patients were also significantly older at the time of transplantation (p = 0.0211) and immunosuppression withdrawal (p = 0.0002) than recipients who rejected their graft after weaning. Finally, these patients were at lower risk of infectious disease. Among the 27 patients defined as operationally tolerant at the time of inclusion, 19 still display stable graft function (mean 9 ± 4 years after transplantation) whereas 30% presented slow deterioration of graft function. Six of these patients tested positive for pre-graft anti-HLA antibodies. Biopsy histology studies revealed an active immunologically driven mechanism for half of them, associated with DSA in the absence of C4d. This study suggests that operational tolerance can persist as a robust phenomenon, although eventual graft loss does occur in some patients, particularly in the setting of donor-specific alloantibody.

[Caracterization of HLA allo-immunization and clinical impact in transfusion and organ transplantation]. / Caractérisation de l'allo-immunisation anti-HLA et impact clinique en transfusion et en transplantation d'organe.

Allo-immunizations against HLA antigens are known to be deleterious in transfusion and organ transplantation. The development of new tests based on solid phase assays for screening and identification of HLA antibodies in particular those using Luminex® bead based technology has completely changed the way of allo-immunization monitoring because of their extreme sensitivity. They allow a better characterization of these antibodies, identification of acceptable antigens and the use of virtual cross-matches. All these new possibilities improve the managing of patients before and after platelets transfusion or organ transplantation. However, this technology displays some limits that should be known in order to interpret correctly the results. Beside these bead based assays, cellular cross-matches based on Complement Dependent Cytotoxicity (CDC) and flow cytometry are still used and useful in organ transplantation since beads are produced in vitro and do not reflected exactly what happens physiologically. Moreover, differences of sensitivity between these methods make results interpretation and decision making difficult in some cases.

Is there any impact of HLA-DPB1 disparity in 10/10 HLA-matched unrelated hematopoietic SCT? Results of a French multicentric retrospective study.

We retrospectively analyzed the impact of HLA-DPB1 mismatches in a large cohort of 1342 French patients who underwent 10/10 HLA-matched unrelated HSCT. A significant impact of HLA-DPB1 allelic mismatches (2 vs 0) was observed in severe acute GVHD (aGVHDIII-IV) (risk ratio (RR)=1.73, confidence interval (CI) 95% 1.09-2.73, P=0.019) without impact on OS, TRM, relapse and chronic GVHD (cGVHD). According to the T-cell epitope 3 (TCE3)/TCE4 HLA-DPB1 disparity algorithm, 37.6% and 58.4% pairs had nonpermissive HLA-DPB1, respectively. TCE3 and TCE4 disparities had no statistical impact on OS, TRM, relapse, aGVHD and cGVHD. When TCE3/TCE4 disparities were analyzed in the graft-vs-host or host-vs-graft (HVG) direction, only a significant impact of TCE4 nonpermissive disparities in the HVG direction was observed on relapse (RR=1.34, CI 95% 1.00-1.80, P=0.048). In conclusion, this French retrospective study shows an adverse prognosis of HLA-DPB1 mismatches (2 vs 0) on severe aGVHD and of nonpermissive TCE4 HVG disparities on relapse after HLA-matched 10/10 unrelated HSCT.

The influence of HLA A-B-DR matching on cytomegalovirus disease after renal transplantation. Evidence that HLA-DR7-matched recipients are more susceptible to cytomegalovirus disease.

We examined the prevalence of cytomegalovirus infectious episodes, as defined by clinical, virological, and serological criteria (i.e., CMV disease), in 660 kidney graft recipients; 109 patients (16.5%) developed the disease, and 551 did not. No significant statistical link between CMV disease prevalence and a given HLA-A, -B, or -DR allele was observed. However, patients with HLA-DR7 matched grafts were statistically more frequently found (P < 0.01) in the group of recipients who developed CMV disease as compared with the group who did not develop CMV disease. Furthermore, among patients who developed CMV disease, a significant increase of HLA-DR7 matched over DR7 mismatched patients was noted, whereas no difference between matched and mismatched recipients for the other HLA-DR alleles was found. No difference in the severity of graft failure, often observed during, or immediately after, the CMV episode, was noted between patients matched or mismatched for HLA-DR7. Our data suggest that donor/recipient matching for HLA-DR7 is associated with increased CMV disease.

Susceptibility to alloimmunization to platelet HPA-1a antigen involves TAP1 polymorphism.

The alloimmunization against platelet HPA-1a antigen in mothers of thrombocytopenic neonates is strongly associated with HLA class II structures (DR3 and DR13) and especially with HLA-DR52a antigen (98% of the cases reported here). Because new genes have recently been mapped within the MHC class II region, we typed TAP1 and TAP2 gene polymorphisms by ARMS-PCR in order to characterize more effectively MHC genes involved in this alloimmunization. Our results showed that TAP1*0102 allele was significantly associated with NAIT only in the population of HLA-DR 13-DR52a-immunized women (50%) versus HLA-DR 13-DR52a controls (20%) (p < 0.05), and not in HLA-DR3-DR52a-immunized women versus HLA-DR3-DR52a controls. There is no linkage disequilibrium between TAP1*0102 and DRB1*13 alleles (delta = -0.0063) that could account for this result. The higher frequency of TAP1*0102 allele among HLA-DR 13-DR52a-immunized women suggests that HPA-1a antigen presentation and recognition may be influenced by nonclassic HLA class II gene polymorphisms, or that other linked but yet unknown genes could interfere.

Crucial role of the third and fourth hypervariable regions of HLA-DPB1 allelic sequences in the mixed lymphocyte reaction.

Since HLA-DP mismatches are known to induce proliferative response in MLR I, we investigated the real impact of the different DP alleles and the possible role of one or several hypervariable regions of the DPB allelic sequences. Accordingly, we performed MLR I between HLA-A, B, DR, DQ, and Dw identical individuals DP oligotyped after DNA amplification. A total of 23 one-DP-mismatched healthy stimulator and responder cells displaying nine different DP specificities were thus evaluated in 52 MLRs I. This allowed us to analyze the impact of amino acid composition of each of the six hypervariable regions independently of the amino acid matching or mismatching in the five others. We show here that DP combinations sharing the same amino acid sequence in the third (C) and fourth (D) hypervariable regions are associated with a low proliferative response in vitro (p less than 0.01). These data imply that a perfect HLA-DP matching may not be requisite in selecting bone marrow donors. Indeed, the choice of donors may rely on determination of these particular mismatched HVRs between the DP alleles involved especially in GvHD direction. This policy including prospective DP oligotyping should be of great interest, especially when MLRs I are false negative or nonevaluable. It will enable a better definition of which DP mismatches are acceptable in BMT.

HLA-DP and allogeneic bone marrow transplantation.

HLA-DP typing is not routinely performed before allogeneic BMT. This highly polymorphic class II locus is implicated in immune response and DP molecules may act as transplantation antigens. HLA-DP incompatibilities contribute to MCL. In BMT performed between siblings, HLA-DP mismatches are rare and the role of such incompatibility in GVHD is probably lower than minor histocompatibility antigen disparity. In unrelated BMT, the rate of HLA-DP mismatches is high and DP incompatibility cannot be used as an exclusion criterion in the selection of unrelated donors. Even if in vitro studies show that the HLA-DP antigen may be the target for GVHD, analysis of large numbers of unrelated BMT shows that DP incompatibility is not a risk factor for acute GVHD.

Influence of HLA-DP mismatches on primary MLR responses in unrelated HLA-A, B, DR, DQ, Dw identical pairs in allogeneic bone marrow transplantation.

The success of bone marrow transplantation relies on class I and class II HLA identity between donor and recipient but until now the impact of DP mismatches on primary mixed lymphocyte reaction (MLR I) responses has not yet been clearly established. HLA-DP typing has been performed by a RFLP method on 10 patients and their 22 selected potential donors (HLA-A, B, DR, DQ, Dw identical according to serological, RFLP and oligotyping methods). HLA-DP-matching was then correlated with MLR I responses obtained (1) in 22 HLA-A, B, DR, DQ, Dw identical donor-recipient pairs (patient series) and (2) in 30 HLA-A, B, DR, DQ, Dw identical donors pairs used as the control series. We showed that MLR I responses involving patients cells were always lower than those involving control cells (p less than 0.02 in case of two DP-mismatches and p less than 0.001 in the case of one DP-mismatch). Moreover, in the control series two or one DP mismatches influenced MLR I responses in 91% and 77% of the cases respectively; however, there was a greater scatter of response values which could be explained by the degree of sequence homology between the DP mismatched alleles. In cases with no DP mismatch, no proliferative response was observed. Overall, these results suggest that the conventional technical conditions of MLR I do not allow detection of mismatches other than the well known HLA specificities.

Lack of evidence for a role of HLA-DP in unexplained recurrent spontaneous abortion.

Using the "Polymerase Chain Reaction-Sequence Specific Oligoprobes" (PCR-SSOp) technique, we studied the HLA-DPB locus in both partners of 59 couples with a history of three spontaneous abortions, and of 38 control couples in order to determine the role of this centromeric region of the major histocompatibility complex (MHC) in the immune reaction needed for a favorable course of pregnancy. As no particular phenotypes were noted, and also neither excessive HLA-DP homozygosity in sterile women nor excessive HLA-DP allele sharing between sterile partners, this MHC class II sub-region would seem to play no role either directly or by linkage disequilibrium, in the development of normal pregnancy.

[Immunological treatment of spontaneous repeated abortions. The value of transfusing the partner's leukocytes in the third week of gestation]. / Traitement immunologique des fausses couches spontanées itératives. Intérêts des transfusions de leucocytes de conjoint durant la troisième semaine de gestation.

Twenty-two nulli- all primipara who had had previous repeated spontaneous abortions and who did not have anti-HLA antibodies for the partner, received immunological treatment consisting of a single transfusion of the partner's lymphocytes in the third week of pregnancy, and giving natural progesterone supplements after the kinetic of Beta-HCG in the plasma had been assessed. The number of pregnancies which went to terme (94% success) was significantly better than those obtained in our first protocol which was to give one to three transfusions of the partner's lymphocytes before the pregnancy started (58% success rare after 24 treatments). Apart from obtaining much better results the second protocol made it possible to avoid giving a significant number of useless transfusions (22% of pre-conceptual transfusions were not followed by a pregnancy at all).

Pretransplant HLA mistyping in diagnostic samples of acute myeloid leukemia patients due to acquired uniparental disomy.

Although acquired uniparental disomy (aUPD) has been reported in relapse acute myeloid leukemia (AML), pretransplant aUPD involving chromosome 6 is poorly documented. Such events could be of interest because loss of heterozygosity (LOH) resulting from aUPD in leukemic cells may lead to erroneous results if HLA typing for hematopoietic stem cell donor searches is performed on blood samples drawn during blastic crisis. We report here six AML patients whose HLA typing was performed on DNA extracted from peripheral blood obtained at diagnosis. We observed LOH involving the entire HLA region (three patients), HLA-A, B, C (two patients) and HLA-A only (one patient). An array-comparative genomic hybridization showed that copy number was neutral for all loci, thus revealing partial aUPD of chromosome 6p21. When HLA typing was performed on remission blood samples both haplotypes were detected. A 3-4% LOH incidence was estimated in AML patients with high blast counts. Based on DNA mixing experiments, we determined by PCR sequence-specific oligonucleotide hybridization on microbeads arrays a detection threshold for HLA-A, B, DRB1 heterozygosity in blood samples with <80% blasts. Because aUPD may be partial, any homozygous HLA result should be confirmed by a second typing performed on buccal swabs or on blood samples from the patient in remission.