Kidney Transplantation for High-Risk Sensitized Patients – The “Heidelberg Algorithm”

Herpesvirus microRNAs for use in gene therapy immune-evasion strategies

Transplantation of allogeneic cells as well as of genetically corrected autologous cells are potent approaches to restore cellular functions in patients suffering from genetic diseases. The recipient's immune responses against non-self-antigens may compromise the survival of the grafted cells. Recipients of the graft may therefore require lifelong treatment with immunosuppressive drugs. An alternative approach to reduce graft rejection could involve the use of immune-evasion molecules. Expression of such molecules in cells of the graft may subvert recognition by the host's immune system. Viruses in particular are masters of exploitation and modulation of their hosts immune response. The Herpesviridae family provides a proof of concept for this as these viruses are capable to establish latency and a lifelong persistence in the infected hosts. While several viral proteins involved in immune evasion have been characterized, the Herpesviridae also encode a multitude of viral microRNA (miRNAs). Several of these miRNAs have been demonstrated to reduce the sensitivity of the infected cells to the destructive action of the host's immune cells. In this review, the miRNAs of some common herpesviruses that are associated with immune modulation will be discussed with a focus on their potential use in strategies aiming at generating non-immunogenic cells for transplantation.

[Ten years' experience in the research of abdominal compartment syndrome (2004-2014)]

Intra-abdominal hypertension and abdominal compartment syndrome are frequent findings among severe surgical ill patients. In spite of the fast diagnostic methods and effective therapeutic procedures the mortality is high. The causing factors lead to increased intra-abdominal pressure and abdominal compartment syndrome. It can be defined as adverse physiologic consequences that occur as a result of an acute increase in the intra-abdominal pressure. The most common causes are retroperitoneal haemorrhage, pancreatitis, bowel obstruction, tense ascites, peritonitis and serious visceral edema due to massive fluid resuscitation. The affected systems are cardiovascular, respiratory, renal, central nervous systems, splanchnic organs, and finally the whole body. The diagnostic method is the intra-abdominal pressure monitoring. The bases of the treatment are adequate fluid resuscitation, non-surgical management and decompression. The authors review the topic including the international and Hungarian references based on their ten years experience.

A closer look at rituximab induction on HLA antibody rebound following HLA-incompatible kidney transplantation

Rituximab has been used to increase the efficacy of desensitization protocols for HLA incompatible kidney transplantation, however, controlled comparisons have not been reported. Here we examined 256 post-transplant HLA antibody levels in 25 recipients desensitized with or 25 without rituximab induction, to determine the impact of B cell depletion. We found significantly less HLA antibody rebound in the rituximab-treated patients (7% of donor specific antibodies (DSAs) and 33% of non-DSAs) compared to a control cohort desensitized and transplanted without rituximab (32% DSAs and 55% non-DSAs). The magnitude of the increase was significantly larger among patients who did not receive rituximab. Interestingly, in rituximab treated patients, of the 39 HLA antibodies that increased post-transplant, 34 were specific for HLA mismatches present in previous allografts or pregnancies, implying limited efficacy in memory B cell depletion. Compared to controls, rituximab-treated patients had a significantly greater mean reduction in DSA (−2505 versus −292 mean fluorescence intensity), but a similar rate of DSA persistence (52% in rituximab treated and 40% in non-treated recipients). Thus, rituximab induction in HLA incompatible recipients reduced the incidence and magnitude of HLA antibody rebound, but did not impact DSA elimination, antibody mediated rejection, or 5 year allograft survival when compared to recipients desensitized and transplanted without rituximab.

HLA antibody screening in kidney transplantation: current guidelines

BACKGROUND

In organ transplantation, the introduction of the solid phase immunoassay technology radically changed the practice of antibody monitoring against human leukocyte antigens (HLA).

PURPOSE

Precise identification of antibody specificities in complex sera of sensitized patients and monitoring of low levels of donor-specific HLA antibodies in the posttransplant phase became possible. However, at the same time, new technical problems and great variation emerged in the interpretation of test results, indicating a need for standardization.

CONCLUSION

In May 2012, The Transplantation Society (TTS) recruited a panel of laboratory and clinical experts to discuss emerging testing and clinical management issues that are associated with antibody testing in organ transplantation. In this article, we provide a summary of the TTS recommendations formulated in this international effort on the standardization of antibody monitoring in kidney transplantation.

Analysis of anti-HLA antibodies in sensitized kidney transplant candidates subjected to desensitization with intravenous immunoglobulin and rituximab

BACKGROUND

Preexisting donor-specific antibodies against human leukocyte antigens are major risk factors for acute antibody-mediated and chronic rejection of kidney transplant grafts. Immunomodulation (desensitization) protocols may reduce antibody concentration and improve the success of transplant. We investigated the effect of desensitization with intravenous immunoglobulin and rituximab on the antibody profile in highly sensitized kidney transplant candidates.

METHODS

In 31 transplant candidates (calculated panel-reactive antibody [cPRA], 34%-99%), desensitization included intravenous immunoglobulin on days 0 and 30 and a single dose of rituximab on day 15. Anti-human leukocyte antigen antibodies were analyzed before and after desensitization.

RESULTS

Reduction of cPRA from 25% to 50% was noted for anti-class I (5 patients, within 20-60 days) and anti-class II (3 patients, within 10-20 days) antibodies. After initial reduction of cPRA, the cPRA increased within 120 days. In 24 patients, decrease in mean fluorescence intensity of antibodies by more than 50% was noted at follow-up, but there was no reduction of cPRA. Rebound occurred in 65% patients for anti-class I antibodies at 350 days and anti-class II antibodies at 101 to 200 days. Probability of rebound effect was higher in patients with mean fluorescence intensity of more than 10,700 before desensitization, anti-class II antibodies, and history of previous transplant.

CONCLUSIONS

The desensitization protocol had limited efficacy in highly sensitized kidney transplant candidate because of the short period with antibody reduction and high frequency of rebound effect.

Clinical relevance of human leukocyte antigen antibodies in liver, heart, lung and intestine transplantation

PURPOSE OF REVIEW

Solid phase assays identify human leukocyte antigen (HLA) antibodies with a great sensitivity. Whether to accept or decline an organ if the virtual crossmatch is positive, when to monitor and whether to treat de-novo donor-specific antibody (DSA) posttransplant remain challenging issues for the transplant clinician.

RECENT FINDINGS

Technologies that can differentiate which antibodies pose the greatest risk for antibody-mediated rejection (AMR) are evolving. Complement fixing luminex assays have been used to predict high-risk antibodies, but using these assays alone will miss some preformed antibodies. How these technologies fit into the laboratory's testing algorithm will likely need to be individualized. Posttransplant de-novo DSAs are associated with inferior outcomes. In hearts, similar to renal transplantation, acute rejection is a risk factor for developing de-novo DSA. Further data are needed to determine whether other risk factors are similar to those reported for renal transplants. Antibodies to self-antigens are increasingly recognized posttransplant and how the alloimmune response contributes to altered autoregulation is a current research focus.

SUMMARY

Identification of DSA enables the clinician to make informed decisions regarding whether or not to accept an organ and if augmented immunosuppression is indicated. Monitoring for DSA posttransplant identifies recipients at a greater risk for AMR and can guide management. However, the best approach to dealing with de-novo DSA remains unclear.

Algorithm to manage highly sensitized kidney transplant recipients in Poland

OBJECTIVE

Programs for immunized transplant recipients are essential to achieve graft survivals comparable to those of non-immunized recipients. The threshold in Poland is a PRA by the complement-dependent cytotoxicity (CDC) method greater than 50%, which includes approximately 3.8% of the patients. At the same time the United Network for Organ Sharing there recipients represent approximately 16% of the waiting list in the United Network for Organ Sharing (UNOS). The underestimation of the immunized group in Poland may be due to differences in laboratory techniques to assess alloantibodies.

MATERIALS AND METHODS

This study investigated 55 potential recipients with a PRA by CDC>50%. We used the following algorithm to assess their immunization: Luminex screening test for an HLA antibody; specificity assessed with Luminex Single Antigen, vPRA (evaluation of immunization of the patient); and analysis of acceptable HLA incompatibilities (HLAMatchmaker).

RESULTS

All recipients were positive class I anti-HLA antibodies and 94.5% were positive for class II. For the groups of subjects with PRA-CDC from 50% to 79% versus those greater than 80%, the average values of PRA-CDC were 62.2% and 89.5%, respectively. The virtual PRA results for these groups were 95.7% and 97.2%, respectively. In addition, anti-HLA-Cw, anti-DQ and anti-DP antibodies were detected in 77%, 84%, and 51% of recipients, respectively. Immunized recipients reported to the next transplant were characterized by the antibodies against mismatch only in 68%. For all potential recipients, additional acceptable non-compliance was determined with HLAMatchmaker: 152 specificity for locus A and 252 for locus B.

CONCLUSIONS

Evaluation of immunization status of recipient candidates should be routinely performed using tests to assess class and specificity as well as level of alloantibodies to enable determination of a safe potential donor. As a routine test, PRA-CDC underestimates the number of highly immunized patients. Exclusion from the list of patients with repeated non-compliance is a simplification, which reduces their chance for transplantation.