Effect of persistent versus transient donor-specific HLA antibodies on graft outcomes in pediatric cardiac transplantation.

BACKGROUND: De novo donor-specific HLA antibodies (DSA) are a risk for poor graft outcomes, but there is little evidence of their long-term effect in pediatric cardiac transplantation or of the effect of transient versus persistent DSA found using newer antibody testing methods. METHODS: Archived serum samples were obtained from patients <18 years of age who underwent primary cardiac transplantation during the period from 1996 to 2009. Luminex antibody testing was performed at 3 months, 6 months and 1 year post-transplant, and then annually. Outcomes including cardiac allograft vasculopathy (CAV), rejection and graft loss were correlated with the presence or absence of DSA or non-donor-specific HLA (non-DSA) antibodies. RESULTS: Six hundred ninety-one samples from 108 patients, with mean age at transplant of 7.4 (0.1 to 15.9) years and mean follow-up 8.2 (1.9 to 15.7) years, were studied. Forty-three (40%) patients had DSA (which were persistent in 58%), 41 (38%) had non-DSA (persistent in 46%) and 24 (22%) had no antibodies. In those with DSA, 30% had Class I antibodies, 47% Class II and 23% both Class I and II, whereas, in the subgroup with persistent DSA, 88% had Class II antibodies. There were 14 cases of graft loss, 9 of these in patients with persistent DSA. All had Class II antibodies. There was an increased incidence of CAV, rejection and graft loss in those with persistent DSA. Outcomes were similar between the group with non-DSA antibodies and the group with no antibodies. CONCLUSIONS: De novo HLA antibodies are detectable post-transplant in the majority of patients, but non-DSA and transient DSA do not appear to be associated with poor outcomes. Patients with persistent DSA, especially those with Class II DQ antibodies, have worse survival.

ABO-incompatible cardiac transplantation in pediatric patients with high isohemagglutinin titers.

BACKGROUND: ABO-incompatible (ABOi) cardiac transplantation is now used widely in infants with isohemagglutinin titers <1:4, but there is increasing evidence that ABOi transplantation can also be used in children with significantly higher titers. We reviewed our high-titer ABOi transplants and report our results here. METHODS: Patients who underwent ABOi cardiac transplantation from 2000 to 2013 with pre-existing isohemagglutinin titers of ≥1:16 were identified from departmental databases. Outcomes were reviewed using medical and laboratory records. RESULTS: Thirty patients underwent ABOi cardiac transplantation between 2000 and 2013. Twelve (40%) had pre-transplant isohemagglutinin titers of ≥1:16 and were included for further study. Median age was 14.9 (range 9.8 to 107.3) months and median weight was 9.6 (range 7.6 to 25) kg. Five (42%) were male. Pre-transplant diagnosis was cardiomyopathy in 8 of 12 (67%) and congenital heart disease in 4 of 12 (33%). Highest pre-transplant isohemagglutinin titer was 1:256 in 2 patients. Four patients (33%) had early antibody-mediated rejection (AMR), all within 15 days post-transplant. Management included use of rituximab, bortezomib, immunoadsorption and eculizumab. Three patients died but no deaths were associated with high isohemagglutinin titers. CONCLUSIONS: ABOi cardiac transplantation in patients with isohemagglutinin titers ≥1:16 is possible. AMR may occur early and immunoadsorption has proven effective at decreasing antibody titers.

Anti-donor HLA class I antibodies: pathways to endothelial cell activation and cell-mediated allograft rejection.

BACKGROUND: The development of donor-specific human leukocyte antigen (HLA) class I antibodies after organ transplantation is associated with subsequent acute and chronic rejection. The aim of this study was to examine the role of anti-HLA class I antibody in modulating endothelium-leukocyte interaction. METHODS: Human microvascular endothelial cells (HMEC-1) stimulated with HLA class I antibody (W6/32) or allospecific antibodies from sensitized patients (n=6) were examined for activation of transcription factor CREB by Western blotting. Up-regulation of endothelial adhesion molecules and chemokines was measured by flow cytometry and quantitative polymerase chain reaction, respectively. Leukocyte adhesion was evaluated by chemotaxis and in vitro flow-based assays. RESULTS: Treatment of HMEC-1 cells with HLA class I antibody resulted in the phosphorylation of CREB in protein kinase A-dependent pathway. Furthermore, there was a significant increase in the expression of cell surface VCAM-1 (Akt-dependent) and ICAM-1 in Akt-dependent and extracellular signal-regulated kinase-dependent manner (P<0.001). Additionally, exposure to W6/32 antibody induced significant expression of interleukin-6, CXCL8, CXCL10, and CCL5. Knockdown of CREB produced a reduction in W6/32-induced CXCL8 expression (P<0.001). Media from W6/32-treated endothelial cells induced a significant monocyte chemotaxis (P<0.001) and flow-based adhesion assay demonstrated an increase in monocyte adhesion to endothelial cells compared with the control group (P<0.001). Importantly, allospecific antibodies from sensitized patients also activated endothelial CREB and significantly up-regulated VCAM-1, ICAM-1, and CXCL8. CONCLUSION: These findings suggest that donor-specific HLA class I antibodies directly activate endothelial cells leading to an increase in their potential to recruit and bind recipient leukocytes, thereby increasing the potential for allograft inflammation.

Vimentin antibody production in transplant patients and immunomodulatory effects of vimentin in-vitro.

We investigated the presence of antibodies to vimentin in 150 patients awaiting transplant, (50 kidney, 50 liver and 50 thoracic) and in 51 previously transplanted kidney patients whose grafts had failed. Patients with primary end stage thoracic or kidney disease did not have increased levels of vimentin antibodies, but those with primary liver failure and those with kidney graft failure did. Those with kidney graft failure were more likely to form vimentin antibodies if the patient was HLA-DQ2 positive (p=<0.001). Further to this, we observed antibody mediated rejection in five HLA-DQ2 positive re-transplant patients where no other antibodies were identified. We investigated the effects of vimentin protein on cytokine production in phytohaemagglutinin stimulated and unstimulated peripheral blood mononuclear cells. When exposed to vimentin at low levels there was increased production of IL-10. When cultures were stimulated, there was a decrease in IL-10, IL-2 and IFN-gamma production and a large increase in IL-4 production (p=0.028) compared to the controls. These results suggest that under normal conditions exposure to vimentin can lead to regulation of the immune response. However, if the immune system is active, exposure to vimentin can enhance Th-2 immunity.

Donor-specific HLA antibodies in paediatric cardiac transplant recipients are associated with poor graft survival.

There is increasing evidence that DSA are associated with poor graft survival, although there are little data in children. We aimed to describe the incidence of DSA in this group and to determine correlation with graft survival. HLA antibodies were analysed in 59 paediatric cardiac transplant recipients. Mean age 10.4 (0.7-18.5) yr, mean time post-transplant 5.1 (0.3-17.3) yr. Antibody detection/identification was performed on the Luminex platform with subsequent identification using Lifescreen Identification kits/One-Lambda Single antigen kits. Forty patients (69%) had no HLA antibodies. DSA were found in four (7%). One had transient Class I antibodies and normal cardiac function. The other three had persistent Class II antibodies (two subsequently required re-transplantation, the third had cardiac failure due to CAV). Non-DSA were found in 15 (25%), all with normal graft function and without rejection. There was no difference in function or CAV prevalence between those with non-DSA and those without antibodies. HLA DSA is uncommon in paediatric cardiac allograft recipients but, if persistent, suggests poorer prognosis. In our series, antibodies to HLA class II on donor tissue were associated with increased graft loss. Routine screening and regular testing are recommended.

My approach to cardiothoracic transplantation and the role of the histocompatibility and immunogenetics laboratory in a rapidly developing field.

Cardiothoracic transplantation presents specific challenges. The lack of long-term replacement therapy (such as dialysis for kidney patients) creates a more urgent situation than for other forms of transplantation, necessitating a different approach. This review looks at ways in which the challenges are being met and the integral role of the histocompatibility and immunogenetics laboratory.

MHC-correlated odour preferences in humans and the use of oral contraceptives.

Previous studies in animals and humans show that genes in the major histocompatibility complex (MHC) influence individual odours and that females often prefer odour of MHC-dissimilar males, perhaps to increase offspring heterozygosity or reduce inbreeding. Women using oral hormonal contraceptives have been reported to have the opposite preference, raising the possibility that oral contraceptives alter female preference towards MHC similarity, with possible fertility costs. Here we test directly whether contraceptive pill use alters odour preferences using a longitudinal design in which women were tested before and after initiating pill use; a control group of non-users were tested with a comparable interval between test sessions. In contrast to some previous studies, there was no significant difference in ratings between odours of MHC-dissimilar and MHC-similar men among women during the follicular cycle phase. However, single women preferred odours of MHC-similar men, while women in relationships preferred odours of MHC-dissimilar men, a result consistent with studies in other species, suggesting that paired females may seek to improve offspring quality through extra-pair partnerships. Across tests, we found a significant preference shift towards MHC similarity associated with pill use, which was not evident in the control group. If odour plays a role in human mate choice, our results suggest that contraceptive pill use could disrupt disassortative mate preferences.

A case of acute humoral rejection in liver transplantation: successful treatment with plasmapheresis and mycophenolate mofetil.

We present a case of a 23-year-old female who underwent orthotopic liver transplantation (OLTx) for biliary atresia, 22 years after a failed Kasai operation. Unusually, her postoperative course was complicated by severe acute humoral rejection. In this case report, we discuss her management as well as the role of plasmapheresis in treating allograft dysfunction secondary to acute humoral rejection in liver transplant patients.

Donor CD31 genotype impacts on transplant complications after human leukocyte antigen-matched sibling allogeneic bone marrow transplantation.

Mismatch for the adhesion molecule CD31 (PECAM-1) has been associated in some studies with graft-versus-host disease (GVHD), suggesting a role for CD31 as a minor histocompatibility antigen. We examined polymorphisms of the CD31 (PECAM-1) gene in 74 patients and their human leukocyte antigen-matched sibling donors, comparing CD31 genotype with outcomes of occurrence of GVHD and survival using regression analysis. Polymorphisms in codon 125, 563, and 670 are strongly linked forming conserved haplotypes. Donor CD31 (val/asn/gly) haplotype was associated with acute GVHD (P=0.004, odds ratio 7.5). In addition, donor heterozygosity at codon 563 was significantly associated with worse overall survival after correcting for other known variables by regression modeling. Peptide binding predictions support the hypothesis that CD31 could act as a minor histocompatibility antigen. Assessment for CD31 gene status may be of value in pretransplant assessment of bone marrow transplant recipients and donors for prediction of likely transplant-related complications.

MHC-assortative facial preferences in humans.

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.