Revealing the influence of steric bulk on the triplet-triplet annihilation upconversion performance of conjugated polymers.

A series of poly(phenylene-vinylene)-based copolymers are synthesized using the Gilch method incorporating monomers with sterically bulky sidechains. The photochemical upconversion performance of these polymers as emitters are investigated using a palladium tetraphenyltetrabenzoporphyrin triplet sensitizer and MEH-PPV as reference. Increased incorporation of sterically bulky monomers leads to a reduction in the upconversion efficiency despite improved photoluminescence quantum yield. A phosphorescence quenching study indicates issues with the energy transfer process between the triplet sensitizer and the copolymers. The best performance with 0.18% upconversion quantum yield is obtained for the copolymer containing 10% monomer with bulky sidechains.

A Complex Comprising a Cyanine Dye Rotaxane and a Porphyrin Nanoring as a Model Light-Harvesting System.

A nanoring-rotaxane supramolecular assembly with a Cy7 cyanine dye (hexamethylindotricarbocyanine) threaded along the axis of the nanoring was synthesized as a model for the energy transfer between the light-harvesting complex LH1 and the reaction center in purple bacteria photosynthesis. The complex displays efficient energy transfer from the central cyanine dye to the surrounding zinc porphyrin nanoring. We present a theoretical model that reproduces the absorption spectrum of the nanoring and quantifies the excitonic coupling between the nanoring and the central dye, thereby explaining the efficient energy transfer and demonstrating similarity with structurally related natural light-harvesting systems.

Mechanisms of IR amplification in radical cation polarons.

Break down of the Born-Oppenheimer approximation is caused by mixing of electronic and vibrational transitions in the radical cations of some conjugated polymers, resulting in unusually intense vibrational bands known as infrared active vibrations (IRAVs). Here, we investigate the mechanism of this amplification, and show that it provides insights into intramolecular charge migration. Spectroelectrochemical time-resolved infrared (TRIR) and two-dimensional infrared (2D-IR) spectroscopies were used to investigate the radical cations of two butadiyne-linked conjugated porphyrin oligomers, a linear dimer and a cyclic hexamer. The 2D-IR spectra reveal strong coupling between all the IRAVs and the electronic π-π* polaron band. Intramolecular vibrational energy redistribution (IVR) and vibrational relaxation occur within ∼0.1-7 ps. TRIR spectra show that the transient ground state bleach (GSB) and excited state absorption (ESA) signals have anisotropies of 0.31 ± 0.07 and 0.08 ± 0.04 for the linear dimer and cyclic hexamer cations, respectively. The small TRIR anisotropy for the cyclic hexamer radical cation indicates that the vibrationally excited polaron migrates round the nanoring on a time scale faster than the measurement, i.e. within 0.5 ps, at 298 K. Density functional theory (DFT) calculations qualitatively reproduce the emergence of the IRAVs. The first singlet (S1) excited states of the neutral porphyrin oligomers exhibit similar IRAVs to the radical cations, implying that the excitons have similar electronic structures to polarons. Our results show that IRAVs originate from the strong coupling of charge redistribution to nuclear motion, and from the similar energies of electronic and vibrational transitions.

Changes in successive measures of de novo donor-specific anti-human leukocyte antigen antibodies intensity and the development of allograft dysfunction.

BACKGROUND: Many patients develop de novo donor-specific anti-human leukocyte antigen antibodies (dnDSA) after transplantation. Despite development of dnDSA, not all patients will immediately fail. This study analyzes dnDSA intensity and longitudinal trends as prospective clinical parameters to assess subsequent allograft function. METHODS: Twenty-four patients with dnDSA onset in the first 2 years after transplantation received antibody monitoring by LABScreen single antigen beads. Estimated glomerular filtration rate (eGFR) was recorded at time of dnDSA onset and up to 24 months thereafter. The dnDSA mean fluorescence intensity (MFI) of the stable function patient group (n=8; eGFR decline ≤ 25%) was compared with the impaired function patient group (n=16; eGFR decline>25%) using first year peak MFI (pMFI), eight month MFI change (ΔMFI), and eighteen month MFI trend (MFI slope). RESULTS: Both groups showed similar dnDSA characteristics (time to onset after transplantation, class I/II distribution, and initial MFI). Between groups, MFI trends were analyzed. Impaired patients showed a higher pMFI during the first year (median pMFI, 13,055 vs. 2,397; P=0.007). Longitudinal analysis revealed that ΔMFI was strongly associated with dysfunction. Both a ΔMFI increase greater than 20% as well as a stronger increase (ΔMFI>50%) were followed by graft dysfunction in almost all patients and could significantly differentiate between stable and impaired function patients (P=0.001 and P=0.04, respectively). CONCLUSION: Our study suggests that tracking dnDSA intensity, particularly in the early period after onset, is important to estimate the impact of dnDSA on the allograft and could, therefore, determine help on how best to monitor patients with dnDSA.

Impact of IgM and IgG3 anti-HLA alloantibodies in primary renal allograft recipients.

BACKGROUND: With standard IgG donor-specific anti-HLA antibody (DSA) testing, it is unclear which immunoglobulin-G (IgG) DSA positive patients will fail. We looked further into the immune response by studying immunoglobulin-M (IgM) and IgG subclass 3 (IgG3) DSA to determine if these identify the IgG DSA patients at highest risk for allograft loss. METHODS: In 189 consecutively transplanted primary renal allograft recipients, sera were collected sequentially pre- and posttransplant. Of the 189, 179 patients had sera available to retrospectively test for anti-HLA IgG, IgM, and IgG3 antibodies via LABScreen single-antigen bead assay and were included in the study. All patients had a negative crossmatch. Per patient, all DSA (IgM, IgG3, and IgG) refers to the same serologic specificity. RESULTS: Overall, 100 (56%) patients developed an alloimmune response (IgM or IgG DSA positive, or both). Ninety-five patients developed IgM DSA and 47 patients developed IgG DSA. IgM DSA was detected in 42 of 47 patients with IgG DSA. IgM DSA alone did not increase the allograft loss risk, whereas IgG DSA did (P=0.002). Once IgG DSA appeared, IgM DSA persisted in 33 patients and an isotype switch to IgG3 positive DSA occurred in 25 patients. Patients with IgM persistent IgG3 positive DSA (n=19) were more likely to have allograft failure than those without (P=0.02). CONCLUSION: This study shows the evolution of the humoral immune response from IgM to IgG DSA posttransplant. We found that development of IgM persistent IgG3 positive DSA identifies the most dangerous IgG DSA subpopulation.

Improved Long-Term Survival in Kidney Transplant Recipients with Donor-Specific HLA Antibodies After Mycophenolic Acid Escalation.

The development of donor specific antibodies (DSA) post transplant has been associated with chronic rejection and graft failure. In a longitudinal study, we have shown that increases in DSA precede rejection by months, thus allowing time for intervention. We hypothesized that mycophenolic acid (MPA) dose increases may reduce and/or stabilize DSA strength and also preserve renal function. Thirty stable DSA positive kidney transplant recipients participated in this Institutional Review Board approved, exploratory, open-label, single center study to assess the efficacy of MPA dose escalation in patients with DSA. MPA escalation was well tolerated and most patients were able to take higher doses for at least two years (duration of the study). In addition, MPA escalation is safe and participants had no significant side effects such as cytomegalovirus and BK infections. Long-term allograft survival of the MPA escalation group was superior when compared with the control group (p = 0.018). This pilot study indicates that escalation of MPA is safe and may stabilize DSA. In addition, five-year follow up demonstrates improved long-term survival with MPA escalation compared with DSA positive recipients receiving the standard of care. Additional studies using larger cohorts are warranted.

Trends and characteristics in early glomerular filtration rate decline after posttransplantation alloantibody appearance.

BACKGROUND: Approximately 7% to 9% of patients with donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA) fail within 1 year post-DSA onset. However, little is known as to how this DSA-associated failure temporally progresses. This longitudinal study investigates DSA's temporal relationship to allograft dysfunction and identifies predictors of allograft function's progressive deterioration post-DSA. METHODS: A cohort of 175 non-HLA identical patients receiving their first transplant between March 1999 and March 2006 were analyzed. Protocol testing for DSA via single antigen beads was done before transplantation and at 1, 3, 6, 9, and 12 months after transplantation then annually. Estimated glomerular filtration rate (eGFR) was analyzed before and after DSA onset. RESULTS: Forty-two patients developed DSA and had adequate eGFR information for analysis. Before DSA onset, the 42 patients had stable eGFR. By 1 year post-DSA, the cohort's eGFR was significantly lower (P<0.001); however, 30 of 42 had stable function. Twelve patients had failure or early allograft dysfunction (eGFR decline >25% from DSA onset). Those who failed early (by 1 year post-DSA) had more antibody-mediated rejection than stable patients (P=0.03). Late failures (after 1 year post-DSA) were predictable with evidence of early allograft dysfunction (eGFR decline >25% by 1 year post-DSA; P<0.001). Early allograft dysfunction preceded late failure by nearly 1 year. CONCLUSIONS: DSA is temporally related to allograft function deterioration. However, in many cases, late allograft failures are preceded by early allograft dysfunction. Therefore, monitoring for early allograft dysfunction provides treating physicians with a window of opportunity for treatment or continued monitoring.

The role of immunoglobulin-G subclasses and C1q in de novo HLA-DQ donor-specific antibody kidney transplantation outcomes.

BACKGROUND: Anti-HLA-DQ antibodies are the predominant HLA class II donor-specific antibodies (DSAs) after transplantation. Recently, de novo DQ DSA has been associated with worse allograft outcomes. The aim of this study was to determine the further complement-binding characteristics of the most harmful DQ DSA. METHODS: Single-antigen bead technology was used to screen 284 primary kidney transplant recipients for the presence of posttransplantation DQ DSA. Peak DSA sera of 34 recipients with only de novo DQ DSA and of 20 recipients with de novo DQ plus other DSAs were further analyzed by a modified single-antigen bead assay using immunoglobulin (Ig)-G subclass-specific reporter antibodies and a C1q-binding assay. RESULTS: Compared with recipients who did not have DSA, those with de novo persistent DQ-only DSA and with de novo DQ plus other DSAs had more acute rejection (AR) episodes (22%, P=0.005; and 36%, P=0.0009), increased risk of allograft loss (hazards ratio, 3.7, P=0.03; and hazards ratio, 11.4, P=0.001), and a lower 5-year allograft survival. De novo DQ-only recipients with AR had more IgG1/IgG3 combination and C1q-binding antibodies (51%, P=0.01; and 63%, P=0.001) than patients with no AR. Furthermore, the presence of C1q-binding de novo DQ DSA was associated with a 30% lower 5-year allograft survival (P=0.003). CONCLUSIONS: The presence of de novo persistent, complement-binding DQ DSA negatively impacts kidney allograft outcomes. Therefore, early posttransplantation detection, monitoring, and removal of complement-binding DQ might be crucial for improving long-term kidney transplantation outcomes.

Incidence and impact of de novo donor-specific alloantibody in primary renal allografts.

BACKGROUND: To date, limited information is available describing the incidence and impact of de novo donor-specific anti-human leukocyte antigen (HLA) antibodies (dnDSA) in the primary renal transplant patient. This report details the dnDSA incidence and actual 3-year post-dnDSA graft outcomes. METHODS: The study includes 189 consecutive nonsensitized, non-HLA-identical patients who received a primary kidney transplant between March 1999 and March 2006. Protocol testing for DSA via LABScreen single antigen beads (One Lambda) was done before transplantation and at 1, 3, 6, 9, and 12 months after transplantation then annually and when clinically indicated. RESULTS: Of 189 patients, 47 (25%) developed dnDSA within 10 years. The 5-year posttransplantation cumulative incidence was 20%, with the largest proportion of patients developing dnDSA in the first posttransplantation year (11%). Young patients (18-35 years old at transplantation), deceased-donor transplant recipients, pretransplantation HLA (non-DSA)-positive patients, and patients with a DQ mismatch were the most likely to develop dnDSA. From DSA appearance, 9% of patients lost their graft at 1 year. Actual 3-year death-censored post-dnDSA graft loss was 24%. CONCLUSION: We conclude that 11% of the patients without detectable DSA at transplantation will have detectable DSA at 1 year, and over the next 4 years, the incidence of dnDSA will increase to 20%. After dnDSA development, 24% of the patients will fail within 3 years. Given these findings, future trials are warranted to determine if treatment of dnDSA-positive patients can prevent allograft failure.

Novel biomarker combination predicts long-term allograft outcome.

Donor specific human leukocyte antigen (HLA) antibodies (DSA) are a significant cause of allograft failure. However, it has been reported that some DSA negative patients still experience allograft failure. In addition, some DSA positive patients maintain good graft function for >20 years. These findings suggest that while DSA is a cause of failure, it is not the sole risk factor for graft dysfunction and that the presence of DSA alone may not predict the time course of graft failure. Here, we report the predictive value of a proprietary panel of four biomarkers in long-term renal allograft outcome. A total of 310 consecutive patients, who received kidney transplants between 1999 and 2012, were included in this study. Recipient sera was tested for HLA antibodies and biomarkers at 3, 6, 12, 24, and 36 months post-transplant. HLA antibodies were identified using Labscreen single antigen beads. The biomarker combination (BMC) test consisted of a proprietary panel of 4 biomarkers and was performed using Luminex. Sera were defined as positive when any one of the 4 biomarkers became detectable. Sera of normal healthy people were used as negative controls. Graft survival analyses were performed and compared between different patient groups based on the positivity of DSA and BMC. Our results indicate that 57% of DSA negative patients and 54% of DSA positive patients had detectable biomarkers. There was no significant difference in BMC positive patients between the DSA positive and negative groups, which suggests that presence of BMC is not associated with HLA DSA. DSA positive patients had a 10% lower 10-year graft survival rate than patients without DSA, while BMC positive patients had a 25% lower 10-year graft survival rate than patients without detectable BMC. When DSA negative patients were divided into two groups based on the positivity of BMC, BMC positive patients had a 20% lower 10-year graft survival rate compared to BMC negative patients (p<0.05). Similarly, when DSA positive patients were divided into two groups based on the positivity of BMC, BMC positive patients had a 30% lower 10-year graft survival rate compared to BMC negative patients (p<0.01). When both DSA and BMC testing results were considered, DSA and BMC double positive patients had the lowest and double negative patients had the highest graft survival rates. The survival rates for the BMC alone and DSA alone positive groups were in between (p<0.001). Multivariate Cox models confirmed that BMC was an independent risk factor for graft failure, with a higher hazard ratio than DSA (BMC=2.60 versus DSA=1.64). In conclusion, serum BMC is an independent predictor of graft failure. BMC was more significantly associated with graft failure than DSA. In combination with DSA, BMC better predicted graft outcome than DSA or BMC alone.

A report of the epidemiology of de novo donor-specific anti-HLA antibodies (DSA) in "low-risk" renal transplant recipients.

The donor specific anti-HLA antibody (DSA) has been increasingly recognized as the major cause of allograft loss. Despite this, no published reports exist describing the true epidemiology of de novo DSA.Here we describe the epidemiology of DSA based on the results of one of the longest running antibody study in consecutive renal transplant recipients. The study includes 224 non-sensitized, non-HLA-identical patients who received a primary kidney transplant between 3/1999-3/2006. Protocol testing for DSA was done pre-transplant, at 1, 3, 6, 9, and 12 months, and then annually. DSA was tested using single antigen beads. Data from the East Carolina University transplant cohort indicate that the prevalence of DSA in the first year post-transplant is 12.1 cases per 100. The average annual incidence of DSA is 4.7 per 100 cases, per year. The highest incidence of DSA was in the first year post transplant. Although deceased donors and African-Americans have a higher incidence rate of DSA than the comparator living donors and non-African American groups, respectively, these factors were not associated with DSA onset. The one factor found to be predictive of DSA was DQ mismatch (p = 0.036). Based on these epidemiologic findings in combination with previous reports showing DSA is a cause of allograft failure, it seems reasonable that at least annual testing should be done even in "low-risk" transplant patients, because every year a new 5% of patients will develop DSA.

Risk factors and impact of recurrent lupus nephritis in patients with systemic lupus erythematosus undergoing renal transplantation: data from a single US institution.

OBJECTIVE: To determine the risk factors for recurrent lupus nephritis, allograft loss, and survival among patients with systemic lupus erythematosus (SLE) undergoing kidney transplantation. METHODS: The archival records of all kidney transplant recipients with a prior diagnosis of SLE (according to the American College of Rheumatology criteria) from June 1977 to June 2007 were reviewed. Patients who had died or lost the allograft within 90 days of engraftment were excluded. Time-to-event data were examined by univariable and multivariable Cox proportional hazards regression analyses. RESULTS: Two hundred twenty of nearly 7,000 renal transplantations were performed in 202 SLE patients during the 30-year interval. Of the 177 patients who met the criteria for study entry, the majority were women (80%) and African American (65%), the mean age was 35.6 years, and the mean disease duration was 11.2 years. Recurrent lupus nephritis was noted in 20 patients (11%), allograft loss in 69 patients (39%), and death in 36 patients (20%). African American ethnicity was found to be associated with a shorter time-to-event for recurrent lupus nephritis (hazard ratio [HR] 4.63, 95% confidence interval [95% CI] 1.29-16.65) and death (HR 2.47, 95% CI 0.91-6.71), although, with the latter, the association was not statistically significant. Recurrent lupus nephritis and chronic rejection of the kidney transplant were found to be risk factors for allograft loss (HR 2.48, 95% CI 1.09-5.60 and HR 2.72, 95% CI 1.55-4.78, respectively). In patients with recurrent lupus nephritis, the lesion in the engrafted kidney was predominantly mesangial, compared with a predominance of proliferative or membranous lesions in the native kidneys. CONCLUSION: African American ethnicity was independently associated with recurrent lupus nephritis. Allograft loss was associated with chronic transplant rejection and recurrence of lupus nephritis. Recurrent lupus nephritis is infrequent and relatively benign, without influence on a patient's survival.