Maik Stein

BK virus-specific immunity kinetics: a predictor of recovery from polyomavirus BK-associated nephropathy.

Impaired BKV‐specific immunity is associated with development of BKV‐associated nephropathy. Suitable immunological parameters to identify patients at risk, however, are still debated. We monitored 18 kidney‐transplant recipients through the course of self‐limited BKV‐reactivation (n = 11) and BKV‐associated nephropathy (n = 7). BKV‐specific cellular immunity directed to nonstructural small and Large T‐antigen, and structural VP1–3 was analyzed in an interferon‐γ Elispot assay. BKV‐specific IgM and IgG were measured using an enzyme‐linked immunosorbent assay simultaneously. BKV‐specific cellular immunity directed to five BKV‐proteins increased significantly from diagnosis to resolution of BKV‐reactivation (p < 0.001). Patients with self‐limited BKV‐reactivation developed BKV‐specific T cells without therapeutic interventions, and cleared BKV‐reactivation within a median period of 1 month. Patients with BKV‐associated nephropathy, however, showed BKV‐specific T cells after a median period of 5 months after therapeutic interventions only, and cleared BKV‐reactivation after a median period of 8 months. Anti‐structural T cells were detected earlier than anti‐nonstructural T cells, which coincided with BKV‐clearance. Patients with BKV‐associated nephropathy showed the highest frequencies of BKV‐specific T cells at recovery, the highest increase in BKV‐specific IgG and persistence of increased IgM levels (p < 0.05). Our results suggest prognostic values of BKV‐specific immune monitoring to identify those patients at risk of BKV‐associated nephropathy and to aid in the management of therapeutic interventions.

The Loss of BKV-specific Immunity From Pretransplantation to Posttransplantation Identifies Kidney Transplant Recipients at Increased Risk of BKV Replication.

Quantification of BKV‐load and BKV‐specific immunity have been evaluated to monitor BKV‐replication and outcomes in kidney transplant recipients (KTRs) with BKV‐infection. However, it remains crucial to better understand how immune markers can predict the risk for later infection. We studied all KTRs between 2008 and 2011. Twenty‐four KTRs were diagnosed with BKV‐replication and a control group of 127 KTRs was used for comparison. Samples were collected before at +1, +2, and +3 months posttransplantation. BKV‐specific and alloreactive T cells were measured using an interferon‐γ Elispot assay. The extent of immunosuppression was quantified by lymphocyte subpopulations and interferon‐gamma levels. KTRs with a loss of BKV‐specific T cells directed to Large T‐antigen from pretransplantation to posttransplantation were at increased risk of BKV‐replication (p < 0.001). In contrast, KTRs with stable/rising BKV‐specific T cells were more likely not to develop BKV‐replication (p < 0.05). KTRs developing BKV‐replication showed significantly lower CD3+, CD4+, CD8+ T cells and interferon‐γ levels posttransplantation, but significantly higher alloreactive T cells (p < 0.05). Monitoring pretransplant and posttransplant BKV‐specific T cells is suggested a sensitive marker to identify KTRs at increased risk of BKV‐replication. Increased susceptibility to immunosuppression predisposes KTRs to a loss of protective BKV‐specific immunity that results in impaired virus control and BKV‐replication.

ABO desensitization affects cellular immunity and infection control after renal transplantation

The impact of ABO desensitization on overall immunity, infectious control, and alloreactivity remains unknown. We compared 35 ABO‐incompatible kidney transplant recipients (KTRs) to a control of 62 ABO compatible KTRs. Samples were collected before, at +1, +2, +3, +6, and +12 months post‐transplantation. CMV‐, BKV‐specific, and alloreactive T cells were measured using an interferon‐γ ELISPOT assay. The extent of immunosuppression was quantified by enumeration of lymphocyte subpopulations and cytokines. No differences were observed for 5‐year allograft survival and function between both groups (P > 0.05). However, ABO‐incompatible KTRs were more likely to develop CMV infection, BKV‐associated nephropathy, and severe sepsis (P = 0.001). Interestingly, ABO‐incompatible KTRs with poor HLA‐match showed the highest rates of infections and inferior allograft function (P < 0.05). CD3+, CD4+ T‐cell counts, interferon‐γ and IL‐10 levels were lower in ABO‐incompatible KTRs early post‐transplantation (P < 0.05). Likewise, ABO‐incompatible KTRs showed impaired BKV‐ and CMV‐specific T‐cell immunity (P < 0.05). ABO‐incompatible KTRs showed lower frequencies of alloreactive T cells (P < 0.05). Our data suggest T‐cell depletion due to ABO desensitization, which may contribute to the increased risk of T‐cell‐dependent infections. Elimination of B cells serving as antigen‐presenting cells, thereby causing impaired T‐cell activation, plays a significant role in both impaired infection control and reduced alloreactive T‐cell activation.

Inflammatory activation and recovering BKV-specific immunity correlate with self-limited BKV replication after renal transplantation.

As BKV‐associated nephropathy has emerged as an important cause of allograft failure, it has been of major importance to find immune mechanisms suitable to identify kidney transplant recipients (KTRs) at increased risk of BKV replication. We monitored 29 KTRs with seven measurements during the first year post‐transplantation. BKV‐specific T cells directed to 5 BKV proteins were analyzed in an interferon‐γ ELISPOT assay. BKV‐specific antibodies were measured using an ELISA. The extent of immunosuppression and inflammatory activation were quantified by measures of immune function including lymphocyte subpopulations, IP‐10, and adhesion molecule serum levels. All 5 BKV‐specific T cells increased significantly from diagnosis to resolution of BKV replication (P < 0.001). While antistructural T cells were significantly higher in KTRs with BKV replication (P < 0.05), no differences were observed for antismall t‐ and large T‐antigen‐directed T cells (P > 0.05). Interestingly, 65% of KTRs without BKV replication showed transient appearance of antismall t‐ and large T‐antigen‐directed T cells. Although no significant differences were observed for T‐cell subpopulations and adhesion molecules, IP‐10 levels increased significantly during BKV replication (P < 0.05). Assessment of BKV‐specific T cells identifies recovering BKV‐specific immunity in KTRs with BKV replication and suggests their protective ability in KTRs without BKV replication. Increases in IP‐10 levels stress the importance of infiltrating inflammatory leukocytes in the regulation of BKV replication and point to inflammatory activation in the pathogenesis of BKV replication.

CMV-Specific T Cell Monitoring Offers Superior Risk Stratification of CMV-Seronegative Kidney Transplant Recipients of a CMV-Seropositive Donor

Background Detectable cytomegalovirus (CMV)-specific T cells in CMV-seronegative kidney transplant recipients (KTRs) have been attributed to an absence of circulating antibodies despite CMV sensitization. The diagnostic value of CMV-specific T cells, however, needs to be implemented in risk stratification for CMV replication. Methods Three hundred twenty-six KTRs were studied and classified with respect to CMV serostatus and presence of CMV-specific T cells. Samples were collected pretransplantation, at +1, +2, and +3 months posttransplantation. CMV-specific T cells directed to CMV-IE1 and CMV-pp65 were measured by interferon-&ggr; Elispot assay. Results Nineteen (28%) of 67 D+R− KTRs showed pretransplant CMV-specific T cells. Although no differences were observed for CMV replication, KTRs with CMV-specific T cells presented with lower initial and peak CMV loads (P < 0.05). KTRs with decreasing/undetectable CMV-IE1–specific T cells pretransplantation and posttransplantation were at greatest risk of CMV replication. KTRs with stable/increasing CMV-IE1–specific T cells from pretransplantation to posttransplantation, however, showed low risk of CMV replication (P < 0.001). One hundred sixty-two (80%) of 203 R+ KTRs showed pretransplant CMV-specific T cells. Decreasing/undetectable CMV-IE1–specific T cells from pretransplantation and posttransplantation identified those R+ KTRs at increased risk of CMV replication (65/80 KTRs; 81%; P < 0.001). Conclusions Despite CMV prophylaxis, D+R− KTRs are at greatest risk of CMV disease. Our data suggest that monitoring CMV-specific T cell kinetics from pretransplantation to posttransplantation, particularly directed to CMV-IE1, offers superior risk stratification compared with CMV serostatus alone.

Kidney transplant recipients after nonrenal solid organ transplantation show low alloreactivity but an increased risk of infection

The number of kidney transplant recipients (KTRs) after nonrenal solid organ transplantation (SOT) has increased to almost 5%. Knowledge on patient and allograft outcomes, infections, and alloreactivity, however, remains scarce. We studied 40 KTRs after nonrenal SOT. Seven hundred and twenty primary KTRs and 119 repeat KTRs were used for comparison. Samples were collected pretransplantation, at +1, +2, and +3 months post‐transplantation. Alloreactive and CMV‐specific T cells were measured by interferon‐γ ELISPOT assay. Patient survival in KTRs after SOT, primary and repeat KTRs was comparable. While death‐censored allograft survival was comparable between KTRs after SOT and primary KTRs, KTRs after SOT showed superior 5‐year death‐censored allograft survival of 92.5% compared to 81.2% in repeat KTRs. Interestingly, KTRs after SOT show less preformed panel‐reactive antibodies, frequencies of alloreactive T cells, and acute rejections compared to repeat KTRs. KTRs after SOT, however, show higher incidences of EBV viremia and PTLD, sepsis, and death from sepsis. Impaired CMV‐specific cellular immunity was associated with more CMV replication compared to repeat KTRs. Our results suggest comparable patient and allograft outcomes in KTRs after SOT and primary KTRs. The observed low alloreactivity may contribute to excellent allograft outcomes. Caution should be taken in KTRs after SOT regarding infectious complications due to overimmunosuppression.

Sepsis after renal transplantation: Clinical, immunological, and microbiological risk factors

As immunosuppressive therapy and allograft survival have improved, the increased incidence of sepsis has become a major hurdle of disease‐free survival after renal transplantation.

Differential T cell response against BK virus regulatory and structural antigens: A viral dynamics modelling approach

BK virus (BKV) associated nephropathy affects 1–10% of kidney transplant recipients, leading to graft failure in about 50% of cases. Immune responses against different BKV antigens have been shown to have a prognostic value for disease development. Data currently suggest that the structural antigens and regulatory antigens of BKV might each trigger a different mode of action of the immune response. To study the influence of different modes of action of the cellular immune response on BKV clearance dynamics, we have analysed the kinetics of BKV plasma load and anti-BKV T cell response (Elispot) in six patients with BKV associated nephropathy using ODE modelling. The results show that only a small number of hypotheses on the mode of action are compatible with the empirical data. The hypothesis with the highest empirical support is that structural antigens trigger blocking of virus production from infected cells, whereas regulatory antigens trigger an acceleration of death of infected cells. These differential modes of action could be important for our understanding of BKV resolution, as according to the hypothesis, only regulatory antigens would trigger a fast and continuous clearance of the viral load. Other hypotheses showed a lower degree of empirical support, but could potentially explain the clearing mechanisms of individual patients. Our results highlight the heterogeneity of the dynamics, including the delay between immune response against structural versus regulatory antigens, and its relevance for BKV clearance. Our modelling approach is the first that studies the process of BKV clearance by bringing together viral and immune kinetics and can provide a framework for personalised hypotheses generation on the interrelations between cellular immunity and viral dynamics.

Transplantectomy is associated with presensitization with donor-reactive T cells and graft failure after kidney retransplantation: a cohort study

Background The number of kidney transplant recipients (KTRs) being waitlisted for a subsequent transplantation has disproportionately increased to almost 25%. Evidence for the optimal management of the failed allograft, however, remains inconsistent. Methods We studied 111 KTRs who underwent their second kidney transplantation from 1998 to 2015. In 51/111 KTRs (46%) the failed allograft was removed and in 60/111 (54%) the failed allograft was retained. KTRs with primary non-function and allograft loss <12  months of the first failed allograft were excluded from analysis. Samples were collected before transplantation and at  1  month posttransplantation and donor-reactive T cells were measured using an interferon-γ enzyme-linked immunosorbent spot assay. Results KTRs with the previous allograft removed showed significantly higher rates of acute cellular rejection compared with KTRs with the previous allograft retained [27/51 KTRs (53%) versus 18/60 KTRs (30%); P = 0.019]. KTRs with the previous allograft removed showed significantly inferior death-censored allograft survival compared with KTRs with the previous allograft retained (P = 0.022). Here, KTRs with the previous allograft removed showed significantly higher donor-reactive T cells pretransplantation compared with KTRs with the previous allograft retained (P = 0.012). Interestingly, no differences were observed for the presence of panel reactive antibodies and for the development of de novo donor-specific antibodies. Conclusions Our data suggest higher cellular presensitization among KTRs with the previous allograft removed, which is associated with higher rates of acute cellular rejection and inferior allograft survival. Immunological mechanisms that may account for these differences may include prolonged maintenance immunosuppression to save urine output in KTRs with the first kidney allograft retained and cellular presensitization after withdrawal of maintenance immunosuppression, which lead to allograft rejection and ultimately to allograft nephrectomy.

Diabetic kidney transplant recipients: Impaired infection control and increased alloreactivity

Post‐transplantation diabetes mellitus (PTDM) has been associated with inferior patient and allograft outcomes. However, previous studies did not identify differences in infection control and alloreactivity.