CMV accelerates tubular apoptosis in a model of chronic renal allograft rejection

Delayed-onset primary cytomegalovirus disease and the risk of allograft failure and mortality after kidney transplantation

BACKGROUND

During the contemporary era of antiviral prophylaxis, the impact of delayed-onset primary cytomegalovirus (CMV) disease on the outcome of kidney transplantation is not known. We evaluated the incidence, clinical features, risk factors, and outcomes of CMV disease among high-risk kidney transplant recipients.

METHODS

The medical records of CMV-seronegative recipients of kidney transplants from CMV-seropositive donors were reviewed. Cox proportional hazards regression was used to identify factors associated with CMV disease and to assess its impact on allograft loss and mortality.

RESULTS

None of the 176 CMV-seronegative recipients of kidney transplants from CMV-seropositive donors developed breakthrough CMV disease during a median of 92 days (interquartile range, 90-92 days) of oral ganciclovir or valganciclovir prophylaxis. Thereafter, 51 patients (29%) developed CMV disease at a median of 61 days (interquartile range, 40-143 days) after stopping antiviral prophylaxis. Early-onset bacterial and fungal infection (hazard ratio, 3.61; 95% confidence interval, 1.78-7.33; p < .001) and a Charlson comorbidity index > or =3 (hazard ratio, 2.21; 95% confidence interval, 1.15-4.22; p = .011) were associated with a higher risk of delayed-onset primary CMV disease, and postrejection antiviral prophylaxis (hazard ratio, 0.29; 95% confidence interval, 0.09-0.94; P = .039) was associated with a lower risk of such CMV disease. A time-dependent Cox regression analysis revealed a statistically significant association between tissue-invasive CMV disease and allograft loss or mortality (hazard ratio, 2.85; 95% confidence interval, 1.22-6.67; P = .016).

CONCLUSION

This study of a large cohort of CMV-seronegative recipients of kidney transplants from CMV-seropositive donors illustrates the ongoing challenge of delayed-onset primary CMV disease and its impact on transplantation outcomes despite antiviral prophylaxis. Better strategies for CMV disease prevention after kidney transplantation are warranted.

CMV increases tubular apoptosis through the TNF-alpha-TNF-R1 pathway in a rat model of chronic renal allograft rejection

INTRODUCTION

Destruction of transplanted kidneys through chronic allograft nephropathy [CAN], also known as chronic rejection, is the greatest obstacle in successful kidney transplantation. Causes behind CAN are many, from pre-transplant causes to infections. Viral infections, especially CMV, are a risk factor for chronic rejection. We have previously developed a rat kidney transplant model, in which CMV enhances the development of chronic rejection under triple drug treatment. In this model we have now further studied the routes of apoptosis in virus induced early CAN vs. the routes of apoptosis in a later developing non-infectious CAN.

MATERIALS AND METHODS

Renal transplantations were performed in a strain combination of DA/BN under immunosuppression. One group of animals was infected with RCMV and the other was left uninfected. The grafts were harvested on days 3-40 after transplantation. Apoptotic cells were visualised by in situ terminal transferase mediated dUTP nick end labelling [TUNEL] from paraffin embedded, formalin fixed kidney grafts. Cytokines were labelled imunohistochemically from frozen sections, among them tumour necrosis factor alpha [TNF-alpha] and its receptor-protein 1 [TNF-R1] as well as CD 95 [FAS], caspase 3 and CD14. The results were semi-quantitatively scored from 0 to 3+ over various tissues structures separately.

RESULTS

In the CMV infected grafts, we could demonstrate a more intense TUNEL reaction in tubular epithelium [2.0+/-1.0 vs. 0.8+/-0.5 at day 14, P<0.05] as well as an earlier increase in the expression TNF-alpha in the vascular endothelium [2.0+1.0 vs. 0.0+0.0 at days 3-5, P<0.05] than in the non-infected group. There was also an earlier increase in the tubular TNF-R1 expression [2.2+0.8 vs. 1.0+0.0 at days 5-7, P<0.05]. There was no difference in the expression of CD14, caspase 3 or FAS between the groups.

CONCLUSIONS

CMV enhanced development of CAN was associated with tubular apoptosis and concomitant increase of TNF-alpha-TNF-R1, rather than the FAS-FAS-ligand activation.

The human cytomegalovirus-encoded chemokine receptor US28 induces caspase-dependent apoptosis

Viral subversion of apoptosis regulation plays an important role in the outcome of host/virus interactions. Although human cytomegalovirus (HCMV) encodes several immediate early (IE) antiapoptotic proteins (IE1, IE2, vMIA and vICA), no proapoptotic HCMV protein has yet been identified. Here we show that US28, a functional IE HCMV-encoded chemokine receptor, which may be involved in both viral dissemination and immune evasion, constitutively induces apoptosis in several cell types. In contrast, none of nine human cellular chemokine receptors, belonging to three different subfamilies, induced any significant level of apoptosis. US28-induced cell death involves caspase 10 and caspase 8 activation, but does not depend on the engagement of cell-surface death receptors of the tumour necrosis factor receptor/CD95 family. US28 cell-death induction is prevented by coexpression of C-FLIP, a protein that inhibits Fas-associated death domain protein (FADD)-mediated activation of caspase 10 and caspase 8, and by coexpression of the HCMV antiapoptotic protein IE1. The use of US28 mutants indicated that the DRY sequence of its third transmenbrane domain, required for constitutive G-protein signalling, and the US28 intracellular terminal domain required for constitutive US28 endocytosis, are each partially required for cell-death induction. Thus, in HCMV-infected cells, US28 may function either as a chemokine receptor, a phospholipase C activator, or a proapoptotic factor, depending on expression levels of HCMV and/or cellular antiapoptotic proteins.

Transplanting kidneys from CMV-seropositive donors to CMV-seronegative recipients is not associated with poorer renal allograft function or survival

BACKGROUND

Cytomegalovirus (CMV)-seronegative recipients of renal allografts from CMV-seropositive donors (D+/R-) have a higher rate of acute rejection than other renal transplant recipients. A relationship between CMV infection/disease and chronic allograft nephropathy (CAN) has been proposed from animal studies, although human studies have been inconclusive. The objective of this study was to determine if CMV seromatching has an effect on renal allograft function and allograft survival.

METHODS

A retrospective single centre study was carried out in 333 first cadaveric transplant recipients from January 1, 1991 to December 31, 1997. The primary end-point was creatinine clearance at 3 years post-transplant in groups based on CMV seromatching. The secondary end-point was renal allograft survival.

RESULTS

Mean creatinine clearance 3 years post-transplant was 53.4 ml/min/1.73 m2 of body surface area. There was no significant difference in the mean creatinine clearance for groups formed on the basis of CMV seromatching. Delayed graft function and acute rejection were associated with a lower creatinine clearance at 3 years and reduced overall graft survival [hazard ratios 2.35 (1.56-3.54) (P<0.001) and 1.57 (1.0-2.46) (P = 0.046), respectively]. Considering the end-point of graft loss due to acute rejection (censoring for death with a functioning graft) identified the D+/R- group as having an increased hazard of graft loss due to acute rejection [hazard ratio 3.12 (1.16-8.57) (P = 0.024)].

CONCLUSIONS

The D+/R- group does not appear to have poorer renal allograft function 3 years post-transplant. This group does, however, have an increased risk of early allograft loss due to acute rejection.

Acute rejection and graft survival in renal transplanted patients with viral diseases

Transplanted patients are susceptible to viral infections; thus, the aim of this study was to evaluate the features of acute rejections and the outcome of the renal graft in transplanted patients with herpes virus diseases. Renal biopsies from 30 renal transplanted patients undergoing early acute rejection (type IA and IB according to the Banff 97 classification) were evaluated. In total, 15 of these patients experienced cytomegalovirus (CMV) or Epstein-Barr virus disease within the first year following transplantation (group I) and 15 patients showed no evidence of viral infection (group II). No significant differences between the groups in terms of age, male/female ratio, living/cadaveric donor ratio, cold ischemia time, HLA A-B matching, pretransplant panel reactive antibody test, occurrence of post-transplant tubular necrosis, plasma levels of cyclosporin A and mean percent increase of serum creatinine at the time of the biopsy were observed. In group I biopsies, the mean number of interstitial plasma cells, as well as the mean number of CD79a-positive cells (B lymphocytes and plasma cells) was significantly higher than in group II (P<0.01 and <0.01, respectively). There was a positive correlation between the number of infections and the number of plasma cells (P<0.05). In transplanted patients, CMV can trigger the formation of anti-endothelial cell antibodies, which have been proposed to play a role in antibody-mediated rejections. We investigated whether a deposition of C4d, a marker of antibody-mediated reactions, was present in renal peritubular capillaries. In group I C4d deposition was found in five cases, while in group II it was not observed (P<0.05). In group I, 7/15 patients developed chronic allograft nephropathy vs 1/15 patients in group II (P<0.05). The estimated 1-, 5- and 8-year cumulative graft survival rates were 80, 66 and 57%, respectively, in group I, while in group II the estimated 8-year cumulative survival rate was 100% (P<0.05). In conclusion, acute rejection biopsies of patients with viral infections displayed plasma cell infiltrates and, in several cases, C4d deposition. Our study suggests a role of B lymphocytes in the pathology of these rejections and confirms the association between viral infections and poor graft survival.