Impaired kidney transplant survival in patients with antibodies to hepatitis C virus

Miguel A. Gentil, José L. Rocha, Gabriel Rodríguez-Algarra, Porfirio Pereira, Raquel López, Gabriel Bernal, José Muñoz, Macarena Naranjo and Julián Mateos

Servicio de Nefrología, Hospital Universitario Virgen del Rocío, Sevilla, Spain

Correspondence and offprint requests to: Dr Miguel A. Gentil, Servicio de Nefrología, Hospital U. Virgen del Rocío, C/ Manuel Siurot s/n, E-41013 Sevilla, Spain.



   Abstract
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
Background. With a few exceptions, most published studies do not show an influence of antibodies to the hepatitis C virus (HCV) on the success of a kidney transplant.

Methods. We studied all our renal transplant recipients who had received kidneys from cadaver donors (n=335) and had been treated with quadruple immunosuppression (steroids, azathioprine, and antilymphocyte antibodies, followed by cyclosporin). We had information on the status of the hepatitis C antibodies before and/or after the transplant in 320 cases (95.5%; in 300, pre-transplant). Patients with HCV antibodies before and/or after the transplant were considered to be HCV positive (HCV+).

Results. The HCV+ patients had more time in dialysis and a greater number of transfusions, hyperimmunized cases, and re-transplants. The evolution in the first post-transplant year was similar in both groups, but afterwards, the HCV+ patients had proteinuria more often as well as worse kidney function. The survival rate of the graft was significantly less in the HCV+ cases: 90.6, 68.3 and 51.0% at respectively 1, 5 and 10 years, compared with 91.5, 84.7 and 66.5% in HCV- patients (P<0.01). The patient survival rate was: 96.4, 87.0, and 71.9% in the HCV+ patients at 1, 5, and 10 years, compared with 98.2, 96.0 and 90.0% in the HCV- cases respectively (P<0.01). The differences remained the same in stratified studies according to time spent in dialysis or pre/post-transplant evolution of HCV antibodies, even when immunologically high-risk patients were excluded. In multivariant analysis, the presence of HCV antibodies acted as a independent prognostic factor for the survival of the kidney and the patient: 3.0 (1.8–5.0) and 3.1 (1.2–7.8) odds-ratio (95% of the confidence interval), respectively. The main cause of death among HCV+ patients was cardiovascular; there was no apparent increase in mortality rate due to infections or chronic liver disease. The loss of organs was mainly due to chronic nephropathy or death with a functioning kidney.

Conclusion. The presence of hepatitis C antibodies, before or after transplantation, is associated with a worse long-term survival rate for both the patient and the transplanted kidney in our patients treated with quadruple therapy.

Keywords: acute transplant rejection; chronic liver disease; chronic renal failure; hepatitis C; kidney transplantation; survival



   Introduction
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
The relationship between hepatitis C and kidney transplant survival is far from being clarified [1]. Most of the studies published [29] have not established a significant influence of the hepatitis C antibody carrier status (HCV+) on recipient or kidney survival. However, there are studies that indicate otherwise [1013]. Pereira et al. [14] demonstrated that pre-transplant HCV+ recipients had a worse survival, and Legendre and colleagues [15] found that both HCV+ recipients and their grafts had poorer long-term outcomes. The aim of the present study is to investigate the influence of HCV antibodies in a group of patients initially treated with a quadruple immunosuppressive therapy using antilymphocyte globulin.



   Subjects and methods
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
All patients in our centre with an allograft transplant and undergoing induction therapy with antilymphocyte globulins were studied. A total of 335 cases were included between January 1986 and February 1997.

Initial immunosuppressive therapy consisted of steroids, azathioprine, and antilymphocyte globulins. Once graft function was verified, oral cyclosporin was progressively introduced. The mean length of therapy with globulins was 9.7 days and cyclosporin was introduced on an average of 3.7 days post-transplant, at a dose of 4.8 mg/kg/day. Immunosuppression maintenance therapy consisted initially of steroids, azathioprine (1–2 mg/kg) and cyclosporin. Azathioprine was withdrawn in certain cases, mainly because of leucopenia or liver disorders. Acute rejection was diagnosed by biopsy or clinically after a positive response to anti-rejection therapy. Graft rejections were treated with steroid bolus and rescue therapy with anti-thymocyte globulins or OKT3 in steroid-resistant cases.

Considering the 335 cases treated with this quadruple therapy, 47.7% of the patients received treatment for acute rejection at least once during the first year and 5.4% of all the patients were treated with rescue globulins or OKT3. Clinical cytomegalovirus disease occurred in 12.2% of the patients, and there were only four cases of pneumonitis (1.2%) and no death attributable to this cause. One case of lymphoma (0.3%) was documented.

Anti-hepatitis C antibodies were determined by ELISA I between November 1989, and the end of 1991. After this time ELISA II was employed, with verification by RIBA II. The determination of pre-transplant antibodies for all the cases prior to 1990 was achieved with ELISA II on frozen samples. The pre-transplant determination was available in 300 cases and the post-transplant determination in 291 patients. Altogether, the pre- and/or post-transplant antibody status was determined in 320 patients (95.5%). The 15 cases omitted corresponded to deaths or early failures for which pre-transplant samples were not preserved. Of the 271 cases with the pre- and post-transplant determinations, 73% were negative pre- and post-transplant, 2% changed from positive to negative post-transplant, 17% were positive pre- and post-transplant and 8% changed from negative to positive post-transplant. The HCV+ patients are those with antibody positivity pre and/or post-transplant (85 cases, 26.6%) and the HCV- patients are those who were negative pre and post transplant (235 cases). Because of the limited correlation found between liver chemistry and the severity of histological damage, we decided to classify a case with pre-transplant clinical liver disease as any patient with a past history of abnormal liver enzymes (transaminase and/or gamma-glutamyl transpeptidase) of any degree, continuous or intermittent, but lasting longer than 6 months. The same criteria were applied for the presence or absence of post-transplant clinical liver disease.

The comparison of variables between the groups was done by applying the {chi}2 test (Pearson), the Mann–Whitney's test and Student's t-test. Survival was studied using the Kaplan–Meier method, and comparisons made with the log-rank method. With reference to organ survival, death with a functioning kidney was considered as a failure. In addition, a separate estimation of the graft survival curve was done, excluding those cases of death with a functioning kidney. In order to estimate recipient survival, patient follow-up was prolonged for 4 months after definitive graft failure and shift to dialysis. The Cox method of proportional risks was applied to the multivariate analysis, with stepwise backward analysis. The prognostic variables studied included: donor gender, donor age, the cause of brain death, recipient age, recipient gender, time on dialysis, the disease causing kidney failure, number of transplants, pre-transplant transfusions, peak and immediate pre-transplant immunization, number of HLA A+B and HLA DR mismatches, year of transplantation, cold ischaemia time, anti-HCV antibody status and pre-transplant clinical liver disease.



   Results
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
Characteristics and course of the patients
In Table 1Go we compare the characteristics of the HCV+ patients with the constantly negative cases (HCV-). As generally found in other studies, the HCV+ patients have had longer treatment with dialysis, a greater number of transfusions and re-transplants and, consequently, a greater proportion of these patients have a high degree of anti-HLA immunization. There were no differences in the technique used for dialysis (haemodialysis or peritoneal dialysis) nor in recipient body size. In 12.9% of the HCV+ patients and in 1.3% of the HCV- patients a diagnosis of chronic hepatitis was verified by liver biopsy prior to transplant. The proportion of HBsAg carriers was 3.9% among the HCV- patients and 1.9% for the HCV+ patients, while the proportion of the HBcAb carriers with a negative HBsAg, was 31.8 and 38.8% respectively (n.s.).


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Table 1. Recipient characterístics according to HCV status
 
Table 2Go describes donor characteristics showing no remarkable differences between the two groups.


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Table 2. Donor characteristics and histocompatibility according to HCV status
 
A mean follow-up period of almost 5 years (Table 3Go) revealed similar initial functional course in relation to the incidence of tubular necrosis and renal function, no significant difference in the incidence of acute rejection, a greater frequency of significant proteinuria after the first year, worse middle-term kidney function (significant after the 3rd year), and a greater incidence of abnormal liver biochemistry. Remarkably, the incidence of new cases of insulin-dependent diabetes mellitus in the HCV+ patient was threefold that of HCV- cases (odds ratio 3.4; 95% confidence interval 1.5–7.6).


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Table 3. Postoperative course
 
There were no significant differences in the immunosuppressive treatment given to both groups, although the number of cases in which azathioprine was withdrawn was greater in the HCV+ group (20.5% vs 13.5% for the HCV- group).



   Survival
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
For all of the 335 patients treated with the quadruple therapy (including the 15 cases without a determination of anti-HCV antibodies), graft survival was 87.5 and 58% at the end of the 1st and 10th year respectively. Patient survival was 96.5 and 81.2% for the same periods.

Graft survival is significantly lower in the HCV+ patients, being 90.6, 68.3 and 51.0%, at 1, 5 and 10 years, compared to the HCV- patients, with 91.5, 84.7 and 66.5% respectively (Figure 1Go). The same applies to recipient survival (Figure 2Go), with percentages of 96.4, 87.0 and 71.9%, at 1, 5 and 10 years for the HCV+ cases and 98.2, 96.0 and 90.0% respectively for the HCV- patients. When cases of death with a functioning kidney were considered as censored, graft survival was better for HCV- patients, but not statistically significant (P=0.068). Patient and graft survival are similar for both groups (Figures 1 and 2GoGo) during the first 2 or 3 years, with differences appearing at a relatively late stage of the post-operative period.



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Fig. 1. Graft survival for HCV + (– – – –) and HCV - (——) patients.

 


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Fig. 2. Patient survival after kidney transplantation for HCV + (– – – –) and HCV - (——) recipients.

 
Table 4Go shows the causes of death and kidney loss for each group. It should be pointed out that in the HCV+ group only two patients died of liver failure directly, with cardiovascular pathology being the main cause of death. The incidence of lethal infections in this small group does not seem to be greater compared to the HCV- patients. The HCV+ patients lost the organ mainly due to chronic transplant dysfunction (principally chronic rejection, although biopsy confirmation was not available in all cases) and because of death with a functioning kidney. On the other hand, proportionally fewer kidneys were lost due to uncontrolled acute rejection in the HCV+ group than in the HCV- group.


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Table 4. Causes of mortality and graft failure
 
In order to avoid the bias introduced by the great heterogeneity between both groups, the following verifications were carried out in the univariate analysis:

Graft and patient survival were similar between the pre-transplant HCV+ cases and the assumed seroconversions, which were lower than for the HCV- cases.

Considering all the patients, there was no difference in survival with respect to time on dialysis above or below the median. At both levels of dialysis time, middle-term graft and patient survival was lower for the HCV+ patients.

In the multivariate analysis of graft survival, the statistically significant independent risk factors (odds ratio with a 95% confidence interval >1, P<0.05) were: donor greater than 50 years of age, brain death due to a cerebrovascular accident, female donor, recipient with a systemic disorder or diabetes, the number of HLA mismatches, and an HCV+ status. This last carried a relative risk of 3.0 (95% CI 1.8–5.0). In previous analyses (not included in the final model), the following factors were close to statistical significance (P of 0.057–0.12): re-transplant, current hyperimmunization, male recipient, and recipient age greater than 50 years. Neither the presence of pre-transplant clinical liver disease, the time of dialysis nor the year of transplantation act as independent factors.

Significant independent risk factors for patient survival were: brain death by cerebrovascular accident, female donor, currently hyperimmunized recipient, number of HLA mismatches, and an HCV+ status (relative risk of 3.1, with a CI of 1.2–7.8). Factors that narrowly failed to reach statistical significance were recipient age (0.06), male gender of the recipient, and re-transplant (not included in the final model). Again, the time of dialysis and the pre-transplant clinical liver disease seem to lack influence. Considering the limited number of events, a phenomenon of overfitting could take place in a model with so many factors. However, in different models with a smaller number of factors (2–3), it was always possible to include an HCV+ status as an independent risk factor.



   Discussion
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 
Most of the studies published report no differences in kidney transplant survival with respect to hepatitis C [29]. Some of these studies have a low number of patients or a very short post-transplant follow-up period, which could affect the statistical power for demonstrating differences between the groups. However, extensive studies such as those of Roth et al. [4], Orloff et al. [5] and others, do not share these limitations and do not document variations in survival (although in certain cases there is a greater frequency of infection and rejection in HCV+ patients). On the other hand, Pereira et al. [14] encounters greater mortality in the pre-transplant HCV+ recipients compared to HCV- patients due to infections and liver disease. These results were confirmed in more recent extensions of the study [16], although they are not applicable to patients who acquired HCV by transmission at the moment of the transplant. The author tries to explain this latter finding by the slow-developing course of hepatitis C. Recently, Legendre et al. [15] demonstrated worse graft and patient survival for HCV+ recipients in a study on a larger series of patients with long periods of follow-up during dialysis and after transplantation. Our results agree with this study with regards to survival, although we did not find evidence of greater mortality due to infection or liver disease. The demonstration of differences in survival for HCV+ patients is more difficult because of the characteristics of these patients (number of transfusions, immunization status, re-transplants) that change their immunological risk. We believe that we have demonstrated in our group that the presence of pre- or post-transplant antibodies to HCV constitutes a risk factor that does not depend on such confounding data.

The disagreement in results between the transplant centres, excluding those studies with limitations in methodology, can have two explanations. The worse survival in HCV+ patients could be a generalized phenomenon but a longer follow-up period is required, not only during the post-transplant period but from the beginning of the infection (which includes, for most patients, a great amount of the time on haemodialysis). In addition, we cannot discard the possibility of different behaviours between centres, due to multiple factors, such as ethnic or genetic factors of the organ recipients, the magnitude of the viral load, the predominant HCV genotype in the area, the number of transfusions, or the immunosuppressive therapy. With reference to this last factor, the use of globulins has been directly related to the course of liver disease. It should be emphasized that both H. Necker's group and ours generally apply induction therapy with antilymphocyte antibodies, which could lead to especially active viral replication during the early course of the transplant. Nevertheless, the quadruple therapy has not been associated with a high incidence of cytomegalovirus infection or lymphomas in our study, two conditions that suggest over-immunosuppression.

The influence of HCV on organ survival could be mediated by various mechanisms (besides an increase in losses due to death with a functioning kidney). Hepatitis C can cause de novo glomerulopathies, as has been clearly demonstrated for membranoproliferative glomerulonephritis [17] and suggested for membranous glomerulopathy [18,19]. A greater incidence of acute rejection [4] and proteinuria [9], both traditionally associated with a greater frequency of chronic transplant nephropathy, has been reported. Cosio et al. [20] recently described a high incidence of renal vascular lesions in HCV+ transplant patients by an as yet unknown mechanism. In the absence of renal biopsy, we cannot dismiss the possibility of de novo glomerulopathy, clinically indistinguishable from the glomerulopathy of chronic rejection. A reduction in immunosuppressive therapy, especially the withdrawal of azathioprine, could incite or worsen chronic rejection in a few cases.

It is surprising that in our group of HCV+ patients the causes of mortality are not apparently related to the hepatitis, but are similar to the general distribution of causes of death in the middle to late post-operative period. We could not explain this by a longer duration of the end-stage renal failure (long-term dialysis of the HCV+ patients resulting in more advanced chronic vascular disease). On the other hand, the HCV+ patients showed worse renal function at middle term and this could have increased the risk of death from vascular causes. The greater frequency of insulin-dependent diabetes mellitus among the HCV+ patients [21] is quite relevant for vasculopathies, and has been previously described for liver transplant patients [22] and the general population [23].

Despite the advances achieved in the prevention of infection by HCV in countries with previous high prevalence rates of HCV+ in patients on dialysis, this factor will continue to be of importance in the coming years. Long-term systematic analyses of large groups are justified in order to elucidate the influence of hepatitis C on transplant survival.



   References
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Survival
 Discussion
 References
 

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Received for publication: 29. 9.98
Accepted in revised form: 18. 5.99