Objectives: Vitamin D may modulate immune function. The purpose of this study was to evaluate the association of 25-hydroxyvitamin D level at kidney transplant with outcomes after transplant, including opportunistic viral infections (cyto-megalovirus infection and BK viremia), acute allograft rejection, and delayed graft function.
Materials and Methods: A retrospective review was performed in kidney transplant recipients who had 25-hydroxyvitamin D levels drawn within 30 days before or after of transplant from January 2004 to May 2009 at Henry Ford Hospital and who were followed for 1 year after transplant.
Results: There were 89 patients included in the study (mean age, 51 ± 14 y; male, 66%; African American, 49%; living-donor transplant, 26%). There was a significantly lower frequency of opportunistic viral infections in the vitamin D sufficient group (3 patients, 12%) than vitamin D insufficient group (24 patients, 38%; P ≤ .01). Multivariate analysis showed that male sex and vitamin D insufficiency were independently associated with increased incidence of opportunistic viral infection.
Conclusions: In kidney transplant recipients, male sex and vitamin D insufficiency are inde-pendently associated with increased incidence of opportunistic viral infection. The risk of developing opportunistic viral infections after kidney transplant may be modified by ensuring adequate 25-hydroxy-vitamin D levels before transplant.
Key words : BK virus, Chronic kidney disease, Cytomegalovirus, Polyomavirus
Vitamin D is a steroid hormone that mediates calcium and phosphate homeostasis.1,2 Deficiency of vitamin D may cause rickets (a disease associated with skeletal deformities), muscle weakness, and an increased incidence of infectious diseases such as pneumonia and tuberculosis.1,3,4 Within the past 15 to 20 years, vitamin D deficiency has also been linked to various diseases including osteoporosis, cardiovascular disease, hypertension, autoimmune diseases (multiple sclerosis, Crohn’s disease, and type 1 diabetes mellitus), malignancies (colon, prostate, and breast cancer), and depression.1,5-15
Vitamin D deficiency occurs in 1 billion people worldwide and may affect people of all ages and races, but is more prevalent in African Americans, patients who have kidney dysfunction, and the elderly.1,16,17 Vitamin D deficiency may be caused by multiple factors including inadequate intake from diet or supplements or insufficient sun exposure. Vitamin D has immune modulating properties, and vitamin D receptors are located on many immune cells including macrophages, T and B lymphocytes, and dendritic cells.2,7,18 When activated, these cells express 1-α-hydroxylase that converts 25-hydroxyvitamin D to the active form, 1,25-dihydroxyvitamin D2. Activated vitamin D attenuates the adaptive immune system by decreasing the maturation of dendritic cells.2 Activated vitamin D also acts directly on T lymphocytes to inhibit proliferation.19
Vitamin D insufficiency has been linked to various infectious diseases.20 Low levels of vitamin D are associated with clinical progression and increased mortality in patients who have human immuno-deficiency virus.21 In addition, vitamin D supple-mentation is associated with improved outcomes in patients who have tuberculosis and lower incidence of seasonal influenza.22,23 Vitamin D insufficiency within 7 days after starting critical care is associated with higher mortality.24 However, a literature search showed no studies in humans that evaluated the potential effects of vitamin D status on the incidence of opportunistic viral infections in kidney transplant patients.
The purpose of the present study was to evaluate the relation between 25-hydroxyvitamin D level at transplant and infectious outcomes after transplant including the incidence of cytomegalovirus infection and polyomavirus (BK) viremia.
Materials and Methods
This was a retrospective cohort study of patients who received a kidney transplant from January 2004 to July 2009 at Henry Ford Hospital, an 802-bed tertiary care and multiorgan transplant center. There were 547 patients [mean age, 53 ± 13 years; male, n=366 (67%); African American, n=268 (49%] who received a kidney transplant [(living-donor transplant, n=142 (26%)] during this period (average, 97 kidney transplants per year) (Figure 1).25 Among these 547 patients, 119 (4.6%) patients had 25-hydroxyvitamin D levels drawn 30 days before or after transplant. Patients were included in the study when they were aged ≥ 18 years at transplant and received a kidney transplant with follow-up care at Henry Ford Hospital. Patients were excluded from the study if they did not have a 25-hydroxyvitamin D level drawn within 30 days of transplant (428 patients), were participants in an investigational drug study (20 patients), received multiple organs (5 patients), or received follow-up care at another institution (5 patients). Therefore, there were 89 patients enrolled in the study. Participants were divided into 2 groups according to 25-hydroxyvitamin D level; patients were characterized as vitamin D sufficient (25-hydroxyvitamin D > 50 nmol/L) or vitamin D insufficient (25-hydroxyvitamin D ≤ 50 nmol/L). The study protocol was approved by the institutional review board at Henry Ford Hospital and a waiver of informed consent was granted because of the retrospective study design. All protocols conformed with the ethical guidelines of the 1975 Helsinki Declaration.
All recipients received immunosuppression regimens with 3 or 4 drugs. Patients who were at high risk for rejection (African American, peak panel-reactive antibody ≥ 20%, or delayed graft function) received anti-thymocyte globulin; patients who were at lower risk received basiliximab; and patients who had living-related kidney transplant with a 2-haplotype match received no induction immunosuppression. All patients received maintenance therapy with tacrolimus (goal, 124.4 to 186.6 nmol/mL for the first 3 months, then lower based on risk), mycophenolate mofetil (1 gram twice daily), and methylprednisolone (tapered to 30 mg by postoperative day 7; further taper directed by the outpatient nephrologist).
All patients received sulfamethoxazole-trimethoprim (double strength tablets, 3 times weekly) or pentamidine inhalation monthly for 1 year for prophylaxis against Pneumocystis jirovecii. Antiviral prophylaxis was given whether the recipient tested seropositive (R+) or seronegative (R-) or whether the donor tested seropositive (D+) or seronegative (D-) for cytomegalovirus. All cytomegalovirus seropositive recipients (R+) received oral ganciclovir (500 mg twice daily). Recipients who were defined as high risk for cytomegalovirus infection (D+/R-) received valganciclovir (900 mg daily for 6 months), and recipients who were at low risk for cytomegalovirus infection (D-/R-) received acyclovir for herpes simplex virus prophylaxis. Detection of cytomegalovirus and BK virus was based on serologic data in patients who were suspected of having infection.
Clinical data collection was performed using a standardized case report form. Baseline data (time of transplant) included age, sex, race, history of previous transplant, indication for kidney transplant, receipt of chronic hemodialysis or peritoneal dialysis, panel-reactive antibody, cytomegalovirus serologic test results and risk of infection, donor type (living or deceased donor), age of the donor, warm ischemia time, cold ischemia time, 25-hydroxyvitamin D level, and immunosuppressive induction regimen. For the year after transplant, data collected included 25-hydroxyvitamin D levels, serology for BK and cytomegalovirus, maintenance immunosuppressive regimen, and receipt of supplemental vitamin D (ergocalciferol and/or cholecalciferol).
Outcomes and definitions
Clinical outcomes included cytomegalovirus infection (defined as biopsy-proven or cytomegalovirus (polymerase chain reaction viremia > 2000 viral copies/mL), BK viremia (defined as biopsy-proven or BK virus detected in blood by polymerase chain reaction), episodes of treated acute cellular rejection (defined as biopsy-proven rejection or administration of high-dose steroids in the absence of a biopsy), presence of delayed graft function (defined as the need for renal replacement therapy within 7 days after transplant), graft loss, and death. The primary composite endpoint was a comparison of the incidence of opportunistic viral infections (cytomegalovirus and BK virus) within 1 year after kidney transplant between insufficient and sufficient vitamin D groups. Secondary endpoints included acute cellular rejection, delayed graft function, graft loss, and death. In addition, a post hoc analysis was performed to evaluate the relation between vitamin D supplementation and transplant outcomes.
Data analyses were performed with statistical software (SPSS, version 13.0, SPSS Inc., Chicago, IL, USA; and SAS, version 9.2, SAS Institute, Cary, NC, USA). Categorical variables were analyzed with chi-square test or 2-sided Fisher exact test. Continuous variables were analyzed with independent-samples t test or the nonparametric Mann-Whitney U test. Multivariate analysis was performed to determine factors independently associated with opportunistic viral infections; variables that had P < .1 in univariate analysis were analyzed in the multivariate analysis. Statistical significance was defined by P < .05.
Of the 89 patients enrolled in the study (Figure 1) (mean age, 51 ± 14 years; male, 60 patients [67%]; African American, 44 patients [49%]; living-donor transplant, 35 patients [39%]), most patients were vitamin D insufficient at transplant and most patients had no opportunistic viral infection by 1 year after transplant (Table 1). Age, sex, history of previous transplant, and most indications for transplant were similar between groups (Table 1). The vitamin D insufficient patients were more frequently African American, less frequently recipients of a living-donor transplant, and more frequently seropositive for cytomegalovirus than vitamin D sufficient patients (Table 1).
There was a significantly lower frequency of opportunistic viral infections in the vitamin D sufficient group (3 patients, 12%) than in the vitamin D insufficient group (24 patients, 38%; P ≤ .01) (Figure 2). Only 3 vitamin D sufficient patients developed an opportunistic viral infection. Infection with BK virus occurred less frequently in vitamin D sufficient (1 patient, 4%) than vitamin D insufficient patients (14 patients, 22%; P ≤ .04). Vitamin D sufficient and insufficient patients had similar frequency of cytomegalovirus infection, acute rejection, and delayed graft rejection.
Patients who had opportunistic viral infections were more frequently male and less frequently living-donor transplant recipients than patients who had no opportunistic viral infection (Table 1). There were no differences between patients who had or did not have opportunistic viral infection in frequency of delayed graft function (infection, 6 patients, 22%; no infection, 14 patients, 23%; not significant), acute cellular rejection (infection, 8 patients, 30%; no infection, 9 patients, 15%; not significant), graft loss (infection, 3 patients, 11%; no infection, 3 patients 5%; not significant), or death (infection, 2 patients, 7%; no infection, 3 patients, 5%; not significant). There was no difference in frequency of opportunistic viral infections in patients who received (21 patients, 78%) or did not receive anti-thymocyte globulin for induction immunosuppression (35 patients, 57%; not significant). Multivariate regression analysis showed that male sex and vitamin D insufficiency were independently associated with increased incidence of opportunistic viral infection (Table 2).
Most patients (72 patients [81%]) received vitamin D supplementation (ergocalciferol or cholecalciferol) after transplant regardless of baseline vitamin D level. There was no difference in frequency of opportunistic viral infections between patients who received (16 patients, 22%) or did not receive supplements (5 patients, 29%; not significant). There was no difference in frequency of acute cellular rejection between patients who received (12 patients, 17%) or did not receive supplements (5 patients, 29%; not significant).
This study showed a correlation between vitamin D status and incidence of immune-related outcomes after kidney transplant. Adequate vitamin D levels within 30 days of transplant were associated with decreased incidence of opportunistic viral infections during the year after transplant. However, vitamin D supplementation after transplant did not affect these outcomes. The data suggest that the risk of developing opportunistic viral infections may be modified by ensuring adequate 25-hydroxyvitamin D status before transplant.
One study found that most (90%) patients receiving a kidney transplant were deficient in vitamin D and were on chronic hemodialysis before transplant.26 Although most patients in the present study were deficient in vitamin D at time of transplant (Table 1), this was consistent with treatment strategies suggested by the National Kidney Foundation Disease Outcomes Quality Initiative guidelines. These guidelines suggested supplementings patients who had low 25-hydroxy-vitamin D levels and chronic kidney disease stages 3 and 4, and there was no recommendation for patients on hemodialysis.27 Guidelines from the Kidney Disease: Improving Global Outcomes initiative (KDIGO) suggest that sufficient levels of vitamin D should be maintained in all patients with chronic kidney disease, including patients on hemodialysis, which accounts for most patients who receive kidney transplant.28 These guidelines acknowledged that 1-α-hydroxylation of 25-hydroxyvitamin D is independent of kidney function in tissues throughout the body.28 The present findings supported the KDIGO recommendations and identified a potential benefit of restoring vitamin D levels before transplant to improve infectious outcomes after transplant.
BK viremia may occur in 35% to 67% kidney transplant recipients and may cause nephropathy, rejection, and graft failure.29-31 The only known strategy that may lower the risk of BK nephropathy is reduction of the immunosuppressive regimen when detectable serum levels of BK virus are observed, but decreasing the level of immuno-suppression may increase the risk of rejection.32-33 Treatment options are limited and are associated with major toxicity, including damage to the new graft.34
Cytomegalovirus is associated with major morbidity and mortality in kidney transplant recipients. This infection usually occurs within 3 months after transplant, but onset may be delayed in patients who receive prophylactic antiviral therapy.35 The risk of cytomegalovirus infection is highest in D+R- patients.36 The incidence of cytomegalovirus disease is 37% in high risk patients who receive prophylaxis for 3 months, but fewer patients (16%) may develop cytomegalovirus with prophylaxis for 6 months, comparable to the frequency in the present study population (11%).35 At our institution, patients who have intermediate or high risk for cytomegalovirus infection receive prophylactic antiviral therapy for 6 months, and low-risk patients (D-R-) receive no cytomegalovirus prophylaxis. This may explain the low frequency of cytomegalovirus infection observed in the present study.
In the present study, there was a higher prevalence of African American patients who were vitamin D insufficient, consistent with previous studies.37,38 This may have been caused by the darker skin pigmentation which may decrease the amount of vitamin D production in the skin.39 However, this finding did not correlate with a higher incidence of opportunistic viral infection in African American study patients. Although immunologic and non-immunologic causes of acute rejection and worse graft outcomes in African American patients have been suggested, vitamin D deficiency has not been implicated previously as a potential risk factor.40,41
In the present study, more patients in the vitamin D sufficient than insufficient group received a kidney transplant from a living donor (Table 1). Patients that received a living-donor transplant also had lower incidence of opportunistic viral infections in univariate but not multivariate analysis (Tables 1 and 2). Recipients of deceased-donor kidneys may receive more aggressive immunosuppression and may be more debilitated before transplant than recipients of living-donor kidneys. Anti-thymocyte globulin is a potent polyclonal antibody that produces marked T-cell depletion for several months, and has been linked to various infectious complications, including increased incidence of viral infections after deceased-donor kidney transplant.42,43 In the 54 deceased-donor kidney transplant recipients in the present study, most (82%) received anti-thymocyte globulin for induction, but only 34% living-donor recipients received anti-thymocyte globulin. Nevertheless, anti-thymocyte globulin induction was not independently associated with a higher incidence of opportunistic viral infections.
Limitations of the present study include the observational study design, which precluded controlling for all potential confounding factors. We attempted to account for confounding factors by performing a multivariate analysis. In addition, this study was limited by the small sample size because only 119 patients (22%) had a vitamin D level drawn within 30 days before or after of transplant. Nevertheless, the present sample was representative of transplant recipients at our center.
In summary, the present study supports the immune role of vitamin D and showed that patients who have vitamin D insufficiency have a higher incidence of opportunistic viral infections during the year after transplant. The risk for opportunistic viral infections may be modified by ensuring adequate 25-hydroxyvitamin D levels before transplant, consistent with current guidelines. Further evaluation in a larger patient sample or randomized controlled trial may provide additional information to help guide therapy.
Volume : 12
Issue : 2
Pages : 95 - 100
DOI : 10.6002/ect.2013.0201
From the 1Department of Pharmacy Services and the 2Department
of Internal Medicine, Division of Nephrology and Hypertension, Henry Ford
Hospital, Detroit, MI, USA
Acknowledgements: The authors thank Gordon Jacobsen, MS, at the Henry Ford Health System Biostatistics Department, for statistical support. Preliminary results of this study were presented at the American Transplant Congress in Boston, Massachusetts, June 2012. The authors have no conflicts of interest to report, and there was no funding for this study.
Corresponding author: Megan Rech, PharmD, BCPS, Loyola University Medical Center, Department of Emergency Medicine, 2160 S 1st Avenue, Maywood, IL 60513, USA
Phone: +1 708 327 2567
Fax: +1 708 327 2548
Figure 1. Vitamin D Deficiency and Opportunistic Viral Infection After Kidney Transplant
Figure 2. Opportunistic Viral Infections After Kidney Transplant
Table 1. Characteristics of Patients Who Received a Kidney Transplant*
Table 2. Multivariate Analysis To Determine Factors That Were Independently Associated with Opportunistic Viral Infections in Patients Who Had Kidney Transplant*