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j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6

Available online at w

journal homepage: www.JournalofSurgicalResearch.com

Renal dysfunction by BK virus infection is correlated withactivated T cell level in renal transplantation

Ming-Che Lee, MD,a,g Ming-Chi Lu, MD, PhD,b,g Ning-Sheng Lai, MD, PhD,b,g

Su-Chin Liu, MS,c Hui-Chun Yu, MS,c Teng-Yi Lin, MS,d Shueh-Ping Hung, h

Hsien-Bin Huang, PhD,e and Wen-Yao Yin, MD, FACSf,g,*aDepartment of Surgery, Buddhist Hualien Tzu Chi General Hospital, Hualien, TaiwanbDepartment of Rheumatology, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, TaiwancDepartment of Research, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, TaiwandDepartment of Laboratory Medicine, Buddhist Tzu Chi General Hospital, Hualien, TaiwaneDepartment of Life Sciences and Institute of Molecular Biology, National Chung Cheng University, Chia-Yi, TaiwanfDepartment of Organ Transplantation, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, TaiwangTzu Chi University, Hualien, TaiwanhNursing Department, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan

a r t i c l e i n f o

Article history:

Received 7 January 2012

Received in revised form

5 April 2012

Accepted 26 April 2012

Available online 17 May 2012

Keywords:

Renal dysfunction

BK virus

Activated T cell

Immunosuppression

* Corresponding author. Department of GeneTaiwan. Tel.: þ886 5 2648000, ext. 5247; fax:

E-mail address: yaowen@mail.tcu.edu.tw0022-4804/$ e see front matter ª 2013 Elsevdoi:10.1016/j.jss.2012.04.064

a b s t r a c t

Background: BK virus (BKV) is known to be associated with nephropathy. Here, we inves-

tigated the relationships between BKV levels, T-cell activation, and kidney function in

kidney transplant recipients.

Materials and methods: In renal transplant patients and controls, urine BKV levels were

detected by quantitative real-time PCR, and the percentage of activated T lymphocytes in

blood was determined by flow cytometry. The correlations between viral load, activated T

cell percentage, and renal function were determined.

Results: Urine BKV viral loads and the activated T cell percentage were significantly

elevated in transplant recipients. Correlational analysis indicated that transplant recipi-

ents that had BKV levels of more than 106 copies/mL and an activated T lymphocyte

percentage of less than 20% were likely to have poor renal function.

Conclusions: Urine BKV levels and the percentage of activated T lymphocytes can be used as

clinical indices to optimize the dosage of immunosuppressive drugs.

ª 2013 Elsevier Inc. All rights reserved.

1. Introduction packaged in an unenveloped icosahedral capsid that is

BK virus (BKV) is one of the 13 members of the Polyomavirus

family, and was first characterized in a ureter of a renal

transplantation patient in London in 1970 [1]. The genome of

BKV shows 75%homology to the JC virus and 70%homology to

SV40 [2]. The double-stranded DNA genome of the virus

(w5300 base pairs) wraps around host cell histones and is

ral Surgery, Buddhist Dalþ886 5 2648006.(W.-Y. Yin).ier Inc. All rights reserved

approximately 40e50 nm in diameter. Under electron

microscopy, BKV can be seen organized in 40-nm clusters

within the nucleus of infected cells [1].

Primary infectionwith BKV usually happens in infancy and

is asymptomatic [2,3]. Nearly 80% of people become infected

with BKV over their lifetime, but very few of these infections

are pathogenic [4,5]. However, BKV infection in renal

in Tzu Chi General Hospital, No.2, Min-Cheng Road, Daliln, Chia-I,

.

j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6 331

transplantation patients can lead to serious damage in the

transplanted kidney [6e8]. BK virus allograft nephropathy

(BKVAN) is the most serious pathologic consequence of BKV

infection in renal transplantation patients [9e14]. BKVAN is

not a prevalent disease in the general population, but is much

more common in kidney transplant recipients. This is espe-

cially true in the first year after surgery and in cases that

involve the use of stronger immunosuppressive treatments

such as mycophenolic acid, tacrolimus, and sirolimus [7].

BKVAN, which usually occurs in conjunction with other

complications such as ureteropelvic junction obstruction,

lymphocytic pleural fluid, and bacterial urinary tract infec-

tion, can lead to damage to or loss of function of the affected

kidney. Therefore, BKV research is a topic of great interest in

the field of transplant medicine [15e20]. The immune

response in kidney transplant recipients is known to play an

important role in their long-term survival.

To avoid rejection of the allograft tissue after trans-

plantation, recipients must take immunosuppressive medi-

cines for the remainder of their life. However, this

medication also decreases the recipient’s ability to mount an

effective immune response, thus increasing the risk of viral

infection [21e24]. It is therefore imperative to find a balance

between the control of the alloreactive immune response

and the prevention of viral infection. Our research aims to

address this concern, particularly in regard to controlling

BKV levels in kidney transplant recipients. Previous reports

have shown that the activation of lymphocytes is a clinical

marker for lung diseases. Activation of T-cell receptors on

naı̈ve T lymphocytes will induce these T cells to proliferate

and secrete cytokines that inhibit the activation-induced cell

death apoptosis response. In the T-cell activation-induced

cell death mechanism, HLA-DR, a MHC class II cell surface

antigen, is one of themost important activationmarkers [25].

Upon T-cell activation by mitogens, HLA-DR upregulation

can be observed 24 to 32 h after stimulation. Thus, increased

expression of HLA-DR can be used as a marker of T-cell

activation [26]. Previous reports have also shown that in non-

Hodgkin lymphoma patients, the activation status of T cells,

obtained via lymph node biopsy, could be used as a clinical

marker for the immune response [27]. Moreover, the

expression level of HLA-DR on CD4þ T cells has been widely

used as a marker for activated T cells because it has been

shown to positively correlate with CD4þ/CD45ROþ memory

T-helper cells [28,29]. In sum, activated T cells are a good

marker for immune activity, and therefore we use the

percentage of activated T cells as an index for immune

activity.

Here, we investigated the correlations between BKV level,

the percentage of activated T cells, and kidney function by

analyzing the urine and blood of transplant patients and

a healthy control population.

2. Materials and methods

2.1. Patients

A prospective study was conducted in which 67 renal allograft

recipientswereenrolled into ourprotocol, entitled “Monitoring

of immune status in renal transplant patients with or without

BK virus infection.” Themale-to-female ratio of the transplant

patientswas31:36,andthemeanagewas45.5y (range21e67y).

Forty-seven healthy subjects, all of whom were not receiving

immunosuppressants, were included as controls. The control

population consisted of 15 male and 32 female subjects with

a mean age of 38.6 y. The collection of urine specimens for BK

virus levels and blood for activated T cells was done between

February 2007 and July 2008. The mean duration between

transplant and sample collection was 31.3 mo (range 3e168

mo). Any abnormal change in BUN, creatinine (CRE), and urine

analysis was tentatively worked up by clinical examination,

laboratory data including white blood cell and differential

count, C-reactive protein, panel reactive antibody (PRA), urine

andbloodculture, immunosuppressant level, imagestudy,and

renal biopsy (if needed) to rule out the causes for renal

dysfunction rather than BKV as a presumable etiology. We did

not doprotocol biopsy in this studybutunderwent renal biopsy

for everypatientwith sudden increase inCreatinine levelmore

than 20% compared to the previous one.

2.2. Immunosuppressive therapy

The transplant patients were divided into three groups: 1) 46

patients who were prescribed the protocol of a tacrolimus

(FK-506)-based double or triple regimen combined with

mycophenolic acid and/or prednisolone 2) 8 patientswhowere

given a cyclosporine (CSA)-based regimen (CSA in place of FK-

506) and rapamycin was used in 13 patients. No induction

therapy was used for our patients. The FK-506 level was

adjusted to 10e15 ng/mL during the first month post-

transplantation, 8e12 ng/mL in the secondmonth, and 6e8 ng/

mL thereafter. The maintenance dose of CSA was adjusted to

between 200e800 ng/mL in the first month and then 100e300

ng/mL thereafter. Decreasing intravenous doses of methyl-

prednisolone were given to both immunosuppressant groups

for the first 5 d (500e750, 200, 160, 120, and 80 mg/d). This was

followed by oral prednisolone at a dose of 20 mg/d that was

tapered to 10 mg/d by the end of 3e6 mo. Acute rejection was

noted in21of thepatients (31.3%), andmostof thesecaseswere

controlled with pulse therapy (Table 1).

2.3. ExtractionofBKVDNAandquantificationofviral loadin urine by reverse transcription quantitative PCR (RT-qPCR)

Bressollette-Bodin et al. reported that the occurrence of BKV

viremiaandviruriawereclosely associated [20], and it hasbeen

proposed that the reactivation of BK in the renal tubular

epithelium leads to systemic infection [30]. Therefore, the

measurement of urine BKV viral load is a sensitive and

noninvasive surrogate marker for BKV reactivation. Single

urine specimens were collected in a sterile container without

transport medium and were immediately frozen at �20�C,where they remained until analysis. Genomic DNA was

extracted from200 mLmidstreamurine using theQIAampDNA

kit (cat. no. 51106; Qiagen, Hilden, Germany) according to the

manufacturer’s protocol. The purified DNA was suspended in

a volume of 50 mL. The method reported by Nada et al. [31] was

followed with some modifications in order to quantify BKV

viral copynumbersbyRT-qPCR. Inbrief,primersweredesigned

Table 1 e Demographics and viral status of the groups.

Transplantpatients(n ¼ 67)

Healthycontrols(n ¼ 47)

Sex (M/F) 31/36 15/32

Acute rejection (%) 21 (31.3%) Nil

Immunosuppressants (%)

Prednisolone 60 (89.6%) None

Tacrolimus 46 (68.7%) None

Cyclosporin 8 (11.9%) None

Mycophenolic acid 57 (85.1%) None

Rapamycin 13 (19.4%) None

Time between surgery and sample

collection (mean, mo)

31.3 Nil

Nil ¼ not relevant; None ¼ no immunosuppressant use.

j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6332

based on the BKV capsid protein-1 (VP1) gene: forward primer:

50-GCAGCTCCCAAAAAGCCAAA-30; reverse primer: 50-CTGGGTTTAGGAAGCATTCTA-30. RT-qPCR was performed

using theABI7500 real-timePCRsystemina reactionvolumeof

25 mL that contained 0.5 mL forward primer (20 pmol/mL), 0.5 mL

reverse primer (20 pmol/mL), 12.5 mL 2� SYBRGreenMasterMix

(Qiagen), 0.5 mL uracil-N-glycosylase (0.5 units/reaction), 5 mL

DNA sample, and 6 mL double distilled water. After an incuba-

tion of uracil-N-glycosylase at 50�C for 2min and denaturation

at 95�C for 5min, thermal cycling was initiated. This consisted

of 40 cycles of 94�C for 1min, 52�C for 1min, and 72�C for 1min,

with the fluorescence read at the end of each cycle. The

amplification datawere analyzed usingABI SDS 7500 software.

Standardcurves for thequantificationofBKVwereconstructed

using serial dilutions of a plasmid containing the entire line-

arized genome of the BKV Dun strain inserted into the EcoRI

restriction site of the pCR2.1-TOPO plasmid (Invitrogen;

Carlsbad, California). The plotted plasmid concentrations

ranged from 100 to 1011 copies of the BKV genome per PCR. All

patient samples were tested in duplicate, and the number of

BKV copies was calculated from the standard curve. A total of

103 copies of the BKV genome per sample were regularly

detected, but 102 copies were detected only in some experi-

ments. Thus, the assay reproducibly detected 103 genome

copies per sample. In all RT-qPCR assays, the correlation

coefficient of the standard curve was greater than 0.980. Data

were expressed as copies of viral DNA per milliliter of urine.

Standard precautions to prevent contamination during RT-

qPCR were followed. No-template control reactions and

negative-control samples (DNA extracted from hetronuclear

cells of healthy humans) were included in each run.

Fig. 1 e Percentage of individuals with BKV infection in

renal transplantation and control groups. (Color version of

figure is available online.)

2.4. Activated CD3þ T lymphocytes in posterenaltransplantation

A whole-blood staining method was used with the following

monoclonal antibodies: anti-CD4 (phycoerythrin), anti-CD3/

HLA-DR (fluorescein isothiocyanate), and control IgG1/IgG2.

Samples of 100 mL whole blood were lysed in lysis buffer

(BD Biosciences; San jose, California) at room temperature for

10 min. Monoclonal antibodies were then added to each

sample, and samples were incubated at room temperature for

30 min and then washed with phosphate-buffered saline

once. A total of 15,000 cells within the lymphocyte gate were

analyzed with a cooled 488-nm argon-ion laser flow (BD

FACSCalibur; BD Biosciences).

2.5. Creatinine blood test

The concentration of creatininewas analyzed in the plasma of

transplant patients to give an estimation of kidney function.

CRE levels below 1.5 mg/100 mL are associated with normal

kidney function, while levels equal to or greater than 1.5 mg/

100 mL indicate kidney dysfunction.

2.6. Statistical analysis

Statistical analysis was performed using either the c2 test, the

Fisher exact test, or the Student t-test using Stagraphics Plus

3.0 software (Manugistic, Inc., Rockville, MD).

2.7. Institutional review board approval

This research was initiated and accomplished by our team

following the permission of the Ethics Committee of our

hospital.

3. Results

3.1. BKV infection rate and expression level in urine

The BKV infection rate and expression level in urine was

analyzed in 67 renal transplantation patients taking immu-

nosuppressants and in 47 healthy controls. In the renal

transplantation group, 64.2% (43/67) were infected with BKV,

while only 34.0% (16/47) of the controll group were infected

(Fig. 1). Within the BKV-infected populations, the average BKV

expression level (number of BKV genome copies/mL urine) is

similar: log values of 6 � 1.68 copies (n ¼ 43) and 6.2 � 0.8 (n ¼16) for the renal transplantation and control groups, respec-

tively (Table 2).

Table 2e BKV infection rate and expression level in urine.

Transplant(n ¼ 67)

Control(n ¼ 47)

P value

Average of total viral

load, log number of

copies/mL urine

3.88 (�0.39) 2.11 (�0.44) 0.0035

Infection rate 43/67 (64%) 16/47 (34%) 0.002

Fig. 2 e Relationships between BKV expression level,

percentage of activated T (CD3D) lymphocytes, and kidney

function index (CRE). *Zone A indicates a viral load of >106

copies/mL and <20% activated T (CD3D) cells; Zone B

indicates a viral load of >106 and ‡20% activated T (CD3D)

cells; Zone C indicates a viral load of <106 and >20%

activated T (CD3D) cells; and Zone D indicates a viral load

of <106 and <20% activated T (CD3D) cells.

Table 4 e Demographics and Specific Events in 1 2 Caseswith Renal Dysfunction

Demographic parameters Results

Age

Average (range) 40 (25-49) y/o

Gender

j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6 333

3.2. Percentage of activated T lymphocytes in renaltransplant recipients and controls

The renal transplant recipients in this study were being

treated with immunosuppressants such as FK-506 and cyclo-

sporine. Interestingly, the percentage of activated T cells was

still higher in transplant recipients than in controls: 23.0% �1.5% versus 14.6% � 0.8%, P < 0.001 (Table 3).

3.3. Relationships of BKV levels and percentage ofactivatedCD3þT lymphocyteswithan indexofkidney function

To investigate any correlation between BKV levels,

percentage of activated T cells, and kidney function in renal

transplantation patients, the available complete samples

obtained from the 33 BKV-positive transplant patients were

further processed to determine the CRE concentration. An

increased CRE level (CRE �1.5 mg/100 ml) in the blood is

associated with diseases or conditions that affect kidney

function. We found that 36.4% (12/33) of the BKV-positive

patients had an elevated CRE level. The distribution of these

samples can be divided into four zones: zone A indicates

more than 106 (>106) BKV genome copies and less than 20%

(<20%) activated CD3þ T lymphocytes; zone B indicates >106

BKV genome copies and>20% activated CD3þ T lymphocytes;

zone C indicates<106 BKV genome copies and>20% activated

CD3þ T lymphocytes; zone D indicates <106 BKV genome

copies and<20% activated CD3þT lymphocytes (Fig. 2). Of the

high CRE (CRE �1.5 mg/100 mL) population, 50% (6/12) fell

within zone A, 8.3% (1/12) in zone B, 25% (3/12) in zone C, and

16.7% (2/12) in zone D. Finally, to identify a high-risk group for

BKV nephropathy, we found that patients that had both

a high urine BKV viral load (>106 copies/mL) and a low

percentage of activated T cells (<20%) (patients that fell into

zone A of Fig. 2) had worse renal function than patients in all

other groups (P ¼ 0.015). Analyzing the 12 patients with renal

dysfunction (marked as solid dark circles in Fig. 2), we

Table 3 e Percentage of activated T cells in renaltransplantation patients and controls.

Transplant(n ¼ 67)

Control(n ¼ 47)

P value*

BKV (þ) 22.9% � 10.7% 14.6% � 6.4% 0.0101

BKV (�) 23.1% � 9.2% 13.8% � 4.4% 0.0059

BKV (þ/�) 23.0% � 1.5% 14.6% � 0.8% <0.0001

Data represent mean � standard deviation.

* Transplant/control ¼ P.

realized that 11 out of 12 cases received biopsy for change in

CRE level and only 3 out of 12 cases revealed rejection (acute

cellular rejection in two patients and antibody-mediated

rejection in one). We also have two cases of BK nephropathy

in this study and only one of them showed renal dysfunction

during this study period (a solid circle in zone A). The other

one possessed good renal function with high viral load but

good immune condition (a hollowed triangle in zone B) during

this study period. In addition, the remaining 7 patients out of

11 biopsied cases did not show any rejection episode during

the study period (Table 4). Overall, we have one case with

rejection in each zone except for zone D, where both viral load

and activated T cell % are low (Fig. 2).

Male: Female 4:8

High PRA level (20%) Nil

ESRD due to GN 2 (IgAN)*

Nephro- toxic drug (Non-CNI) Nil

Biopsy 11/12 ( 92%)

Abnormal Drug level Nil

Recurrence of underlying GN Nil

Acute cellular rejection 2

Antibody mediated rejection 1

Pulse therapy 2

BK nephropathy 1

* IgAN ¼ IgA Nephropathy; Nil ¼ Not detected; CNI ¼ Calcineurin

Inhibitor.

j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6334

4. Discussion

Infection by viruses such as cytomegalovirus, polyomavirus

BK, adenovirus, and herpes simplex virus is a common

complication in renal allograft patients [30,31]. Before 1995,

BKV nephritis was rare [16,17,32,33], but the use of stronger

immunosuppressants such as mycophenolic acid and FK-506

in renal allograft patients has led to a dramatic increase in

BKV nephritic infections [13,34]. BKV infection rarely causes

disease in healthy individuals [5,6]. However, in kidney

transplant patients, once BKV levels are sufficiently high, viral

particles can pass through tubular vessels to infect renal

tubular epithelial cells and induce renal graft dysfunction

[35e38]. Therefore, monitoring BKV levels in renal trans-

plantation patients may be important in predicting and pre-

venting BKV nephropathy [32,34,39,40]. Randhawa et al.

correlated BK viral load with both the clinical course and the

presence of BK virus in renal biopsy specimens. BK viral loads

were measured in urine, plasma, and kidney biopsy samples

in three clinical settings: 1) patients with asymptomatic BK

viruria, 2) patients with active BKVAN, and 3) patients with

resolved BKVAN. Active BKVAN was associated with BK

viremia greater than 5 � 103 copies/mL and BK viruria greater

than 107 copies/mL in all cases [41]. However, it is still not clear

how and why high levels of BKV cause pathologic effects only

in some patients. In this study, we further analyzed BKV levels

in patient and control groups. While BKV can be detected in

approximately 34% of the control group, this percentage is

almost double in renal transplantation patients, as approxi-

mately 64% of transplant recipients are positive (Fig. 1 and

Table 1).

Our study found that only 34% of healthy controls were

infectedwith BKV, a percentage considerably lower thanwhat

has been reported elsewhere. This could be due to differences

in the ages of the participants in the studies (38.6 � 16.7 y old

in this study) or to the relatively small sample size (n ¼ 47).

However, it is clear that the BKV infection ratio is 2-fold higher

in renal transplantation patients (n ¼ 67) than in the controls

in this study. This suggests that renal transplantation patients

are more susceptible to infection by BKV. However, we also

found that among subjects infected with BKV, the level of BKV

is similar in renal transplant recipients and controls (Fig. 2 and

Table 1). This implies that even though renal transplantation

patients are more susceptible to BKV infection than healthy

individuals (Fig. 1), they are not susceptible to harbor higher

viral loads when infected (Table 2). This was surprising to us,

as we expected that BKV expression might be higher in the

transplant group because these patients were receiving

immunosuppressive therapy.

It is currently difficult to discriminate between BKV

nephropathy and acute rejection (AR) in the clinical diagnosis

of kidney recipients. This can create a dilemma in identifying

a treatment strategy, as treating AR patients for BKV

nephropathy can lead to serious problems. Here, we suggest

diagnostic criteria that are based on the percentage of acti-

vated CD3þ T lymphocytes, the BKV level, and the CRE

level (index of kidney function) in kidney recipients to help

elucidate the likelihood of BKV nephropathy in posterenal

transplantation patients. To establish such criteria, we

investigated the correlations between these three factors

(Fig. 2).

In Fig. 2, the incidence of poor renal functionwas highest in

zone A (6/8, 75%) followed by zone D (2/7, 28.6%), zone C (3/12,

25%), and zone B (1/6, 16.7%). Further, among patients with

a high viral load (zone Aþ zone B, >106 copies/ mL), 50% (7/14)

had elevated CRE levels, while only 26.3% (5/19) with a low

viral load (zone C þ zone D) had elevated levels of CRE. This

suggests that higher viral loads might increase the risk of

having kidney dysfunction. However, the incidence of poor

kidney function was extremely low in zone B (1/6), which

includes the patients that had high viral loads and high

percentages of activated T cells. Further, 66.7% (8/12) of the

infected transplant patients that had elevated CRE levels also

had activated T cell percentages of less than 20% (Fig. 2). Thus,

high viral loads and a low percentage of activated T cells seem

to be important risk factors for developing BKV nephropathy.

There was no evidence of high PRA level, toxic immuno-

suppressant level, urinary tract obstruction, abnormal blood

flow, urinary tract infection, taking drugs capable for renal

toxicity, and recurrence of glomerulonephritis to deteriorate

the renal function (Table 4). In addition, we had 3 patientswith

AR out of 12 patients with renal dysfunction. One had high

activated T cell percentage combinedwith low viral load (zone

C) and it is reasonable to assume that renal dysfunction due to

rejection rather than BK virus. The other patient with acute

cellular rejection though in zoneB (high viral load, highATC%),

she only had borderline increment of viral load (106.5 copies) in

contrast to very high activated T cell percentage (37%) and it

might explain for some extent why she suffered from rejection

at that time point. The third patient with antibody-mediated

rejection fell into zone A (danger zone), and high viral load for

this case should be attributed to consequence of upregulation

of immunosuppressants during suspicion of acute rejection.

The results described above suggest that when the

immune activity has been suppressed to avoid allorejection of

the transplanted kidneys, the patients’ immune systems are

less able to control BKV, and that once BKV level reaches

a certain level, the incidence of kidney dysfunction increases.

We therefore suggest that when the percentage of the acti-

vated CD3þ T lymphocytes is less than 20% and the level of

BKV ismore than 106 copies/mL in the urine, a reduction in the

immunosuppressive treatment should be considered and the

CRE level should be closely monitored.

However, our study did have the drawback of including

only 67 transplant cases and only the samples from the 33

BKV-positive transplant patients with available data were

further processed to determine the correlation with renal

function (Fig. 2). This sample size is not sufficient to draw

a solid conclusion. A prospective randomized trial is needed to

track the short- and long-term effects of controlling viral load

and immune status.

In summary, a major dilemma in the treatment of poste

renal transplantation patients is the need to balance the

immunosuppression adequate to limit rejection of the trans-

planted kidney with the immune responsiveness necessary to

elicit suitable immune responses to control BKV and prevent

nephropathy. Therefore, measuring of activated T cell level

can focus on the most high-risk group for modulation of

immunosuppressant to prevent renal dysfunction and,

j o u r n a l o f s u r g i c a l r e s e a r c h 1 8 0 ( 2 0 1 3 ) 3 3 0e3 3 6 335

conversely, to avoid unnecessary complications like acute

rejection on the other side.

Acknowledgment

This work was supported in part by grant TCRD-I9607-01 from

the Buddhist Tzu Chi General Hospital, Chia-Yi, Taiwan.

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