Kidney transplantation is now considered the most appropriate choice for treatment of most patients suffering from end-stage renal disease (ESRD). However, rejection (acute or chronic) remains the most challenge facing the success of this maneuver. To overcome such challenge, immunosuppressive drugs have been successfully used but not without adverse effect. An effect gives a golden chance for opportunist microorganisms like polyomaviruses to exert their masked detrimental action inside the body [
The CD30 molecule is 120-kDa transmembrane glycoprotein which is a member of tumor necrosis factor receptor (TNF-R) super family lacking a death domain [
Following membrane expression of CD30 molecule, it is proteolytically cleaved to produce an 88-kDa soluble molecule in the body fluid [
BK virus is a nonenveloped, double-stranded DNA virus of the polyomavirus family that primarily affects immunocompromised patients. BKV may cause nephropathy in renal transplant recipients receiving immunosuppressive therapy, resulting in renal dysfunction and, possibly, graft loss [
About 15% of RTRs have this virus in the absence of an effective strategy [
A total of 50 RTRs with histopathologically confirmed nephropathy (based on the chronic interstitial fibrosis and tubular atrophy of the renal allograft) who were attending the Center of Kidney Diseases and Transplantation in the Medical City/Baghdad during the period from March 2014 to February 2015 were recruited for this study. The mean posttransplantation period was 16.134 months (less than 12 months in 29 patients and 12 months or more in 21 patients). From each participant, a consent form was obtained which includes information about the age, sex, and the date of transplantation. Exclusion criteria were delayed graft function, previous allograft, and history of episodes of infection during the first month after transplantation. Other 30 individuals (19 male and 11 female, mean age 47.68 years) were recruited as healthy control group. Anyone from this group who had a history of autoimmune disease or graft transplantation was excluded. Three mL of venous blood was collected from each patient in a plane tube where the serum was separated.
Enzyme-linked immunosorbent assay (Diagnostic Automation Inc., USA) was used to estimate serum levels of sCD30 using a commercially available kit (Invitrogen/USA) following manufacturer’s instructions. Briefly, 150
Viral DNA was extracted from 400
Nontemplate control was used to determine whether the sample is contaminated in the process of sample pretreatment, nucleic acid extraction, and PCR preparation. Taqman probe with FAM and TAMRA as fluorophore and quencher, respectively, was employed for the detection of PCR product. The real-time data was collected at the second step of the amplification cycle.
A standard curve (Figure
Standard curve. The five standards are 103, 104, 105, 106, and 107 copies/mL.
Statistical package for social sciences version 16.0 (Chicago, USA) was used to analyze the data. Values were expressed as mean ± standard deviation (SD). Independent sample
This study included 50 RTRs with confirmed nephropathy and 30 individuals as healthy control group. Table
Demographic and clinical features of the nephropathic patients.
Variable | Value |
---|---|
Age (mean ± SD) | 48.14 ± 12.7 |
Sex M : F (No) | 36 : 14 |
|
|
Proteinuria | 48 (96%) |
Hypertension | 21 (42%) |
Hematuria | 32 (62%) |
Anemia | 12 (24%) |
Thrombotic microangiopathy | 6 (12%) |
Dyslipidemia | 28 (56%) |
Glomerulonephritis | 3 (6%) |
Chronic pyelonephritis | 1 (2%) |
Diabetic nephropathy | 3 (6%) |
Renal amyloidosis | 2 (4%) |
Preeclampsia | 1 (2%) |
Obstructive uropathy | 1 (2%) |
|
|
Related | 38 (76%) |
Unrelated | 12 (24%) |
Out of 33 RTRs whose ages are less than 40 years, only 4 (12.12%) were positive for BKV compared to 7 (41.11%) out of 17 RTRs whose ages are ≥40 years with significant difference (OR = 5.075, 95% CI = 1.223–21.065) (Table
Risk factor for infection with BKV.
Risk factor | Total number for positive cases = 11 | OR (95% CI) |
---|---|---|
Age | ||
<40 years (33) | 4 (12.12%) | 1.0 |
≥40 years (17) | 7 (41.11%) | 5.075 (1.223–21.065) |
Gender | ||
Male (36) | 9 (25%) | 1.0 |
Female (14) | 2 (14.28%) | 0.5 (0.094–2.673) |
Posttransplantation period | ||
<12 months (29) | 8 (27.58%) | 1.0 |
≥12 months (21) | 3 (14.28%) | 0.348 (0.101–1.90) |
OR = odds ratio and CI = confidence interval.
Out of 50 enrolled RTRs, 11 (22%) showed detectable BK viremia with viral load which ranged from 6.12
BK virus load in renal transplant recipients.
Well | Sample ID | IPC |
BKV |
BKV |
BKV |
---|---|---|---|---|---|
A1 | NTC | Valid | Undetermined | — | Valid |
B1 | SPC1 | Valid | 31.04 |
|
Valid |
C1 | SPC2 | Valid | 28.42 |
|
Valid |
D1 | SPC3 | Valid | 25.00 |
|
Valid |
E1 | SPC4 | Valid | 20.97 |
|
Valid |
F1 | SPC5 | Valid | 17.92 |
|
Valid |
G1 | Sample 01 | Valid | — | — | Not Detected |
H1 | Sample 02 | Valid | 31.89 |
|
|
A2 | Sample 03 | Valid | — | — | Not detected |
B2 | Sample 04 | Valid | — | — | Not detected |
C2 | Sample 05 | Valid | — | — | Not detected |
D2 | Sample 06 | Valid | — | — | Not detected |
E2 | Sample 07 | Valid | 28.76 |
|
|
F2 | Sample 08 | Valid | — | — | Not detected |
G2 | Sample 09 | Valid | — | — | Not detected |
H2 | Sample 10 | Valid | — | — | Not detected |
A3 | Sample 11 | Valid | — | — | Not detected |
B3 | Sample 12 | Valid | 23.24 |
|
|
C3 | Sample 13 | Valid | — | — | Not detected |
D3 | Sample 14 | Valid | — | — | Not detected |
E3 | Sample 15 | Valid | — | — | Not detected |
F3 | Sample 16 | Valid | — | — | Not detected |
G3 | Sample 17 | Valid | — | — | Not detected |
H3 | Sample 18 | Valid | — | — | Not detected |
A4 | Sample 19 | Valid | 32.76 |
|
|
B4 | Sample 20 | Valid | — | — | Not detected |
C4 | Sample 21 | Valid | — | — | Not detected |
D4 | Sample 22 | Valid | — | — | Not detected |
E4 | Sample 23 | Valid | — | — | Not detected |
F4 | Sample 24 | Valid | 18.29 |
|
|
G4 | Sample 25 | Valid | — | — | Not detected |
H4 | Sample 26 | Valid | — | — | Not detected |
A5 | Sample 27 | Valid | — | — | Not detected |
B5 | Sample 28 | Valid | — | — | Not detected |
C5 | Sample 29 | Valid | 32.1 |
|
|
D5 | Sample 30 | Valid | — | — | Not Detected |
E5 | Sample 31 | Valid | 22.42 |
|
|
F5 | Sample 32 | Valid | — | — | Not detected |
G5 | Sample 33 | Valid | — | — | Not detected |
H5 | Sample 34 | Valid | — | — | Not detected |
A6 | Sample 35 | Valid | — | — | Not detected |
B6 | Sample 36 | Valid | — | — | Not detected |
C6 | Sample 37 | Valid | — | — | Not detected |
D6 | Sample 38 | Valid | 20.12 |
|
|
E6 | Sample 39 | Valid | — | — | Not detected |
F6 | Sample 40 | Valid | 21.27 |
|
|
G6 | Sample 41 | Valid | — | — | Not detected |
H6 | Sample 42 | Valid | — | — | Not detected |
A7 | Sample 43 | Valid | — | — | Not detected |
B7 | Sample 44 | Valid | 23.48 |
|
|
C7 | Sample 45 | Valid | — | — | Not detected |
D7 | Sample 46 | Valid | — | — | Not detected |
E7 | Sample 47 | Valid | 32.2 |
|
|
F7 | Sample 48 | Valid | — | — | Not detected |
G7 | Sample 49 | Valid | — | — | Not detected |
H7 | Sample 50 | Valid | — | — | Not detected |
Renal transplant recipients showed relatively high levels of sCD30 which ranged from 2.252 U/mL to 97.144 U/mL, mean =
Mean serum level of sCD30 in renal transplant recipients and controls.
All serum sample positive for BKV had serum level of sCD30 beyond the normal limit (20 U/mL). Correlation test revealed positive significant correlation between the log of BKV loads and serum levels of sCD30 (
The association between sCD30 and BKV load.
The quantification of BK virus load in blood is a useful tool not only for diagnosis of BKV nephropathy but also for monitoring the response to the therapy. When this quantification is associated with estimation of serum levels of sDC30, it can give valuable information to decide how to deal with the immunosuppressive regime that is given for the patients and represent a prognostic factor for the possible graft rejection.
The only significant risk factor for BKV in this study was patient’s age. In fact, it is unfair to exclude the other factors which appeared nonsignificant perhaps due to the relative small size of the sample. Anyhow, it is well documented that older age is a risk factor for BKV [
The result of the current study revealed that 22% of the RTRs are positive for BKV. This result disagreed with that of Al-Obaidi et al. [
There is no consensus about the cut-off viral load of BKV which could be considered of clinical importance, although a retrospective study has suggested that a BK virus load > 4 log copies/mL is strongly associated with finding BKV on biopsy [
In many cases, viral infections could result in an elevation in sCD30. For instance, Fattovich et al. [
To explain this discrepancy, we must keep in mind that immune suppressors skew the balance in favor of graft tolerance by promoting the regulatory (Foxp3+, CD4+, and CD25+) T cells while inhibiting the cytotoxicity of T effector cells [
Elevated serum levels of sCD30 in RTRs were recorded in many previous studies and were used as a bad prognostic factor for graft rejection [
One limitation of this study is that both BKV load and sCD30 levels were only evaluated once due to technical and funding difficulties. It is expected that BKV load undergoes fluctuations with the time influenced by host’s immunity status. On the other hand, sCD30 levels do not just reflect the activation of immunity against the virus but may also reflect the activation of alloreactive cells. Thus, performing serial measurements of sCD30 and BKV load can give better evaluation of sCD30 as a sensible biomarker for BKV infection in RTRs with nephropathy.
However, the results of the present study positively suggest that BKV associates with an elevation in the serum levels of sCD30, and this marker can be used as an indicator not only for the risk of graft rejection but also for the possible replication of BKV.
The authors have declared that no conflict of interests exists.
The authors thank all the staff of Virology/Al-Kadhimiya Hospital for help in collection of patient samples and Medical Research Unit, School of Medicine, University of AL-Nahrain, for all support during the work period and they thank Dr. Qasim Sharhan for critical comments and technical assistance.