Abstract
Objectives:
Many studies have attempted to locate a connection between various genetic factors and the pathogenesis of certain diseases. A number of these have found human leukocyte antigens (HLAs) to be the most significant genetic factors affecting the susceptibility of an individual to a certain disease. The present case-control study aimed to determine the connection between class I and class II HLAs and cases of hypertensive end-stage renal failure (HESRF), as contrasted with healthy controls, in Yemen.
Methods:
The study was carried out between March 2013 and March 2014 and included 50 HESRF patients attending the Urology & Nephrology Center at Al-Thawra University Hospital in Sana’a, Yemen, and 50 healthy controls visiting the same centre for kidney donation. Among both patients and controls, HLA class I (A, B and C) and class II (DRB1) genotypes were determined by polymerase chain reactions.
Results:
There was an association (odds ratio: 4.0) with HLA-A9(24) and HESRF, although this was not statistically significant. A significant protective function was found for the HLA-CW3 and DRB1-8 genes against the development of HESRF. Although HLA-B14 was present in some patients (0.06) and not in the controls, this difference was not statistically significant enough to conclude that HLA-B14 plays a role in the genetic predisposition for end-stage renal disease development. There was a high frequency of HLA-A2, B5, CW6, DRB1-3, DRB1-4 and DRB1-13 in both patients and controls.
Conclusion:
Although no HLAs were found to play a highly significant role in genetic predisposition to HESRF, certain HLA genes could be considered as protective genes against HESRF development.
Keywords: Hypertension; Renal Failure, End-Stage; HLA Antigens; Case-Control Study; Yemen
Advances in Knowledge
- This study gives information about human leukocyte antigens (HLA) in individuals from Yemen and investigates the relationship between HLAs and hypertensive end-stage renal failure (HESRF).
- This study provides important information as it is the first time that the frequency of HLA genes in the general Yemeni population and in HESRF Yemeni patients has been investigated.
- The findings revealed an association between HLA-A9(24) and HESRF and a highly significant protective function for the HLA-CW3 and DRB1-8 genes against HESRF development.
Application to Patient Care
- Research in the HLA field is still in its early stages in Yemen. It is therefore necessary to study the relationship between HLAs and various diseases in Yemen in order to improve treatment options for affected patients.
- The incidence and social burden of end-stage renal disease is growing. Slowing or preventing the progression of this disease to renal failure is an important public health priority.
The progression of chronic renal failure (CRF) usually leads to end-stage renal disease (ESRD), at which point renal replacement therapy is the only option. Since the mid-1980s, there has been a noticeable rise in the incidence and prevalence of ESRD around the world.1–4 Gender, genetic profile, ethnicity, lipids, hypertension and smoking have been identified as factors which can influence the development of ESRD.4,5 However, there is a need for further research to be carried out on the role of the immune system in renal diseases, as this could be the origin or cause of the disease and its progression.6 This theory is the outcome of investigations into positive relations between human leukocyte antigens (HLAs) and a broad variety of renal diseases.6 Studies have illustrated some significant associations between HLA class I and II alleles with renal diseases. Methods for associating HLAs with renal disease have been developed since the late 1980s, mostly as a result of more detailed knowledge of class I and II molecules and their structure and function. HLA phenotypes are interrelated, with an increased or reduced risk of alloantibody sensitisation in ESRD candidates for first or repeat kidney transplantation.6
The incidence and prevalence of ESRD and its relationship with class I and II HLA alleles in patients from Yemen and other Middle Eastern and Arab countries has only recently been studied due to deficiencies in national epidemiological research. Prior to this study, no information was available on the frequency of class I and II HLAs, either in the Yemeni population in general or in hypertensive end-stage renal failure (HESRF) patients. As such, this case-control study aimed first to determine the relationship between HLA class I (A, B and C) and class II (DRB1) with HESRF. Second, it aimed to compare the HLAs found to have a relationship with HESRF with those from other races or national groups outside of Yemen in a literature review. Third, this study was designed to determine the potential genes that might give protection from HESRF development.
Methods
This case-control study was carried out over a 12-month period between March 2013 and March 2014. A total of 100 individuals were enrolled in the study; the patient group comprised 50 adults with HESRF while the control group consisted of 50 healthy adult individuals. All patients and controls originated from Sana’a, Yemen. The patient group consisted of 40 males and 10 females (aged from 18 to 57 years) who had attended the Urology & Nephrology Center at Al-Thawra University Hospital in Sana’a for a kidney transplant. Hypertension was the cause of renal failure in all of these patients. All of the patients showed proteinuria and underwent a kidney biopsy to exclude an extensive focal and global glomerulosclerosis association with the APOL1 gene. All HESRF patients in the study were on haemodialysis before they underwent kidney transplantation.
The control group consisted of 32 males and 18 females (aged from 18 to 57 years) who had visited the Urology & Nephrology Center at Al-Thawra University Hospital for a kidney donation. They were confirmed to be healthy following a clinical examination by specialist physicians. As age and gender does not influence an individual’s HLA frequency profile, the control group was not age- and gender-matched with the patient group. Both the patients and controls were required to undergo certain tests, including blood pressure, abdominal ultrasound, complete blood count, blood sugar, kidney and liver function tests. In addition, a general urine examination and a 24-hour urine examination for protein detection and creatinine clearance were carried out. Results for all of the aforementioned tests were normal in the control group.
HLA genotyping was completed for each individual in the patient and control groups. Blood specimens were collected and treated with ethylenediaminetetraacetic acid. As the time of blood collection has no effect on genotyping results, blood specimens were collected whenever patients arrived at the hospital. Blood specimens from both groups were used for HLA class I (A, B and C) and class II (DRB1) genotyping.
The typing of all of the subjects’ HLA-A, -B, -C and -DRB1 alleles were identified using low-resolution BAGene Sequence Specific Primers polymerase chain reaction kits (BAG Health Care GmbH, Lich, Germany). The tests were carried out according to the manufacturer’s instructions. The genomic DNA of each sample was purified using the spin columns method of the QIAGEN DNA purification kit (QIAGEN, Hilden, Germany). Allele frequencies in HESRF patients and controls were calculated by direct counting.7
The association of HESRF with HLA-I alleles was analysed by comparing the frequency of HLA-A and -B alleles in the HESRF patients with those in the 50 healthy controls. The maximum likelihood method was used to evaluate the haplotype frequencies for the two loci of HLA. The Chi-squared test for two-way tables after Yates correction for continuity was used to define the differences between allele frequencies in patients and controls, using the Epi Info™ programme, Version 6 (Centers for Disease Control and Prevention, Atlanta, USA). The odds ratios (OR) with 95% confidence intervals (CI) were calculated. A P value of <0.05 was considered significant.
The study was approved by the Department of Medical Microbiology & Clinical Immunology in the Faculty of Medicine & Health Sciences at Sana’a University, Yemen. Written consent was obtained from all of the participants in the study.
Results
The age and gender of the subjects in the patient and control groups are shown in Table 1. The HESRF patients’ mean age was 38.03 ± 10.9 years and that of the controls was 35.15 ± 8.9 years (range: 18–57 years for both groups). A total of 40 patients (80%) were male and the remaining 10 patients (20%) were female. There were 32 male (64%) and 18 female (36%) controls [Table 1].
Table 1:
Age and gender of Yemeni hypertensive-end stage renal failure cases and controls
| Characteristic | Patient group | Control group | Total | |||
|---|---|---|---|---|---|---|
| n | % | n | % | n | % | |
| Age in years | ||||||
| 18–27 | 35 | 70 | 31 | 62 | 66 | 66 |
| 28–37 | 8 | 16 | 12 | 24 | 20 | 20 |
| 38–47 | 5 | 10 | 6 | 12 | 11 | 11 |
| 48–57 | 2 | 4 | 1 | 2 | 3 | 3 |
| Gender | ||||||
| Male | 40 | 80 | 32 | 64 | 72 | 72 |
| Female | 10 | 20 | 18 | 36 | 28 | 28 |
| Total | 50 | 100 | 50 | 100 | 100 | 100 |
The results showed that HLA-A2 and A9 had the highest frequency among HLA-A alleles in the patients (0.48 and 0.18); HLA-A2 and A3 were most frequent among the controls (0.48 and 0.16). HLA-A28 and A1 were the next most frequent alleles in the patient group, whereas HLA-A28 and A9 were the next most frequent alleles in the controls. A comparison of the frequency of HLA-A alleles in the patients and controls showed higher frequencies of HLA-A9(24) (OR = 4.0, 95% CI = 0.42–103.9; P = 0.16) and A9 (OR = 1.98; P = 0.24) and lower frequencies of HLA-A19(30) (OR = 0.0; P = 0.04) and A19(33) (OR = 0.23; P = 0.16) in the HESRF patients [Table 2].
Table 2:
Human leukocyte antigen-A (HLA-A) and gene frequency in Yemeni hypertensive-end stage renal disease patients and healthy controls (N = 100)
| HLA-A | Patients | Controls | Odds ratio (95% confidence interval) | P value* | ||||
|---|---|---|---|---|---|---|---|---|
| n | Antigen frequency | Gene frequency | n | Antigen frequency | Gene frequency | |||
| 1 | 7 | 0.14 | 0.072 | 4 | 0.08 | 0.040 | 1.9 (0.5–8.3 | 0.33 |
| 2 | 24 | 0.48 | 0.279 | 24 | 0.48 | 0.279 | 1 (0.4–2.4) | 0.84 |
| 3 | 3 | 0.06 | 0.030 | 8 | 0.16 | 0.083 | 0.34 (0.1–1.5) | 0.11 |
| 9 | 9 | 0.18 | 0.094 | 5 | 0.10 | 0.051 | 1.98 (0.54–7.5) | 0.24 |
| 9(23) | 5 | 0.10 | 0.051 | 3 | 0.06 | 0.030 | 1.74 (0.3–9.8) | 0.48 |
| 9(24) | 4 | 0.08 | 0.040 | 1 | 0.02 | 0.010 | 4.0 (0.42–103.9) | 0.16 |
| 10 | 1 | 0.02 | 0.010 | 4 | 0.08 | 0.040 | 0.23 (0.01–2.3) | 0.18 |
| 10(25) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.3 |
| 10(26) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.3 |
| 11 | 2 | 0.04 | 0.020 | 3 | 0.06 | 0.030 | 0.65 (0.1–5.1) | 0.6 |
| 19 | 3 | 0.06 | 0.015 | 5 | 0.10 | 0.051 | 0.6 (0.1–2.99) | 0.46 |
| 19(24) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 19(29) | 1 | 0.02 | 0.010 | 1 | 0.02 | 0.010 | 1 (0.0–37.8) | 0.84 |
| 19(30) | 0 | 0.00 | 0.000 | 4 | 0.08 | 0.040 | 0.0 (0.0–1.5) | 0.04 |
| 19(31) | 0 | 0.00 | 0.000 | 2 | 0.04 | 0.020 | 0.0 (0.0–4.1) | 0.15 |
| 19(32) | 3 | 0.06 | 0.030 | 2 | 0.04 | 0.020 | 1.5 (0.2–13.8) | 0.64 |
| 19(33) | 1 | 0.02 | 0.010 | 4 | 0.08 | 0.040 | 0.23 (0.01–2.37) | 0.16 |
| 23 | 0 | 0.00 | 0.000 | 2 | 0.04 | 0.020 | 0.0 (0.0–4.1) | 0.15 |
| 24 | 0 | 0.00 | 0.000 | 2 | 0.04 | 0.020 | 0.0 (0.0–4.1) | 0.15 |
| 28 | 8 | 0.16 | 0.083 | 6 | 0.12 | 0.062 | 1.4 (0.4–5.03) | 0.56 |
| 29 | 2 | 0.04 | 0.020 | 0 | 0.00 | 0.000 | Undefined | 0.15 |
| 30 | 2 | 0.04 | 0.020 | 4 | 0.08 | 0.04 | 0.48 (0.06–3.2) | 0.4 |
| 31 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 32 | 2 | 0.04 | 0.020 | 1 | 0.02 | 0.010 | 2.04 (0.14–58.9) | 0.55 |
| 33 | 3 | 0.06 | 0.030 | 5 | 0.10 | 0.051 | 0.6 (0.1–2.99) | 0.46 |
| 36 | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0.0 (0.0–17.6) | 0.31 |
| 80 | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0.0 (0.0–17.8) | 0.31 |
P <0.05 was considered statistically significant.
The most numerous HLA-B allele in the patients was HLA-B5. This allele was articulated in the HESRF patients at a higher frequency in comparison to the controls (0.26 versus 0.18; OR = 1.65; P = 0.33). On the other hand, the HLA-B16(38), 21(49), 70 and 73 alleles were among the least expressed HLA-B alleles in the patients. A total of 10 alleles were not found at all in the control group (B14, 21[44], 21[45], 27, 40, 40[60], 50, 51, 53, 62 and 78). The most frequent alleles expressed in the control subjects was HLA-B5 (OR = 1.65; P = 0.33) and B35 (OR = 0.46; P = 0.21). HLA-B21 and 21(50) were also observed at a lower frequency in the patients compared to the controls (OR = 0.47; P = 0.29 each) [Table 3].
Table 3:
Human leukocyte antigen-B (HLA-B) and gene frequency in Yemeni hypertensive end-stage renal disease patients and healthy controls (N = 100)
| HLA-B | Patients | Controls | Odds ration (95% confidence interval) | P value* | ||||
|---|---|---|---|---|---|---|---|---|
| n | Antigen frequency | Gene frequency | n | Antigen frequency | Gene frequency | |||
| 5 | 13 | 0.26 | 0.139 | 9 | 0.18 | 0.094 | 1.65 (0.6–4.6) | 0.33 |
| 5(51) | 4 | 0.08 | 0.040 | 4 | 0.08 | 0.040 | 1.0 (0.2–5.1) | 0.84 |
| 5(52) | 2 | 0.04 | 0.020 | 1 | 0.02 | 0.010 | 2 (0.14–5.8) | 0.55 |
| 7 | 3 | 0.06 | 0.030 | 5 | 0.10 | 0.051 | 0.6 (0.1–2.99) | 0.46 |
| 8 | 4 | 0.08 | 0.040 | 3 | 0.06 | 0.030 | 1.4 (0.24–8.2) | 0.7 |
| 12 | 1 | 0.02 | 0.010 | 2 | 0.04 | 0.020 | 0.49 (0.02–7.23) | 0.55 |
| 12(44) | 7 | 0.14 | 0.073 | 5 | 0.10 | 0.051 | 1.47 (0.38–5.8) | 0.53 |
| 13 | 2 | 0.04 | 0.020 | 1 | 0.02 | 0.010 | 2.04 (0.14–5.8) | 0.55 |
| 14 | 3 | 0.06 | 0.030 | 0 | 0.00 | 0.000 | Undefined | 0.07 |
| 16 | 1 | 0.02 | 0.010 | 3 | 0.06 | 0.030 | 0.32 (0.01–3.6) | 0.3 |
| 16(38) | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0 (0.0–17.5) | 0.31 |
| 16(39) | 1 | 0.02 | 0.010 | 2 | 0.04 | 0.020 | 0.49 (0.02–7.2) | 0.55 |
| 17 | 6 | 0.12 | 0.062 | 6 | 0.12 | 0.062 | 1 (0.26–3.1) | 0.84 |
| 17(57) | 2 | 0.04 | 0.020 | 5 | 0.10 | 0.051 | 0.38 (0.05–2.3) | 0.23 |
| 17(58) | 1 | 0.02 | 0.010 | 1 | 0.02 | 0.012 | 1 (0.0–37.8) | 0.84 |
| 18 | 5 | 0.10 | 0.051 | 3 | 0.06 | 0.030 | 1.7 (0.3–9.8) | 0.46 |
| 21 | 3 | 0.06 | 0.030 | 6 | 0.10 | 0.060 | 0.47 (0.1–2.3) | 0.29 |
| 21(44) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 21(45) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 21(49) | 0 | 00.00 | 0.000 | 2 | 0.04 | 0.020 | 0.0 (0.0–4.1) | 0.15 |
| 21(50) | 3 | 0.06 | 0.030 | 6 | 0.12 | 0.062 | 0.47 (0.09–2.3) | 0.29 |
| 22 | 1 | 0.02 | 0.010 | 1 | 0.02 | 0.010 | 1 (0.0–37) | 0.84 |
| 27 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 35 | 4 | 0.08 | 0.041 | 8 | 0.16 | 0.083 | 0.46 (0.11–1.8) | 0.21 |
| 37 | 2 | 0.04 | 0.020 | 2 | 0.04 | 0.020 | 1 (0.1–10.5) | 0.84 |
| 40 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 40(60) | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 41 | 4 | 0.08 | 0.041 | 4 | 0.08 | 0.041 | 1 (0.19–5.14) | 0.84 |
| 50 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 51 | 2 | 0.04 | 0.020 | 0 | 0.00 | 0.000 | Undefined | 0.15 |
| 52 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 53 | 6 | 0.12 | 0.062 | 4 | 0.08 | 0.041 | 1.6 (0.4–7.2) | 0.5 |
| 62 | 1 | 0.02 | 0.010 | 0 | 0.00 | 0.000 | Undefined | 0.31 |
| 70 | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0.0 (0.0–17.5) | 0.31 |
| 72 | 1 | 0.02 | 0.010 | 2 | 0.04 | 0.020 | 0.49 (0.02–7.2) | 0.55 |
| 73 | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0.0 (0.0–17.5) | 0.31 |
| 78 | 2 | 0.04 | 0.020 | 0 | 0.00 | 0.000 | Undefined | 0.15 |
P <0.05 was considered statistically significant.
The results showed that HLA-CW6 and CW7 had the highest frequency among HLA-CW alleles in the patients (0.44 and 0.38, respectively) and the controls (0.52 and 0.38, respectively). HLA-CW4 and CW2 were the next most frequent alleles in the patients (0.28 and 0.12, respectively); HLA-CW4 and CW3 were next most frequent in the controls (0.26 and 0.14, respectively). In comparison, the HLA-CW3 allele was not found among the patients (P = 0.006), indicating a probable protective function [Table 4].
Table 4:
Human leukocyte antigen-CW (HLA-CW) and gene frequency in Yemeni hypertensive end-stage renal disease patients and healthy controls (N = 100)
| HLA-CW | Patients | Controls | Odds ratio (95% confidence interval) | P value* | ||||
|---|---|---|---|---|---|---|---|---|
| n | Antigen frequency | Gene frequency | n | Antigen frequency | Gene frequency | |||
| 1 | 1 | 0.02 | 0.010 | 1 | 0.02 | 0.010 | 1 (0.0–3.7) | 0.84 |
| 2 | 6 | 0.12 | 0.062 | 6 | 0.12 | 0.062 | 1 (0.26–3.9) | 0.84 |
| 3 | 0 | 0.00 | 0.000 | 7 | 0.14 | 0.072 | 0 (0.0–0.72) | 0.006 |
| 4 | 14 | 0.28 | 0.151 | 13 | 0.26 | 0.139 | 1.1 (0.42–2.9) | 0.82 |
| 5 | 1 | 0.02 | 0.010 | 3 | 0.06 | 0.030 | 0.3 (0.01–3.6) | 0.30 |
| 6 | 22 | 0.44 | 0.252 | 26 | 0.52 | 0.307 | 0.73 (0.3–1.7) | 0.42 |
| 7 | 19 | 0.38 | 0.213 | 19 | 0.38 | 0.213 | 1 (0.41–2.4) | 0.84 |
P <0.05 was considered statistically significant.
The results showed that DRB1-4 and 13 had the highest frequency among DRB1 alleles in the patients (0.32 and 0.34, respectively) and controls (0.42 and 0.30, respectively). DRB1-3 was the next most frequent allele in the patients and controls (0.26 each). A comparison of the frequency of DRB1 alleles among those in the patient and control groups showed higher frequencies of DRB1-8 in the controls (0.12), while in the patients it was 0.02 (OR = 0.15; P = 0.05), indicating a probable protective function. In addition, a comparison of the frequency of DRB1 alleles between both groups showed higher frequencies of DRB1-10 (OR = 2.3, 95% CI = 0.71–7.8; P = 0.11) and 15 (OR = 2.3, 95% CI = 0.63–8.4; P = 0.16) and lower frequencies of 8 (OR = 0.15; P = 0.05) in the HESRF patients [Table 5].
Table 5:
Human leukocyte antigen-DRB1 (HLA-DRB1) and gene frequency in Yemeni hypertensive end-stage renal disease patients and healthy controls (N = 100)
| HLA-DRB1 | Patients | Controls | Odds ratio (95% confidence interval) | P value* | ||||
|---|---|---|---|---|---|---|---|---|
| n | Antigen frequency | Gene frequency | n | Antigen frequency | Gene frequency | |||
| 1 | 7 | 0.14 | 0.072 | 9 | 0.18 | 0.094 | 0.74 (0.22–2.4) | 0.58 |
| 3 | 13 | 0.26 | 0.139 | 13 | 0.26 | 0.139 | 1 (0.37–2.7) | 0.84 |
| 4 | 16 | 0.32 | 0.175 | 21 | 0.42 | 0.238 | 0.65 (0.26–1.6) | 0.3 |
| 7 | 7 | 0.14 | 0.073 | 9 | 0.18 | 0.094 | 0.74 (0.22–2.4) | 0.58 |
| 8 | 1 | 0.02 | 0.010 | 6 | 0.12 | 0.060 | 0.15 (0.01–1.3) | 0.05 |
| 10 | 12 | 0.24 | 0.128 | 6 | 0.12 | 0.060 | 2.3 (0.71–7.8) | 0.11 |
| 11 | 5 | 0.10 | 0.051 | 3 | 0.06 | 0.030 | 1.74 (0.33–9.9) | 0.46 |
| 12 | 0 | 0.00 | 0.000 | 1 | 0.02 | 0.010 | 0.0 (0.0–176) | 0.31 |
| 13 | 17 | 0.34 | 0.188 | 15 | 0.30 | 0.163 | 1.2 (0.48–3.0) | 0.66 |
| 14 | 3 | 0.06 | 0.030 | 1 | 0.02 | 0.010 | 3.13 (0.3–80.9) | 0.30 |
| 15 | 10 | 0.20 | 0.106 | 5 | 0.10 | 0.051 | 2.3 (0.63–8.4) | 0.16 |
| 16 | 4 | 0.08 | 0.040 | 5 | 0.10 | 0.051 | 0.78 (0.16–3.7) | 0.72 |
P <0.05 was considered statistically significant.
Discussion
Renal failure is mainly caused by a patient suffering from chronic high blood pressure over a period of many years. Hypertension is also the second main cause, after diabetes, of ESRD and is accountable for 25–30% of all reported cases.8 Hypertension is an important risk factor for the progression of ESRD in women as well as men.9 Certain ethnicities, such as those of black African origin, have a high prevalence of the more severe form of hypertension; in addition, these patients have a higher prevalence of hypertension occurring at an earlier age than patients of white Caucasian origin.10 Essentially, hypertension suggests that at least one of the genes to blame for the genetic susceptibility to ESRD is to be found in or close to the HLA complex.11,12
Many studies have been performed worldwide on the HLA complex and disease, including in various Arab countries, but this type of research is still in its infancy in Yemen. Indeed, to the best of the authors’ knowledge, the current study was the first in Yemen on HLA typing. The annual incidence of ESRD in Yemen is 120 per million which is comparable to the incidence reported in other countries of the same region.13 This study aimed mainly to investigate the association between HLAs (A, B, CW and DRB1) and HESRF in comparison with healthy individuals.
In this study, the male-to-female patient ratio was 4:1. The high prevalence of renal disease among males might be due to physiological differences between the genders as well as the higher susceptibility of males to hypertension, which can lead to renal failure. The higher prevalence of hypertension among males in this study was in agreement with the findings of another study, which reported a male-to-female ratio of 2:1.14 The present study also concurred with that of Hsu et al., who reported that the male gender was a risk factor for ESRD.15 Another possible reason could be the statistically small sample size of females in the current study, partly due to the fact that Yemeni females have less access than males to medical services due to social and cultural reasons.16
The findings of this study revealed the phenotypic and gene frequencies of the HLA-A, HLA-B, HLA-CW and HLA-DRB1 genes in 100 Yemenis (50 patients and 50 controls). HLA-B14 was found in three patients, but was not identified in the controls. The patients, as compared to the controls, had lower frequencies of certain HLA genes such as HLA-A19(30), CW3 and DRB1-8. These genes were found in the controls but not in the patients, apart from DRB1-8 which was found in one patient.
On the other hand, there was no statistically significant difference between the renal failure patients and the controls; this suggests that there are no HLA genes predisposing to ESRD. This result was in agreement with those of Agrawal et al. and Prasanavar et al. who determined that HLA and haplotype frequencies were not significantly different in renal transplant patients and healthy donors.17,18 This contrasts sharply with another study that compared race-matched controls of white Caucasian and black African ethnicity and showed how genetic differences associated with the HLA system accounted for racial differences in hypertensive renal failure.19 A comparison between patients of white Caucasian and black African ethnicity with hypertensive renal failure demonstrated that the patients of black African origin had an increased frequency of HLA-DR3 alleles, which was greater than that normally known to exist among healthy individuals.19
These outcomes differ from the results of the current study which found no statistically significant differences between the patients and controls. However, this might be due to the fact that patients and healthy controls in this study were genetically similar; in fact, some of the patients and controls were related by family. However, the authors of the current study were of the opinion that it can be helpful to compare relatives; if there is a higher frequency of similar genes it is easier to indicate susceptibility to the disease rather than to race. It may also be the case that patients and controls were subjected to similar racial, genetic and environmental factors that may contribute to the development of ESRD.
Zachary et al. also found that frequencies of HLA alleles and their distribution among donors and renal patients in the United Network for Organ Sharing (UNOS) registry varied between races.20 However, no difference was found in disease susceptibility; this was in agreement with the current study. Similarly, several studies have indicated racial differences in HLAs and their relationships with many diseases.4 The results of the current study were similar to those of Crispim et al. who described associations of class I and II HLAs with ESRD, independent of other factors, among CRF patients with a variety of diagnoses.21 Crispim et al. found that the antigens positively associated with ESRD were HLA-A78 and HLA-DR11.21
In a previous study among Mapuche and non-Mapuche people in Chile, HLA-B8 alleles were found significantly more frequently in Mapuche recipients than in non-Mapuche recipients and Mapuche donors.22 This result differs to that of the current study, in which HLA-B8 alleles were roughly similar in both the patients and the controls. On the other hand, there was no positive association of HLA-A2 alleles with ESRD in the current study; this is similar to the findings reported among the Zulian population in Venezuela, in which HLA-A2 alleles were also not associated with ESRD.6
The most numerous HLA-B allele in patients was HLA-B5. This allele was articulated in the HESRF patients at a higher frequency in comparison to the controls (0.26 versus 0.18). This result is different from that reported among the Zulian population in Venezuela, in which HLA-B5 was less frequent in both ESRF patients and controls (3.9% and 2.4%, respectively).6
In the current study, a comparison of the frequency of HLA-CW alleles showed considerably higher frequencies of HLA-CW3 among the controls than the patients (P = 0.006), indicating the protective function of HLA-CW3. This result is different from that reported in thyrotoxicosis patients, in whom HLA-CW3 was found to be significantly increased in patients with endocrine ophthalmopathy (EOP) compared to thyrotoxic patients without EOP.23 However, as yet, there have been no reported findings regarding the protective function of HLA-CW3 alleles in renal diseases.
A comparison of the frequency of DRB1 alleles in the patients and controls showed higher frequencies of DRB1-8 in the control group than the patient group (P = 0.05), indicating the protective function of DRB1-8. This result is different to that reported among Hispanic renal recipient patients, in which DRB1-8 was found to be significantly increased in patients with renal failure compared with healthy donors (15% versus 0%).17
The results of this study demonstrate that HLA-A2, A9, B5, CW6, CW7, DRB1-4 and DRB1-13 have very high frequencies among the HLA alleles in both patients and controls in the studied population. This result matches those of studies performed on the frequency of HLAs in Iraqi, Emirati and Lebanese populations.24–26 In addition, comparing the antigen frequencies in the current study to those from kidney recipients and donors of other ethnic groups (i.e. African-Americans, Caucasians, Asians and Hispanics) included in the UNOS renal registry data on HLA-A, B and DR loci showed that, while the population in the current study differed from the other groups in certain respects, there was a similarity with Hispanics and Caucasians in the highest frequencies of HLA alleles.17
The diversity of the findings of different researchers may be due to the considerable irregularity in the frequency of HLA alleles present in different populations or ethnic groups. A further cause may be the unequal relationship between these HLA alleles and other nearby genes involved in accommodating the immune response. An example of this is reported by Ranganath et al.; they stated that polymorphisms in genes encoding certain cytokines, including interleukin (IL)-6, IL-4 and tumour necrosis factor, may be affected in the progression to ESRD.27
This study had the limitation of being under-powered as only 50 patients were studied. However, it has laid the groundwork for future case-control studies in Yemen with larger sample sizes of cases and controls. These future studies should aim to confirm the connection between class I and II HLAs and cases of HESRF as compared with healthy controls.
Conclusion
This study found a high association between HLA-A9(24) and HESRF and a highly significant protective function for the HLA-CW3 and DRB1-8 genes against HESRF development. At the same time, the findings showed no significant role for other HLA molecules in the predisposition to developing ESRD among Yemeni patients. Although the HLA-B14 gene was found only in the patients and not in the control group, this difference was not statistically significant enough to conclude that the B14 gene is involved in a genetic predisposition to ESRD development. Certain HLA genes, such as HLA-A2, B5, CW6 and DRB1-3, DRB1-4 and DRB1-13, were found to have a high frequency in both the patients and the controls.
Footnotes
CONFLICT OF INTEREST
The authors declare no conflicts of interest.
References
- 1.National Kidney Foundation K/DOQI clinical practice guidelines for chronic kidney disease: Evaluation, classification, and stratification. Am J Kidney Dis. 2002;39:S1–266. doi: 10.1016/S0272-6386(02)70084-X. [DOI] [PubMed] [Google Scholar]
- 2.National Institutes of Health . United States Renal Data System, USRDS 2010 Annual Data Report: Atlas of Chronic Kidney Disease and End-Stage Renal Disease in the United States. Bethesda, Maryland, USA: National Institute of Diabetes and Digestive and Kidney Diseases; 2010. [Google Scholar]
- 3.National Institutes of Health United . States Renal Data System USRDS 2013 Annual Data Report: Atlas of Chronic Kidney Disease and End-Stage Renal Disease in the United States. Bethesda, Maryland, USA: National Institute of Diabetes and Digestive and Kidney Diseases; 2013. [Google Scholar]
- 4.Centers for Disease Control and Prevention (CDC) Prevalence of chronic kidney disease and associated risk factors: United States, 1999–2004. MMWR Morb Mortal Wkly Rep. 2007;56:161–5. [PubMed] [Google Scholar]
- 5.de Menthon M, LaValley MP, Maldini C, Guillevin L, Mahr A. HLA–B51/B5 and the risk of Behçet's disease: A systematic review and meta-analysis of case-control genetic association studies. Arthritis Rheum. 2009;61:1287–96. doi: 10.1002/art.24642. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Sergio RP, Marquez G, Cipriani AM, Hassanhi M, Villalobos CC, Fuenmayor A, et al. HLA class I association with progression to end-stage renal disease in patients from Zulia, Venezuela. Inmunologia. 2012;31:37–42. doi: 10.1016/j.inmuno.2011.12.001. [DOI] [Google Scholar]
- 7.Excoffier L, Laval G, Schneider S. Arlequin (version 3.0): An integrated software package for population genetics data analysis. Evol Bioinform Online. 2005;1:47–50. [PMC free article] [PubMed] [Google Scholar]
- 8.Narins B, editor. The Gale Encyclopedia of Genetic Disorders. 2nd ed. Farmington Hills, Michigan, USA: Thomas Gale; 2005. [Google Scholar]
- 9.Tozawa M, Iseki K, Iseki C, Kinjo K, Ikemiya Y, Takishita S. Blood pressure predicts risk of developing end-stage renal disease in men and women. Hypertension. 2003;41:1341–5. doi: 10.1161/01.HYP.0000069699.92349.8C. [DOI] [PubMed] [Google Scholar]
- 10.Lackland DT, Orchard TJ, Keil JE, Saunders DE, Jr, Wheeler FC, Adams-Campbell LL, et al. Are race differences in the prevalence of hypertension explained by body mass and fat distribution? A survey in a biracial population. Int J Epidemiol. 1992;21:236–45. doi: 10.1093/ije/21.2.236. [DOI] [PubMed] [Google Scholar]
- 11.Gerbase-DeLima M, Ladalardo MA, DeLima JJ, Silva HB, Bellotti G, Pileggi F. Essential hypertension and histocompatibility antigens: An association study. Hypertension. 1992;19:400–2. doi: 10.1161/01.HYP.19.4.400. [DOI] [PubMed] [Google Scholar]
- 12.Frei U, Schindler R, Wieters D, Grouven U, Brunkhorst R, Koch KM. Pre-transplant hypertension: A major risk factor for chronic progressive renal allograft dysfunction? Nephrol Dial Transplant. 1995;10:1206–11. [PubMed] [Google Scholar]
- 13.El-Nono IH, Al-Ba'adani TH, Ghilan AM, Asba NW, Al- Alimy GM, Al-Massani MM, et al. Adult-to-adult living related donor renal transplantation in Yemen: The first experience. Saudi J Kidney Dis Transpl. 2007;18:265–9. [PubMed] [Google Scholar]
- 14.Roderick PJ, Raleigh VS, Hallam L, Mallick NP. The need and demand for renal replacement therapy in ethnic minorities in England. J Epidemiol Community Health. 1996;50:334–9. doi: 10.1136/jech.50.3.334. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Hsu CY, Iribarren C, McCulloch CE, Darbinian J, Go AS. Risk factors for end-stage renal disease: 25-year follow-up. Arch Intern Med. 2009;169:342–50. doi: 10.1001/archinternmed.2008.605. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Hennekens CH, Buring JE. Analysis of Epidemiologic Studies. In: Mayrent SL, editor. Epidemiology in Medicine. Philadelphia: Lippincott, Williams & Wilkins; 1987. pp. 272–82. [Google Scholar]
- 17.Agrawal S, Singh AK, Sharma RK. HLA gene and haplotype frequency in renal transplant recipients and donors of Uttar Pradesh (North India) Indian J Nephrol. 2001;11:88–97. [Google Scholar]
- 18.Prasanavar D, Shankarkumar U. HLA-antigen and haplotype frequencies in renal transplant recipients and donors of Maharashtra (Western India) Int J Hum Genet. 2004;4:155–9. [Google Scholar]
- 19.Freedman BI, Espeland MA, Heise ER, Adams PL, Buckalew VM, Jr, Canzanello VJ. Racial differences in HLA antigen frequency and hypertensive renal failure. Am J Hypertens. 1991;4:393–8. doi: 10.1093/ajh/4.5.393. [DOI] [PubMed] [Google Scholar]
- 20.Zachary AA, Steinberg AG, Bias WB, Leffell MS. The frequencies of HLA alleles and haplotypes and their distribution among donors and renal patients in the UNOS registry. Transplant. 1996;62:272–83. doi: 10.1097/00007890-199607270-00021. [DOI] [PubMed] [Google Scholar]
- 21.Crispim J, Mendes-Júnior C, Wastowski IJ, Palomino GM, Saber LT, Rassi DM, et al. HLA polymorphisms as incidence factor in the progression to end-stage renal disease in Brazilian patients awaiting kidney transplant. Transplant Proc. 2008;40:1333–6. doi: 10.1016/j.transproceed.2008.02.086. [DOI] [PubMed] [Google Scholar]
- 22.Droguett MA, Beltran R, Ardiles R, Raddatz N, Labraña C, Arenas A, et al. Ethnic differences in HLA Antigens in Chilean donors and recipients: Data from the National Renal Transplantation Program. Translplant Proc. 2008;40:3247–50. doi: 10.1016/j.transproceed.2008.03.065. [DOI] [PubMed] [Google Scholar]
- 23.Mayr WR, Ludwig H, Schernthaner G, Höfer R. HLA CW3 in thyrotoxicosis patients with and without endocrine ophthalmopathy. Tissue Antigens. 1976;7:243–6. doi: 10.1111/j.1399-0039.1976.tb01062.x. [DOI] [PubMed] [Google Scholar]
- 24.Nuwayri-Salti N, Shaya M. Major histocompatibility class I antigens in the Lebanese population. East Mediterr Health J. 1997;3:101–7. [Google Scholar]
- 25.Al-Hassan AAA, Al-Naseri S, Al-Ghurabi BH, Al-Faham M, Al-Nnema AJ, Shereef SM. Distribution of HLA antigens class I and II in Iraqi Arab population. Iraqi J Gastroenterol. 2005;5:2–9. [Google Scholar]
- 26.Valluri V, Mustafa M, Santhosh A, Middleton D, Alvares M, El Haj E, et al. Frequencies of HLA-A, HLA-B, HLA-DR, and HLA-DQ phenotypes in the United Arab Emirates population. Tissue Antigens. 2005;66:107–13. doi: 10.1111/j.1399-0039.2005.00441.x. [DOI] [PubMed] [Google Scholar]
- 27.Ranganath P, Tripathi G, Sharma RK, Sankhwar SN, Agrawal S. Role of non-HLA genetic variants in end-stage renal disease. Tissue Antigens. 2009;74:147–55. doi: 10.1111/j.1399-0039.2009.01276.x. [DOI] [PubMed] [Google Scholar]