Parkinson’s disease-mild cognitive impairment (PD-MCI) is garnering attention as a key interventional period for cognitive impairment. Currently, there are no approved treatments for PD-MCI and encouraging results of transcranial direct current stimulation (tDCS) combined with other interventions have been proposed, though the efficacy and neural mechanisms of tDCS alone have not been studied in PD-MCI yet. The present double-blind, randomized, sham-controlled study assessed the effects of tDCS over the dorsolateral prefrontal cortex on cognitive functions via neuropsychological and electrophysiological evaluations in individuals with PD-MCI for the first time. Twenty-six individuals with PD-MCI were administered 10 sessions of active (n = 13) or sham (n = 13) prefrontal tDCS twice a day, for 5 days. Changes were tested through a comprehensive neuropsychological battery and event-related potential recordings, which were performed before, immediately, and 1 month after the administrations. Neuropsychological assessment showed an improvement in delayed recall and executive functions in the active group. N1 amplitudes in response to targets in the oddball test-likely indexing attention and discriminability and NoGo N2 amplitudes in the continuous performance test-likely indexing cognitive control and conflict monitoring increased in the active group. Active stimulation elicited higher benefits 1 month after the administrations. The present findings substantiate the efficacy of tDCS on cognitive control and episodic memory, along with the neural underpinnings of cognitive control, highlighting its potential for therapeutic utility in PD-MCI. Trial registration. NCT 04,171,804. Date of registration: 21/11/2019.

Human leukocyte antigens (HLA) diversity has a tremendous impact on shaping the transplantation practices, transfusion-associated graft versus host disease prevention strategies, and host–pathogen interactions. Here, we conducted a retrospective study of HLA class I and class II homozygosity at allelic and haplotype levels in unrelated individuals genotyped from 2012 to 2016 in a tertiary hospital in the capital of Saudi Arabia. Among 5,000 individuals, 2,773 individuals meet inclusion criteria and were retrospectively analyzed for HLA-A, -B, -C–DRB1, and -DQB1 homozygosity at allelic and haplotype levels. HLA molecular typing was performed using a commercial reverse sequence-specific oligonucleotide (rSSO) kit. We were able to identify 15 HLA-A, 20 HLA-B, 11 HLA-C, 13 HLA-DRB1, and five HLA-DQB1 homozygous alleles demonstrating a very low genetic diversity in the Saudi population. The highest homozygosity in HLA class I was found in locus C followed by A and B (20.3% > 16.1% > 15.5%; p < 0.001) where the most homozygote alleles were A*02 (9.2%), B*51 and B*50 (5.7% and 3.7%), and C*07, C*06, and C*15 (7.2%, 5.48%, and 3.3%) and in HLA class II, the highest homozygosity was found in locus DQB1 compared to DRB1 (31.71% > 19.2%; p < 0.001), with the most common homozygote alleles being DRB1*07 and DRB1*04 (5.33% and 4.2%) and DQB1*02, DQB1*06, and DQB1*03 (13.55%, 7.92%, and 7.64%). The frequency of finding an individual with one homozygote allele was (24.6%), two homozygote alleles (13.5%), three homozygote alleles (4.7%), four homozygote alleles (3.4%), and five alleles were (4.8%). The most frequent homozygote haplotypes are A*23∼C*06∼B*50∼DRB1*07∼DQB1*02 and A*02∼C*06∼B*50∼DRB1*07∼DQB1*02. This study shows low diversity of both class I and II alleles and haplotypes in the Saudi population, which would have a significant impact on shaping the transplantation practices, transfusion-associated graft versus host disease prevention strategies, and host–pathogen interactions.

Human leukocyte antigen (HLA) allele and haplotype frequency distribution varies widely between different ethnicities and geographical areas. Matching for HLA alleles is essential for successful related and unrelated stem cell transplantation. Among the Saudi population, data on HLA alleles and haplotypes are limited. A cross-sectional study was performed on 28,927 bone marrow donors. The most frequent HLA alleles were HLA-A*02:01:01G (20.2%), A*24:02:01G (7.5%); B*51:01:01G (19.0%), B*50:01:01G (12.3%); C*06:02:01G (16.7%), C*07:02:01G (12.2%); DRB1*07:01:01 (15.7%), DRB1*03:01:01G (13.3%); DQB1*02:01:01G (29.9%), DQB1*03:02:01G (13.2%); and DPB1*04:01:01G (35.2%), DPB1*02:01:02G (21.8%). The most frequent HLA-A~C~B~DRB1~DQB1 haplotypes were A*02:01:01G~C*06:02:01G~B*50:01:01G~DRB1*07:01:01G~DQB1*02:01:01G (1.9%) and A*02:05:01G~C*06:02:01G~B*50:01:01G~DRB1*07:01:01G~DQB1*02:01:01G (1.6%). The most frequent HLA-A~C~B~DRB1~DQB1~DPB1 haplotypes were A*02:01:01G~C*15:02:01G~B*51:01:01G~DRB1*04:02~DQB1*03:02:01G~DPB1*04:01:0G (1%) and A*02:01:01G~C*07:02:01G~B*07:02:01G~DRB1*15:01:01G~DQB1*06:02:01G~ DPB1*04:01:01G (0.9%). Based on these haplotype frequencies, we provide forecasts for the fraction of patients with full matching and single mismatched donors for 3 to 6 loci depending on the registry size. With one million donors, about 50% of the patients would find an 8/8 match and 90% a 7/8 match. These data are essential for registry planning, finding unrelated stem cell donors, population genetic studies, and HLA disease associations.

We analyzed HLA allele and haplotype frequencies from donors from the Eastern region of Saudi Arabia. A cross-sectional study was performed on 2405 bone marrow donors from the Eastern region. HLA typing was carried out by sequencing. The most common HLA allele groups were HLA-A*02:01:01G (11.08%), A*01:01:01G (10.40%), HLA-B*52:01:01G (8.79%), B*18:01:01G (8.07%), HLA-C*04:01:01G (17.88%), C*12:03:01G (10.23%), HLA-DRB1*10:01 (14.89%), DRB1*03:01:01G (14.10%), HLA-DQB1*02:01:01G (24.53%) and DQB1*05:01:01G (20.17%). The most frequent HLA-A~ C~ B~ DRB1~ DQB1 haplotypes were HLA-A*01:03~ C*15:05:01G~ B*73:01~ DRB1*10:01:01~ DQB1*05:01:01G (3.11%) and HLA-A*01:01:01G~ C*12:02:01G~ B*52:01:01G~ DRB1*15:02:01~ DQB1*06:01:01G (2.25%). When comparing the allele and haplotype frequencies of the Eastern regions' population to those from the Central region we found significant differences in several allele frequencies including A*01:01:01G (P ≤ 0.0001), B*52:01:01G (P ≤ 0.0001), B*18:01:01G (P = 0.0001), C*12:03:01G (P < 0.0001), DRB1*10:01:01 (P < 0.0001) and DQB1*05:01:01G (P < 0.0001). Our data confirms genetic heterogeneity among the Saudi population.

BACKGROUND AND OBJECTIVES:Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by humoral autoimmunity. The etiology of SLE is thought to be multifactorial including environmental, hormonal, and genetic factors. The human leukocyte antigen (HLA) has extensively been associated with the susceptibility to SLE; however, the association is heterogeneous among different ethnic groups. The aim of this study was to determine the association of HLA-A, HLA-B, HLA-DRB1, and HLA-DQB1 with SLE susceptibility in the Saudi population.DESIGN AND SETTINGS:A total of 86 consecutive SLE patients attending the rheumatology clinic at King Abdulaziz Medical City, Riyadh, were recruited for this study.METHODS:HLA types were determined by the polymerase chain reaction sequence-specific oligonucleotide (PCR-SSP) method in 86 patients and 356 control subjects.RESULTS:The following HLA alleles were found to be positively associated with SLE: HLA-A*29 (OR=2.70; 95% CI=1.03-7.08; P=.0035), HLA-B*51 (OR=1.81; 95% CI=1.17-2.79; P=.0066), HLA-DRB1*15 (OR=1.45; 95% CI=0.98-2.29; P=.063), and HLA-DQB1*06 (OR=1.67; 95% CI=1.19-2.36; P=.0032), whereas HLA-DRB1*16 was negatively associated with the disease (OR=0.18; 95% CI=0.02-1.3; P=.055). HLA-DRB1*15 haplotypes were significantly associated with SLE (OR=2.01, 95% CI=1.20-3.68, P=.008); this was mainly due to the HLADRB1*15-DQB1*06 association.CONCLUSIONS:Our data suggest an association between MHC class I and class II (HLA-A*29, HLA-B*51, HLA-DRB1*15, and HLA-DQB1*06) and susceptibility to SLE in the Saudi population. HLA-DRB1*15-DQB1*06 haplotype showed the highest risk factor for the disease that is similar to what was seen in the African American patients, suggesting shared susceptibility genetic factors among these ethnic groups.

Next generation sequencing (NGS) is a promising technique that can reveal the entire gene sequences and to the highest possible resolution without any phase ambiguities. We have used this technique to investigate the frequencies of HLA-A, -B, -C, -DRB1 and -DQB1 in a Saudi cohort of healthy individuals. We used NGS using the 454 genome sequence (GS) FLX System and Conexio assign atf 454 software to human leukocyte antigen (HLA) genotype eight class I and class II loci. A total of 158 healthy Saudi adults were analyzed. The most frequently observed allele for HLA-A was HLA-A*02:01:01:01 (13.6%); for HLA-B, HLA-B*50:01:01 (15.8%); for HLA-C, HLA-C*06:02:01:01 (18.7%); for HLA-DRB1, HLA-DRB1*07:01:01:01 (26.6%); and for HLA-DQB1, HLA-DQB1*02:01:01 (20.3%). The most common four loci haplotypes in the Saudi population were HLA-A*24:02:01:01-B*08:01:01-C*07:02:01:01-DRB1*03:01:01:01 and HLA-A*23:01:01-B*50:01:01-C*06:02:01:01-DRB1*07:01:01:01.. We have used a highly informative technique for HLA typing of a Saudi healthy cohort to establish allele and haplotype frequencies. These results should prove useful for population studies, disease associations and future planning of the unrelated bone marrow donor registry.

Aim Next generation sequencing is a promising technique that can reveal the entire gene sequences and to the highest possible resolution without any phase ambiguities. We have employed this technique to investigate the frequencies of HLA-A, -B, -C, -DRB3/4/5, -DRB1, -DQA1, -DQB1 and -DPB1 in a Saudi cohort of healthy individuals. Methods We employed Next Generation Sequencing using the 454 genome sequence (GS) FLX System and Conexio Assign ATF 454 software to HLA genotype eight class I and class II loci. A total of 158 healthy Saudi adults were analyzed. Results The most frequent allele for HLA-A was HLA-A∗02:01:01:01 (13.6%); for HLA-B, HLA-B∗50:01:01 (15.8%); for HLA-C, HLA-C∗06:02:01:01 (18.7%); for HLA-DRB1, HLA-DRB1∗07:01:01:01 (26.6%); for HLA-DRB3/4/5, HLA-DRB4∗01:01:01:01 (44.0%); for HLA-DQA1, HLA- DQA1∗02:01(26.3%); for HLA-DQB1, HLA- DQB1∗02:01:01 (20.3%) and for HLA-DPB1, HLA- DPB1∗04:01:01 (33.2%). By studying Linkage Disequilibrium in this population the following two loci combinations were well represented; B∗50:01:01-C∗06:02:01:01; DRB1∗03:01:01:01-DQB1∗02:01:01; DRB1∗07:01:01:01-DQB1∗02:02. Two extended, conserved haplotypes were well represented in this population; A∗24:02:01:01-B∗08:01:01-C∗07:02:01:01- DRB1∗03:01:01:01-DRB3∗02:02:01-DQA1∗05:01:01- DQB1∗02:01:01-DPB1∗03:01:01 and A∗30:02:01-B∗53:01:01-C∗04:01:01:01-DRB1∗07: 01:01:01-DRB4∗01:01:01:01-DQA1∗02:01-DQB1∗03:03:02- DPB1∗04:01:01. Expected heterozygosity was significantly higher than observed. Conclusions We have used a highly informative technique for HLA typing of a Saudi healthy cohort to establish allele and haplotype frequencies. This should be of great importance for population studies, disease associations and future planning of the unrelated bone marrow donor registry.

The typing for HLA-C in transplantation was rather neglected in the past. However, several recent studies have emphasized its role in transplantation and its association with the outcome. Serological typing of HLA-C could identify only a limited number of HLA-C antigens, resulting in a number of HLA-C blanks. This was mainly due to the low expression of surface HLA-C and the small number of available specific anti-sera. Performing molecular methods has identified new HLA-C alleles and filled the blank of most serological typed antigens. In this study, we compared serological and molecular typing of HLA-C in two cohorts of healthy Saudis. Our serological typing method identified HLA-C1-7 with different frequencies, 23.5% of the alleles were not identified and thus defined as blank. Using the SSP molecular method, all samples were typed and all alleles were defined. Both methods showed that C∗07 and C∗06 have the highest frequency in the Saudi population. Our study emphasizes the importance of molecular methods in identifying all possible HLA-C alleles.

BACKGROUND:Association of NOD2 (CARD15) gene mutations with inflammatory bowel diseases (IBD) is well known. We herein aimed to investigate the role of familial Mediterranean fever-associated MEFV variations in IBD patients as additional regional-specific risk factor.STUDY:One hundred thirty-seven (78 female, 56.9%) IBD patients [62 Crohn's disease (CD), 75 ulcerative colitis (UC)] were enrolled into the study. The diagnosis of all patients was confirmed by colonoscopy, histopathology, and the clinical findings. One hundred one healthy donors' samples were used as healthy controls. All patients were genotyped for the most common E148Q, M608I, M694V, and V726A variations of the MEFV and R702W, G908R, and 1007fs of the NOD2.RESULTS:The overall MEFV variation frequency was found to be higher in the IBD (25.5%) patients (28% in UC, 22.6% in CD) compared with controls (9.9%, P=0.006). This association was stronger with the penetrant exon 10 variations (M694V, M680I, V726A; odds ratio =4.5, P=0.001). Contribution of M694V was higher compared with the other variations (14.5% in CD, 17.3% in UC and 3% in controls, odds ratio =6.039, 95% confidence intervals, 1.7-20.7, P=0.002). The overall frequency of 3 NOD2 variants in the IBD group was not different from that of controls.CONCLUSIONS:The results of this study suggest that the MEFV variations may be an additional susceptibility factor for IBD in certain parts of the world where the carrier rate is high, and the genetic background of the IBD patients may show regional changes.

INTRODUCTION:HLA-B*51 and HLA-B*52 are two close human leukocyte antigen (HLA) allele groups with minor amino acid differences. However, they are associated with two different vasculitides (HLA-B*51 in Behçet's disease and HLA-B*52 in Takayasu's arteritis (TAK)) and with major clinical and immunological differences. In this study, we aimed to screen a large cohort of TAK patients from Turkey for the presence of HLA-B*51 and HLA-B*52 as susceptibility and severity factors.METHODS:TAK patients (n = 330) followed at a total of 15 centers were included in the study. The mean age of the patients was 37.8 years, and 86% were women. DNA samples from the patients and healthy controls (HC; n = 210) were isolated, and the presence of HLA-B*51 or HLA-B*52 was screened for by using PCR with sequence-specific primers.RESULTS:We found a significant association of HLA-B*52 with TAK (20.9% vs HC = 6.7%, P = 0.000, OR = 3.7, 95% CI = 2.02 to 6.77). The distribution of HLA-B*51 did not differ between TAK patients and HCs (22.7% vs 24.8%, OR = 0.9, 95% CI = 0.60 to 1.34). The presence of HLA-B*52 decreased in late-onset patients (> 40 years of age; 12.0%, P = 0.024, OR = 0.43, 95% CI = 0.20 to 0.91). Patients with angiographic type I disease with limited aortic involvement also had a lower presence of HLA-B*52 compared to those with all other disease subtypes (13.1% vs 26%, P = 0.005, OR = 0.43, 95% CI = 0.23 to 0.78).CONCLUSIONS:In this study, the previously reported association of TAK with HLA-B*52 in other populations was confirmed in patients from Turkey. The functional relevance of HLA-B*52 in TAK pathogenesis needs to be explored further.

OBJECTIVES:Takayasu's arteritis (TA) is a chronic arterial inflammation of unknown etiology involving mainly the aorta and its major branches. Based on the associations of programmed death-1 (PD-1) protein encoding gene (PDCD1) with connective tissue diseases and vasculitides, PDCD1 polymorphisms are studied for susceptibility to TA in this study.METHODS:The study group is made up of TA patients (n=229) fulfilling the 1990 ACR classification criteria and compared to 193 healthy controls (HC). PD-1.3, PD-1.5 and PD-1.6 single nucleotide polymorphisms of PDCD1 gene are genotyped by polymerase chain reaction and restriction analysis (PCR-RFLP).RESULTS:The distribution of PD-1.5 polymorphism in TA patients and HC revealed a similar presence of TT genotype in patients and controls (13.3% vs. 11.4%). PD-1.3 and PD-1.6 were less polymorphic and did not differ between the groups. Rare AA genotype of PD-1.3 (1.4% vs. 1.0%) and AG genotype of PD-1.6 was again similarly (22.4% vs. 19.2%) present in TA and HC.CONCLUSIONS:PD-1.3, 1.5 and 1.6 polymorphisms of PDCD1 gene, which were shown to be associated with various autoimmune disorders and vasculitides, are not associated with a susceptibility to TA in Turkish population.

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

Takayasu's arteritis (TA) is a chronic arterial inflammation of unknown etiology involving mainly the aorta and its major branches. Genetic polymorphisms of cytokines are screened as susceptibility factors for TA in Turkey. A total of 94 patients with TA were investigated for the genetic polymorphisms of the interleukin genes IL12, IL2,and IL6 and were compared with 108 healthy control subjects using polymerase chain reaction-sequence-specific primer method. The frequencies of IL12B 1188 C allele (p = 0.03, OR = 1.7) and CC genotype (p = 0.007, OR = 3.7) were both higher in TA patients than in control subjects. TT genotype at IL2-330 (p = 0.006, OR = 2.4) and GG genotype at IL6-174 (p = 0.04, OR = 1.9) were more frequent in TA patients. Lower prevalence of GT genotype at IL2-330 (p = 0.005, OR = 0.4), CG genotype at IL6-174 (p = 0.001, OR = 0.4), and AG genotypes at IL6-598 (p = 0.01, OR = 0.4) were also detected. The polymorphism of IL-12 as well as IL-6 and IL-2 genes may contribute to susceptibility and pathogenesis of TA by altering cytokine production and inducing inflammation.

Three common genetic variations, namely, R702W, G908R, and 1007fs, on CARD15 have been shown to increase the risk for Crohn's disease (CD) in Caucasian populations. In this study the frequencies of these CARD15 variants were determined by genotyping in 56 patients with CD and 100 healthy ethnically matched controls from Turkey. Overall frequency of all three variants was 10.7% in CD patients, compared with 1.5% in controls (odds ratio [OR]: 7.9). Among them, the frequency of the G908R variant allele was 8% in CD cases, compared with 0% in controls (OR: 36.8). The allele frequencies of three CD-related CARD15 variants were considerably lower in the control group compared to the reported Caucasian populations. Among the described CARD15 variants, G908R confers an increased susceptibility to CD, whereas the more frequently reported associations in Europeans with R702W and 1007fs are not confirmed in this Turkish population.

OBJECTIVE:Genetic susceptibility to Behçet's disease (BD) is well documented for HLA-B51; however, contribution of other genetic polymorphisms is estimated to be substantial. Interleukin 8 (IL-8), a potent chemoattractant for neutrophils, has been found to be elevated in BD serum, and the serum concentrations correlate with disease activity. Novel polymorphisms in IL-8 (CXCL8) and in one of its receptors, CXCR2 gene, may have a role in enhanced IL-8 activity in BD.METHODS:Three single nucleotide polymorphisms (SNP; -353 A/G, +1530 T/C, +3331 A/G) of the IL-8 gene and 2 SNP (+785 C/T and +1208 T/C) of the CXCR2 gene were screened in 100 patients with BD (61 men, 39 women, mean age 42.1 yrs) and 100 healthy controls (50 men, 50 women, mean age 36.8 yrs) by genotyping with PCR-RFLP and PCR-SSP methods.RESULTS:No differences were observed between BD patients and controls for the allele and genotype frequencies of the screened IL-8 and CXCR2 gene polymorphisms. Distribution of these polymorphisms revealed no significant differences between clinical subgroups of BD patients. Each pair of the SNP -353/+1530, -353/+3331, and +1530/+3331 of IL-8 and +785/+1208 of CXCR2 showed strong linkage disequilibrium in both patients and controls (p < 0.001 for all). The distribution of the estimated IL-8 and CXCR2 haplotypes revealed no association with BD or any of its clinical subsets.CONCLUSION:These results suggest that the IL-8 gene -353 A/G, +1530 T/C, and +3331 A/G and the CXCR2 gene +785 C/T and +1208 T/C polymorphisms have no role in the increased expression of IL-8 in BD.