I. Sfar

Distribution of HLA-B*27 subtypes in Tunisians and their association with ankylosing spondylitis.

OBJECTIVE The human leukocyte antigen HLA-B27 is a class I antigen of the major histocompatibility complex strongly associated with ankylosing spondylitis (AS) and other related spondyloarthropathies (SpAs). The mechanism of this association remains unknown. HLA-B27 is a serologic specificity that represents a family of at least 25 different HLA-B27 alleles (2701-2725). These alleles are closely related by nucleotide sequence homology, but differ in ethnic distribution. The purpose of the present study is to investigate the distribution of HLA-B27 alleles in healthy controls and in patients with ankylosing spondylitis (AS). METHODS We selected 160 HLA-B27-positive individuals (39 controls and 121 patients with ankylosing spondylitis). Typing of HLA-B27, and Cw alleles were performed by polymerase chain reaction amplification with sequence specific primers (PCR-SSP), and by serological typing (microlymphocytotoxicity). RESULTS Seven B27 subtypes were identified: B*2702, 03, 04, 05, 07, 09 and B*2714. The distribution of these alleles in the population of patients was B*2702 (47.1%) and B*2705 (47.1%). These subtypes were also detected in 16 (41%) and 16 (41%), respectively of the 39 control subjects. HLA-B*2707 was detected in 4 (3.31%) patients and in 3 (7.6%) controls. B*2704, 09 and B*2714 were relatively rare and were detected in one subject each. No significant differences were noticed in the frequencies and distribution of HLA-B27 alleles between patients and controls. CONCLUSIONS Our results show a restricted number of HLA B27 subtypes associated with AS. B*2702 and B*2705 were equally common in patients and controls. The most prominent B27/Cw haplotypes in the patient groups and controls were B*2702/Cw02022 and B*2705/Cw02022.

(AT) Repeat in the 3′ Untranslated Region of the CTLA-4 Gene and Susceptibility to Acute Allograft Rejection in Tunisian Renal Transplantation

Allograft rejection is an immune response relying on the proliferation and the differentiation of T cells. CTLA-4 is a co-stimulatory molecule, expressed on activated T lymphocytes, which has been shown to play a crucial role in the down-regulation of T-cell activation. Herein, we have examined the impart of a genetic marker in the CTLA-4 gene on renal transplant outcomes. A cohort of 144 renal recipients and 100 healthy subjects were genotyped by the fragments analysis method using an automated sequencer. Patients were classified into two groups: Group I included 31 HLA-identical haplotype allograft recipients and Group II, 113 showing one or more HLA haplotype mismatches. Forty patients (27.78%) developed at least one acute rejection episode (ARE): 9 in Group I and 31 in Group II. Before transplantation, 20 patients were lymphocytotoxic antibodies (LCT) positive: 4 Group I, 2 of whom developed an ARE, and sixty in Group II, including 8 with an ARE. The occurrence of an ARE was associated with the presence of LCT before transplantation among the entire cohort of patients (P = .032) and among Group II (P = .037). The allelic frequencies of (AT)n polymorphism did not reveal significant differences between patients and controls. The most prevalent alleles were the 88 bp (51% in controls and 44.44% in patients) and the 106 bp (8% and 10.76%, respectively). We noticed an increase of the 120 bp allele frequency among patients who had undergone an ARE compared with those who did not display this complication (8.75% vs 3.85%). Likewise, among LCT-negative Group I, recipients the incidence of the 120 bp allele was higher in ARE than non-ARE patients. Although the differences were not statistically significant, we propose that the 120 bp allele of the CTLA-4 gene (AT)n microsatellite a predisposes to acute rejection episodes in renal transplantation.

Y402H Polymorphism in Complement Factor H and Age-Related Macular Degeneration in the Tunisian Population

To evaluate a possible association between the complement factor H (CFH) Y402H polymorphism and susceptibility to age-related macular degeneration (AMD) in the Tunisian population, as well as the impact of the genotype distribution among different phenotypes and the response to treatment with intravitreal bevacizumab, exon 9 of CFH was analyzed for the Y402H polymorphism by direct sequencing in 135 healthy controls and 127 sporadic unrelated AMD patients classified into the following groups: 12 atrophic AMD (group G1), 115 exudative AMD (G2) and 10 AMD patients who had fibrovascular scarring (G3) that did not allow a precise grading of the phenotype. Seventy patients in G2 were treated with 1.25 mg intravitreal bevacizumab at 6-week intervals until choroidal neovascularization (CNV) was no longer active. The frequency of the CFH 402H allele was significantly higher in AMD patients than in controls (p = 2.62 × 10–16). However, subgroup analysis does not reveal any association between the variant allele H and phenotypes of AMD or CNV. Also, there was no significant difference in response to bevacizumab treatment according to Y402H CFH genotype (p = 0.59). A strong association of the 402H allele with susceptibility to AMD in the Tunisian population was confirmed; however, this variant does not appear to be involved in the clinical progression of this disease or in the postintravitreal bevacizumab response.

Genetic Polymorphisms of Inflammatory Molecules in Tunisian Kidney Transplantation

As chemokines and adhesion molecules play major roles in the process by which leukocytes are recruited from the bloodstream into sites of inflammation, genetic variations in the production or activity of molecules may influence susceptibility to acute rejection episodes. This study sought to determine the impact of recipient monocyte chemoattractant protein-1 (MCP-1), chemokine receptor (CCR2, CCR5), and adhesion molecule (ICAM-1, PECAM-1 and L/E selectin) polymorphisms on acute rejection after renal transplantation. We selected 169 healthy blood donors and 173 renal transplant recipients for analysis according to the presence or absence of graft rejection in the first 30 days after transplantation. Using molecular methods DNA was genotyped for 11 polymorphisms of these inflammatory molecules genes. Results were stratified by the incidence of rejection episodes and by human leukocyte antigen (HLA) mismatching. No association was detected between adhesion molecule polymorphisms and the incidence of acute rejection episodes. However, a significant risk of acute renal loss was observed among HLA-identical recipients who possessed the CCR2-64I allele (odds ratio 0.24, 95% confidence interval, 0.05 to 1.06; P=.035). In conclusion, the observed association of CCR2-64I with acute rejection episodes should be added to the spectrum of immunogenetic factors known to be involved in renal allograft rejection.

Toll-Like Receptor 4 and CD14 Gene Polymorphisms in Tunisian Kidney Transplantation

BACKGROUND Acute and chronic rejections remain an important cause of graft loss after renal transplantation. Currently, activation of innate immune responses through Toll-like receptors (TLRs) is suspected to be implied in the loss of the transplant tolerance. OBJECTIVES We investigated functional single nucleotide polymorphisms (SNPs) of TLR4 and its coreceptor CD14 in kidney transplantation and looked for any potential role in acute rejection (AR) and chronic allograft nephropathy (CAN) and impact on graft survival. PATIENTS AND METHODS TLR4 (Asp299Gly) and CD14 (C/T -159) SNPs were detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 209 kidney transplant recipients (KTRs) including 132 treated with mycophenolate mofetil (MMF+). AR occurred in 59 patients and 24 were identified as having CAN by biopsy and scored according to the Banff criteria. RESULTS There were no significant associations between TLR4 and CD14 genotypes and alleles and the occurrence of both AR episodes and CAN. Moreover, TLR4 and CD14 SNPs did not seem to influence kidney graft survival. Analysis according to human leukocyte antigen (HLA) compatibility status, positivity of anti-HLA antibodies, and immunosuppression by MMF confirmed the absence of correlation of the investigated SNPs with the graft outcome. In addition, incidence of post-transplantation infections, including cytomegalovirus (CMV) infections, was not influenced by both TLR4 and CD14 SNPs. CONCLUSION These results suggest that TLR4 (Asp299Gly) and CD14 (C/T -159) functional SNPs do not play a major role in AR, CAN, and kidney graft survival. Therefore, intragraft monitoring of TLR4/CD14 genes expression by messenger RNA (mRNA) would provide clarity on the exact role of these receptors in graft injuries.

The PTPN22 C1858T (R620W) Functional Polymorphism in Kidney Transplantation

To investigate the association between kidney transplant rejection and PTPN22 (protein tyrosine phosphatase non-receptor 22) polymorphism, genomic DNA of 175 renal transplant recipients and 100 healthy blood donors were genotyped by restriction fragment length polymorphism-polymerase chain reaction. The patients were classified in two groups: G1 included 33 HLA-identical recipients and G2 included 142 with one or more HLA mismatches. Forty-nine patients developed an acute rejection episode (ARE): 8 in G1 and 41 in G2. The allelic frequencies of PTPN22 R620W revealed a significant difference between patients and controls. In fact, the W-allele was significantly more frequent in graft recipients than in blood donors (0.05 vs 0.01, P < .05). Furthermore, the frequency of this allele was increased in G1 patients with an ARE (0.188) compared with those without an ARE (0.040), but the difference was not statistically significant. Thus, we concluded that the PTPN22 W-variant allele could be involved in the susceptibility to acute allograft rejection in Tunisian kidney transplant patients.

Short- and Long-Term Outcomes of Living Donors in Tunisia: A Retrospective Study

Despite initiatives to increase cadaveric donation, there is still a shortfall in donor organs. Kidneys from living donors now makes a significant contribution to increasing the number of organs available for transplantation in Tunisia. We performed a retrospective study of 405 kidney transplantations, including 321 (79.3%) from living donors performed from June 1986 to December 2007. We obtained information on only 162 (50.4%), namely, 64 men (39.5%) and 98 women (60.5%), whose mean age at the time of donation was 42.3 ± 12.2 years. Twelve (8.22%) perioperative complications occurred: wound infections (n = 4), pneumothorax (n = 4), phlebitis (n = 1), hematomas (n = 2), and urinary infection (n = 1). The mean follow-up period was 117.4 ± 74.4 months. Hypertension occurred in 42 donors (25.9%) with mean values of 134 ± 20 for systolic and 79 ± 10 for diastolic blood pressure. Twelve donors (7.4%) developed proteinuria (mean proteinuria, 0.08 ± 1.25 g/d). Renal insufficiency was found in 28 donors (19.44%), 2 of whom developed chronic renal failure requiring dialysis at intervals of 36 and 84 months. In both cases, we diagnosed a familial form of focal segmental glomerulosclerosis. Two donors (1.2%) died within 10 years after kidney donation due to senility. The relatively favorable outcomes suggest that living-donor kidney transplantation is an acceptable approach, in view of the superior results it yields in recipients. However, efforts to increase the number of cadaveric donors in Tunisia should be made. It is also important to develop a registry of long-term kidney function after kidney donation.

Cytokines and apoptosis genes polymorphisms influence the outcome of hepatitis C virus infection

Chronic hepatitis C virus (HCV) infection persists despite the presence of specific humoral and cellular immune [1,2] responses and the factors leading to viral clearance or persistence are poorly understood [3-6].

Mannose binding lectin (+54) exon 1 gene polymorphism in Tunisian kidney transplant patients.

Mannose-binding lectin (MBL), a collagen-like serum protein, is a key component of innate immunity. MBL binding to carbohydrates present on pathogens mediates lectin-dependent activation of the complement pathway. There is growing interest in the importance of innate immunity in host defense, particularly when adaptive immunity is compromised. Three single nucleotide polymorphisms (SNPs) of the MBL gene have been described in the first exon to be associated with low MBL serum concentrations as well as impaired MBL structure and function. Clinical studies have shown that these MBL SNPs are associated with increased susceptibility to infections, especially in immunocompromised patients. To investigate the association between acute kidney transplant rejection and polymorphism at codon 54 of the MBL gene, the DNA genomic of 133 renal transplant recipients and 117 healthy blood donors was analyzed by restriction fragment length polymorphism-polymerase chain reaction. The patients were classified into two groups: group 1 included 32 HLA-identical recipients and group 2, 101 one haplo-identical recipients. Forty-eight (36.1%) subjects had developed one or more acute rejection episodes (AREs) within the first 6 months after transplantation: 9 in group 1 (28.12%) and 39 in group 2 (38.61%). The genotype and allele frequencies of (+54) MBL gene polymorphism among patients and controls did not reveal a significant difference. However, the frequency of MBL-B mutant allele was increased among patients with AREs compared with those without AREs: group 1 (0.167 vs 0.065) versus group 2 (0.205 vs 0.105). Although the difference was not significant, perhaps because of the small number of patients, the MBL at codon (+54) polymorphism could be involved in the susceptibility of Tunisian kidney transplant recipients to acute allograft rejection episodes.

Genetic polymorphisms of inflammatory molecules in Tunisian inflammatory bowel diseases

As chemokines and adhesion molecules play a major role in the process by which leukocytes are recruited from the bloodstream into sites of inflammation [1], genetic variation in these production or activity molecules may influence susceptibility to inflammatory diseases [2-4].