Immune Evasion of SARS-CoV-2 Emerging Variants: What Have We Learnt So Far?

Despite the slow evolutionary rate of SARS-CoV-2 relative to other RNA viruses, its massive and rapid transmission during the COVID-19 pandemic has enabled it to acquire significant genetic diversity since it first entered the human population. This led to the emergence of numerous variants, some of them recently being labeled "variants of concern" (VOC), due to their potential impact on transmission, morbidity/mortality, and the evasion of neutralization by antibodies elicited by infection, vaccination, or therapeutic application. The potential to evade neutralization is the result of diversity of the target epitopes generated by the accumulation of mutations in the spike protein. While three globally recognized VOCs (Alpha or B.1.1.7, Beta or B.1.351, and Gamma or P.1) remain sensitive to neutralization albeit at reduced levels by the sera of convalescent individuals and recipients of several anti-COVID19 vaccines, the effect of spike variability is much more evident on the neutralization capacity of monoclonal antibodies. The newly recognized VOC Delta or lineage B.1.617.2, as well as locally accepted VOCs (Epsilon or B.1.427/29-US and B1.1.7 with the E484K-UK) are indicating the necessity of close monitoring of new variants on a global level. The VOCs characteristics, their mutational patterns, and the role mutations play in immune evasion are summarized in this review.

Cytokine Gene Polymorphism Profiles in Kidney Transplant Patients - Association of +1188A/C RS3212227 SNP in the IL12B Gene Prevents Delayed Graft Function.

BACKGROUND AND AIMS: Transplantation is the best treatment option for end stage kidney disease. The most common early complications in post-transplant period are acute rejection (AR) of the graft and delayed graft function (DGF). The underlying mechanisms in these events are heterogeneous and at least in part involve cytokine genes which regulate immune response to allograft. We have investigated whether functional single nucleotide polymorphisms (SNP) in the genes encoding IFN-γ (IFNG), TNF (TNFA), IL-10 (IL10) and p40 subunit of IL-12/IL-23 (IL12B) could predict risk of AR and DGF in kidney allograft recipients. METHODS: Our study involved 152 kidney transplant recipients on standard immunosuppressive regimen which included calcineurin inhibitors, mycophenolic acid derivatives and corticosteroids. Genotyping of IFNG, TNFA, IL10 and IL12B was performed using commercial TaqMan assays. RESULTS: We found association between the carriers of AA genotype of IL12B +1188A/C polymorphism (rs3212227) and a lower rate of DGF (p = 0.037, OR = 0.45, 95% CI = 0.21-0.96), implying protective role of A allele in the pathogenesis of DGF in kidney transplant recipients, whereas no such association was observed with AR. None of the analyzed SNPs in TNFA (-308G/A), IFNG (+874T/A), IL10 (-1082G/A, -819T/C, -592C/A) were associated with AR or DGF in our patients. CONCLUSIONS: Our study shows a preliminary evidence that the AA genotype of rs3212227 SNP in the IL12B gene might be associated with a lower risk for DGF after kidney transplantation. In the future, additional well-designed large studies are required for the validation of our results.

MDR1 gene polymorphisms are associated with ulcerative colitis in a cohort of Serbian patients with inflammatory bowel disease.

BACKGROUND: Inflammatory bowel disease (IBD) is a chronic disease of unknown etiology in which genetic factors contribute to development of disease. Single nucleotide polymorphisms (SNPs) in multidrug resistance 1 (MDR1) gene encoding transporter P-glycoprotein have been associated with IBD, but their role in disease susceptibility remains unclear. Therefore, the aim of this study was to investigate the association of three MDR1 polymorphisms, C1236T (rs1128503), G2677T/A (rs2032582) and C3435T (rs1045642), with Serbian IBD patients. METHODS: A total of 206 IBD patients, 107 Crohn's disease (CD) and 99 ulcerative colitis (UC), and 255 healthy controls were included in the study. All subjects were genotyped using TaqMan SNP genotyping assays. Comparisons between the groups were performed using the Pearson Chi-square test. False discovery rate according to Benjamini-Hochberg procedure was applied to adjust for multiple comparisons. RESULTS: Carriers of T allele of all three MDR1 SNPs were more common in UC patients compared to healthy controls, suggesting predisposing role of T allele of these SNPs in UC pathogenesis. Consistently, TT genotype of C1236T and TTT haplotype were also found more frequently in UC patients. On the other hand, C allele and CC genotype of C1236T and C3435T, as well as G allele and GG genotype of G2677T/A were more frequent in healthy subjects, implying protective role of these variants in UC. Likewise, CGC haplotype and CGC/CGC diplotype were more frequent in controls. Contrary to UC, no statistical difference was observed between CD patients and controls in any of the SNPs analyzed. CONCLUSION: MDR1 gene variants and haplotypes were associated with UC in Serbian IBD patients, further supporting their potential role in susceptibility to UC.

Autophagy-independent increase of ATG5 expression in T cells of multiple sclerosis patients.

Autophagy, a process of controlled self-digestion which regulates cell homeostasis, is involved in innate and adaptive immunity. We investigated the expression of autophagy genes and autophagic activity in distinct lymphocyte populations in treatment-naive MS patients. The mRNA and protein levels of autophagy-related (ATG)5, required for autophagosome formation, were increased in CD4+ and CD4- T cells, but not B cells of MS patients compared to control subjects. The expression of other investigated autophagy genes, as well as the autophagic activity, did not significantly differ between the two groups. ATG5 mRNA levels in CD4+ T cells from MS patients were positively correlated with those of the proinflammatory cytokine tumor necrosis factor. These data suggest that autophagy-independent increase in ATG5 expression might be associated with the proinflammatory capacity of T cells in multiple sclerosis.

The Polymorphism rs3024505 (C/T) Downstream of the IL10 Gene Is Associated with Crohn's Disease in Serbian Patients with Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD), manifesting as Crohn's disease (CD) and ulcerative colitis (UC), is characterized by recurring episodes of inflammation in gastrointestinal tract, in which aberrant production of regulatory cytokine interleukin-10 (IL-10) presumably plays important role. Single nucleotide polymorphisms (SNPs) that affect IL-10 production, such as rs1800896 (G/A) at position -1082 and rs1800871 (C/T) at position -819 in the promoter region of the IL10 gene, have been associated with CD and/or UC, but the results were inconsistent. Another SNP that may alter IL-10 production, rs3024505 (C/T) located immediately downstream of the IL10 gene has been recently identified. T allele of rs3024505 was associated with both UC and CD in Western populations, but the studies from East European countries are lacking. Therefore, our aim was to assess the association of rs3024505, rs1800896 and rs1800871 with Serbian IBD patients. To this end, 107 CD and 99 UC patients and 255 healthy controls were genotyped. As a result, T allele of rs3024505 was associated with CD at allelic, genotypic (GT genotype) and haplotypic (GCCT haplotype) level, suggesting potential role of this variant in susceptibility to CD. In contrast, CD patients carrying C allele of rs3024505 had significantly increased risk of anemia and stricturing/penetrating behavior. No association was observed between rs3024505 and UC or SNPs in IL10 promoter region and any form of IBD. In conclusion, rs3024505 SNP flanking the IL10 gene is associated with susceptibility and severity of disease in Serbian CD patients, further validating its role as a potential biomarker in IBD.

Prediction of Warfarin Dose in Pediatric Patients: An Evaluation of the Predictive Performance of Several Models.

OBJECTIVES: The objective of this study was to evaluate the performance of pediatric pharmacogenetic-based dose prediction models by using an independent cohort of pediatric patients from a multicenter trial. METHODS: Clinical and genetic data (CYP2C9 [cytochrome P450 2C9] and VKORC1 [vitamin K epoxide reductase]) were collected from pediatric patients aged 3 months to 17 years who were receiving warfarin as part of standard care at 3 separate clinical sites. The accuracy of 8 previously published pediatric pharmacogenetic-based dose models was evaluated in the validation cohort by comparing predicted maintenance doses to actual stable warfarin doses. The predictive ability was assessed by using the proportion of variance (R(2)), mean prediction error (MPE), and the percentage of predictions that fell within 20% of the actual maintenance dose. RESULTS: Thirty-two children reached a stable international normalized ratio and were included in the validation cohort. The pharmacogenetic-based warfarin dose models showed a proportion of variance ranging from 35% to 78% and an MPE ranging from -2.67 to 0.85 mg/day in the validation cohort. Overall, the model developed by Hamberg et al showed the best performance in the validation cohort (R(2) = 78%; MPE = 0.15 mg/day) with 38% of the predictions falling within 20% of observed doses. CONCLUSIONS: Pharmacogenetic-based algorithms provide better predictions than a fixed-dose approach, although an optimal dose algorithm has not yet been developed.

Evaluation of cytokine genetic polymorphisms in adult patients with common variable immunodeficiency: A single-center study.

Common variable immunodeficiency (CVID) is a heterogeneous disease characterized by impaired B-cell differentiation and maturation accompanied with the defective antibody production. Several investigators addressed the possibility that disturbed cytokine production of TNF, IL-6, IFN-γ and IL-10, among a variety of others, may be implicated in CVID. The aim of this study was to test the hypothesis that genetic polymorphisms involving TNF (-308G/A), IFNG (+874 T/A), IL10 (-1082G/A, -819T/C and -592A/C), and IL6 (-174G/C) cytokine genes might contribute to susceptibility to CVID. Thirty five patients with CVID and 250 healthy controls were genotyped for indicated single nucleotide polymorphisms (SNP) in TNF, IL6, IFNG and IL10 using Taqman-based assays. CVID patients had significantly higher frequency of TNF A allele and AA genotype than in healthy subjects (p=0.006; OR=2.27; 95%CI=1.24-4.17 and p=0.038, OR=15.64; 95%CI=1.38-177.20, respectively). In addition, the frequency of GG genotype was significantly higher in healthy controls than in patient group (p=0.019, OR=0.43, 95%CI=0.21-0.89). Genetic analysis of IL6 SNP showed that allele G confers increased risk for CVID (p=0.037, OR=1.78, 95% CI=1.03-3.08) while IFNG allele T was associated with splenomegaly in CVID (p=0.032; OR=2.86; 95% CI=1.08-7.56). We observed no association between genotypes, alleles and haplotypes of IL-10 gene and CVID or its clinical complications. In conclusion, our results indicated association between CVID and cytokine gene polymorphisms -308G/A TNF and -174G/C IL6. In addition, we demonstrated that splenomegaly, one of the most common complications in this disease, is associated with +874T/A IFNG polymorphism. These findings add further support to the notion that cytokines may play significant role in pathogenesis of this primary antibody deficiency. However, further investigation that would involve a larger study group of CVID patients is warranted to confirm our findings.

The importance of MDR1 gene polymorphisms for tacrolimus dosage.

Polymorphisms of the multi drug resistance (MDR1) gene cause variability in P-glycoprotein mediated metabolism of tacrolimus. The aim of this study was to examine the relationship between MDR1 gene single nucleotide polymorphisms (SNPs) and their haplotypes with dosage of tacrolimus in kidney transplant recipients who were cytochrome (CYP) 3A5*3 homozygotes. This study included 91 kidney transplant recipients followed two years after transplantation. Detection and analysis of MDR1 gene polymorphisms in positions C1236T, G2677T/A and C3435T were performed using PCR method. Patients with variant alleles for SNPs G2677T/A and C3435T required higher doses of tacrolimus and had a lower level/dose (L/D) ratio than patients with wild alleles or heterozygotes. That difference was the most obvious for SNP G2677T/A where TT homozygotes required significantly higher doses of tacrolimus during whole follow-up. Their L/D was significantly lower in the first month after transplantation. Recipients with CTT/TTT haplotype also had lower L/D than those with CGC/TTT and CGC/CGC, significantly in the 10th and 20th days after transplantation respectively (p<0.05). Our results demonstrate that TT homozygotes at positions G2677T/A and C3435T required a higher tacrolimus dose than those with wild alleles or heterozygotes. It may be helpful in the prevention of tacrolimus nephrotoxicity early after transplantation.

TNF, IL12B, and IFNG Gene Polymorphisms in Serbian Patients with Psoriasis.

BACKGROUND: Psoriasis is a common chronic inflammatory skin disease with a strong genetic basis. Cytokines such as tumor necrosis factor alpha (TNF-α), interleukins (ILs) such are IL-12 and IL-23, and interferon gamma (IFN-γ) are released from various inflammatory and resident cells, and have been implicated in the initiation/maintenance of inflammation. Certain alleles of the aforementioned cytokines may be associated with disease susceptibility/severity. OBJECTIVE: To investigate the association of three common functional gene polymorphisms, namely TNF -308 G/A (rs1800629), IL12B (encoding the p40 subunit of IL-12/23) +1188 A/C (rs3212227), and IFNG +874 T/A (rs2430561) with psoriasis development and severity in Serbian patients. METHODS: We genotyped 130 patients with psoriasis (26 of whom also had psoriatic arthritis) and 259 controls; rs1800629 and rs3212227, and rs2430561, by real-time PCR assay. RESULTS: The TNF GG genotype was detected at a higher frequency in patients with psoriasis compared to control subjects (OR, 1.420; 95% CI, 0.870~2.403) without statistical significance (p=0.191). Lack of the TNF G allele was associated with lower psoriasis severity (p=0.007). The IL12B AC genotype was underrepresented in the patients with psoriatic arthritis compared to healthy subjects (OR, 0.308; 95% CI, 0.090~1.057; p=0.049). The distribution of the rs2430561 allele and genotype frequencies was similar between patients with psoriasis and controls. CONCLUSION: Our study demonstrates an effect of the rs1800629 on psoriasis severity, and a marginal impact of the rs3212227 on susceptibility to psoriatic arthritis. Collectively, our results obtained in a Serbian cohort expand current knowledge regarding individual predisposition to psoriatic disease.

TNF-α and IFN-γ gene variation and genetic susceptibility to type 1 diabetes and its microangiopathic complications.

BACKGROUND: TNF-α has accelerating role in development of type 1 diabetes. Although an immunosupressor function and leading protecting role in T1DM also has been claimed for this pro-inflammatory cytokine. Over-expression of pro-inflammatory and type 1 cytokines (Th1, like IFN-γ) drive insulitis toward the destructive form that leads to type 1 diabetes (T1DM). Among type 1 cytokines only IFN-γ has been detectable in the islet ß cells. In deletion studies IFN-γ was also the only Th1 cytokine for which its ablation or blockade caused delayed or decreased incidence of T1DM. METHODS: Functional polymorphisms of TNF-α at position -308*G/A and at position +874*T/A of IFN-γ gene were employed as markers and the comparative distribution of derived genotypes/alleles were assessed in 248 British Caucasian T1DM patients and 118 healthy controls. RESULTS: There was no significant association between IFN-γ gene polymorphism and T1DM or the diabetic complication triad. There was a marginal association between TNF-α -308*G/A polymorphism in nephropaths (vs healthy controls) (p = 0.06), which its insignificancy may be due to survivor factor. No significant association was evident between the genotype/allele of the applied marker and T1DM or diabetic complication triad. CONCLUSION: Our results are in contrast with previous reports suggesting that these polymorphisms are not related to T1DM. This study also underlines the importance of replication of association studies to confirm the previous interpretation.

TGF-ß1 and IGF-I gene variations in type 1 diabetes microangiopathic complications.

BACKGROUND: Growth factors are generally believed to have a perpetuating role in the development of diabetic complications, However there is ample of evidence of a protective or therapeutic potential for some of them. IGF-I, according to some reports, may contribute to complication development, although a protective role for IGF-I has been claimed for all late diabetic complications, making it an exception among growth factors. Transforming growth factor (TGF)-ß1 as a pleiotropic cytokine is a key player in immunoregulation. Dysregulation of TGF-ß1 in diabetes has been addressed as a leading event of kidney pathologies, while there is no similar pivotal role for TGF-ß1 in diabetic retinopathy or neuropathy. An association study was conducted to evaluate the distinctive roles of TGF-ß1 and IGF-I in T1DM microvascular complications by gene variation-based regulatory mechanisms that are operational in modulation of both in situ and systemic levels of the gene product. METHODS: Two polymorphisms of the IGF-I gene at positions -383*C/T and -1089*C/T and two functional TGF-ß1 gene polymorphisms, including codons 10 (+869*C/T) and 25 (+915*G/C) were examined in 248 British Caucasian T1DM patients and 113 healthy controls. RESULTS: The distribution of IGF-1 gene polymorphisms did not reflect any significant association with different endpoints among the cases or different subgroups (complication triad) and controls. For TGF-ß1 gene codon 25 polymorphism the low producer variant (allele C) were more frequent in cases than controls, which is compatible with the anti-inflammatory role of TGF-ß1 and for codon 10 polymorphism the frequency of allele C was highest in retinopaths and, on the contrary and expectedly, nephropathy was more frequently accompanied by allele T (high producer). The frequency of allele G (high producer) of codon 25 polymorphism was slightly higher in the complication free group than in other subgroups. CONCLUSION: Although there were some differences in distribution of allele and genotype frequencies of TGF-ß1 gene polymorphism in diabetes microvascular complications the differences were not statistically significant. Regarding IGF-1 our result firstly questions the functionality of the employed polymorphic marker and secondly may entail that the main regulator of IGF-I functionality resides elsewhere rather than the IGF-I gene itself, such as post-transcriptional regulation.

Genetics-based pediatric warfarin dosage regimen derived using pharmacometric bridging.

BACKGROUND: Warfarin dosage regimens using CYP2C9 and VKORC1 polymorphisms have been extensively studied in adults and is included in US Food and Drug Administration-approved warfarin labeling. However, no dosage algorithm is available for pediatric patients. OBJECTIVE: To derive a genetics-based pediatric dosge regimen for warfarin, including starting dose and titration scheme. METHODS: A model-based approach was developed based on a previously validated warfarin dosage model in adults, with subsequent comparison to pediatric data from pediatric warfarin dose, genotyping, and international normalized ratio (INR) results. The adult model was based on a previously established model from the CROWN (CReating an Optimal Warfarin dosing Nomogram) trial. Pediatric warfarin data were obtained from a study conducted at the Children's Hospital of Los Angeles with 26 subjects. Variant alleles of CYP2C9 (rs1799853 or *2, and rs1057910 or *3) and the VKORC1 single nucleotide polymorphism (SNP) rs9923231 (-1639 G>A) were assessed, where the rs numbers are reference SNP identification tags assigned by the National Center for Biotechnology Information. RESULTS: A pediatric warfarin model was derived using the previously validated model and clinical pharmacology considerations. The model was validated, and clinical trial simulation and stochastic modeling were used to optimize pediatric dosage and titration. The final dosage regimen was optimized based on simulations targeting a high (≥60%) proportion of INRs within the therapeutic range by week 2 of warfarin therapy while minimizing INRs >3.5 or <2. CONCLUSIONS: The proposed pediatric warfarin dosage scheme based on individual CYP2C9 (alleles *1,*2,*3) and VKORC1 rs9923231 (-1639 G>A) genotypes may offer improved dosage compared to current treatment strategies, especially in patients with variant CYP2C9 and VKORC1 alleles. This pilot study provides the foundation for a larger prospective evaluation of genetics-based warfarin dosage in pediatric patients.

Multiple sclerosis: individualized disease susceptibility and therapy response.

Multiple sclerosis (MS) is a heterogeneous disease in which diverse genetic, pathological and clinical backgrounds lead to variable therapy response. Accordingly, MS care should be tailored to address disease traits unique to each person. At the core of personalized management is the emergence of new knowledge, enabling optimized treatment and disease-modifying therapies. This overview analyzes the promise of genetic and nongenetic biomarkers in advancing decision-making algorithms to assist diagnosis or in predicting the disease course and therapy response in any given MS patient.

Distinctive frequencies of +874T/A IFN-γ gene polymorphism in a healthy Serbian population.

PURPOSE: Single nucleotide polymorphism (SNP) in IFN-γ gene (+874T/A) that determines high (TT), low (AA), and intermediate (TA) responder phenotypes has shown associations with susceptibility to infectious and chronic inflammatory diseases, as well as disease outcome. Therefore, the susceptibility to and outcome of certain diseases can vary in different ethnic populations partially due to the notable differences in frequencies of genotypes and alleles between them. The aim of this study was to determine the distribution of +874T/A genotype and allele frequencies in a healthy Serbian population as a reference for further disease association studies. MATERIALS AND METHODS: Genomic DNA samples from 166 healthy volunteers were evaluated for IFN-γ SNP at position +874 using TaqMan SNP genotyping assay. RESULTS: The frequencies of AA, AT, and TT genotypes were 28.9%, 49.4%, and 21.7%, respectively. The A and T allele frequencies were 53.6% and 46.4%. CONCLUSIONS: Analysis of genotype and allele frequencies for IFN-γ+874T/A SNP in healthy subjects revealed, for the first time, the genetic profile for this polymorphism in a Serbian population resembling most European populations, but differing from some Asian and African ethnic groups.

Single nucleotide polymorphisms in multiple sclerosis: disease susceptibility and treatment response biomarkers.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system characterized by unpredictable and variable clinical course. Etiology of MS involves both genetic and environmental factors. New technologies identified genetic polymorphisms associated with MS susceptibility among which immunologically relevant genes are significantly overrepresented. Although individual genes contribute only a small part to MS susceptibility, they might be used as biomarkers, thus helping to identify accurate diagnosis, predict clinical disease course and response to therapy. This review focuses on recent progress in research on MS genetics with special emphasis on the possibility to use single nucleotide polymorphism of candidate genes as biomarkers of susceptibility to disease and response to therapy.

Inosine 5'-monophosphate dehydrogenase 1 haplotypes and association with mycophenolate mofetil gastrointestinal intolerance in pediatric heart transplant patients.

MMF, the most commonly used adjuvant immunosuppressant in pediatric heart transplantation, has frequent GI adverse events. SNPs in inosine 5'-monophosphate dehydrogenase I (IMPDH1) may contribute to MMF GI intolerance. Phased haplotypes may have more utility than individual SNPs in candidate gene association studies for complex traits. This study defined common IMPDH1 haplotypes and investigated whether these haplotypes influence MMF GI intolerance in 59 pediatric heart recipients. Genotypes were assessed by Taqman analysis of IMPDH1 rs2288553, rs2288549, rs2278293, rs2278294, and rs2228075, and haplotypes were inferred using Arlequin 3.01 software. GI intolerance was defined as diarrhea, vomiting, nausea, or abdominal pain requiring MMF dose holding for > 48 h or MMF discontinuation. GI intolerance occurred in 21 patients (35.6%). Ten IMPDH1 haplotypes were identified in this population. In univariable analyses, one haplotype was strongly associated with MMF GI intolerance with 59.1% of carriers of this haplotype experiencing MMF GI intolerance compared to 21.6% of non-carriers (p = 0.005). In this study, we identify a common IMPDH1 haplotype associated with MMF GI intolerance in a population of pediatric heart transplant patients. This haplotype of interest did not demonstrate stronger association with MMF GI intolerance than an individual IMPDH1 SNP.

eNOS gene polymorphism association with retinopathy in type 1 diabetes.

PURPOSE: Nitric oxide (NO) is a major mediator in vascular biology, regulating blood pressure and regional blood flow. NO and the enzymes required for its production may contribute to the aetiology of vascular pathologies. In diabetes, over-production of NO might play a role in the development of diabetic nephropathy, while reduced NO production may be related to the development of diabetic retinopathy and neuropathy, where VEGF (vascular endothelial growth factor) levels are increased in a counter regulatory manner. Among the three nitric oxide synthase (NOS) enzymes most attention has focussed on endothelial NOS (eNOS) because of its relevance to angiopathies. METHODS: In this study the influence of a single nucleotide polymorphism at position -786 in the eNOS gene, where there is a C/T base substitution, on development of type 1 diabetes mellitus (T1DM) and its microvascular complications was studied in 249 British Caucasian type 1 diabetics using a case-control association design. Genotyping was carried out using PCR-RFLP technique. RESULTS: There was a significant association between the polymorphism -786*C/T and both T1DM and diabetic retinopathy. The distribution of eNOS gene polymorphism genotype frequencies showed a significant difference observed between diabetic patients and healthy controls [CC+CT vs. TT p = 0.05, OR = 1.5 95%CI(0.9-2.5)]. The genotype frequencies for eNOS gene polymorphism was also significantly different between diabetic retinopaths and healthy controls [CC+CT vs. TT p = 0.0000 OR = 3.4 95%CI(1.9-6.1) No significant differences for eNOS allele and genotype frequencies were found in other groups compared to the controls. CONCLUSION: Therefore, eNOS gene variation may be a factor in the genetic propensity to T1DM and diabetic retinopathy that may have a prognostic value or may suggest interventional approaches to regulate eNOS in patients with diabetes.

VEGF gene polymorphism association with diabetic neuropathy.

Vascular factors beside metabolic problems are involved in both etiopathogenesis of diabetic neuropathy, and more remarkably, later in "repair" phase, that governs the net balance between neuro-regenerative/degenerative reactions. Regarding ischemic nature of diabetic neuropathy that highlights necessity of blood vessels re-establishment during tissue healing, VEGF (vascular endothelial growth factor) has been recently the subject of extensive investigations in diabetic neuropathy (DNU). This growth factor possesses angiogenic potentials in addition to the hemodynamic functions. The distribution of VEGF gene polymorphisms at positions -7*C/T, -1001*G/C, -1154*G/A and -2578*C/A were analysed by ARMS-PCR in 248 type 1 diabetic British-Caucasian subjects (81 DNU+, 167 DNU-). We have found that distribution of a VEGF gene polymorphism at promoter region (-7*C/T) was significantly different between diabetic subjects with vs. without neuropathy and the allele (C) conferred susceptibility to DNU (P = 0.02; OR = 1.78, 95% CI 1.0-3.1). The present study indicates that polymorphism of the VEGF gene at position -7*C/T might be implicated in the pathogenesis of diabetic neuropathy as it may harbour some functional/regulatory potential in VEGF gene expression. However, this requires further studies in order to better understand its phenotypic impact and to investigate the prognostic value of this polymorphism in diabetic neuropathy as a chronic complication of diabetes.

Genetic polymorphisms influence mycophenolate mofetil-related adverse events in pediatric heart transplant patients.

BACKGROUND: Mycophenolate mofetil (MMF) is an effective and commonly used immunosuppressant but has frequent adverse events. Genetic polymorphisms may contribute to variability in MMF efficacy and related complications. In this study we explore the distribution frequencies of common single nucleotide polymorphisms (SNPs) of IMPDH1, IMPDH2 and ABCC2 and investigate whether these SNPs influence MMF adverse events in 59 pediatric heart recipients. METHODS: Genotypes were assessed by TaqMan analysis of: ABCC2 rs717620; IMPDH2 rs11706052; and IMPDH1 rs2288553, rs2288549, rs2278293, rs2278294 and rs2228075. Gastrointestinal (GI) intolerance was defined as diarrhea, vomiting, nausea or abdominal pain requiring dose-holding for >48 hours or MMF discontinuation. Bone marrow toxicity was evaluated using Common Terminology Criteria for Adverse Events Version 3 (CTCAE). RESULTS: GI intolerance occurred in 21 patients, and 21 had bone marrow toxicity. The ABCC2 rs717620 A variant was significantly associated with GI intolerance leading to drug discontinuation (p < 0.001); the IMPDH1 rs2278294 A variant and rs2228075 A variant were also associated with greater GI intolerance (p = 0.029 and p = 0.002, respectively). The IMPDH2 rs11706052 G variant was associated with more frequent neutropenia requiring dose-holding (p = 0.046). CONCLUSIONS: In this small sample of pediatric heart transplant patients receiving MMF, ABCC2, IMPDH1 and IMPDH2 SNPs were associated with MMF GI intolerance and bone marrow toxicity. Thus, genetic polymorphisms may directly influence MMF adverse events.

Genetic polymorphisms of MRP2 and UGT2B7 and gastrointestinal symptoms in renal transplant recipients taking mycophenolic acid.

The aim of this study was to determine the relationship between single nucleotide polymorphisms in multidrug resistance protein 2 (MRP2) and uridine diphosphate glucuronosyltransferase (UGT) 2B7 and the severity of gastrointestinal (GI) symptoms in patients receiving mycophenolic acid (MPA). A total of 67 renal transplant recipients taking MPA derivatives were included in the study. Genotypes for MRP2 C-24 T and UGT2B7 C802 T were determined. The incidence and severity of GI symptoms were assessed using the validated Gastrointestinal Symptom Rating Scale (GSRS) at baseline, 2 weeks, 3 months, and 6 months after transplantation. The mean overall GSRS score and the score on the subscale for diarrhea were compared using the Kruskal-Wallis test. The overall GSRS scores (23.5 +/- 4.5 vs. 26.7 +/- 9.9, P = 0.68) or diarrhea subscores (3.5 +/- 0.9 vs. 5.1 +/- 3.3, P = 0.08) were not significantly different among patients with the heterozygous variant MRP2 C-24 T and those with the homozygous wild type. For UGT2B7, the overall mean GSRS scores were significantly different between the homozygous wild type and the variant type (CC vs. CT + TT, 29.2 +/- 9.3 vs. 24.0 +/- 8.2, P = 0.009), although diarrhea subscale scores did not reach statistical significance (CC vs. CT + TT, 5.7 +/- 4.1 vs. 4.1 +/- 1.9, P = 0.13). When the genotypes for MRP2 and UGT2B7 were considered together, patients with the variant forms of MRP2 and UGT2B7 had significantly lower overall GSRS scores (CC-CC vs. CT-CT/TT, 22.5 +/- 4.3 vs. 30.1 +/- 10.1, P = 0.04) and diarrhea subscale scores compared to wild type (CC-CC vs. CT-CT/TT, 3.4 +/- 0.7 vs. 6.2 +/- 4.4, P = 0.03). However, there were no differences in GSRS scores between patients receiving either mycophenolic mofetil (MMF) or enteric-coated mycophenolic acid (EC-MPA) regardless of whether the patients were receiving different calcineurin inhibitors. In conclusion, this study suggests that among patients receiving MPA, those with UGT2B7 variant genotypes are protected from the GI side effects of MPA regardless of the formulation used or concurrent calcineurin inhibitors administered. MRP2 genotypes did not show significant differences in GI side effects among patients taking MPA therapy.