Novel and functional regulatory SNPs in the promoter region of FOXP3 gene in a Gabonese population

Heat shock protein 60 in parasitic helminths: A role in immune responses and therapeutic applications

Heat shock protein 60 (HSP60) is an unique member of the heat shock protein family, being involved in parasite infections. To cope with harsh environments where parasites live, HSP60s are indispensable and involved in a variety of biological processes. HSP60s have relative low similarity among parasites, but their ATPase /Mg²⁺ active sites are highly conserved. The interactions of HSP60s with signaling pathway regulators in immune cells suggest a crucial role in immune responses, rendering them a potential therapeutic target. This paper reviews the current understandings of HSP60s in parasitic helminths in aspects of molecular characteristics, immunoregulatory responses and HSP60-based therapeutics.

Forkhead box P3 gene polymorphisms predispose to type 2 diabetes and diabetic nephropathy in the Han Chinese populations: a genetic-association and gender-based evaluation study

BACKGROUND

Functional mutations or polymorphisms affecting forkhead box P3 (FOXP3) can lead to their abnormal FOXP3 gene expression and/or defective Treg cells generation, thus resulting in autoimmune disease and inflammatory disorders. FOXP3 also plays a key role in Type 2 diabetes mellitus (T2DM) and its complications, because the disease usually involves chronic low-grade inflammatory disorders and is associated with long-term immune system imbalance. This study aimed to investigate the association between FOXP3 polymorphisms and the susceptibility to T2DM and type 2 diabetes nephropathy (T2DN) within the Han Chinese populations.

METHODS

Polymorphisms in rs3761548C/A and rs2294021C/T were examined in 400 patients (which include an equal number of T2DM and T2DN groups) and 200 healthy controls using PCR-HRM and sequence analysis.

RESULTS

The genotype and allelic frequencies of the two single nucleotide polymorphisms (SNPs) were significantly different in T2DM and the progression of diabetes developing to T2DN. The further gender-based evaluation showed that in female subjects, rs3761548C/A was associated with an approximately 3-fold higher threat for T2DM and 4.5-fold for T2DN, while there was no noticeable association with rs2294021C/T; in males, the promoter polymorphism showed an increased predisposition of 5.4-fold and 3.4-fold predisposition to T2DM and T2DN, respectively, while rs2294021 polymorphism could impart a nearly 2-fold risk of developing T2DN. An additional analysis of combined genotypes (rs3761548 C/A-rs2294021C/T) revealed that CC-CC and CC-CT can be considered protective combinations in the predisposition of males with diabetes towards T2DN, while AA-CC and AA-TT have the opposite effect.

CONCLUSIONS

This study demonstrated the possible involvement of individual and combined genetic associations of rs3761548C/A and rs2294021C/T polymorphisms with the susceptibility to diabetes and diabetic nephropathy in the Han Chinese population, as well as gender bias.

Associations of FOXP3 gene polymorphisms with susceptibility and severity of preeclampsia: A meta-analysis

OBJECTIVE

FOXP3 single nucleotide polymorphisms (SNPs) were recently elucidated to influence the development of preeclampsia (PE), but the results on this issue still remained controversial. Thus, a meta-analysis was implemented to systematically investigate the roles of FOXP3 SNPs in PE.

METHODS

Eligible publications were identified by retrieving relevant electronic databases. Meanwhile, the association intensity was estimated by calculating odds ratios (ORs) and 95% confidence intervals (CIs) in various genetic models.

RESULTS

Totally eight investigations involving 3446 subjects were enrolled in the final meta-analysis. The AC and AC + CC genotypes of FOXP3 rs3761548 were related to the susceptibility of PE in over-dominant (OR = 1.19, 95%CI = 1.02-1.38, P = 0.03) and recessive (OR = 0.59, 95% CI: 0.36-0.97, P = 0.04) models. Furthermore, correlation between rs2232365 and PE was observed in recessive model (GG vs. GA + AA) (OR = 0.79, 95%CI: 0.65-0.97, P = 0.03). Moreover, rs2232365 GA and GG + GA genotypes were associated with the severity of PE. However, rs4824747, rs3761547 and rs2280883 polymorphisms had no significant impact on PE susceptibility.

CONCLUSIONS

FOXP3 rs3761548 and rs2232365 SNPs influenced the PE susceptibility and therefore may be potential biomarkers for prediction of PE risk.

Effect of circRNA_FOXO3 rs12196996 polymorphism and FOXO3 rs2232365 polymorphism on survival rate and severity of intensive care unit-acquired sepsis

The expression of circRNA_FOXO3 was found to be positively associated with the expression of Forkhead Box O3 (FOXO3), which is targeted and regulated by miR-23a. Polymorphisms in rs12196996 and rs2232365 have been reported in various diseases. In this study, we recruited intensive care unit (ICU)-acquired sepsis patients and grouped them according to their genotypes of rs12196996 and rs2232365. Quantitative real-time PCR was performed to analyze the expression of circRNA_FOXO3, FOXO3 mRNA, and miR-23a. ELISA was carried out to evaluate the abundance of cytokines and luciferase assay was used to explore the inhibitory role of miR-23a on circRNA_FOXO3 and FOXO3. Accordingly, we found that rs12196996 GG and rs2232365 AA were significantly correlated with prolonged survival of ICU-acquired sepsis patients. Rs12196996 GG and rs2232365 AA were also correlated with increased level of miR-23a, IL-10 and decreased level of TNF, IL-2, IFN, IL-6 and IL-1β in the peripheral blood cell samples of patients with ICU-acquired sepsis. The luciferase activity of wild-type (WT) circRNA_FOXO3 and FOXO3 were severely reduced by miR-23a. MiR-23a precursors could effectively suppress the expression of circRNA_FOXO3 and FOXO3 in the cells. Moreover, LPS-induced cell viability loss and dysregulation of cytokines were effectively restored by the knockdown of FOXO3 or circRNA_FOXO3 siRNA in the cells. This study revealed that the minor allele of rs12196996 polymorphism and rs2232365 polymorphism collaboratively contributed to the increased survival and suppressed severity of ICU-acquired sepsis.

A review of the risk factors associated with juvenile-onset recurrent respiratory papillomatosis: genetic, immune and clinical aspects

BACKGROUND

Juvenile-onset recurrent respiratory papillomatosis (JoRRP) is one of the most common benign lesions of hyperplastic respiratory epithelial tissue in children and is predominantly caused by human papillomaviruses (HPVs) 6 and 11. The clinical course of the disease is variable, and some patients even develop a malignancy. The purpose of this review was to summarize the related factors affecting the disease course in patients with JoRRP.

DATA SOURCES

We used databases, including PubMed and Google Scholar, to search for publications on factors associated with the genetic, immune, and clinical aspects of JoRRP. The most relevant articles to the scope of this review were chosen for analysis.

RESULTS

Mother-to-child transmission is the most important mode of disease transmission; other factors, such as immune condition or genetic susceptibility, may be important determinants of JoRRP occurrence. Genetically, the presence of DRB1*0301 and HPV 6/11 E6/E7 is associated with a more severe disease. Immunewise, patients have an enhanced T helper 2-like response. In addition, regulatory T cells are enriched in tumors and may become one of the effective prognostic indicators. For clinical characteristics, patients infected with HPV-11 have more aggressive disease. However, compared with HPV type, age at first onset is a more important factor related to the aggressiveness of JoRRP. Furthermore, socioeconomic status may also affect the course.

CONCLUSIONS

Genetic, immune, and some clinical factors have been noted to play an important role in the course of JoRRP. Exploring definite influencing factors will be an important direction of research in the future.

FOXP3 and GATA3 Polymorphisms, Vitamin D3 and Multiple Sclerosis

BACKGROUND

Regulatory T cells (Tregs) alterations have been implicated in the pathogenesis of Multiple Sclerosis (MS). Recently, a crucial role of the X-Linked Forkhead Box P3 (FoxP3) for the development and the stability of Tregs has emerged, and FOXP3 gene polymorphisms have been associated with the susceptibility to autoimmune diseases. The expression of Foxp3 in Tregs is regulated by the transcription factor GATA binding-protein 3 (GATA3) and vitamin D3. The aim of this retrospective case-control study was to investigate the potential association between FOXP3 and GATA3 genetic variants, Vitamin D3, and MS risk.

METHODS

We analyzed two polymorphisms in the FOXP3 gene (rs3761547 and rs3761548) and a polymorphism in the GATA3 gene (rs3824662) in 106 MS patients and 113 healthy controls. Serum 25(OH)D3 was also measured in all participants.

RESULTS

No statistically significant genotypic and allelic differences were found in the distribution of FOXP3 rs3761547 and rs3761548, or GATA3 rs3824662 in the MS patients, compared with controls. Patients that were homozygous for rs3761547 had lower 25(OH)D3 levels.

CONCLUSIONS

Our findings did not show any association among FOXP3 and GATA3 SNPs, vitamin D3, and MS susceptibility.

Association of FOXP3 gene polymorphisms with chronic immune thrombocytopenia in a Chinese Han population

INTRODUCTION

Forkhead box P3 (Foxp3) is encoded by the human FOXP3, an X-chromosome gene, and is a transcription factor that regulates regulatory T-cell (Treg) development and function. FOXP3 gene polymorphisms have recently been investigated as candidate risk factors in various autoimmune diseases. This study aimed to investigate the possible influence of FOXP3 gene polymorphisms on genetic predisposition to chronic immune thrombocytopenia (ITP).

METHODS

The study cohort comprised 329 chronic ITP patients and 279 healthy controls, who were genotyped for three polymorphisms in the promoter region of FOXP3 gene, -6054 del/ATT, -3279 A/C, and -924 A/G.

RESULTS

Of the three polymorphisms identified, the -3279 AA genotype was more frequent in female patients with chronic ITP than in female controls (P = .035, OR 0.434, 95% CI 0.223-0.846), and the -3279 A carrier was shown to be associated with the risk of chronic ITP in female cohort (P = .003, OR 0.610, 95% CI 0.437-0.851). Furthermore, the female patients with chronic ITP had remarkably more frequent haplotype -6054 del/-3279 A/-924 A (P = .027, OR 3.584, 95% CI 1.148-11.186) and less haplotype -6054 del/-3279 C/-924 G (P = .039, OR 0.445, 95% CI 0.204-0.973) in comparison with female healthy controls. Although there were no significant differences in the male cohort, when the combined alleles and haplotypes of the two genders were analyzed, the results obtained were similar to those of females.

CONCLUSION

According to our data, the -3279 A/C polymorphism of FOXP3 gene may be associated with the susceptibility to chronic ITP in Chinese Han population.

FOXP3rs3761548 gene variant and interleukin-35 serum levels as biomarkers in patients with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS). Aberrant expression of transcription factor forkhead box P3 (FoxP3) has been suggested to underlie different immunological disorders as FOXP3 expression is essential for T regulatory cells (Tregs) to maintain their suppressive and anti-inflammatory functions and exert immunologic self-tolerance. Interleukin-35 (IL-35) is an important immunosuppressive cytokine that is produced mainly by CD4+ FOXP3+ Tregs.

OBJECTIVES

To assess the possible role of the FOXP3 rs3761548 (C/A) single-nucleotide variation (SNV) in relapsing-remitting multiple sclerosis (RRMS). Also, measurement of the serum IL-35 concentration and study its relation to different genotypes and the degree of disease-related disability.

METHODS

A total of 100 RRMS patients and 90 healthy control subjects were subjected to genotyping for the FOXP3 (rs3761548) variant by TaqMan real-time PCR, and measurement of the IL-35 level in their sera by Elisa.

RESULTS

The frequencies of the AA genotype and A allele were significantly higher in the MS patients than in the healthy controls (P=0.008, OR=2.53, 95% CI=1.27-5.04; P=0.001, OR=1.98, 95% CI=1.31-3.00, respectively). There was a significant association between FOXP3 rs3761548 variant and female MS patients. The serum IL-35 level was significantly higher in MS patients (1372 [575-2192] pg/mL) compared to healthy controls (604 [454-696] pg/mL) (P<0.0001). No significant differences were found between the different FOXP3 genotypes and EDSS score (P=0.730).

CONCLUSION

The FOXP3rs3761548 gene variant may influence the genetic susceptibility to MS rather than affecting its course, severity or progression. The serum IL-35 level might have a role in the development of the disease, however its role in disease-related disability is questionable.

Meta-analysis of FOXP3 gene rs3761548 and rs2232365 polymorphism and multiple sclerosis susceptibility

BACKGROUND

Multiple sclerosis (MS) is a common autoimmune disease of the central nervous system (CNS), and is associated with genetic factors. FOXP3 gene polymorphism has been reported as the risk factor for MS, however, previous studies have showed conflicting results. The purpose of this study is to investigate the association between FOXP3 gene polymorphism and the susceptibility to MS.

METHODS

Pubmed, Embase, library of Cochrane, and Web of Science were used to search the eligible articles from January 1980 up to October 2018. The odds ratio (ORs) and its 95% confidence intervals (CI) were used to evaluate the strength of association. Allele model, homozygote model, heterozygote model, dominant model, and recessive model were used to evaluate the association between FOXP3 gene polymorphism and MS.

RESULTS

A total of 5 studies contained 1276 MS patients and 1447 controls (for rs3761548) and 600 MS patients and 640 controls (for rs2232365) were enrolled in this meta-analysis. The association showed significant differences in allele and dominant model for rs3761548 polymorphism. In addition, a clear tendency to significance was detected in homozygote and recessive model for rs3761548 (P = .052). Subgroup analysis indicated a significant risk of MS in all genotype models but heterozygotes in Asians.

CONCLUSION

FOXP3 gene polymorphism rs3761548 was associated with a higher MS risk, especially in Asians. This conclusion needs to be validated in more large samples and multiracial studies.

LEVEL OF EVIDENCE

Level III diagnostic study.

The FOXP3 rs3761547 Gene Polymorphism in Multiple Sclerosis as a Male-Specific Risk Factor

The FOXP3 gene encodes a transcription factor and is predominantly expressed in the CD4+CD25+ regulatory T cells which plays a pivotal role in the maintenance of immune homeostasis. The defect of FOXP3 gene may provide a critical link between autoimmunity and immune deficiency. The purpose of our study was to evaluate the association of chosen polymorphisms of FOXP3 gene (rs3761549, rs3761548, rs3761547) with different clinical multiple sclerosis (MS) data of our relapsing-remitting groups of patients and in control group. The study was performed on a group consisting of 174 relapsing-remitting MS patients, diagnosed under 40 years of life, and 174 healthy volunteers. Genotyping was performed using a real-time PCR-based method by TaqMan Assays. Significant differences in distribution of allele C rs3761547 were found in male MS patients in comparison to the male healthy group (p = 0.046, OR 1.95, CI 95%). No association between MS and the other two polymorphisms was observed in males and females of both studied groups. Our data may suggest that FOXP3 rs3761547 gene polymorphism are related notably with the increased risk of MS development in males patients. To our knowledge this is the first study which indicates gender-specific relation between rs3761547 FOXP3 gene polymorphism and multiple sclerosis.

Associations of FoxP3 gene polymorphisms with severe recurrent respiratory papillomatosis in Korean patients

Background

FoxP3 is the most dependable marker for regulatory T cells which play a major role in immune tolerance. Foxp3 gene polymorphisms were associated with various autoimmune diseases and clearance of viral infections. We studied the association of Foxp3 polymorphisms in severe RRP patients.

Methods

A total of 30 Korean severe RRP patients and 195 healthy controls were enrolled. Foxp3 polymorphisms (rs5902434 del/ATT, rs3761548 C/A, rs3761549 C/T, and rs2232365 G/A) were determined by PCR and sequencing.

Results

Genotype frequencies (GF) of rs5902434 ATT/ATT and rs2232365 GG were significantly decreased in female RRP patients than controls (0.0% vs 23.0%, p = 0.039, OR = 9.4 for both).

Conclusions

We showed that Foxp3 polymorphism of rs5902434 and rs2232365 could be an important protective factor in the susceptibility of severe RRP in female Koreans. Further studies on larger number of patients and other ethnic groups are needed to clarify the association.

Single nucleotide polymorphisms in the FOXP3 gene are associated with increased risk of relapsing-remitting multiple sclerosis

BACKGROUND

Although Multiple Sclerosis (MS) is an autoimmune multifactorial disease with unknown etiology, various genetic and environmental factors are known to contribute to the pathogenesis of the disease.

OBJECTIVE

Recent studies have confirmed that the suppressive function of regulatory T cells (T (reg)) is impaired in MS patients and that the FOXP3 gene is a crucial transcription factor in the regulation of CD4+CD25+FOXP3+ Treg cells. Polymorphisms in the promoter region of the FOXP3 gene may alter the gene expression level and, therefore, contribute to the disease susceptibility.

METHODS

The present study aimed to investigate the possible association between single nucleotide polymorphisms (SNPs) rs3761548 and rs2232365 in the FOXP3 gene and predisposition to MS. We conducted a case-control study on 410 patients with sporadic MS and 446 healthy controls. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Significant differences in distribution of both rs3761548 and rs2232365 A allele were found in MS patients in comparison to controls. Haplotype frequencies were also different among the studied groups. The A-A and C-G haplotype blocks showed a significant difference between case and controls.

CONCLUSION

we have provided further evidence for the association between genetic variations and haplotypes in FOXP3 and MS in Iranian population.

Role of FOXP3 gene polymorphism in the susceptibility to Tunisian endemic Pemphigus Foliaceus

OBJECTIVE

Forkhead box P3 (FOXP3) is an essential and crucial transcription factor of regulatory T-cells. Genetic polymorphisms in the promoter region of FOXP3 gene may alter the gene expression level and, therefore, contribute to several autoimmune diseases susceptibility. We aimed to investigate the possible role of genetic variants of four SNPs (rs3761547, rs3761548, rs3761549 and rs2294021) and a (GT)_n microsatellite located in FOXP3 gene in the susceptibility to Tunisian Pemphigus Foliaceus (PF).

METHOD

A case-control study was conducted on 98 patients with different clinical features of PF and 182 matched healthy controls using PCR-RFLP method.

RESULTS

According to the epidemio-demographic features of the disease, patients were classified into two groups: an endemic group (n=33, mean age=31 [18-48]) versus a sporadic one (n=65, mean age=36 [19-84]). In the whole population, rs3761548, rs3761549 and rs2294021 were associated with the susceptibility to PF. Interestingly, significant differences of gene distributions between the two sub-groups of patients were observed. In the endemic group, all associations observed in the whole population were maintained and reinforced and a new association was revealed with rs3761547; while in the sporadic group, only the association with rs3761549 was conserved. Further, the haplotype analysis showed that the G-A-C-15-C risk haplotype was significantly much more expressed in PF patients and specially in the endemic group. The phenotype-genotype correlation revealed that the rs3761548>AA genotype was significantly correlated with the severity of the disease including Nickolsky sign, generalized form of the disease and the earliest age onset.

CONCLUSION

These results underline the particular genetic background of the Tunisian endemic PF and suggest the implication of FOXP3 gene in the susceptibility and the clinical course of the disease.

Association of aplastic anemia and FoxP3 gene polymorphisms in Koreans

OBJECTIVES

Aplastic anemia (AA) is characterized by pancytopenia and bone marrow failure, and most acquired AA is an immune-mediated disorder. Regulatory T cells (T_regs) suppressing autoreactive T cells were decreased in AA patients. FoxP3 is a major regulator for the development and function of T_regs. Polymorphism in FoxP3 was shown to be associated with various autoimmune diseases, however, has not yet been studied in AA. In this study, we examined the association between FoxP3 polymorphisms and AA in Korean patients.

METHODS

The study population consisted of 94 patients diagnosed by bone marrow examination in Seoul National University Hospital (SNUH) during 1997-2012 and 195 healthy controls. FoxP3 polymorphisms (rs5902434 del/ATT, rs3761548 C/A, rs3761549 C/T, rs2232365 A/G) were analyzed by PCR-sequencing method. We analyzed differences of genotype and allele frequencies between patients and controls. We also compared differences of genotype and allele frequencies between responder and non-responder in patients treated with immunosuppressive therapy (IST). For the statistical analysis, the chi-square test and Fisher's exact test were used and P < 0.05 was regarded as statistically significant.

RESULTS

There was no significant difference in the genotype frequencies of FoxP3 polymorphisms between patients and controls. With regards to the allele frequencies, rs3761548 C allele was significantly higher in AA patients than in controls (87.4% vs. 79.7%, P = 0.047). In patients treated with IST, rs3761549 C allele was significantly higher in non-responder patients than in responders (89.6% vs. 66.7%, P = 0.036) and female rs3761549 C/C genotype carriers were associated with greater risk for non-response to IST (84.2% vs. 16.7%, P = 0.006).

CONCLUSION

Polymorphisms in rs3761548 and rs3761549 of FoxP3 in our population were associated with disease susceptibility and response for IST, respectively. This study suggests an association between FoxP3 polymorphisms and AA in Korean patients and will be useful in further understanding the genetic basis of disease susceptibility and response to IST in AA patients.

FOXO3A regulatory polymorphism and susceptibility to severe malaria in Gabonese children

The clinical course of malaria varies between affected individuals and host genetic factors have been shown to influence the outcome of malaria. The role of FOXO3-driven pathway in modulating inflammatory responses, including mediation of distinct functions of regulatory T effector cell populations (Tregs) by the transcription factor FOXO3, has recently been recognized. We aimed to study possible associations of a non-coding polymorphism in intron 2 of the FOXO3A gene (rs12212067T>G) that was shown earlier to modulate the FOXO3 expression and to be associated with the prognosis of distinct inflammatory and infectious diseases. The FOXO3A polymorphism rs12212067T>G was genotyped by direct sequencing in a group of Gabonese children with confirmed Plasmodium falciparum malaria. Severe cases of malaria were compared with asymptomatic/mild cases. The FOXO3A variant rs12212067T>G was associated with the phenotype of severe malaria, but not with asymptomatic/mild malaria (allelic model: OR = 1.54, 95 % CI = 1.15-2.05, P = 0.0028; dominant model: OR = 1.94, 95 % CI = 1.36-2.77, P = 0.0002). The FOXO3A variant rs12212067T>G is associated with increased inflammatory responses to Plasmodium falciparum malaria, indicating a role of the FOXO3-dependent pathway in malaria.

Analysis of genetic variants in the IL4 promoter and VNTR loci in Indian patients with Visceral Leishmaniasis

Visceral Leishmaniasis (VL) is the most severest form of Leishmaniasis and resistance to infection is mediated by cellular immune responses. Interleukin 4 (IL-4) orchestrates of Th2 and Th1 immune responses during infections. In this study, we aimed to investigate possible association between three functional IL-4 polymorphisms -590C/T (rs2243250), -34C/T (rs2070874) and 70bp VNTR (rs79071878 in intron3) with VL in an Indian cohort comprising of 197 VL patients and 193 healthy controls. The three investigated IL-4 polymorphisms were in strong linkage disequilibrium. The investigated IL-4 alleles, genotypes and the reconstructed haplotypes were not significantly distributed between the VL patients and healthy controls. Our study signifies no possible association of functional IL-4 polymorphisms with Indian VL and postulate other vital genes involved in the IL-4 pathway may provide genetic clues to elucidate of IL-4 regulation and immune-pathogenesis during VL.

Analysis of polymorphic sites in the promoter of the nitric oxide synthase 2 gene in Brazilian patients with leprosy

Leprosy is one of the most neglected infectious tropical diseases of the skin and the nerves caused by the intracellular pathogen Mycobacterium leprae. The inducible NOS isoform encoded by NOS2A plays a vital role in host defence against bacterial infections. The functional promoter polymorphisms in NOS2A are associated with various autoimmune and infectious diseases. We investigated the association of NOS2A variants with progression of leprosy in a Brazilian cohort including 221 clinically classified patients and 103 unrelated healthy controls. We observed a novel variant ss528838018A/G in the promoter region at position -6558. The other functional variants were observed with low frequency of minor allele (<0.005). NOS2A promoter variant (-954G/C) was not observed in Brazilian populations, and the new observed promoter variant (ss528838018A/G) as well as other promoter variants were not associated with any clinical forms of leprosy in the Brazilian populations.

Genetic polymorphism in FOXP3 gene: imbalance in regulatory T-cell role and development of human diseases

The FOXP3 gene encodes a transcription factor thought to be important for the development and function of regulatory T cells (Treg cells). These cells are involved in the regulation of T cell activation and therefore are essential for normal immune homeostasis. Signals from microenvironment have a profound influence on the maintenance or progression of diseases. Thus, Tregs have an important marker protein, FOXP3, though it does not necessarily confer a Treg phenotype when expressed. FOXP3 polymorphisms that occur with high frequency in the general populations have been studied in common multifactorial human diseases. Dysfunction of FOXP3 gene product could result in lack of Treg cells and subsequently chronically activated CD4+ T cells which express increased levels of several activation markers and cytokines, resulting in some autoimmune diseases. In contrast, high Treg levels have been reported in peripheral blood, lymph nodes, and tumour specimens from patients with different types of cancer. The present study discusses the polymorphisms located in intron, exon and promoter regions of FOXP3 which have already been investigated by many researchers. FOXP3 has received considerable attention in attempts to understand the molecular aspect of Treg cells. Therefore, in the present study, the relationship between genetic polymorphism of FOXP3 in Treg-cell role and in disease development are reviewed considering the interactive effect of genetic factors.

Genetic evidence of regulatory gene variants of the STAT6, IL10R and FOXP3 locus as a susceptibility factor in uncomplicated malaria and parasitaemia in Congolese children

Background

Regulatory T cells (Tregs) are a subset of T cells that play an important role in modulating T effector responses during infectious challenges. The aim of this study was to evaluate possible associations between regulatory gene polymorphisms and the risk of uncomplicated malaria and the control of Plasmodium falciparum parasite density levels.

Methods

Twelve regulatory single nucleotide polymorphisms (SNPs) in the promoter regions of FOXP3 (ss270137548, rs11091253), IL10RA (rs56356146, rs7925112), IL10RB (rs8178433, rs8178435, rs999788), STAT6 (rs3024941, rs3024943, rs3024944) and TNFRSF18 (ss2080581728, rs3753344) were genotyped in a cohort of Congolese children. Studied subjects were followed up (passively) during one year. The children who experienced one or several clinical episodes were genotyped as “uncomplicated malaria” group (n=179) and those children who did not experience any episode were genotyped as “asymptomatic children” group (n=138).

Results

The prevalence of rs3024944CC genotype of STAT6 was significantly higher in the group of asymptomatic children compared to that of uncomplicated malaria (P=0.003). Similarly, the minor allele rs3024944C was more prevalent in the group of asymptomatic children (P=0.019). Two novel SNPs were observed including -163T/G (ss491228441) in IL10RA gene and -163C/T (ss491228440) in TNFRSF18 gene. The genotype ss491228441TT and the minor allele ss491228441G of the IL10RA were more frequent in the group of asymptomatic children (P=0.006 and P=0.007, respectively). The genotype rs11091253CT of the FOXP3 was associated with high parasite density levels. In addition, a new promoter IL10RA variant (ss491228441) contributes to shield against mild malaria.

Conclusion

The study indicated that the STAT6 promoter polymorphism rs3024944 was associated with uncomplicated malaria, whereas the FOXP3 promoter variant rs11091253 was associated with significant P. falciparum parasitaemia levels. These genetic data may contribute to the understanding of molecular mechanisms that regulate immune response to P. falciparum infections.

In-vitro characterization of novel and functional regulatory SNPs in the promoter region of IL2 and IL2R alpha in a Gabonese population

Background

The selection pressure imposed by the parasite has a functional consequence on the immune genes, leading to altered immune function in which regulatory T cells (Tregs) induced by parasites during infectious challenges modulate or thwart T effector cell mechanism.

Methods

We identified and investigated regulatory polymorphisms in the immune gene IL2 and its receptor IL2R alpha (also known as CD25) in Gabonese individuals exposed to plentiful parasitic infections.

Results

We identified two reported variants each for IL2 and its receptor IL2R alpha gene loci. Also identified were two novel variants, -83 /-84 CT deletions (ss410961576) for IL2 and -409C/T (ss410961577) for IL2R alpha. We further validated all identified promoter variants for their allelic gene expression using transient transfection assays. Three promoter variants of the IL2 locus revealed no significant expression of the reporter gene. The identified novel variant (ss410961577C/T) of the IL2R alpha revealed a significant higher expression of the reporter gene in comparison to the major allele (P<0.05). In addition, the rs12722616C/T variant of the IL2R alpha locus altered the transcription factor binding site TBP (TATA box binding protein) and C/EBP beta (CCAAT/enhancer binding protein beta) that are believed to regulate the Treg function.

Conclusions

The identification and validation of such regulatory polymorphisms in the immune genes may provide a basis for future studies on parasite susceptibility in a population where T cell functions are compromised.

Regulatory T cells and parasites

Human host encounters a wide array of parasites; however, the crucial aspect is the failure of the host immune system to clear these parasites despite antigen recognition. In the recent past, a new immunological concept has emerged, which provides a framework to better understand several aspects of host susceptibility to parasitic infection. It is widely believed that parasites are able to modulate the magnitude of effector responses by inducing regulatory T cell (Tregs) population and several studies have investigated whether this cell population plays a role in balancing protective immunity and pathogenesis during parasite infection. This review discusses the several mechanism of Treg-mediated immunosuppression in the human host and focuses on the functional role of Tregs and regulatory gene polymorphisms in infectious diseases.