Polymorphism in promoter region of inducible nitric oxide synthase gene and protection against malaria

Inducible Nitric Oxide Synthase iNOS-954-G>C and Ex16+14-C>T Gene Polymorphisms and Susceptibility to Vitiligo in the Saudi Population

Objective

Vitiligo is an acquired pigmentary skin disorder with regional disappearance of melanocytes. Multigenic inheritance has been proposed in the pathogenesis of vitiligo. The present study aimed to investigate the possible association of inducible nitric oxide synthase polymorphisms iNOS-954-G/C (rs1800482 G>C) and iNOS-Ex16+14-C/T (rs2297518 C>T) with vitiligo in the Saudi population, if any.

Methods

We included 120 vitiligo cases and an equal number of age matched healthy controls. Polymerase chain reaction with restriction fragment length polymorphism method was used for the analysis of genetic polymorphisms.

Results

The heterozygous (GC), (GC + CC) combined genotype and variant allele; C allele of rs1800482 G>C were associated significantly (p < 0.005, after Bonferroni correction) with increased risk of vitiligo (OR = 3.46, 95% CI = 1.99–6.01, p = 0.001), (OR = 3.30, 95% CI= 1.93–5.65, p = 0.001) and (OR = 1.94, 95% CI = 1.31–2.87, p = 0.001) respectively. When GC genotype of rs1800482 G>C was co-inherited with common genotype (CC) and heterozygous genotype (CT) of rs2297518 C>T, the risk of vitiligo was significantly increased ((OR = 4.51, 95% CI = 2.18–9.33, p = 0.001) and (OR = 3.60, 95% CI = 1.61–8.01, p = 0.001)) respectively. None of the rs1800482 G>C and rs2297518 C>T genotypes and alleles have been associated with non-segmental vitiligo in terms of gender, age of onset, and types of vitiligo.

Conclusion

The heterozygous (GC), (GC+CC) combined genotype and variants allele; C allele of rs1800482 G>C, may cause overproduction of NO, which has been linked to melanocyte loss by increasing oxidative stress and decreasing melanocyte adhesion to the extracellular matrix components, and thus could be an associative risk factor for vitiligo.

Association of TNF-Alpha, MBL2, NOS2, and G6PD with Malaria Outcomes in People in Southern Ghana

Background

One major issue that has set back the gains of the numerous malaria control interventions that national malaria control programs have implemented is asymptomatic malaria. Certain host genetic factors are known to influence symptomatic malaria; however, not much is known about how host genetics influences the acquisition of asymptomatic malaria.

Methods

Genomic DNA was extracted from whole blood collected from 60 symptomatic and 149 nonfebrile (asymptomatic, N = 109, and uninfected, N = 40) volunteers aged between 2 and 69 years from a high (Obom) and a low (Asutsuare) malaria transmission setting in Southern Ghana. Restriction fragment length polymorphism (RFLP) was used to determine polymorphisms at the MBL2 54, TNF-α 308, NOS2 954, and G6PD 202/376 gene loci.

Results

Polymorphisms at the MBL2 54 and TNF-α 308 loci were significantly different amongst the three categories of volunteers in both Asutsuare (p = 0.006) and Obom (p=0.05). In Asutsuare, a low malaria transmission area, the allele G has significantly higher odds (3.15) of supporting asymptomatic malaria as against symptomatic malaria. There were significantly higher odds of TNF-α genotype GA being associated with symptomatic malaria as against asymptomatic malaria in both sites, Obom (p=0.027) and Asutsuare (p=0.027). The allele B of the G6PD gene was more prevalent in symptomatic rather than asymptomatic parasite-infected individuals in both Obom (p=0.001) and Asutsuare (p=0.003).

Conclusion

Individuals in Southern Ghana carrying the TNF-α 308 GA genotype are more likely to exhibit symptoms of malaria when infected with the malaria parasite as opposed to harboring an asymptomatic infection. Also, the B allele of the G6PD gene is likely to prevent a P. falciparum-infected person from exhibiting symptoms and thereby promote asymptomatic parasite carriage.

Association of Polymorphisms in the Promoter Region of NOS2A Gene with Primary Knee Osteoarthritis in the Greek Population

Introduction

A new emerging role of nitric oxide (NO) in the aetiology of osteoarthritis (OA) has been reported. Inducible NO synthase (iNOS), produced by chondrocytes, is the major source of NO in the osteoarthritic cartilage. The aim of this study is to evaluate the potential association between the -1173C/T (rs9282799), -1026 C/A (rs 2779249) and -954G/C (rs1800482) single nucleotide polymorphisms (SNPs) in the promoter of the iNOS gene (NOS2A) and the incidence of knee OA in Greek population.

Methods

Ninety-six patients with primary knee OA were included in the study along with 44 controls. Genotypes were identified using polymerase chain reaction (PCR) and DNA sequencing techniques. Allelic and genotypic frequencies were compared between patients and controls.

Results

None of the -1173C/T, -1026 C/A and -954G/C SNPs were detected in the studied population, either in patients or controls. However, another SNP was identified at the site -1056 at the promoter region, where the initial G allele was substituted by the T allele. Interestingly, the TT genotype was completely absent in controls, but was detected in six patients with a 6.2% observed frequency. The difference between patients and controls was not statistically significant (p-value = 0.18). In male OA patients, the observed frequency of the TT genotype was higher (28.6%) in comparison to the 0% of the male controls (p-value = 0.1). The frequency of the G allele was 0.82 in controls and 0.78 in OA patients (p-value = 0.53).

Conclusions

The present study demonstrates that the 954G/C, -1026C/A, -1056G/T and -1173C/T SNPs of the NOS2A gene are not a risk factor for primary knee OA in Greek population. Moreover, -954G/C, -1026C/A and -1173C/T are rare, if not completely absent, in the Greek population. Additional research is mandatory in order to investigate the association of these SNPs with OA in different ethnic populations.

Genetics of Malaria Inflammatory Responses: A Pathogenesis Perspective

Despite significant progress in combating malaria in recent years the burden of severe disease and death due to Plasmodium infections remains a global public health concern. Only a fraction of infected people develops severe clinical syndromes motivating a longstanding search for genetic determinants of malaria severity. Strong genetic effects have been repeatedly ascribed to mutations and allelic variants of proteins expressed in red blood cells but the role of inflammatory response genes in disease pathogenesis has been difficult to discern. We revisited genetic evidence provided by inflammatory response genes that have been repeatedly associated to malaria, namely TNF, NOS2, IFNAR1, HMOX1, TLRs, CD36, and CD40LG. This highlighted specific genetic variants having opposing roles in the development of distinct malaria clinical outcomes and unveiled diverse levels of genetic heterogeneity that shaped the complex association landscape of inflammatory response genes with malaria. However, scrutinizing genetic effects of individual variants corroborates a pathogenesis model where pro-inflammatory genetic variants acting in early infection stages contribute to resolve infection but at later stages confer increased vulnerability to severe organ dysfunction driven by tissue inflammation. Human genetics studies are an invaluable tool to find genes and molecular pathways involved in the inflammatory response to malaria but their precise roles in disease pathogenesis are still unexploited. Genome editing in malaria experimental models and novel genotyping-by-sequencing techniques are promising approaches to delineate the relevance of inflammatory response gene variants in the natural history of infection thereby will offer new rational angles on adjuvant therapeutics for prevention and clinical management of severe malaria.

Inducible nitric oxide synthase 2 promoter polymorphism and malaria disease severity in children in Southern Ghana

Objective

We assessed the association of mutant allele frequencies of nitric oxide synthase 2 (NOS2) gene at two SNPs (-954 and -1173) with malaria disease severity in children from a malaria endemic area in Southern Ghana.

Method

Using children recruited at the hospital, assigned into clinical subgroups of uncomplicated and severe malaria and matching with their “healthy control” counterparts, we designed a case control study. Genomic DNA was extracted and genotyping using Restriction Fragment Polymorphism was done.

Result

A total of 123 malaria cases (91 uncomplicated, 32 severe) and 100 controls were sampled. Their corresponding mean Hbs were 9.6, 9.3 and 11.2g/dl and geometric mean parasite densities of 32097, 193252 and 0 parasites/ml respectively. Variant allele frequencies varied from 0.09 through 0.03 to 0.12 for G-954C and 0.06 through 0.03 to 0.07 for C-1173T in the uncomplicated, severe and healthy control groups respectively. There was a strong linkage disequilibrium between the two alleles (p<0.001). For the -954 position, the odds of developing severe malaria was found to be 2.5 times lower with the carriage of a C allele compared to those without severe malaria (χ²; p< 0.05) though this isn’t the case with -1173.

Conclusion

The carriage of a mutant allele in the -954 NOS2 gene may have a protective effect on malaria among Southern Ghanaian children.

Prevalence and Molecular Study of G6PD Deficiency in the Dai and Jingpo Ethnic Groups in the Dehong Prefecture of the Yunnan Province

OBJECTIVES

To estimate the prevalence and mutation types of G6PD deficiency and evaluate the relationship between G6PD genotypes and erythrocyte phenotypes in the Dai and Jingpo ethnic groups in the Dehong prefecture of the Yunnan province, China.

METHODS

G6PD deficiency was screened in Dai (1,530 individuals) and Jingpo (372 individuals) populations using a modified G6PD/6PGD ratio assay. Red blood cell traits were analyzed using the Sysmex XE2100 fully automated blood analyzer. PCR-direct sequencing for G6PD genotyping analysis was performed, and then the linkage disequilibrium blocks of the target SNPs were constructed with Haploview 4.2 software.

RESULTS

The prevalence of G6PD deficiency was higher in the Dai ethnic group (8.63%) than in the Jingpo ethnic group (5.91%). The major mutations in descending order were rs137852314 G>A, rs72554664 G>A, rs72554665 G>T, and rs137852341 G>T. Hemoglobin concentration was significantly lower in the rs137852314 G>A group than in the normal group (p = 0.021). Mean corpuscular volume and mean corpuscular hemoglobin were substantially higher in the rs137852341 G>T group compared to the normal group (p = 0.049, p = 0.042). A linkage disequilibrium block of 13 SNPs was constructed for the G6PD deficiency group from the Dai sample.

CONCLUSIONS

The Dai and Jingpo ethnic groups have distinctive incidence rates and gene frequencies of G6PD deficiency, and the genotypes of G6PD deficiency are associated with erythrocyte phenotypes.

iNOS polymorphism modulates iNOS/NO expression via impaired antioxidant and ROS content in P. vivax and P. falciparum infection

Nitric oxide (NO) has dicotomic influence on modulating host-parasite interplay, synchronizing physiological orchestrations and diagnostic potential; instigated us to investigate the plausible association and genetic regulation among NO level, components of oxidative stress, iNOS polymorphisms and risk of malaria. Here, we experimentally elucidate that iNOS promoter polymorphisms are associated with risk of malaria; employing mutation specific genotyping, functional interplay using western blot and RT-PCR, quantitative estimation of NO, total antioxidant content (TAC) and reactive oxygen species (ROS).

Genotyping revealed significantly associated risk of P. vivax (adjusted OR = 1.92 and 1.72) and P. falciparum (adjusted OR = 1.68 and 1.75) infection with SNP at iNOS-954G/C and iNOS-1173C/T positions, respectively; though vivax showed higher risk of infection. Intriguingly, mutation and infection specific differential upregulation of iNOS expression/NO level was observed and found to be significantly associated with mutant genotypes. Moreover, P. vivax showed pronounced iNOS protein (2.4 fold) and mRNA (2.5 fold) expression relative to healthy subjects. Furthermore, TAC and ROS were significantly decreased in infection; and differentially decreased in mutant genotypes.

Our findings endorse polymorphic regulation of iNOS expression, altered oxidant-antioxidant components and evidences of risk association as the hallmark of malaria pathogenesis. iNOS/NO may serve as potential diagnostic marker in assessing clinical malaria.

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Polymorphism of iNOS revealed significantly associated risk of P. vivax and P. falciparum malaria and vivax showed higher risk of infection.

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We observed mutation and infection specific differential expression of iNOS/NO cascade.

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We investigated mutation specific antioxidant and ROS orchestration and observed lower TAC and ROS content in infection.

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Evaluated the clinical correlation among stratified axillary temperature, NO and haemoglobin content during infection.

Susceptibility to Mycobacterium ulcerans Disease (Buruli ulcer) Is Associated with IFNG and iNOS Gene Polymorphisms

Buruli ulcer (BU) is a chronic necrotizing disease of the skin and subcutaneous fat tissue. The causative agent, Mycobacterium ulcerans, produces mycolactone, a macrolide toxin, which causes apoptosis of mammalian cells. Only a small proportion of individuals exposed to M. ulcerans develop clinical disease, as surrounding macrophages may control the infection by bacterial killing at an early stage, while mycolactone concentration is still low. Otherwise, bacterial multiplication leads to in higher concentrations of mycolactone, with formation of necrotizing lesions that are no more accessible to immune cells. By typing a cohort of 96 Ghanaian BU patients and 384 endemic controls without BU, we show an association between BU and single nucleotide polymorphisms (SNPs) in iNOS (rs9282799) and IFNG (rs2069705). Both polymorphisms influence promoter activity in vitro. A previously reported SNP in SLC11A1 (NRAMP, rs17235409) tended to be associated with BU. Altogether, these data reflect the importance of IFNG signaling in early defense against M. ulcerans infection.

Overview of human genetic susceptibility to malaria: From parasitemia control to severe disease

Malaria is a life-threatening blood disease caused by the protozoan Plasmodium. Infection may lead to several different patterns of symptoms in the host: asymptomatic state, uncomplicated disease or severe disease. Severe malaria occurs mostly in young children and is a major cause of death. Disease is thought to result from the sequestration of parasites in the small blood vessels of the brain and the deregulation of key immune system elements. The cellular and molecular regulatory mechanisms underlying the pathogenesis of disease are however not fully understood. What is known it is that the genetic determinants of the host play an important role in the severity of the disease and the outcome of infection. Here we review the most convincing results obtained through genetic epidemiology studies concerning the genetic control of malaria in human caused by Plasmodium falciparum infection. The identification of genes conferring susceptibility or resistance to malaria might improve diagnosis and treatment.

Correlation of plasma nitrite/nitrate levels and inducible nitric oxide gene expression among women with cervical abnormalities and cancer

Cervical cancer is caused by infection with high risk human papillomavirus (HR-HPV). Inducible nitric oxide synthase (iNOS), a soluble factor involved in chronic inflammation, may modulate cervical cancer risk among HPV infected women. The aim of the study was to measure and correlate plasma nitrite/nitrate levels with tissue specific expression of iNOS mRNA among women with different grades of cervical lesions and cervical cancer. Tissue biopsy and plasma specimens were collected from 120 women with cervical neoplasia or cancer (ASCUS, LSIL, HSIL and invasive cancer) and 35 women without cervical abnormalities. Inducible nitric oxide synthase (iNOS) mRNA from biopsy and plasma nitrite/nitrate levels of the same study subjects were measured. Single nucleotide polymorphism (SNP) analysis was performed on the promoter region and Ser608Leu (rs2297518) in exon 16 of the iNOS gene. Differences in iNOS gene expression and plasma nitrite/nitrate levels were compared across disease stage using linear and logistic regression analysis. Compared to normal controls, women diagnosed with HSIL or invasive cancer had a significantly higher concentration of plasma nitrite/nitrate and a higher median fold-change in iNOS mRNA gene expression. Genotyping of the promoter region showed three different variations: A pentanucleotide repeat (CCTTT) n, -1026T > G (rs2779249) and a novel variant -1153T > A. These variants were associated with increased levels of plasma nitrite/nitrate across all disease stages. The higher expression of iNOS mRNA and plasma nitrite/nitrate among women with pre-cancerous lesions suggests a role for nitric oxide in the natural history of cervical cancer.

IL10A genotypic association with decreased IL-10 circulating levels in malaria infected individuals from endemic area of the Brazilian Amazon

Background

Cytokines play an important role in human immune responses to malaria and variation in their production may influence the course of infection and determine the outcome of the disease. The differential production of cytokines has been linked to single nucleotide polymorphisms in gene promoter regions, signal sequences, and gene introns. Although some polymorphisms play significant roles in susceptibility to malaria, gene polymorphism studies in Brazil are scarce.

Methods

A population of 267 individuals from Brazilian Amazon exposed to malaria was genotyped for five single nucleotide polymorphisms (SNPs), IFNG + 874 T/A, IL10A-1082G/A, IL10A-592A/C, IL10A-819 T/C and NOS2A-954G/C. Specific DNA fragments were amplified by polymerase chain reaction, allowing the detection of the polymorphism genotypes. The polymorphisms IL10A-592A/C and IL10A-819 T/C were estimated by a single analysis due to the complete linkage disequilibrium between the two SNPs with D’ = 0.99. Plasma was used to measure the levels of IFN-γ and IL-10 cytokines by Luminex and nitrogen radicals by Griess reaction.

Results

No differences were observed in genotype and allelic frequency of IFNG + 874 T/A and NOS2A-954G/C between positive and negative subjects for malaria infection. Interesting, the genotype NOS2A-954C/C was not identified in the study population. Significant differences were found in IL10A-592A/C and IL10A-819 T/C genotypes distribution, carriers of IL10A -592A/-819 T alleles (genotypes AA/TT + AC/TC) were more frequent among subjects with malaria than in negative subjects that presented a higher frequency of the variant C allele (p < 0.0001). The presence of the allele C was associated with low producer of IL-10 and low parasitaemia. In addition, the GTA haplotypes formed from combinations of investigated polymorphisms in IL10A were significantly associated with malaria (+) and the CCA haplotype with malaria (−) groups. The IL10A-1082G/A polymorphism showed high frequency of heterozygous AG genotype in the population, but it was not possible to infer any association of the polymorphism because their distribution was not in Hardy Weinberg equilibrium.

Conclusion

This study shows that the IL10A-592A/C and IL10A-819 T/C polymorphisms were associated with malaria and decreased IL-10 levels and low parasite density suggesting that this polymorphism influence IL-10 levels and may influence in the susceptibility to clinical malaria.

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.

Association of candidate gene polymorphisms and TGF-beta/IL-10 levels with malaria in three regions of Cameroon: a case-control study

Background

Plasmodium falciparum malaria is one of the most widespread and deadliest infectious diseases in children under five years in endemic areas. The disease has been a strong force for evolutionary selection in the human genome, and uncovering the critical host genetic factors that confer resistance to the disease would provide clues to the molecular basis of protective immunity and improve vaccine development initiatives.

Methods

The effect of single nucleotide polymorphisms (SNPs) and plasma transforming growth factor beta (TGF-β) and interleukin 10 (IL-10) levels on malaria pathology was investigated in a case–control study of 1862 individuals from two major ethnic groups in three regions with intense perennial P. falciparum transmission in Cameroon. Thirty-four malaria candidate polymorphisms, including the sickle cell trait (HbS), were assayed on the Sequenom iPLEX platform while plasma TGF-β and IL-10 levels were measured by sandwich ELISA.

Results

The study confirms the known protective effect of HbS against severe malaria and also reveals a protective effect of SNPs in the nitrogen oxide synthase 2 (NOS2) gene against malaria infection, anaemia and uncomplicated malaria. Furthermore, ADCY9 rs10775349 (additive G) and ABO rs8176746 AC individuals were associated with protection from hyperpyrexia and hyperparasitaemia, respectively. Meanwhile, individuals with the EMR1 rs373533 GT, EMR1 rs461645 CT and RTN3 rs542998 (additive C) genotypes were more susceptible to hyperpyrexia while both females and males with the rs1050828 and rs1050829 SNPs of G6PD, respectively, were more vulnerable to anaemia. Plasma TGF-β levels were strongly correlated with heterozygosity for the ADCY9 rs2230739 and HBB rs334 SNPs while individuals with the ABO rs8176746 AC genotype had lower IL-10 levels.

Conclusion

Taken together, this study suggests that some rare polymorphisms in candidate genes may have important implications for the susceptibility of Cameroonians to severe malaria. Moreover using the uncomplicated malaria phenotype may permit the identification of novel pathways in the early development of the disease.

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.

Host susceptibility to malaria in human and mice: compatible approaches to identify potential resistant genes

There is growing evidence for human genetic factors controlling the outcome of malaria infection, while molecular basis of this genetic control is still poorly understood. Case-control and family-based studies have been carried out to identify genes underlying host susceptibility to malarial infection. Parasitemia and mild malaria have been genetically linked to human chromosomes 5q31-q33 and 6p21.3, and several immune genes located within those regions have been associated with malaria-related phenotypes. Association and linkage studies of resistance to malaria are not easy to carry out in human populations, because of the difficulty in surveying a significant number of families. Murine models have proven to be an excellent genetic tool for studying host response to malaria; their use allowed mapping 14 resistance loci, eight of them controlling parasitic levels and six controlling cerebral malaria. Once quantitative trait loci or genes have been identified, the human ortholog may then be identified. Comparative mapping studies showed that a couple of human and mouse might share similar genetically controlled mechanisms of resistance. In this way, char8, which controls parasitemia, was mapped on chromosome 11; char8 corresponds to human chromosome 5q31-q33 and contains immune genes, such as Il3, Il4, Il5, Il12b, Il13, Irf1, and Csf2. Nevertheless, part of the genetic factors controlling malaria traits might differ in both hosts because of specific host-pathogen interactions. Finally, novel genetic tools including animal models were recently developed and will offer new opportunities for identifying genetic factors underlying host phenotypic response to malaria, which will help in better therapeutic strategies including vaccine and drug development.

NOS2 variants reveal a dual genetic control of nitric oxide levels, susceptibility to Plasmodium infection, and cerebral malaria

Nitric oxide (NO) is a proposed component of malaria pathogenesis, and the inducible nitric oxide synthase gene (NOS2) has been associated to malaria susceptibility. We analyzed the role of NOS2 polymorphisms on NO bioavailability and on susceptibility to infection, Plasmodium carrier status and clinical malaria. Two distinct West African sample collections were studied: a population-based collection of 1,168 apparently healthy individuals from the Príncipe Island and a hospital-based cohort of 269 Angolan children. We found that two NOS2 promoter single-nucleotide polymorphism (SNP) alleles associated to low NO plasma levels in noninfected individuals were also associated to reduced risk of pre-erythrocytic infection as measured anti-CSP antibody levels (6.25E-04 < P < 7.57E-04). In contrast, three SNP alleles within the NOS2 cistronic region conferring increased NO plasma levels in asymptomatic carriers were strongly associated to risk of parasite carriage (8.00E-05 < P < 7.90E-04). Notwithstanding, three SNP alleles in this region protected from cerebral malaria (7.90E-4 < P < 4.33E-02). Cohesively, the results revealed a dual regimen in the genetic control of NO bioavailability afforded by NOS2 depending on the infection status. NOS2 promoter variants operate in noninfected individuals to decrease both NO bioavailability and susceptibility to pre-erythrocytic infection. Conversely, NOS2 cistronic variants (namely, rs6505469) operate in infected individuals to increase NO bioavailability and confer increased susceptibility to unapparent infection but protect from cerebral malaria. These findings corroborate the hypothesis that NO anti-inflammatory properties impact on different steps of malaria pathogenesis, explicitly by favoring infection susceptibility and deterring severe malaria syndromes.

No association of IFNG+874T/A SNP and NOS2A-954G/C SNP variants with nitric oxide radical serum levels or susceptibility to tuberculosis in a Brazilian population subset

Tuberculosis (TB) is one of the most common infectious diseases in the world. Mycobacterium tuberculosis infection leads to pulmonary active disease in approximately 5-10% of exposed individuals. Both bacteria- and host-related characteristics influence latent infection and disease. Host genetic predisposition to develop TB may involve multiple genes and their polymorphisms. It was reported previously that interferon gamma (IFN-γ) and nitric oxide synthase 2 (NOS2) are expressed on alveolar macrophages from TB patients and are responsible for bacilli control; thus, we aimed this study at genotyping single nucleotide polymorphisms IFNG+874T/A SNP and NOS2A-954G/C SNP to estimate their role on TB susceptibility and determine whether these polymorphisms influence serum nitrite and NOx(-) production. This case-control study enrolled 172 TB patients and 179 healthy controls. Neither polymorphism was associated with susceptibility to TB. NOS2A-954G/C SNP was not associated with serum levels of nitrite and NOx(-). These results indicate that variants of IFNG+874T/A SNP and NOS2A-954G/C SNP do not influence TB susceptibility or the secretion of nitric oxide radicals in the study population.

Co-infection of human parvovirus B19 with Plasmodium falciparum contributes to malaria disease severity in Gabonese patients

Background

High seroprevalence of parvovirus B19 (B19V) coinfection with Plasmodium falciparum has been previously reported. However, the impact of B19V-infection on the clinical course of malaria is still elusive. In this study, we investigated the prevalence and clinical significance of B19V co-infection in Gabonese children with malaria.

Methods

B19V prevalence was analyzed in serum samples of 197 Gabonese children with P. falciparum malaria and 85 healthy controls using polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and direct DNA-sequencing.

Results

B19V was detected in 29/282 (10.28%) of Gabonese children. B19V was observed more frequently in P. falciparum malaria patients (14.21%) in comparison to healthy individuals (1.17%) (P<0.001). Notably, the mild-malaria group revealed significantly lower hematocrit levels in B19V/P. falciparum co-infection than in P. falciparum mono-infection (P<0.05). Genetic analysis revealed a predominance of B19V genotype-1 (71.43%) in the studied population. However, B19V-genotype 2 was observed significantly more often in children with severe-malaria than in mild-malaria (P=0.04).

Conclusion

Our findings reveal that B19V-infection is frequent in Gabonese children with P. falciparum malaria and signifies a possible contribution of B19V on the clinical course of malaria in a genotype-dependent manner. B19V co-infection should be considered as a additional diagnostic measure in malaria patients with life threatening anemia.

Regulation of nitrogen monoxide production in human malaria

The production of nitrogen monoxide (NO(*)) contributes to defence mechanisms of the immune system to fight infectious agents like bacteria and protozoa. The respective gene producing the NO(*) has to be carefully regulated so that an overwhelming response kills the pathogen but does not harm the host. A strong increase in the NO(*) production for efficient anti-microbial activity is achieved by the transcriptional up-regulation of the nitric oxide synthase 2 gene (NOS2 or inducible nitric oxide synthase, iNOS), which is regulated by a number of transcription factors that are vital in the regulation of many genes involved in the immune response. Binding sites for members of the nuclear factor-kappaB (NF-kappaB) and activator protein 1 (AP1) families have been detected and seem to fulfil their function in vitro. Genetic variants of the iNOS genes have been identified that are linked to NO(*) production and to the outcome of malaria in humans.

The host genetic diversity in malaria infection

Populations exposed to Plasmodium infection develop genetic mechanisms of protection against severe disease. The clinical manifestation of malaria results primarily from the lysis of infected erythrocytes and subsequent immune and inflammatory responses. Herein, we review the genetic alterations associated with erythrocytes or mediators of the immune system, which might influence malaria outcome. Moreover, polymorphisms in genes related to molecules involved in mechanisms of cytoadherence and their influence on malaria pathology are also discussed. The results of some studies have suggested that the combinatorial effects of a set of genetic factors in the erythrocyte-immunology pathway might be relevant to host resistance or susceptibility against Plasmodium infection. However, these results must be interpreted with caution because of the differences observed in the functionality and frequency of polymorphisms within different populations. With the recent advances in molecular biology techniques, more robust studies with reliable data have been reported, and the results of these studies have identified individual genetic factors for consideration in preventing severe disease and the individual response to treatment.

Analysis of inducible nitric oxide synthase gene polymorphisms in vitiligo in Han Chinese people

Background

Vitiligo is a chronic depigmented skin disorder with regional melanocytes depletion. The pathogenesis was not completely clarified. Recently, more and more evidence suggested that polymorphisms of some genes are associated with vitiligo risk. Here, we want to examine the association between the inducible nitric oxide synthase (iNOS) gene polymorphisms and the risk of vitiligo in Chinese populations.

Methods and Principal Findings

In a hospital-based case-control study of 749 patients with vitiligo and 763 age- and sex-matched healthy controls, three polymorphisms of iNOS gene were genotyped by using the PCR-restriction fragment length polymorphism (PCR-RFLP) and mutagenically separated PCR (MS-PCR) methods, respectively. We found the iNOS-954 polymorphism was associated with a significantly higher risk of vitiligo (adjusted OR = 1.36, 95% CI = 1.02–1.81). Furthermore, this association is more pronounced in vulgaris vitiligo, active vitiligo and vitiligo without other autoimmune diseases in the stratification study. Analysis of haplotypes showed increased risk for the C_-1173C_-954C_Ex16+14 (OR = 1.44, 95% CI = 1.01–1.74). In addition, the serum iNOS activity is significantly associated with iNOS-954 combined genotype (GC+CC) and is much higher in vitiligo patients than in the controls (P<0.01). Logistic regression analysis of iNOS activity showed increased risk between higher activity and iNOS-954 G→C variant genotype carriers (P_trend<0.001).

Conclusions and Significance

INOS gene polymorphisms may play an important role in the genetic susceptibility to the development of vitiligo.

Nitric oxide for the adjunctive treatment of severe malaria: hypothesis and rationale

We hypothesize that supplemental inhaled nitric oxide (iNO) will improve outcomes in children with severe malaria receiving standard antimalarial therapy. The rationale for the hypothesized efficacy of iNO rests on: (1) biological plausibility, based on known actions of NO in modulating endothelial activation; (2) pre-clinical efficacy data from animal models of experimental cerebral malaria; and (3) a human trial of the NO precursor l-arginine, which improved endothelial function in adults with severe malaria. iNO is an attractive new candidate for the adjunctive treatment of severe malaria, given its proven therapeutic efficacy in animal studies, track record of safety in clinical practice and numerous clinical trials, inexpensive manufacturing costs, and ease of administration in settings with limited healthcare infrastructure. We plan to test this hypothesis in a randomized controlled trial (ClinicalTrials.gov Identifier: NCT01255215).

Inhaled nitric oxide for the adjunctive therapy of severe malaria: protocol for a randomized controlled trial

Background

Severe malaria remains a major cause of global morbidity and mortality. Despite the use of potent anti-parasitic agents, the mortality rate in severe malaria remains high. Adjunctive therapies that target the underlying pathophysiology of severe malaria may further reduce morbidity and mortality. Endothelial activation plays a central role in the pathogenesis of severe malaria, of which angiopoietin-2 (Ang-2) has recently been shown to function as a key regulator. Nitric oxide (NO) is a major inhibitor of Ang-2 release from endothelium and has been shown to decrease endothelial inflammation and reduce the adhesion of parasitized erythrocytes. Low-flow inhaled nitric oxide (iNO) gas is a US FDA-approved treatment for hypoxic respiratory failure in neonates.

Methods/Design

This prospective, parallel arm, randomized, placebo-controlled, blinded clinical trial compares adjunctive continuous inhaled nitric oxide at 80 ppm to placebo (both arms receiving standard anti-malarial therapy), among Ugandan children aged 1-10 years of age with severe malaria. The primary endpoint is the longitudinal change in Ang-2, an objective and quantitative biomarker of malaria severity, which will be analysed using a mixed-effects linear model. Secondary endpoints include mortality, recovery time, parasite clearance and neurocognitive sequelae.

Discussion

Noteworthy aspects of this trial design include its efficient sample size supported by a computer simulation study to evaluate statistical power, meticulous attention to complex ethical issues in a cross-cultural setting, and innovative strategies for safety monitoring and blinding to treatment allocation in a resource-constrained setting in sub-Saharan Africa.

Trial Registration

ClinicalTrials.gov Identifier: NCT01255215

Inducible nitric oxide synthase (iNOS) gene polymorphism and disease prevalence

Nitric oxide synthase gene is present on chromosome 17 and has been implicated in a wide variety of diseases. The nitric oxide synthase enzyme forms nitric oxide that besides being a signalling molecule plays an important role in host immune response. Inducible nitric oxide synthase expression is regulated at the level of transcription. Single-nucleotide polymorphisms, copy number variation and simple sequence repeat are important variations that have been reported in human genome. The presence of such variations in the regulatory region affects the level of gene product in the cell, while variation in the coding region influences the structure of proteins and its activity. This alteration in the level of gene product and the structure of the protein molecule might be responsible for the final outcome of genetic as well as infectious diseases. In the present manuscript, we review the role of inducible nitric oxide synthase (iNOS) gene polymorphisms in different diseases and populations. The iNOS gene with one pentanucleotide repeat, two single-nucleotide polymorphisms in promoter region and one polymorphism in exon 16 has been implicated in several diseases. We have also predicted several polymorphisms in the promoter region of iNOS computationally, which might affect the transcription factor binding site (TFBS) and hypothesize that these polymorphisms have some putative role in the outcome of disease(s).

Ficolin-2 levels and genetic polymorphisms of FCN2 in malaria

Human ficolin-2 (L-ficolin; FCN2) is a serum protein binding to sugar moieties of different human micro-pathogens forcing phagocytosis. Here, we investigate the clinical significance of FCN2 in African children with either mild or severe malaria (n = 130 and n = 108, respectively) from Gabon by analyzing three promoter SNPs (-986G>A, -602G>A, and -4A>G) and one single nucleotide polymorphisms (SNP) in exon 8 (+6424G>T) using quantitative TaqMan, real-time polymerase chain reaction (PCR). In addition, we measured the ficolin-2 plasma levels at two time points: on admission (t(0), acute disease) and 4 weeks after treatment (t(1), healthy phase). Comparison of ficolin-2 plasma levels shows that ficolin-2 concentration is highest during acute severe disease. In addition, we determined polymorphisms in the promoter and all coding regions of FCN2 in 40 Gabonese. Linkage disequilibrium data revealed polymorphic allelic combination patterns in the FCN2 promoter region; strong allelic combinations at -986 and -4, and -557 and -64 were found. No FCN2 promoter haplotypes were significantly distributed between mild and severe cases.

Association of the pentanucleotide repeat polymorphism in NOS2 promoter region with susceptibility to migraine in a Chinese population

Genes involved in the production of nitric oxide (NO) have been suggested as genetic factors for migraine. It has been studied whether polymorphisms in the genes encoding for different types of NO synthase (NOS) could be involved in the liability to migraine; however, most studies yield negative results. The pentanucleotide repeat microsatellite in the promoter region of inducible NOS (NOS2) shows highly significant differences in allelic frequencies among ethnically diverse populations. Thus, variation in the number of pentanucleotide repeats may have some significance in the predisposition to migraine among different human populations. The aim of this study was to investigate the possible association between pentanucleotide repeat polymorphism and the risk for migraine in Chinese population. We studied the genotypic and allelic frequencies of the pentanucleotide repeat polymorphism in the promoter region of NOS2 in 504 patients with migraine and 512 healthy controls, using polymerase chain reaction amplification and polyacrylamide gel electrophoresis analyses. Comparison of global allele counts between patients and controls showed that the difference was significant (p = 0.0014). The carriage of 9-repeat and 10-repeat alleles was significantly more common in controls, whereas 11-repeat allele was more common in patients after Bonferroni correction for multiple comparisons. A specific analysis of the different cutoffs for number of repeats showed that allelic and genotypic frequencies for the 9-repeat and 10-repeat cutoff were significantly different between cases and controls (p = 0.007 and p = 0.005 for allelic frequencies, respectively; p = 0.0086 and p = 0.0033 for genotypic frequencies, respectively). Our results implied an association between NOS2 pentanucleotide repeat polymorphism and migraine susceptibility in a Chinese population. Considering the significant allelic frequency differences in ethnically diverse populations, further replication studies, especially in ethnically different groups, were necessary to fully establish the role of NOS2 polymorphism in migraine susceptibility.

Nitric oxide generation in children with malaria and the NOS2G-954C promoter polymorphism

Previous epidemiological studies have demonstrated a protective association between the NOS2G-954C (NOS2(Lambaréné)) polymorphism in inducible nitric oxide synthase and severe malaria. The polymorphism is commoner in children with uncomplicated compared with severe malaria. We now show that the likely mechanism for such protection is increased flux of nitrogen from arginine to nitric oxide (NO) during episodes of malaria. Forty-seven boys with uncomplicated malaria received an infusion of (15)N-arginine to measure directly whole body in vivo NO production. The NOS2G-954C genotype previously associated with reduced risk of severe malaria in Gabon was also assessed. Evaluable data were obtained from 40 boys, of whom 6 were NOS2G-954C heterozygotes. Heterozygotes had higher urinary (15)N nitrate enrichments, 2.3 ± 0.6 vs. 1.4 ± 0.5 atoms percent excess (P = 0.001) and higher ratios of (15)N between urine nitrate and plasma arginine (87 ± 11 vs. 57 ± 18%, P = 0.001) consistent with accelerated NO production. We also derived total NO production rates, combining data with total urine production rate and nitrate concentration; these showed no difference by genotype (0.62 ± 0.36, n = 6 vs. 0.83 ± 0.50 μmol/kg·h, n = 16; P = 0.36), but data were confounded by very high variability in measurements of urine output and nitrate concentrations. This study supports the idea that NOS2 genotype protects against severe malaria by increasing NO production during episodes of uncomplicated malaria.

Mechanisms of genetically-based resistance to malaria

Malaria remains one of the most prevalent parasitoses worldwide. About 350 to 500 million febrile episodes are observed yearly in African children alone and more than 1 million people die because of malaria each year. Multiple factors have hampered the effective control of this disease, some of which include the complex biology of the Plasmodium parasites, their high polymorphism and their increasingly high resistance to antimalarial drugs, mainly in endemic regions. The ancient interaction between malarial parasites and humans has led to the fixation in the population of several inherited alterations conferring protection against malaria. Some of the mechanisms underlying protection against this disease are described in this review for hemoglobin-inherited disorders (thalassemia, sickle-cell trait, HbC and HbE), erythrocyte polymorphisms (ovalocytosis and Duffy blood group), enzymopathies (G6PD deficiency and PK deficiency) and immunogenetic variants (HLA alleles, complement receptor 1, NOS2, tumor necrosis factor-α promoter and chromosome 5q31-q33 polymorphisms).

Gastric cancer is associated with NOS2 -954G/C polymorphism and environmental factors in a Brazilian population

BACKGROUND

Gastric cancer can progress from a chronic inflammation of the gastric mucosa resulting from Helicobacter pylori infection that activates the inflammatory response of the host. Therefore, polymorphisms in genes involved in the inflammatory response, such as inducible nitric oxide synthase (NOS2), have been implicated in gastric carcinogenesis. The aim of this study was to evaluate the association of NOS2 polymorphisms Ser608Leu (rs2297518) in exon 16, -954G/C and -1173C/T, both in the promoter region, with gastric cancer and chronic gastritis and the association of cancer with risk factors such as smoking, alcohol intake and H. pylori infection.

METHODS

We conducted a population-based case-control study in 474 Southeast Brazilian individuals (150 with gastric cancer, 160 with chronic gastritis, and 164 healthy individuals), in which we performed NOS2 genotyping by PCR-RFLP.

RESULTS

SNP Ser608Leu was not associated with risk of chronic gastritis or gastric cancer. The polymorphic allele -1173T was not found in the studied population. However, the frequency of -954GC+CC genotypes was significantly higher (p < 0.01) in the cancer group (48.7%) than in both the gastritis (28.1%) and the control (29.9%) groups. Multivariate logistic regression showed that the NOS2 SNP -954G/C was associated with higher risk of gastric cancer (OR = 1.87; 95% CI = 1.12-3.13). We also observed an association with risk factors such as smoking and alcohol intake in both the gastric cancer (OR = 2.68; 95% CI = 1.58-4.53; OR = 3.60; 95% CI = 2.05-6.32, respectively) and the chronic gastritis (OR = 1.93; 95% CI = 1.19-3.13; OR = 2.79; 95% CI = 1.55-5.02, respectively) groups. This is the first report of increased risk of gastric cancer in association with the -954G/C polymorphism. These findings show that several polymorphisms in the promoter region of the NOS2 gene may contribute to the susceptibility to gastric cancer.

CONCLUSIONS

Polymorphism NOS2 -954 G/C, along with alcohol intake and tobacco smoking, is associated with gastric cancer. However, the NOS2 Ser608Leu polymorphism was not associated with gastric carcinogenesis. The NOS2 -1173C/T polymorphism was absent in the studied population.

Regulation of the expression of inducible nitric oxide synthase

Nitric oxide (NO) generated by the inducible isoform of nitric oxide synthase (iNOS) is involved in complex immunomodulatory and antitumoral mechanisms and has been described to have multiple beneficial microbicidal, antiviral and antiparasital effects. However, dysfunctional induction of iNOS expression seems to be involved in the pathophysiology of several human diseases. Therefore iNOS has to be regulated very tightly. Modulation of expression, on both the transcriptional and post-transcriptional level, is the major regulation mechanism for iNOS. Pathways resulting in the induction of iNOS expression vary in different cells or species. Activation of the transcription factors NF-kappaB and STAT-1alpha and thereby activation of the iNOS promoter seems to be an essential step for the iNOS induction in most human cells. However, at least in the human system, also post-transcriptional mechanisms involving a complex network of RNA-binding proteins build up by AUF1, HuR, KSRP, PTB and TTP is critically involved in the regulation of iNOS expression. Recent data also implicate regulation of iNOS expression by non-coding RNAs (ncRNAs).

Toll-like receptor 4 and inducible nitric oxide synthase gene polymorphisms are associated with Type 2 diabetes

BACKGROUND

The toll-like receptor 4 (TLR4) and inducible nitric oxide synthase are proteins from the innate immune system that, when activated, can induce insulin resistance. Polymorphisms in these genes, TLR4 and NOS2, respectively, could affect the immune response, as well as the prevalence of Type 2 diabetes (T2DM).

OBJECTIVE

The aim of the present study was to investigate the contribution of four polymorphisms (two from TLR4 and two from NOS2) to susceptibility to T2DM in a southeast Brazilian population.

DESIGN

A total of 211 patients with T2DM and 200 unrelated controls were genotyped for the Asp299Gly and Thr399Ile polymorphisms of the TLR4 gene and for the insertion (I)/deletion (D) AAAT and (CCTTT)n polymorphisms of the NOS2 promoter gene.

RESULTS

With regard to the NOS2 promoter region, the data showed that the I allele of the I/D AAAT polymorphism was more prevalent in the T2DM group and that the L/L genotype of the (CCTTT)n polymorphism was also more frequent in the same group. In contrast, the 299Gly allele and the 399Ile allele from the Asp299Gly and Thr399Ile TLR4 gene polymorphisms, respectively, were associated with protection of T2DM. It is believed that the persistence of these genetic variations in human populations may be indicative of a selective advantage in the face of different environmental pressures.

CONCLUSIONS

Genetic variations in the NOS2 gene promoter and TLR4 coding sequence may lead to deleterious and protective effects, respectively, arising from altered function of the innate immune system in patients with T2DM.

The relationship between blood groups and disease

The relative contribution of founder effects and natural selection to the observed distribution of human blood groups has been debated since blood group frequencies were shown to differ between populations almost a century ago. Advances in our understanding of the migration patterns of early humans from Africa to populate the rest of the world obtained through the use of Y chromosome and mtDNA markers do much to inform this debate. There are clear examples of protection against infectious diseases from inheritance of polymorphisms in genes encoding and regulating the expression of ABH and Lewis antigens in bodily secretions particularly in respect of Helicobacter pylori, norovirus, and cholera infections. However, available evidence suggests surviving malaria is the most significant selective force affecting the expression of blood groups. Red cells lacking or having altered forms of blood group-active molecules are commonly found in regions of the world in which malaria is endemic, notably the Fy(a-b-) phenotype and the S-s- phenotype in Africa and the Ge- and SAO phenotypes in South East Asia. Founder effects provide a more convincing explanation for the distribution of the D- phenotype and the occurrence of hemolytic disease of the fetus and newborn in Europe and Central Asia.

NOS2A, TLR4, and IFNGR1 interactions influence pulmonary tuberculosis susceptibility in African-Americans

Tuberculosis (TB) has substantial mortality worldwide with 5-10% of those exposed progressing to active TB disease. Studies in mice and humans indicate that the inducible nitric oxide synthase (iNOS) molecule plays an important role in immune response to TB. A mixed case-control association study of individuals with TB, relatives, or close contact controls was performed in 726 individuals (279 case and 166 control African-Americans; 198 case and 123 control Caucasians). Thirty-nine single nucleotide polymorphisms (SNPs) were selected from the NOS2A gene for single SNP, haplotype, and multilocus interaction analyses with other typed candidate genes using generalized estimating equations. In African-Americans, ten NOS2A SNPs were associated with TB. The strongest associations were observed at rs2274894 (odds ratio (OR) = 1.84, 95% confidence interval (CI) [1.23-2.77], p = 0.003) and rs7215373 (OR = 1.67, 95% CI [1.17-2.37], p = 0.004), both of which passed a false discovery rate correction for multiple comparisons (q* = 0.20). The strongest gene-gene interactions were observed between NOS2A rs2248814 and IFNGR1 rs1327474 (p = 0.0004) and NOS2A rs944722 and IFNGR1 rs1327474 (p = 0.0006). Three other SNPs in NOS2A interacted with TLR4 rs5030729 and five other NOS2A SNPs interacted with IFNGR1 rs1327474. No significant associations were observed in Caucasians. These results suggest that NOS2A variants may contribute to TB susceptibility, particularly in individuals of African descent, and may act synergistically with SNPs in TLR4 and IFNGR1.

Malaria severity and human nitric oxide synthase type 2 (NOS2) promoter haplotypes

Nitric oxide (NO) mediates host resistance to severe malaria and other infectious diseases. NO production and mononuclear cell expression of the NO producing enzyme-inducible nitric oxide synthase (NOS2) have been associated with protection from severe falciparum malaria. The purpose of this study was to identify single nucleotide polymorphisms (SNPs) and haplotypes in the NOS2 promoter, to identify associations of these haplotypes with malaria severity and to test the effects of these polymorphisms on promoter activity. We identified 34 SNPs in the proximal 7.3 kb region of the NOS2 promoter and inferred NOS2 promoter haplotypes based on genotyping 24 of these SNPs in a population of Tanzanian children with and without cerebral malaria. We identified 71 haplotypes; 24 of these haplotypes comprised 82% of the alleles. We determined whether NOS2 promoter haplotypes were associated with malaria severity in two groups of subjects from Dar es Salaam (N = 185 and N = 250) and in an inception cohort of children from Muheza-Tanga, Tanzania (N = 883). We did not find consistent associations of NOS2 promoter haplotypes with malaria severity or malarial anemia, although interpretation of these results was potentially limited by the sample size of each group. Furthermore, cytokine-induced NOS2 promoter activity determined using luciferase reporter constructs containing the proximal 7.3 kb region of the NOS2 promoter and the G-954C or C-1173T SNPs did not differ from NOS2 promoter constructs that lacked these polymorphisms. Taken together, these studies suggest that the relationship between NOS2 promoter polymorphisms and malaria severity is more complex than previously described.

Genetic polymorphisms in vitamin D receptor, vitamin D-binding protein, Toll-like receptor 2, nitric oxide synthase 2, and interferon-gamma genes and its association with susceptibility to tuberculosis

Mycobacterium tuberculosis kills more people than any other single pathogen, with an estimated one-third of the world's population being infected. Among those infected, only 10% will develop the disease. There are several demonstrations that susceptibility to tuberculosis is linked to host genetic factors in twins, family and associated-based case control studies. In the past years, there has been dramatic improvement in our understanding of the role of innate and adaptive immunity in the human host defense to tuberculosis. To date, attention has been paid to the role of genetic host and parasitic factors in tuberculosis pathogenesis mainly regarding innate and adaptive immune responses and their complex interactions. Many studies have focused on the candidate genes for tuberculosis susceptibility ranging from those expressed in several cells from the innate or adaptive immune system such as Toll-like receptors, cytokines (TNF-alpha, TGF-beta, IFN-gamma, IL-1b, IL-1RA, IL-12, IL-10), nitric oxide synthase and vitamin D, both nuclear receptors and their carrier, the vitamin D-binding protein (VDBP). The identification of possible genes that can promote resistance or susceptibility to tuberculosis could be the first step to understanding disease pathogenesis and can help to identify new tools for treatment and vaccine development. Thus, in this mini-review, we summarize the current state of investigation on some of the genetic determinants, such as the candidate polymorphisms of vitamin D, VDBP, Toll-like receptor, nitric oxide synthase 2 and interferon-gamma genes, to generate resistance or susceptibility to M. tuberculosis infection.

Haplotype specific-sequencing reveals MBL2 association with asymptomatic Plasmodium falciparum infection

Background

Mannose binding lectin (MBL) has an important role in the activation of the complement system and opsonization of pathogenic microorganisms. Frequent polymorphisms found in the MBL2 gene affect the concentration and functionality of the protein and are associated with enhanced susceptibility to severe malaria in African children. Most MBL2 typing strategies were designed to the analysis of selected variants, the significance of whole haplotypes is poorly known. In this work, a new typing strategy was developed and validated in an association analysis of MBL2 with adult asymptomatic infection.

Methods

MBL2 allele-specific fragments of 144 healthy Gabonese adults were amplified by using haplotype-specific sequencing (HSS), a new strategy that combines sequence-specific PCR and sequence-based typing. The Gabonese were investigated for the presence of Plasmodium falciparum parasitaemia by the amplification of parasite genes, immunochromatographic antigen detection and microscopic analysis. HSS results were also compared with a previously used real-time PCR (RT-PCR) method in 72 Euro-Brazilians.

Results

Fourteen polymorphisms were identified beside the commonly investigated promoter (H, L; X, Y; P, Q) and exon 1 (A, O; O = B, C or D) variants. The MBL2*LYPA/LYPA genotype was associated with the absence of asymptomatic infection (P = 0.017), whereas the MBL2*LYQC haplotype and YA/YO + YO/YO genotypes were associated with positive parasite counts in asymptomatic adults (P = 0.033 and 0.018, respectively). The associations were specific to LYPA (identical to the reference sequence Y16577) and LYQC (Y16578) and would not have been revealed by standard genotyping, as there was no association with LYPA and LYQC haplotypes carrying new polymorphisms defined by sequence-based typing. In contrast, HSS and RT-PCR produced very similar results in the less diverse European-derived population.

Conclusion

In this work, a new typing strategy for a highly polymorphic gene was developed and validated focusing on the asymptomatic status of P. falciparum-infected adults. In populations with high nucleotide diversity, it allowed for the identification of associations with fine-scaled haplotypes that would not have been found using common typing techniques. In this preliminary study, MBL2 haplotypes or SNPs linked to them were found associated with susceptibility to infection and parasitaemia control of asymptomatic adults.

The CCTTT pentanucleotide microsatellite in iNOS promoter influences the clinical outcome in P. falciparum infection

To assess the hypothesis that nitric oxide (NO) is critical in the pathogenesis of cerebral malaria, we analyzed those single nucleotide polymorphisms (SNPs) and microsatellite (MS) of the promoter region of inducible nitric oxide synthase (iNOS) gene which are known to enhance the NO production in vivo. A total of 428 (204 severe, 224 mild) adult patients living in the eastern part of India were analyzed. The single nucleotide substitutions -954G-->C was found to be very rare, and -1173C-->T was absent in this population. But interestingly, longer forms of MS were found to be significantly associated with severe malaria (OR = 2.89, 95% CI = 1.955-4.295, P < 0.0001), and the linear regression analysis revealed that the risk of severe malaria significantly increases as the summed repeat number in an individual increase (OR = 1.16, P = 0.0013). Further, the median plasma level of nitrate/nitrite (NOx) was observed to be high in mild patients compared to severe patients, and the level of parasitemia was significantly low among mild patients than severe ones. These findings suggest that the CCTTT repeats in iNOS may play a key role in the pathogenesis of severe malaria.

Opposed circulating plasma levels of endothelin-1 and C-type natriuretic peptide in children with Plasmodium falciparum malaria

Background

Molecular mechanisms involved in the pathogenesis of severe Plasmodium falciparum malaria (SM), are not yet fully understood. Both endothelin-1 (ET-1) and C-type natriuretic peptide (CNP) are produced by vascular endothelium and act locally as paracrine regulators of vascular tone, ET-1 being a potent vasoconstrictor and CNP having strong vasorelaxant properties.

Methods

Plasma levels of ET-1 and N-terminal fragments of CNP (NT-proCNP) were studied on admission and after 24 hours of treatment, using enzyme-linked-immunosorbent-assay (ELISA) technique, in Gabonese children with severe falciparum malaria (SM, n = 50), with uncomplicated malaria (UM, n = 39) and healthy controls (HC, n = 25).

Results

Compared to HC, malaria patients had significantly higher plasma levels of ET-1 and significantly lower levels of NT-proCNP (p < 0.001 and p < 0.024 respectively). Plasma levels of NT-proCNP were additionally decreased in SM patients compared to HC (p = 0.034), whereas UM was not significantly different to HC. In the SM group we found a trend towards lower ET-1 levels compared to UM (p = 0.085).

Conclusion

In the present study, an imbalance between the vasoconstricitve and vasorelaxant endothelium-derived substances ET-1 and CNP in the plasma of children with falciparum malaria is demonstrated, presumably in favor of vasoconstrictive and pro-inflammatory effects. These results may indicate involvement of ET-1 and CNP in malaria pathogenesis. Furthermore, results of lower ET-1 and CNP levels in SM may reflect endothelial cell damage.

NCF1 gene and pseudogene pattern: association with parasitic infection and autoimmunity

Background

Neutrophil cytosolic factor 1, p47^phox (NCF1) is a component of the leukocyte NADPH oxidase complex mediating formation of reactive oxygen intermediates (ROI) which play an important role in host defense and autoimmunity. An individual genomic pattern of ncf1 and its two types of pseudogenes (reflected by the ΔGT/GTGT ratio) may influence the individual capacity to produce ROI.

Methods

NCF1ΔGT/GTGT ratios were correlated with clinical parameters and ROI production during Plasmodium falciparum malaria and with susceptibility to the autoimmune disease multiple sclerosis (MS).

Results

Among Gabonese children with severe malaria, ROI production from peripheral blood tended to be higher in individuals with a ΔGT/GTGT ratio ≤ 1:1. ΔGT/GTGT ratios were not associated with susceptibility to MS, but to age-of-onset among MS patients.

Conclusion

The genomic pattern of NCF1 and its pseudogenes might influence ROI production but only marginally influence susceptibility to and outcome of malaria and MS.

A globally occurring indel polymorphism in the promoter of the IFNA2 gene is not associated with severity of malaria but with the positivity rate of HCV

BACKGROUND

Type I Interferons (IFNs) are well known cytokines which exert antiviral activity, antitumor activity and immunomodulatory effects. Single-nucleotide polymorphisms (SNP) and deletions in the gene coding for IFNA2 have been shown to influence the level of expression in vitro. The indel polymorphism -305_-300delAACTTT showed the strongest effect in vitro. To analyse the worldwide distribution of this polymorphism we analyzed five different populations (586 Vietnamese, 199 Central Africans, 265 Brazilians, 108 Kaingang and 98 Guarani). To investigate a possible association with susceptibility to infectious diseases we determined the polymorphism in malaria patients suffering either mild or severe malaria and in a cohort of hepatitis C virus infected individuals.

RESULTS

We could detect the indel polymorphism in all populations analysed. There was no association with this polymorphism and the outcome of malaria but we found an increase of this indel polymorphism in hepatitis C virus positive individuals compared to healthy controls (p = 0.014).

CONCLUSION

Polymorphisms in genes involved in the interferon pathway have been implicated in the resistance or susceptibility against cerebral malaria and HBV. Here we show that an indel polymorphism, which mediates a disadvantageous effect in HBV patients, may also play a disadvantageous role in HCV infections stressing the importance of a fully functional interferon pathway.

Alterations in the Cytoplasmic Domain of CLCN2 Result in Altered Gating Kinetics

Mutations in the human ClC-2 Cl(-) channel have been described to influence its function dramatically. To test for naturally occurring gene variants in a human population and their functionality, all 24 CLCN2 exons from a Central African population were sequenced. Six single amino acid exchanges in the intracellular N-terminus (P48R, R68H), in the pore domain (G199A), or in the intracellular C-terminus (R646Q, R725W, R747H) were identified at low frequency. Heterologous expression of these polymorphisms in Xenopus laevis oocytes demonstrated their functional significance as determined by two-electrode voltage-clamp. The polymorphisms R68H, R725W, and R747H exhibited faster voltage-stimulated gating as compared to the wild type channel, resulting in higher steady state currents of R725W. Probably due to decreased surface expression P48R, R68H, and R646Q mutants generated lower currents than the wild type channels. The inward currents of the mutated channels R725W, R747H, and G199A failed to increase during hypotonic swelling, a defect paralleled by impaired swelling-accelerated voltage-gating in one mutant (G199A). In conclusion, the Africans' gene pool comprises CLCN2 gene variants in the N-terminus, the C-terminus or the pore domain that affect surface expression and voltage- or cell-swelling-stimulated channel gating.

Reactive nitrogen species contribute to innate host defense against Campylobacter jejuni

Campylobacter jejuni, a gram-negative, invasive organism, is a common cause of food-borne bacterial diarrheal disease. However, the relationship between C. jejuni and the innate immune system is not well described. To better characterize host defense against C. jejuni, we investigated the ability of nitric oxide/reactive nitrogen species to kill two strains of C. jejuni. C. jejuni viability was measured after exposure to reactive nitrogen species produced biochemically as acidified nitrite and by bone marrow-derived macrophages. We report that acidified nitrite caused a 3-log-increased kill of C. jejuni (P < 0.05) at doses that did not affect the viability of Salmonella enterica serovar Typhimurium. Expression of NOS2, the gene responsible for the production of inducible nitric oxide, was increased >100-fold in murine macrophages after incubation with C. jejuni (P < 0.001). These macrophages effected a 2-log-increased kill of C. jejuni over 24 h compared to that by NOS2-/- macrophages unable to produce nitric oxide (P < 0.05). These findings suggest that the mammalian host upregulates the production of nitric oxide in response to exposure to C. jejuni and that nitric oxide and reactive nitrogen species comprise part of the innate defense mechanisms that contribute to the resolution of C. jejuni infection.