Ludovica Segat

Evolution of the primate cathelicidin : Correlation between structural variations and antimicrobial activity

Cathelicidin genes homologous to the human CAMP gene, coding for the host defense peptide LL-37, have been sequenced and analyzed in 20 primate species, including Great Apes, hylobatidae, cercopithecidae, callithricidae, and cebidae. The region corresponding to the putative mature antimicrobial peptide is subject to a strong selective pressure for variation, with evidence for positive selection throughout the phylogenetic tree relating the peptides, which favors alterations in the charge while little affecting overall hydrophobicity or amphipathicity. Selected peptides were chemically synthesized and characterized, and two distinct types of behavior were observed. Macaque and leaf-eating monkey RL-37 peptides, like other helical antimicrobial peptides found in insect, frog, and mammalian species, were unstructured in bulk solution and had a potent, salt and medium independent antimicrobial activity in vitro, which may be the principal function also in vivo. Human LL-37 and the orangutan, hylobates, and callithrix homologues instead showed a salt-dependent structuring and likely aggregation in bulk solution that affected antimicrobial activity and its medium dependence. The two types of peptides differ also in their interaction with host cells. The evolution of these peptides has thus resulted in distinct mechanisms of action that affect the direct antimicrobial activity and may also modulate accessory antimicrobial functions due to interactions with host cells.

Two SNPs in NLRP3 gene are involved in the predisposition to type-1 diabetes and celiac disease in a pediatric population from northeast Brazil

Recent findings provide evidence of the critical role of innate immunity NALP1/NLRP1 and NALP3/NLRP3/CIAS1 genes in inflammatory diseases, and also in the predisposition to autoimmune disorders. We evaluated the possible association of five single nucleotide polymorphisms (SNPs), two in NLRP1 gene and three in NLRP3 gene, in pediatric patients from the north eastern region of Brazil affected by type-1 diabetes (T1D, n = 196), celiac disease (CD, n = 59), and atopic dermatitis (AD, n = 165), and in healthy individuals (n = 192). Our results demonstrated that NLRP3 rs10754558 SNP was associated specifically to T1D (p = 4exp-3) and NLRP3 rs358294199 SNP to CD (p = 5exp-4) in the Brazilian population. Despite its strong association with T1D in Norwegian population, NLRP1 was not associated with T1D, in the Brazilian population. According to previous studies in Caucasoid cohorts, NLRP1 and NLRP3 seemed not to be associated to AD. Since it has been reported that IL-1beta has a systemic effect in the lost of the immunologic tolerance and that NALP3 inflammasome is directly involved in the production of this pro-inflammatory cytokine, we hypothesized that variations in NLRP3 could belong to a predisposing genetic background that contribute to the development of autoimmune diseases.

PIN1 promoter polymorphisms are associated with Alzheimer's disease.

In our study, we analyzed the coding and promoter regions of the PIN1 gene in a group of 111 Alzheimers disease (AD) patients looking for a possible genotype-phenotype correlation. The presence of SNPs - which could affect and modify the clinical phenotype of AD patients was also investigated. We identified two single nucleotide polymorphisms (SNPs) at positions -842 (G-->C) and -667 (C-->T) in the promoter region of the PIN1 gene. Our results evidenced a significantly higher percentage of -842C allele carriers in AD subjects with respect to healthy controls. We found that this allele significantly raised the risk of developing AD (OR 3.044, CI 1.42-6.52). The -842 and -667 SNPs were in linkage disequilibrium and combined to form haplotypes. The CC haplotype conferred a higher risk of developing AD (OR 2.95, confidence interval 1.31-6.82). Finally, protein expression analyses revealed that subjects carrying the -842 CC genotype or the CC haplotype showed reduced levels of the PIN1 protein in peripheral mononuclear cells.

DEFB1 gene polymorphisms and increased risk of HIV-1 infection in Brazilian children

In our study we analysed three single nucleotide polymorphisms (SNPs) in the 5′ untranslated region (UTR) of the DEFB1 gene, namely −52(G/A) −44(C/G) and −20(G/A), in three groups of northeastern Brazilian children in order to assess their role in HIV-1 infection. Our results allowed us to hypothesize that the SNPs located in the 5′ UTR of the DEFB1 gene can be employed as a marker of risk for HIV-1 infection.

Association between HLA-G 3'UTR 14-bp polymorphism and HIV vertical transmission in Brazilian children.

Objectives:The aim of our study was to verify the possible association between an HLA-G 14-bp deletion/insertion polymorphism and perinatal HIV transmission in Brazilian children. Design:We analyzed the 14-bp deletion/insertion polymorphisms in seronegative (i.e., exposed uninfected, N = 71) and seropositive (exposed infected, N = 175) Brazilian children born from HIV-positive mothers and in healthy controls (n = 175). Methods:HLA-G 14-bp deletion/insertion polymorphism (rs16375) was detected by PCR amplification of the target sequence followed by agarose gel electrophoresis. All the samples were also analyzed by direct sequencing in order to validate the genotyping results. Results:HIV-exposed uninfected children showed significant differences in their allele and genotype frequencies of the HLA-G 14-bp polymorphism when compared to both seropositive children and healthy controls. The 14-bp-deleted (D) allele was more frequent in exposed uninfected children (79%) than in healthy controls (60%) and HIV-positive children (58%); the higher percentage of the D allele found in the exposed uninfected children with respect to HIV-positive individuals was significantly associated with a reduced risk of vertical transmission. This effect was ascribable to the presence of the D/D homozygous genotype. Conclusion:Our findings support the possible role for the HLA-G 14-bp deletion/insertion polymorphism in the HIV vertical transmission in Brazilian children. The presence of the D allele and D/D genotype is associated with a protective effect toward HIV perinatal infection.

MBL2 Gene polymorphisms protect against development of thrombocytopenia associated with severe dengue phenotype

Dengue disease can clinically evolve from an asymptomatic and mild disease, known as dengue fever (DF), to a severe disease known as dengue hemorrhagic fever (DHF). Recent evidence has shown how host genetic factors can be correlated with severe dengue susceptibility or protection. Many of these genes, such as CD209, TNF-a, vitamin D receptor, and FC gamma receptor IIA, are components of the innate immune system, suggesting that innate responses might have a role in dengue pathogenesis. MBL2 gene polymorphisms have been shown to modulate susceptibility or protection in many viral diseases. We investigated the involvement of MBL2 gene in the dengue clinical outcome through the analysis of MBL2 exon 1 polymorphisms (at codons 52, 54, and 57) known to be associated with reduced serum levels of the MBL protein. The genotypes of 110 well-characterized dengue-positive patients were statistically analyzed to establish possible correlations between MBL2 polymorphisms and parameters such as sex, type of infection (primary or secondary response), race/ethnicity, course of infection, and age. We found significant correlations between wild-type AA MBL2 genotype and age as associated risk factors for development of dengue-related thrombocytopenia.

Transcriptional effect of DEFB1 gene 5' untranslated region polymorphisms

To the Editor: Human β-defensin-1 (hBD-1) has been shown to be a candidate tumor suppressor gene by Sun et al. ( [1][1]) who reported that single nucleotide polymorphisms (SNP) in the DEFB1 gene are able to modify the transcriptional activity of hBD-1 promoter. In particular, the − 44C/G SNP was

Prevalence of autoimmune thyroid disease and thyroid dysfunction in young Brazilian patients with type 1 diabetes.

Abstract:  Patients with an autoimmune condition are known to be at higher risk of developing other autoimmune disorders. Type 1 diabetes may be associated with additional autoimmune disorders including autoimmune thyroid disease. The aim of this study was to investigate the prevalence of thyroid autoantibodies in a group of children, adolescents, and young adults with type 1 diabetes from northeastern Brazil as well as their significance for the development of thyroid disorders. The study design was cross‐sectional and descriptive, analyzing young people with a previous type 1 diabetes diagnosis. Two hundred and fourteen children and adolescents with prior diagnosis of type 1 diabetes were evaluated. Antibodies to thyroperoxidase (anti‐TPO) were determined in all patients and thyroid‐stimulating hormone (TSH) levels. The anti‐TPO antibody test was positive in 54 out of the 214 patients studied, resulting in an overall prevalence of 25.2%. Among the anti‐TPO‐positive subjects, females were predominant (72%) over males (28%) (p < 0.001). A total of 55.5% patients with positive anti‐TPO antibodies had abnormal TSH levels. Clinically significant hypothyroidism was found in 29.6% and subclinical hypothyroidism in 22.2% of patients with positive anti‐TPO. Hyperthyroidism was present in only 3% of them. Our results demonstrate the high prevalence of autoimmune thyroiditis in patients with type 1 diabetes and the need for these patients of regular screening to make a precocious diagnosis of thyroid dysfunction.

DEFB-1 genetic polymorphism screening in HIV-1 positive pregnant women and their children

Objective. In our study we evaluated the frequency of three SNPs (−52 G/A, −44 C/G; −20 G/A) in the 5′ UTR of DEFB-1 gene, in a cohort of 130 HIV-1 infected mothers and their children, collected by the Italian group SIGO in Obstetrics and Gynecology. Methods. The three SNPs (−52 G/A, −44 C/G; −20 G/A) in the 5′ UTR of DEFB-1 gene were genotyped by direct sequencing of PCR products. Results. The C allele at position −44 was shown to be significantly different in both HIV-1 positive mothers and their children when compared to the healthy controls. The odds ratio for −44 C allele in children born to HIV-1 infected mothers is 7.09 (confidence interval 3.38–15.3) while the odds ratio for this allele in HIV-1 infected mothers is 6.42 (confidence interval 3.14–13.4). Conclusions. Our results evidence a high frequency of the −44 CC allele in HIV-1 infected mothers and their children with augmented potential risk of maternal fetal transmission. This potential vertical transmission risk has been successfully prevented by antiretroviral drug treatment and cesarian section of the HIV-1 positive mothers.

IL-18 gene promoter polymorphism is involved in HIV-1 infection in a Brazilian pediatric population

In our study, we identified a polymorphism (C-607A) in the promoter region of the IL-18 gene that shows different frequencies between human immunodeficiency virus (HIV)-1-infected children and healthy controls in a pediatric Brazilian population. The presence of the −607 C allele correlates to HIV-1 infection and confers an increased risk of infection in subjects carrying the single nucleotide polymorphism.