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A Dessein

Publications and source records attributed to A Dessein.

At least 19 recordsLinked to original sources
PubMed2005

An epidemiological study of familial neurocysticercosis in an endemic Mexican community.

Neurocysticercosis (NC) caused by Taenia solium is a frequent parasitic disease of the central nervous system. It is highly endemic in many developing countries, where many people are exposed but few become infected. Here, the relevance of age, gender, and genetic and exposure factors on NC susceptibility was studied in 649 inhabitants of a rural community of Mexico. Endemicity was confirmed by the high prevalence of pig cysticercosis (32.8%) and human seroprevalence (43.8%). Human NC cases were diagnosed by computerised tomography scans. A questionnaire to evaluate risk factors was applied and familial relationships between participants were registered. An overall NC frequency of 9.1% (59/649) was found. NC frequency increased with age but did not associate with gender. Most NC cases were asymptomatic. None of the evaluated risk factors were associated with NC. No familial aggregation was detected when studying all cases, although a significant relationship between mother and child in cases with multiple parasites was found. These findings point to the fact that human NC in high exposure conditions is not simply related to exposure factors and they do not support the participation of a major gene in single-cyst NC. Rather, our results point to a complex interaction of genetic and environmental factors involved in NC.

Adolescent↗
PubMed2005

[Genetic factors predisposing to fibrosis in systemic sclerosis].

PURPOSE: Physiopathology of systemic sclerosis includes autoimmunity factors, endothelial lesions and abnormal fibrotic process which characterizes this disease in the field of systemic autoimmune disorders. Genetic factors of susceptibility are showed by possibility of familial forms of the disease, Choctaw American Indians homogenous population with high disease prevalence of systemic sclerosis and experimental animal models. KEY POINTS: We propose a review of the articles published to date in the literature concerning genetical analysis of genes coding for factors potentially involved in the fibrotic process of systemic sclerosis. This includes cytokines (TNF-alpha, interleukin-1, chemokines), growth factors (TGF-beta), extracellular matrix proteins (collagen, fibrillin, fibronectine) and agents acting on vascular tone (angiotensin-converting enzyme and NO synthase). PERSPECTIVES: Identification of genetic factors involved in the susceptibility to fibrosis of systemic sclerosis would lead to a better understanding of physiopathological mechanisms of this disease and to therapeutic targets using immunomodulation with drugs, such as already performed in rheumatoid arthritis.

Animals↗
PubMed2003

Genetic control of visceral leishmaniasis in a Sudanese population: candidate gene testing indicates a linkage to the NRAMP1 region.

There is some evidence showing that genetic factors are involved in human susceptibility to parasitic diseases such as schistosomiasis and malaria. Studies have shown that the Nramp1 and H-2 genes are implicated in the control of Leishmania donovani infection in mice. We sought genetic loci involved in the control of susceptibility to visceral disease caused by L. donovani in humans. We studied 37 families with at least two affected sibs living in a village in eastern Sudan, where an outbreak of visceral leishmaniasis occurred between 1995 and 2000. The genetic markers located in five chromosomal regions containing candidate genes were typed: 2q35 (NRAMP1), 5q31-q33 (Th2 cytokine cluster), 6p21 (HLA/TNF-alpha), 6q23 (INFGRI) and 12q15 (INF-gamma). Linkage (multipoint lod-score=1.08; P=0.01) was observed for the 5'(CA) repeat polymorphism in the NRAMP1 promoter. This suggests that genetic variations of this gene affect susceptibility to visceral leishmaniasis in this population.

Adolescent↗
PubMed2002

Description of three new polymorphisms in the intronic and 3'UTR regions of the human interferon gamma gene.

Interferon-gamma (IFN-gamma) is a key regulator of the development and functions of the immune system. In particular, this cytokine plays a major role in immune defense against infections by various human pathogens and polymorphisms in the IFN-gamma gene, including the transcription regulatory region, and might affect host resistance to infectious agents such as schistosomes. In this study on the genetics of human schistosomiasis we uncovered three new single nucleotide polymorphisms in the IFN-gamma genes. Two polymorphisms are located in the third intron and the third is in the 3'UTR region of this gene: an A to G transition at position +2109 from the transcription start and two G to A transitions at positions +3810 and +5134. In a SUDANESE population living in an endemic area of malaria and schistosomiasis, the allelic frequenciesare: 0.85 (+2109A), 0.15 (+2109G), 0.92 (+3810G), 0.08 (+3810A), (+5134G) and 0.04 (+5134A).

3' Untranslated Regions↗
PubMed2002

Two new polymorphisms in the human interferon gamma (IFN-gamma) promoter.

Two new single-nucleotide polymorphisms are described within the human interferon gamma (IFN-gamma) promoter in a Sudanese population. One is a G to T transition at position -183 from the transcription start. The other is a A to G transition at position -155. Allelic frequency analysis indicated frequencies of 0.927 (G) and 0.073 (T) at position -183 and 0.977 (A) and 0.023 (G) at position -155. These two polymorphisms have not been detected in the Centre d'Etude du Polymorphisme Humain (CEPH) reference population. The polymorphism -183(G-->T) may alter the AP-1 binding domain and the regulation of transcription. The polymorphism -155(A-->G) is located close to the nuclear factor-activated T-cell site (NFAT site) (-168 TAAAGGAAA-160) and may affect the stability of this region.

Arabs↗
PubMed2002

The sandfly fauna in the visceral-leishmaniasis focus of Gedaref, in the Atbara-River area of eastern Sudan.

Visceral leishmaniasis (VL) is an acute public-health problem in Sudan. Between 1997 and 2000, four, brief entomological surveys were carried out in Barbar El Fugarra, a village in the state of Gedaref, in the Atbara-River area of eastern Sudan. Between 1996 and 1999, 658 cases of VL occurred among the village's population of about 4000. CDC miniature light-traps set inside and outside human dwellings were used to collect a total of 12,745 sandflies, including five species of the genus Phlebotomus and 19 of Sergentomyia. Phlebotomus papatasi and P. orientalis made up 7% and 5% of the collected sandflies, respectively. Seasonal variation was observed in the numbers of P. orientalis, P. papatasi, S. schwetzi and S. magna caught. Almost all (88%) of the sandflies collected were caught inside houses or granaries and there appeared to be particularly large indoor populations of P. orientalis, P. papatasi, S. schwetzi, S. magna and S. clydei. Phlebotomus orientalis could be responsible for the indoor transmission of the parasites causing the local VL, between humans and between humans and local dogs (which have been found infected by some of the Leishmania zymodemes found in humans). The co-occurrence in this focus of P. papatasi and Arvicanthis niloticus, which are known vectors and reservoir hosts, respectively, of L. major, indicates the possibility that outbreaks of human cutaneous leishmaniasis might occur in the area.

Animals↗
PubMed2001

[Schistosoma mansoni schistosomiasis].

Schistosomosis are parasitic diseases caused by blood flukes of the Schistosoma genus. The pathology of schistosomosis is mostly brought about by ova trapped in the tissues. In the liver, granuloma around ova eventually trigger periportal fibrosis and portal hypertension. In S. mansoni infection, the infection intensity and the onset of liver fibrosis are under distinct genetic control. Liver fibrosis is the main cause of death in the 20 millions individuals suffering from chronic schistosomosis. However, liver fibrosis is reversible if antischistosomal drugs are administered before the onset of severe hepatic insufficiency.

Cause of Death↗
PubMed2001

Sudan: the possible original focus of visceral leishmaniasis.

Fifty-two Leishmania strains, obtained from human patients and dogs in a visceral leishmaniasis focus in Sudan, were characterized by isoenzyme electrophoresis (15 enzymes). The phylogenetic analysis showed that the 7 Leishmania zymodemes obtained hold ancestral positions on the phylogenetic tree, supporting the hypothesis of an East African origin of visceral leishmaniasis.

Animals↗
PubMed2001

Genome search for additional human loci controlling infection levels by Schistosoma mansoni.

Schistosomiasis is a major public health problem in many developing countries. Previous studies have shown that infection levels by Schistosoma mansoni in a Brazilian population is controlled by a major gene, denoted as SM1, which was mapped to chromosome 5q31-q33 by use of a model-based (logarithm of the odds [lod] score) analysis method. The present study is an autosome-wide scan searching for additional human loci implicated in the regulation of S. mansoni infection intensities. The weighted pairwise correlation model-free linkage method was used in order to consider large pedigrees and to conduct a 2-locus analysis (i.e., to search for a second locus taking into account linkage to 5q31-q33). The most significant linkage results were again obtained in the 5q31-q33 region. Two additional regions provided linkage results with significance levels around 0.001, 1p21-q23 (results independent of 5q31-q33) and 6p21-q21 (results in interaction with 5q31-q33). The investigation of these regions, which contain some candidate genes, is ongoing in other populations to confirm the role of these regions.

Adult↗
PubMed2000

[Genetic predisposition to bilharziasis in humans: research methods and application to the study of Schistosoma mansoni infection].

The development of genetic epidemiology methods using recent human genetic mapping information together with the growing availability of candidate genes has led to major advances in the identification of host genes in human schistosomiasis. Two phenotypes have been studied so far in the infection by Schistosoma mansoni: infection levels by the parasite as measured by the faecal egg counts, and the severe hepatic fibrosis caused by S. mansoni assessed by ultrasound examination. The first study was performed on Brazilian pedigrees and provided strong evidence for a major gene controlling infection levels by S. mansoni denoted as SM1 which was mapped to chromosome 5q31-q33. This region contains several candidate genes involved in the regulation of the Th1/Th2 response, and the direct role of polymorphisms located within these genes is under investigation. The second study conducted in Sudan also showed the presence of a major gene influencing the development of severe hepatic fibrosis due to S. mansoni infection denoted as SM2. This gene is not located in the 5q31-q33 region, but maps to chromosome 6q22-q23 and is closely linked to the IFN-gamma R1 gene encoding the receptor of the strongly anti-fibrogenic cytokine Interferon-gamma. These findings indicate that two distinct genetic loci control human predisposition to schistosomiasis, SM1 located in the 5q31-q33 region which is likely to play a role in the Th1/Th2 differentiation, and SM2 in 6q22-q23 influencing disease progression with a possible involvement in the regulation of IFN-gamma.

Animals↗
PubMed1999

Full results of the genome-wide scan which localises a locus controlling the intensity of infection by Schistosoma mansoni on chromosome 5q31-q33.

Three hundred million individuals are at risk of infection by schistosomes, and thousands die each year of severe hepatic disease. Previous studies have shown that the intensity of infection by Schistosoma mansoni in a Brazilian population is controlled by a major gene, denoted as SM1. We report here the full results of a genome-wide search that was performed on this population to localise SM1. Two hundred and forty-six microsatellites were used for the primary map, and only one region in 5q31-q33 provided significant evidence of linkage. SM1 was subsequently mapped to this region, which contains several genes encoding cytokines or cytokine receptors which are involved in protection against schistosomes. Three additional regions, 1p22.2, 7q36 and 21q22-22-qter, yielded promising, although not significant, lod-score values. These regions contain candidate genes encoding cytokines or molecules relevant to anti-schistosome immunity.

Animals↗
PubMed1998

Absence of linkage between MHC and a gene involved in susceptibility to human schistosomiasis.

Six hundred million people are at risk of infection by Schistosoma mansoni. MHC haplotypes have been reported to segregate with susceptibility to schistosomiasis in murine models. In humans, a major gene related to susceptibility/resistance to infection by S. mansoni (SM1) and displaying the mean fecal egg count as phenotype was detected by segregation analysis. This gene displayed a codominant mode of inheritance with an estimated frequency of 0.20-0.25 for the deleterious allele and accounted for more than 50% of the variance of infection levels. To determine if the SM1 gene segregates with the human MHC chromosomal region, we performed a linkage study by the lod score method. We typed for HLA-A, B, C, DR and DQ antigens in 11 informative families from an endemic area for schistosomiasis in Bahia, Brazil, by the microlymphocytotoxicity technique. HLA-DR typing by the polymerase chain reaction with sequence-specific primers (PCR-SSP) and HLA-DQ were confirmed by PCR-sequence-specific oligonucleotide probes (PCR-SSOP). The lod scores for the different theta values obtained clearly indicate that there is no physical linkage between HLA and SM1 genes. Thus, susceptibility or resistance to schistosomiasis, as defined by mean fecal egg count, is not primarily dependent on the host's HLA profile. However, if the HLA molecule plays an important role in specific immune responses to S. mansoni, this may involve the development of the different clinical aspects of the disease such as granuloma formation and development of hepatosplenomegaly.

Animals↗
PubMed1998

[Diagnostic approach to hypereosinophilia].

Blood hypereosinophilia is a common finding in medical practice requiring further investigation. There are a wide range of potential causes including atopic disorder, drug allergy, parasitic infection, certain forms of immune deficiency, inflammatory process, hemopathy, and malignant disease. Diagnosis of persistent hypereosinophilia not associated with parasitic infection is one of the major diagnostic dilemmas in medicine. If through investigation fails to achieve diagnosis, idiopathic hypereosinophilia may be suspected including the possibility of essential hypereosinophilic syndrome or Chusid syndrome. The primary determination for diagnosis of hypereosinophilia involves the presence or absence of parasitic infection. If parasitic infection is ruled out, it is often difficult to distinguish benign, self-limiting forms from severe forms requiring careful surveillance and subsequent treatment. From a pathophysiological standpoint, one may ask if some eosinophilic conditions are not due to deregulation of immunologic mechanisms that normally protect the organism against parasitic infection.

Diagnosis, Differential↗
PubMed1998

[Genetic control of hypereosinophilias].

Polynuclear eosinophils play a major role in host defense against infectious diseases and especially helminthiasis. Onset of hypereosinophilia can be attributed to two mechanisms which can occur separately or in combination. The first mechanism involves enhancement of medullary production and differentiation of eosinophils. The second is prolonged life span of eosinophils. Response to eosinophils depends on various cytokines including IL-5, IL-4, IL-3 and GM-CSF. Since it contains the genes coding for these cytokines, the 5q31-q33 region of chromosome 5 is the focus of study on genetic control of human hypereosinophilia. The goal of these studies is to allow screening of subjects predisposed to helminthic infection and to deregulation of immune responses that may lead to atopy and various types systemic inflammatory diseases.

Chromosomes, Human, Pair 5↗
PubMed1997

[Genetic predisposition to infectious diseases].

At the present time more is known about barriers to transmission of infectious agents between species than barriers to transmission within the same species. However differences in resistance to infection have been well-established within given species of various plants and domestic farm animals. Unsurprisingly several similar mechanisms have been observed in humans. A well-known human example of genetic protection is resistance to malaria in endemic areas which has been associated with polymorphism in alpha and beta chain globulin genes, cytoskeleton proteins, and protein/receptors on the surface of red blood cells. Studies regarding infection by Schistosoma mansoni show that the extent of infection depends largely on each individual's intrinsic resistance under the control of a single major gene which has now been located on q31-33 locus of the long arm of chromosome 5. This locus harbors several genes involved in differentiation of auxiliary T lymphocytes. With regard to HIV infection it has been known for several years that a small but significant number of individuals are relatively resistant. This resistance has been attributed to deletion of the gene coding for the chemokine receptor used by the virus as a co-receptor to infect macrophage.

Agriculture↗
PubMed1994

The epidemiology, immunology and morbidity of Schistosoma haematobium infections in diverse communities in Zimbabwe. I. The study design.

Recent studies on the immunology and epidemiology of Schistosoma haematobium infection have led to several new hypotheses regarding the relationships between the transmission of infection and the development of resistance to infection and also the associations between particular antibody and cellular reactivities with resistance or susceptibility to reinfection after chemotherapy. The study will extend the information on the development of protective immune responses during Schistosoma haematobium infection by examining these responses in groups of children and adults from areas in which differences in the peak prevalence of infection have been reported. Our working hypothesis is that, in areas of intense transmission, resistance to infection develops sooner than in areas where transmission is not so intense. We will investigate whether or not this is the case by monitoring levels of reinfection after chemotherapy and by trying to relate observed resistance and susceptibility to reinfection to serological and cellular reactivities. Exposure to infection, cercariometry and malacological studies will also be completed in both areas. The possibility that resistance to infection is associated with T lymphocyte responses classed as Th-2 type will be investigated by assessing reactivities to defined antigens of S. haematobium. This study will generate data which will be used to develop and test mathematical models of the epidemiological determinants which are important in human schistosomiasis.

Adolescent↗