Modeling and comparative study of the spread of zoonotic visceral leishmaniasis from Northern to Central Tunisia

During the last twenty years, zoonotic visceral leishmaniasis (ZVL) spread from the north characterized by humid, sub-humid, and semi-arid bio-climates to the arid areas located in Central Tunisia. In order to understand the eco-epidemiological factors involved in the distribution of ZVL, both a sero-epidemiological and an entomological investigation were performed in two governorates situated in two different bio-geographical areas: Bizerte in the north and Kairouan in the center. A mathematical model for transmission of ZVL was built, describing the disease dynamic in these areas. Among 108 sera collected from clinically healthy owned dogs used for guarding houses in the governorate of Bizerte and tested for anti-L. infantum antibodies by indirect immune-fluorescence antibody test (IFAT), 8.3% were positive. From a total of 191 serum samples collected from clinically healthy owned dogs used for guarding houses in the governorate of Kairouan and tested for anti-L. infantum antibodies by IFAT, 26.7% were sero-positive. The cumulative incidences of ZVL in humans in the governorates of Bizerte and Kairouan were 39.17/100,000 and 0.2/100,000 inhabitants, respectively. The infection rates of sand flies with Leishmania DNA in the governorate of Bizerte and Kairouan were 3.8% and 9.4%, respectively. It is important to point out that ZVL epidemic in humans is preceded or concomitant to a high prevalence of Leishmania infantum in dogs and in sand flies. The model showed also a non-linear relationship between dog infection and ZVL in humans. These results suggest an important force of infection (R0) in emerging foci such as the governorate of Kairouan leading to an increased incidence of ZCL in humans. A high prevalence of L. infantum in dogs will result in high prevalence in the vector and obviously high probability to infect human; that it is a key factor for triggering transmission to humans, and subsequently it is an important parameter in the control of ZVL transmission.

Risk factors for mortality of children with zoonotic visceral leishmaniasis in Central Tunisia

BACKGROUND

Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is endemic with an epidemiological profile of a paediatric disease in Tunisia. In the context of a high fatality rate, identifying risk factors for in-hospital mortality in children treated for ZVL is of major epidemiological importance.

DESIGN

A retrospective (case-control) study included 230 immuno-competent children diagnosed and confirmed with primary ZVL in the paediatric department of the University Hospital of Kairouan between 2004 and 2014. Forty-seven per cent (47%) were children under 18 months of age, and with a male ⁄ female ratio of 1.01:1.

RESULTS

The overall case-fatality was 6% (n = 14). The risk factors for in-hospital death identified by a multivariate analysis were: bleeding at admission (OR = 25.5, 95% CI: 2.26-287.4; p = 0.009), white cell count less than 4000/mm3 (OR = 5.66, 95% CI: 1.16-27.6; p = 0.032), cytolysis (OR = 28.13, 95% CI: 4.55-173.6; p < 0.001), and delay between onset of symptoms and admission ≥ 15 days (OR = 11, 95% CI: 1.68-72; p = 0.012).

CONCLUSION

The results strongly suggest that paediatric patients admitted 15 days after onset of symptoms, with bleeding, white cell counts below 4,000/mm3, and cytolysis at admission should be considered severe cases and subsequently, they are at high risk of mortality. A better understanding of factors associated with death of children from ZVL may contribute to decrease mortality.

Protective effects of Zygophyllum album extract against deltamethrin-induced hyperglycemia and hepato-pancreatic disorders in rats

The current study was designed to investigate the possible mechanism involved in hyperglycemia induced by chronic exposure to deltamethrin (DLM) in rat and to assess whether this damage is amenable to modulation by Zygophyllum album. DLM, a synthetic pyrethroid pesticide, was administrated at a dose of 4 mg/kg body mass, during 60 days. Compared with control, DLM showed a significant increase of blood glucose (p ≤ 0.01) and glycosylated hemoglobin levels (p ≤ 0.01) and a clear decrease (p ≤ 0.01) of insulin and total hemoglobin levels. In addition, hepatic glycogen content and the activity of hexokinase decreased (p ≤ 0.01), whereas the activities of glucose-6-phosphatase and glycogen phosphorylase were significantly increased (p ≤ 0.01). Moreover, pancreatic lipid peroxidation (TBARS level) was higher (p ≤ 0.01) and oxidative stress biomarkers (SOD, CAT, GPx, and GSH) were altered owing to DLM toxicity. However, Z. album, when combined with DLM, significantly ameliorated almost all the hepato-pancreatic disorders induced by DLM alone. Furthermore, Z. album supplement was found to be effective in preserving the normal histological appearance of hepatic and pancreatic tissue. In conclusion, this study suggested that, owing to its antioxidant effects, methanolic extract of Z. album (MEZAL) can potentially prevent the hyperglycemia observed in DLM-treated group.

Chemical Composition, Antioxidant and Antimicrobial Activities of Thymus capitata Essential Oil with Its Preservative Effect against Listeria monocytogenes Inoculated in Minced Beef Meat

The chemical composition, antioxidant and antimicrobial activities, and the preservative effect of Thymus capitata essential oil against Listeria monocytogenes inoculated in minced beef meat were evaluated. The essential oil extracted was chemically analyzed by gas chromatography-mass spectrometry. Nineteen components were identified, of which carvacrol represented (88.89%) of the oil. The antioxidant activity was assessed in vitro by using both the DPPH and the ABTS assays. The findings showed that the essential oil exhibited high antioxidant activity, which was comparable to the reference standards (BHT and ascorbic acid) with IC50 values of 44.16 and 0.463 μ g/mL determined by the free-radical scavenging DPPH and ABTS assays, respectively. Furthermore, the essential oil was evaluated for its antimicrobial activity using disc agar diffusion and microdilution methods. The results demonstrated that the zone of inhibition varied from moderate to strong (15-80 mm) and the minimum inhibition concentration values ranged from 0.32 to 20 mg/mL. In addition, essential oil evaluated in vivo against Listeria monocytogenes showed clear and strong inhibitory effect. The application of 0.25 or 1% (v/w) essential oil of T. capitata to minced beef significantly reduced the L. monocytogenes population when compared to those of control samples (P-value  <0.01).

Assessing the effect of zooprophylaxis on zoonotic cutaneous leishmaniasis transmission: a system dynamics approach

Capturing or diverting the disease carrying vector from humans can reduce the transmission of vector borne diseases such as leishmaniasis. The use of animals that act as dead-end hosts to relieve the vector (sandfly) bites on humans is called zooprophylaxis. However, as the number of blood meal providers especially domestic animals increases, the sandflies enhanced availability of blood meals will improve its number and survival, thereby countering the impact of diverting bites from humans. Thus, the transmission model exhibits the structure of a feedback loop characterizing complex dynamic systems. In order to rigorously assess the effect of zooprophylaxis, we propose a system dynamic model for zoonotic cutaneous leishmaniasis transmission with 3 blood-meal hosts: domestic animals, humans, and a reservoir (rodents). In this context, a simulation study of the proposed model with a follow-up period of 1000 days was performed. We explored how perturbations in the parameters characterizing the transmission, essentially the vector biting rates and the size of the domestic animal population, affect the zooprophylaxis outcome. The results show that the basic reproductive number R0 and the disease incidence in humans are decreasing function of the relative size of the domestic animal population. The speed of this decrease depends also on the vector biting rates of the different mammal species. The key factors influencing the magnitude of zooprophylaxis are: the sizes of the vector, rodent, and domestic animal populations, as well as, the biting rates which incorporate relative attraction and accessibility of the vectors to the mammalian populations.

Prognostic value of Bcl-2 and Bax tumor cell expression in patients with non muscle-invasive bladder cancer receiving bacillus Calmette-Guerin immunotherapy

Apoptosis is the distinctive form of programmed cell death that complements cell proliferation in maintaining normal tissue homeostasis. The significance of constitutive apoptosis in the recurrence of Non Muscle Invasive Bladder Cancer has yet to be investigated. The aim of this study is to investigate the prognostic significance of Bax and Bcl-2 in terms of recurrence after BCG immunotherapy. Immunohistochemical analysis was performed on frozen biopsies to evaluate bcl-2 and Bax proteins expression in 28 cases of NMIBC. All patients with confirmed NMIBC were treated with intravesical BCG-immunotherapy. The follow up was performed for 26 months. The correlation between clinicopathological, immunohistochemical data and the response to BCG therapy was performed. Univariate analysis showed that, PT1 stage, High grade and Bax expression increased significantly the risk of recurrence (P = 0.015, P = 0.015 and P= 0.034 respectively). In addition, multivariate analysis selected the model involving stage, age, Bax and Bcl-2 expression as the best independent variables of recurrence. In conclusion, the expression of Bcl-2 and Bax in NMIBC could have a prognostic value in assessing the risk of recurrence after BCG immunotherapy. These findings require further investigations on larger cohort in order to ascertain new molecular markers of the response to BCG immunotherapy.

Evaluation of antileishmanial, cytotoxic and antioxidant activities of essential oils extracted from plants issued from the leishmaniasis-endemic region of Sned (Tunisia)

In this study, we tested 10 essential oils (EOs) extracted from 10 plants issued from Sned region (Tunisia) to evaluate both their leishmanicidal effects against Leishmania major and L. infantum, and their cytotoxicity against murine macrophage cell line RAW 264.7 (ATCC, TIB-71). The antioxidant activity was also monitored by the DDPH method, while the chemical composition of active EO was assessed by GC-MS analysis. The results showed that the EOs obtained from Thymus hirtus sp. algeriensis (rich on monoterpenoids, especially linalool at 17.62% and camphor at 13.82%) is significantly active against both L. major and L. infantum, whereas Ruta chalepensis EO (rich on 2-undecanone at 84.28%) is only active against L. infantum. Both oil extracts showed low cytotoxicity towards murine macrophages. The characteristic ratios (IC₈₀ Raw264.7 cells/IC₅₀ L. infantum and IC₈₀ Raw264.7 cells/IC₅₀ L. major) were, respectively, 2.7 and 1.57 for T. hirtus sp. algeriensis, and 1.34 and 0.19 for R. chalepensis. However, when measuring the antioxidant effects (DDPH method), the two latter EOs presented a moderate 2,2-diphenyl-2-picrylhydrazyl hydrate scavenging effects compared to EOs from Eucaliptus globulus, Pinus halepensis, Pituranthos tortuosus, Rosmarinus officinalis, Tetraclinis articulata or to BHT.

Colonization of Phlebotomus papatasi changes the effect of pre-immunization with saliva from lack of protection towards protection against experimental challenge with Leishmania major and saliva

Background

Sand fly saliva has been postulated as a potential vaccine or as a vaccine component within multi component vaccine against leishmaniasis. It is important to note that these studies were performed using long-term colonized Phlebotomus papatasi. The effect of sand flies colonization on the outcome of Leishmania infection is reported.

Results

While pre-immunization of mice with salivary gland homogenate (SGH) of long-term colonized (F5 and beyond) female Phlebotomus papatasi induced protection against Leishmania major co-inoculated with the same type of SGH, pre-immunization of mice with SGH of recently colonized (F2 and F3) female P. papatasi did not confer protection against L. major co-inoculated with the same type of SGH. Our data showed for the first time that a shift from lack of protection to protection occurs at the fourth generation (F4) during the colonization process of P. papatasi.

Conclusion

For the development of a sand fly saliva-based vaccine, inferences based on long-term colonized populations of sand flies should be treated with caution as colonization of P. papatasi appears to modulate the outcome of L. major infection from lack of protection to protection.

Characteristics and pathways of bioactive 4-desmethylsterols, triterpene alcohols and 4α-monomethylsterols, from developing Tunisian cultivars and wild peanut (Arachis hypogaea L.)

Seven 4-desmethylsterols, five triterpene alcohols and three 4α-monomethylsterols were identified by GC-MS during the development of wild peanut, which is Arbi (AraA), and cultivars peanut, which are Trabelsia (AraT) and Chounfakhi (AraC). Our results showed that the maximum level of 4-desmethylsterols (881.07 mg/100 g of oil) was reached at 12 days after flowering (DAF) date of peanut plant in AraA, as well as the highest level of triterpene alcohols (31.51 mg/100 g of oil) was reached at 23 DAF in AraA, whilst, the highest level of 4α-monomethylsterols (15.11 mg/100 g of oil) was reached at 41 DAF in AraC. Herein, the level of triterpene alcohols and 4α-monomethylsterols was overwhelmed by the amount of 4-desmethylsterols at each stage of peanut maturity. Differences were observed in each sterol contents among the studied cultivars and wild one especially in immature stage.

Evaluation and modeling of synergy to pheromone and plant kairomone in American palm weevil

BACKGROUND

Many behavioral responses to odors are synergistic, particularly in insects. In beetles, synergy often involves a pheromone and a plant odor, and pest management relies on them for the use of combined lures. To investigate olfactory synergy mechanisms, we need to distinguish synergistic effects from additive ones, when all components of the mixture are active.

RESULTS

As versatile tools and procedures were not available, we developed a bioassay, and a mathematical model to evaluate synergy between aggregation pheromone (P) and host plant odors (kairomone: K) in the American palm weevil, a pest insect showing enhanced responses to P+K mixtures. Responses to synthetic P and natural K were obtained using a 4-arm olfactometer coupled to a controlled volatile delivery system. We showed that: (1) Response thresholds were ca. 10 and 100 pg/s respectively for P and K. (2) Both stimuli induced similar maximum response. (3) Increasing the dose decreased the response for P to the point of repellence and maintained a maximum response for K. (4) P and K were synergistic over a 100-fold range of doses with experimental responses to P+K mixtures greater than the ones predicted assuming additive effects. Responses close to maximum were associated with the mixture amounts below the response threshold for both P and K.

CONCLUSION

These results confirm the role of olfactory synergy in optimizing active host-plant localization by phytophagous insects. Our evaluation procedure can be generalized to test synergistic or inhibitory integrated responses of various odor mixtures for various insects.

Comparison of the concentrations of long-chain alcohols (policosanol) in three Tunisian peanut varieties (Arachis hypogaea L.)

Policosanol (PC) is a mixture of high molecular weight aliphatic primary alcohols. Literature about the contents and compositions of PC derived from peanut varieties is scarce. Total PC composition and content in whole peanut grain samples from three varieties of peanut (two cultivars, AraC and AraT, and a wild one, AraA) were identified using a gas chromatograph system coupled with a mass spectrophotometer. The results show that, qualitatively, 21 components of peanut aliphatic alcohols were identified (C14-C30). Besides (C18=), the results exhibited a previously unreported mixture of PC compositions in the peanuts: the unsaturated PC (UPC), which are (C20=), (C21=), (C22=), and (C24=). The main components of total PC in Tunisian peanut kernels are docosanol (C22), (Z)-octadec-9-en-1-ol (C18=), hexadecanol (C16), and octadecanol (C18). Quantitatively, the total PC content of the whole peanut samples varied from 11.18 to 54.19 mg/100 g of oil and was higher than those of beeswax and whole sugar cane, which are sources of dietary supplements containing policosanol.

Lack of protection of pre-immunization with saliva of long-term colonized Phlebotomus papatasi against experimental challenge with Leishmania major and saliva of wild-caught P. papatasi

Immunity to saliva of Phlebotomus papatasi protects against Leishmania major infection as determined by co-inoculation of parasites with salivary gland homogenates (SGHs) of this vector. These results were obtained with long-term colonized female P. papatasi. We investigated the effect of pre-immunization with SGH of long-term colonized P. papatasi against L. major infection co-inoculated with SGH of wild-caught P. papatasi. Our results showed that pre-exposure to SGH of long-term, colonized P. papatasi do not confer protection against infection with L. major co-inoculated with SGH of wild-caught P. papatasi. These preliminary results strongly suggest that the effectiveness of a vector saliva-based vaccine derived from colonized sand fly populations may be affected by inconsistent immune response after natural exposure.

Differences in the salivary effects of wild-caught versus colonized Phlebotomus papatasi (Diptera: Psychodidae) on the development of zoonotic cutaneous leishmaniasis in BALB/c mice

Preimmunization of mice with salivary gland homogenate (SGH) of long-term colonized (F29) female Phlebotomus papatasi Scopoli (Diptera: Psychodidae) induced protection against Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae) co-inoculated with the same type of SGH. In contrast, preimmunization of mice with SGH of wild-caught female P. papatasi did not confer protection against L. major co-inoculated with the same type of SGH. Similarly, SGH from recently colonized (F1) female P. papatasi did not protect mice against L. major. These results suggest that when developing a sand fly saliva-based vaccine, the natural vector populations should be considered.

Bioinformatic characterizations and prediction of K+ and Na+ ion channels effector toxins

BACKGROUND

K+ and Na+ channel toxins constitute a large set of polypeptides, which interact with their ion channel targets. These polypeptides are classified in two different structural groups. Recently a new structural group called birtoxin-like appeared to contain both types of toxins has been described. We hypothesized that peptides of this group may contain two conserved structural motifs in K+ and/or Na+ channels scorpion toxins, allowing these birtoxin-like peptides to be active on K+ and/or Na+ channels.

RESULTS

Four multilevel motifs, overrepresented and specific to each group of K+ and/or Na+ ion channel toxins have been identified, using GIBBS and MEME and based on a training dataset of 79 sequences judged as representative of K+ and Na+ toxins.Unexpectedly birtoxin-like peptides appeared to present a new structural motif distinct from those present in K+ and Na+ channels Toxins. This result, supported by previous experimental data, suggests that birtoxin-like peptides may exert their activity on different sites than those targeted by classic K+ or Na+ toxins.Searching, the nr database with these newly identified motifs using MAST, retrieved several sequences (116 with e-value < 1) from various scorpion species (test dataset). The filtering process left 30 new and highly likely ion channel effectors.Phylogenetic analysis was used to classify the newly found sequences. Alternatively, classification tree analysis, using CART algorithm adjusted with the training dataset, using the motifs and their 2D structure as explanatory variables, provided a model for prediction of the activity of the new sequences.

CONCLUSION

The phylogenetic results were in perfect agreement with those obtained by the CART algorithm.Our results may be used as criteria for a new classification of scorpion toxins based on functional motifs.

Spatial correlation between Phlebotomus papatasi Scopoli (Diptera: Psychodidae) and incidence of zoonotic cutaneous leishmaniasis in Tunisia

The geographical distribution of Phlebotomus papatasi Scopoli, vector of Leishmania major Yakimoff and Schokhor (Kinetoplastida: Trypanosomatidae), the etiologic agent of zoonotic cutaneous leishmaniasis (ZCL), was assessed during September 2006 through a transect from the north to the south of Tunisia using CDC light traps. P. papatasi was found to be abundant in the arid and Saharan bioclimatic zones and rare in the humid, subhumid, and semiarid bioclimatic zones. Similarly, the highest incidence of ZCL was observed in the arid and Saharan bioclimatic zones and the lowest in the humid, subhumid, and semiarid bioclimatic zones. Our overall findings confirm the close spatial association between the abundance of P. papatasi and the incidence of ZCL.

Natural infection of Phlebotomus (Larroussius) langeroni (Diptera: Psychodidae) with Leishmania infantum in Tunisia

Phlebotomine sand flies were captured from an active transmission focus of sporadic cutaneous leishmaniasis, caused by Leishmania infantum, in El Kef region, northern Tunisia. Both Phlebotomus perniciosus and P. langeroni were found. Phlebotomus langeroni females showed a statistically significant intradomiciliary dominance (P<0.01 for the 2003 and 2004 seasons) when compared to animal shelters. During the 2003 season, dissection of collected female specimens showed the presence of flagellates within the digestive tracts of two P. perniciosus among 1086 observed, but none in 232 P. langeroni. Amplification of kinetoplast minicircles of Leishmania parasites was applied to DNA samples extracted from 298 frozen females including 249 P. perniciosus, 36 P. langeroni, 5 P. longicuspis and 8 P. perfiliewi and revealed by radioactive probe hybridization. Two P. langeroni females showed a signal of the size expected for L. infantum (800bp) indicating infection with these parasites. However, this PCR-hybridization method failed to identify any positive P. perniciosus females in pools of specimens. These results show for the first time the natural infection of P. langeroni with L. infantum in Tunisia, and support the existence of different L. infantum transmission cycles in Tunisia, with a potential role for P. langeroni as a vector.

Comparison of pp65 antigenemia, quantitative PCR and DNA hybrid capture for detection of cytomegalovirus in transplant recipients and AIDS patients

The cytomegalovirus (CMV) antigenemia assay has been used frequently for rapid diagnosis of CMV infection, and antigenemia threshold values are recommended for triggering preemptive therapy. Hybrid capture of CMV's DNA and quantitative polymerase chain reaction (qPCR) are increasingly being adopted for early detection of CMV. The performance of the antigenemia assay, qPCR in plasma and hybrid capture in leukocytes were compared in 110 immunocompromised patients (38 bone-marrow transplants, 50 renal transplants and 22 AIDS patients). The most sensitive test was hybrid capture for transplants, while antigenemia and the qPCR showed similar performance for patients with AIDS. QPCR and hybrid capture thresholds requiring antiviral therapy were calculated using a receiver-operating-characteristic curve for antigenemia values corresponding to 2 positive cells for bone-marrow transplants and to 10 positive cells for renal transplants and AIDS patients. These threshold values varied with the group of patients considered, with corresponding sensitivities higher than 86% and specificities higher than 76% for hybrid capture, and sensitivities higher than 61% and specificities higher than 75% for qPCR in plasma. Hybrid capture in leukocytes can substitute for antigenemia in the case of transplants, and qPCR in plasma can substitute for it in the case of AIDS patients.

Genome scan for loci predisposing to anxiety disorders using a novel multivariate approach: strong evidence for a chromosome 4 risk locus

We conducted a 10-centimorgan linkage autosomal genome scan in a set of 19 extended American pedigrees (219 subjects) ascertained through probands with panic disorder. Several anxiety disorders--including social phobia, agoraphobia, and simple phobia--in addition to panic disorder segregate in these families. In previous studies of this sample, linkage analyses were based separately on each of the individual categorical affection diagnoses. Given the substantial comorbidity between anxiety disorders and their probable shared genetic liability, it is clear that this method discards a considerable amount of information. In this article, we propose a new approach that considers panic disorder, simple phobia, social phobia, and agoraphobia as expressions of the same multivariate, putatively genetically influenced trait. We applied the most powerful multipoint Haseman-Elston method, using the grade of membership score generated from a fuzzy clustering of these phenotypes as the dependent variable in Haseman-Elston regression. One region on chromosome 4q31-q34, at marker D4S413 (with multipoint and single-point nominal P values < .00001), showed strong evidence of linkage (genomewide significance at P<.05). The same region is known to be the site of a neuropeptide Y receptor gene, NPY1R (4q31-q32), that was recently connected to anxiolytic-like effects in rats. Several other regions on four chromosomes (4q21.21-22.3, 5q14.2-14.3, 8p23.1, and 14q22.3-23.3) met criteria for suggestive linkage (multipoint nominal P values < .01). Family-by-family analysis did not show any strong evidence of heterogeneity. Our findings support the notion that the major anxiety disorders, including phobias and panic disorder, are complex traits that share at least one susceptibility locus. This method could be applied to other complex traits for which shared genetic-liability factors are thought to be important, such as substance dependencies.

Comparative evaluation of specific ELISA and RFFIT antibody assays in the assessment of dog immunity against rabies

Two techniques are currently used to evaluate the humoral immune responses to rabies vaccination: ELISA, which detects binding antibodies to viral antigens and the WHO reference rapid fluorescent focus inhibition test (RFFIT), which assays in vitro virus-neutralizing antibodies. In this study, we have comparatively evaluated antibody responses of dogs reared either in an experimental kennel or living in field conditions after vaccination with a cell culture-derived rabies vaccine. In experimental conditions, both ELISA and RFFIT techniques were well correlated. However, in field conditions, they yielded discrepant results particularly in evaluating the residual rabies immunity before vaccine administration and in identifying seroconverted dogs. After rabies vaccination in field conditions, while similar antibody titres and seroconversion rates were obtained using either technique, the discrimination of a given dog according to the seroconversion threshold depended on the assay. We concluded, that whereas in experimental conditions, ELISA and RFFIT were well correlated, in field conditions ELISA yielded upper estimates. Consequently, RFFIT, although a cumbersome test, should continue to be considered as the reference rabies antibody assay technique. A seroconversion threshold of 0.5 IU/ml should be cautiously considered and a higher threshold (1 IU/ml) could be more appropriate in the evaluation of rabies immunity in the field in order to marginalize the interfering factors.

[Association study between diabetic retinopathy and aldose reductase gene polymorphism in Tunisians]

INTRODUCTION

Aldose reductase (ALR2), the enzyme of the polyol pathway, may play an important role in the pathogenesis of diabetic microvascular complications, namely diabetic retinopathy. The study aimed to determine whether the aldose reductase gene is involved in diabetic retinopathy in the Tunisian population.

MATERIAL

and methods: A case-control study was conducted in 47 type 2 diabetic patients who have diabetic retinopathy and 28 diabetic patients without diabetic retinopathy in spite of diabetes lasting for more than 5 years and over 10 years in 13 cases. We investigated the association between the (CA)n polymorphism located at 2.1 kb upstream of the transcription start site of ALR2 and diabetic retinopathy. The distribution of genotypes and alleles was compared between cases and controls by chi2 test using Epi info software.

RESULTS

Genotyping of the two groups did not demonstrate any association between the alleles of this marker and diabetic retinopathy in the Tunisian population studied.

DISCUSSION

An association between one of the alleles (Z - 2) of this microsatellite and diabetic retinopathy was identified in Chinese and Japanese patients with type 2 diabetes. Discordant results were obtained for the different populations studied. The lack of an association between diabetic retinopathy and ALR2 alleles indicates that the ALR2 gene is not a genetic marker of predisposition to diabetic retinopathy for type 2 diabetic patients in the Tunisian population studied.

New multivariate test for linkage, with application to pleiotropy: fuzzy Haseman-Elston

We propose a new method of linkage analysis based on using the grade of membership scores resulting from fuzzy clustering procedures to define new dependent variables for the various Haseman-Elston approaches. For a single continuous trait with low heritability, the aim was to identify subgroups such that the grade of membership scores to these subgroups would provide more information for linkage than the original trait. For a multivariate trait, the goal was to provide a means of data reduction and data mining. Simulation studies using continuous traits with relatively low heritability (H=0.1, 0.2, and 0.3) showed that the new approach does not enhance power for a single trait. However, for a multivariate continuous trait (with three components), it is more powerful than the principal component method and more powerful than the joint linkage test proposed by Mangin et al. ([1998] Biometrics 54:88-99) when there is pleiotropy.

Association analysis of HLA-class II and class III gene polymorphisms in the susceptibility to mediterranean visceral leishmaniasis

HLA-DRB1, -DQB1, TNFalpha, TNFbeta, HSP70-2 and HSP70-hom genetic polymorphisms were analyzed in 156 unrelated patients who developed mediterranean visceral leishmaniasis (MVL) due to Leishmania infantum, and 154 unrelated healthy controls, who have got asymptomatic infection with this parasite and were selected on the basis of a positive leishmanin skin test (LST). A significantly reduced frequency of HLA-DR2 was observed among MVL patients (16.1%), compared with controls (26.3%) (relative risk = 0.54; p = 0.04). HLA-DR2/DR13 as well as HLA-DQB1*0201/- genotype frequencies were significantly lower in patients vs controls (relapse rate = 0.17 and 0.46, respectively; p < 0.05). However, using Bonferroni correction, none of these associations remained significant. No association was found, between either the -308 base pair TNFalpha gene polymorphism or the NcoI polymorphism in the first intron of the TNFbeta gene and susceptibility to MVL. Analysis of PstI and NcoI polymorphisms in the coding region of HSP70-2 and HSP70-hom genes, respectively, revealed a significantly higher frequency of homozygotes for the HSP70-2/PstI negative allele, among patients (21.8%) vs controls (12.6%) (relapse rate = 1.94; p = 0.04). Again, this result was not significant after using Bonferroni correction. These results do not support association between susceptibility to MVL and the MHC class II and class III loci analyzed in this study.