Biomedical subjects

Koussay Dellagi

Publications and source records attributed to Koussay Dellagi.

31 records · Page 2Linked to original sources

PubMed2004

Inbred strains derived from feral mice reveal new pathogenic mechanisms of experimental leishmaniasis due to Leishmania major.

Two inbred mouse strains, derived from feral founders, are susceptible to experimental leishmaniasis due to Leishmania major and support a disease of a severity intermediate between those observed in strains C57BL/6 and BALB/c. Mice of the MAI strain develop a severe, nonhealing, but nonfatal disease with no resistance to a secondary parasite challenge. The immunological responses showed a TH2 dominance characterized by an early peak of interleukin-4 (IL-4) and IL-13. However, neutralization of IL-4, which leads to a resistance phenotype in BALB/c mice, has no effect on disease progression in MAI mice. Mice of strain PWK develop a protracted but self-healing disease, characterized by a mixed TH1-plus-TH2 pattern of immune responses in which IL-10 plays an aggravating role, and acquire resistance to a secondary challenge. These features are close to those observed in human cutaneous leishmaniasis due to L. major and make PWK mice a suitable model for the human disease.

Animals↗

PubMed2004

A novel simple and rapid PCR-based site-directed mutagenesis method.

Site-directed mutagenesis (SDM) is a powerful tool for exploring protein structure and function, and several procedures adjusted to specific purposes are still being developed. Herein we describe a straightforward and efficient method with versatile applications for introducing site-specific alterations in any deoxyribonucleic acid (DNA) sequence cloned in a plasmidic expression vector. In this polymerase chain reaction (PCR)-based SDM method, forward and reverse primers are used to amplify the plasmid containing the sequence of interest. The primers are designed so that the desired modifications are introduced at the 5' end of one of the primers, whereas the other primer starts with the nucleotide at position (-1) of the one to be modified. The PCR is carried out using Pfu DNA polymerase. The blunt-ended PCR-generated DNA fragment is self-ligated and used to transform Escherichia coli. Mutant clones are screened by colony hybridization using the mutagenic primer as probe and the presence of the mutation is confirmed by direct DNA sequencing. This procedure was used efficiently to introduce substitutions, deletions, and insertions in the DNA sequences coding for a recombinant form (scFv) of antibody 107 specific of the human CR3 molecule, the rat alpha integrin CD11b A-domain and the human CD8beta cloned in pPICZalphaB, pGEX-2T, and CDM8 expression vectors, respectively.

Animals↗

PubMed2004

[Molecular study of Fanconi anemia in Tunisia].

Fanconi anemia (FA) is an autosomal recessive rare disease characterized by progressive pancytopenia, congenital malformations and predisposition to acute myeloid leukemia. Fanconi anemia is genetically heterogeneous, with at least eight complementation groups of FA (FAA to FAD2). In order to characterize the molecular defects underlying FA in Tunisia, fourty-one families were genotyped with microsatellite markers linked to known FA gene. Haplotype analysis and homozygosity mapping showed that 92% of these families belong to FAA group. We demonstrated the effectiveness of the molecular analysis for a better selection of bone marrow graft donor and for the evaluation of chimerism after bone marrow transplantation. This study also allows genetic counselling for FA family members.

Adolescent↗

PubMed2003

Post-exposure therapy in mice against experimental rabies: a single injection of DNA vaccine is as effective as five injections of cell culture-derived vaccine.

Two rabies post-exposure therapies were comparatively evaluated: BALB/c mice were challenged at day 0 with rabies virus and then received either a single dose of rabies DNA vaccine administered at day 0, or five doses of cell culture-derived rabies vaccine administered at days 0, 3, 7, 15 and 28. Both regimens, rapidly triggered protective levels of neutralizing antibodies against rabies virus in vaccinated mice. In addition, one injection of DNA vaccine protected 53% of the challenged mice, compared to 40% of mice protected after five injections of cell culture-derived vaccine. We conclude that rabies post-exposure vaccination in BALB/c mice, based on a single administration of rabies DNA vaccine might be at least as effective as five injections of cell culture-derived vaccine.

Animals↗

PubMed2003

A canine study of immunotherapy in scorpion envenomation.

OBJECTIVE: To evaluate the effects of scorpion venom and antivenom in experimental envenomation. DESIGN: Prospective, controlled animal study. SETTING: University research laboratory SUBJECTS: Twenty-nine anesthetized and ventilated dogs. INTERVENTIONS: The first group of animals had venom alone (0.05 mg/kg). Animals from the second group had simultaneous administration of 10 ml of scorpion antivenom (SAV). In the third and fourth groups, 10 ml and 40 ml SAV, respectively, were injected 10 min following venom. MEASUREMENTS AND RESULTS: Hemodynamic parameters using right heart catheter were recorded and dosage of catecholamines, neuropeptide Y (NPY), endothelin-1, and atrial natriuretic peptide (ANP) were performed at baseline and during 60 min following envenomation. In the control group, at 5 min, there was a sharp increase in pulmonary artery occluded pressure (PAOP, from 2 mmHg to 23 mmHg), mean arterial pressure (MAP, from 125 mmHg to 212 mmHg) and systemic vascular resistance (SVR, from 2450 dyn sec(-1 )m(5) to 5775 dyn sec(-1 )m(5), P<0.05 for all). Heart rate, cardiac output, and stroke volume decreased. There was a 40-fold increase in epinephrine and norepinephrine plasma concentrations. Circulating NPY and ANP dosages increased too. PAOP and MAP decreased thereafter to reach baseline levels. Simultaneous administration of SAV with venom totally offset the hallmarks of scorpion envenomation. Delayed administration of SAV at any dosage failed to alter the features of scorpion envenomation. CONCLUSION: While simultaneous administration of SAV and scorpion venom is effective in preventing scorpion envenomation-related manifestations, delayed administration of SAV, either at standard or elevated dosages, failed to alter any of the scorpion envenomation features.

Animals↗

PubMed2003

Fanconi anemia in Tunisia: high prevalence of group A and identification of new FANCA mutations.

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by progressive pancytopenia, congenital malformations, and predisposition to acute myeloid leukemia. Fanconi anemia is genetically heterogeneous, with at least eight distinct complementation groups of FA (A, B, C, D1, D2, E, F, and G) having been defined by somatic cell fusion studies. Six genes (FANCA, FANCC, FANCD2, FANCE, FANCG, and FANCF) have been cloned. Mutations of the seventh Fanconi anemia gene, BRCA2, have been shown to lead to FAD1 and probably FAB groups. In order to characterize the molecular defects underlying FA in Tunisia, 39 families were genotyped with microsatellite markers linked to known FA gene. Haplotype analysis and homozygosity mapping assigned 43 patients belonging to 34 families to the FAA group, whereas one family was probably not linked to the FANCA gene or to any known FA genes. For patients belonging to the FAA group, screening for mutations revealed four novel mutations: two small homozygous deletions 1693delT and 1751-1754del, which occurred in exon 17 and exon 19, respectively, and two transitions, viz., 513G-->A in exon 5 and A-->G at position 166 (IVS24+166A-->G) of intron 24. Two new polymorphisms were also identified in intron 24 (IVS24-5G/A and IVS24-6C/G).

Alleles↗

PubMed2003

[The hyper-IgM syndrome: 13 observations].

INTRODUCTION: The hyper-IgM syndrome (HIGM) is a rare hereditary immune deficiency, characterised by a low or nil level of IgG and IgA and a normal or increased level of IgM, predominately affecting boys. Its clinical manifestations are dominated by recurrent infection, notably of the digestive tube, the ears nose and throat and the lungs. METHODS: We conducted a retrospective study of the medical files of 13 patients with 10 boys and 3 girls from 12 different families. In all the patients, the diagnosis was established on measuring the serum immunoglobulines IgG, IgA and IgM using Mancini's technique. RESULTS: The mean age at the onset of the disease was of 20 months (6 - 42 months). The clinical manifestations were dominated by recurrent and persisting infections, notably digestive (10 cases), respiratory (9 cases), cutaneous (5 cases) and glandular (5 cases). No pulmonary Pneumocystis carinii infection or sclerosing Cryptosporidium cholangitis was observed. Two boys exhibited neurological manifestations, unrelated to an infection. The IgG deficiency was constant and IgA deficieny encountered in 12 patients. Ten patients exhibited a high level of IgM (4.6 - 29,9 g/l) whereas this was normal in the 3 others. The expression of the CD(40) ligand was absent in the 6 boys in whom it was assessed and normal in the only girl studied. Eleven patients exhibited concomitant cellular immune deficiency. Three patients presented moderate neutropenia. Nine patients received replacement therapy with IV immunoglobulines with a residual level of IgG at 8,27 g/l (4 - 14,45 g/l) associated with the regression in the manifestations of infection. One patient died from a Burkitt lymphoma before any treatment was initiated. CONCLUSION: The primary hyper-IgM syndrome in Tunisia is characterised by a relative frequency of autosomal recessive forms (3 girls), the absence of Pneumocystis carinii pulmonary infections and sclerosing cholangitis and the occurrence of neurological manifestations (2 cases).

Adolescent↗

PubMed2003

Frequency and spectrum of hemochromatosis mutations in Tunisia.

The occurrence of the C282Y and H63D mutations of the HFE gene, responsible for toxic iron overload in the liver (hereditary hemochromatosis), was still unknown in Tunisia. We report the screening of 194 chromosomes from 97 randomly collected cord blood samples. The mutations were analyzed by PCR followed by DNA sequencing. The mild H63D and the severe C282Y mutations were found in 17.5+/-5.34% and 0.5+/-0.97% of the alleles, respectively. The allele frequency of the IVS 2+4 T --> C polymorphism is high (46.4+/-7.01%) in this population. Risk for homozygosity for the severe C282Y mutation is present in the Tunisian population at a low theoretical incidence. However, due to the relatively high rate of consanguinity in the country, liver pathology due to HH is not to be disregarded.

Amino Acid Substitution↗

PubMed2003

Community-acquired poliovirus infection in children with primary immunodeficiencies in Tunisia.

The global polio eradication program recommends the use of massive vaccination campaigns with live vaccine through National Immunization Days (NIDs) to displace the wild virus from the community. Immunodeficient patients may be indirectly infected and become chronic excretors and potential reservoirs of polioviruses, a concern for the posteradication era. This prospective study aimed to assess the risk of community-acquired infection of immunodeficient patients following NIDs, the dynamics of viral excretion and the genetic variation of excreted viruses. Sixteen children with various primary immunodeficiencies, who did not receive the vaccine during the campaign, were investigated. Stool samples were collected weekly, shortly after the NIDs, during at least 3 months, and were processed for viral isolation. Isolates were characterized by three intratypic differentiation methods and partial sequencing of the VP1/2A region. Polioviruses were detected in 4 out of 16 patients (serotype 1 in 3 patients and serotype 3 in 1 patient). Sequencing revealed more than 99% homology with homotypic Sabin strains, suggesting recent infection. Duration of viral excretion ranged from 1 to 7 weeks. Nine out of eleven isolates from the three poliovirus serotype 1-infected patients disclosed a non-Sabin-like phenotype by enzyme-linked immunosorbent assay and had recurrent mutations within or close to the neutralizing antigenic sites. In summary, the risk of secondary infection in immunodeficient patients is within the range previously reported for the general population. Although none of the four infected patients developed prolonged viral excretion, particular viral variants were selected and may be of epidemiological significance.

Child↗

PubMed2003

Comparative evaluation of ELISAs based on ten recombinant or purified Leishmania antigens for the serodiagnosis of Mediterranean visceral leishmaniasis.

This study compared a panel of 10 enzyme-linked immunosorbent assays (ELISAs) for the serodiagnosis of Mediterranean visceral leishmaniasis (MVL). The ELISAs were based on either one of the following Leishmania antigens: crude soluble Leishmania antigens (SLAs), recombinant (r) antigens (namely: rgp63, rK39, gene B protein, r H2A and r H2B histones proteins, rLACK, rPSA-2, r P20) and purified lipophosphoglycan. Most of the test antigens showed good performance (sensitivity > 85%, specificity > 80%). rK39 and SLA-based ELISA gave the best results in terms of sensitivity (100%) and predictive value of the negative (100%). The best specificity (97%) and the best predictive value of the positive (92%) were obtained with rK39. These results show that several Leishmania antigens are suitable to design a diagnostic ELISA of MVL. However, recombinant proteins add little to the classic crude SLA, which still represents a very good and less costly alternative.

Animals↗

PubMed2002

Clinical and genetic heterogeneity of inherited autosomal recessive susceptibility to disseminated Mycobacterium bovis bacille calmette-guérin infection.

Five patients from 4 unrelated Tunisian families who presented with disseminated neonatal infection by Mycobacterium bovis bacille Calmette-Guérin strain were investigated. Two unrelated patients had different homozygous interleukin-12 receptor beta1 subunit gene splice-site mutations (64+5G-->A and 550-2A-->G). Two siblings and 1 unrelated patient, all of whom were from the same town, carried the same mutation (297del8) within the interleukin-12p40 gene. This is the first description of familial cytokine deficiency reported so far. All patients had complete lack of expression of the affected polypeptide and a profound deficiency of in vitro interferon-gamma production. The clinical severity of the mycobacterial infection was heterogeneous, even among affected members of the same family, which suggests the intervention of modifying genes.

BCG Vaccine↗

PubMed2002

Molecular spectrum of alpha-thalassemia in Tunisia: epidemiology and detection at birth.

We present the characterization of the molecular spectrum and frequency data of alpha-thal (thal) defects in Tunisia, and an evaluation of the efficacy and limitations of Hb Bart's (gamma4) measurement for the screening of alpha-thal at birth. Cord blood samples were collected from two different areas: the northeast of the country, an area where Hb H (beta4) disease frequently occurs, and Tunis, the capital city, representative of the average Tunisian population. From the first group, 110 samples with Hb Bart's and/or microcytosis at birth were selected from 1270 randomly collected samples. Two additional population samples, one from the same northeastern region (n = 90), the other from Tunis (n = 104) were collected randomly. Nine common deletional alpha-thal defects and nondeletional mutations were screened. In the northeastern samples, selected for the presence of Hb Bart's and microcytosis, the -alpha3.7 deletion was the most common defect (4.5% allele frequency) followed by a polyadenylation (poly A) signal mutation (1.8%), the five nucleotide (nt) deletion and the -alpha4.2 deletion (both 0.9%). The African polymorphism (G-->TCGGCCC at position 7238 and T-->G at 7174) was found with an allele frequency of 11% in the selected northeastern samples. In the random population samples, the overall alpha-thal allele frequency was 4% in the northeast region, against 2% in the average Tunisian population. The +14 (G-->C) polymorphism in the 5'UTR (untranslated region) of the alpha2 gene and the African polymorphism in the second intron of the same gene, were found in 3.5% of the alleles. No alpha0-thal alleles were found among the 304 blood samples studied at the DNA level during this survey.

DNA↗

PubMed2002

Random amplified polymorphic DNA technique for identification and differentiation of old world Leishmania species.

The random amplified polymorphic DNA technique may be used to explore parasite DNA polymorphisms. We assessed its applicability to identification of Old World Leishmania species. A set of 6 random decamer primers (Al, A4, A5, A7, A10, and A15) was applied to a panel of DNA from 57 representatives of different Old World Leishmania species. The amplification profiles allowed discrimination among species belonging to different taxonomic complexes. Two criteria were used to analyze the profiles: the presence of consistent amplicons at the same electrophoretic position for isolates of the same species, and the presence of distinct amplicons for isolates of different species. Three primers--Al, A7 and A10--rendered such products.

Animals↗