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Investigations on Polymorphic Genomic Markers in Relation to Applie d Field Research on the Biology of Leishmania Parasites in VariousEco-Epidemiolo gical Settings in the Mediterranean Basin

Objective

To provide genomic tools to measure the extent of DNA polymorphisms among natural
L. infantum parasite populations and to approach underlying molecular mechanisms to parasite populations diversity; intra-chromosomal recombination; chromosomal assortment, gene rearrangement and chromosomal size variability. These DNA tools will be applied in at least three eco-epidemiological settings in the Mediterranean area: France, Lebanon and Tunisia. In particular, molecular tools will be used to complement field studies in Lebanon which aim at better defining the epidemiology of leishmaniases in this country.
Expected Outcome

A better understanding of the epidemiology of leishmaniasEs in Lebanon is expected at the end of this study. This will provide a better identification of the causal agents. Earlier preliminary studies have pointed to the possible occurrence of the L. donovani complex parasites in this country. It will be particularly interesting to understand why CL is predominantly recorded in this area. PCR tools for studying parasite polymorphisms constitute an innovative approach which will provide new insights in the field situation and on the molecular epidemiology of leishmaniases caused by parasites of the L. donovani complex. The study will provide well characterized DNA tools. Such tools will allow a better understanding of the parasite genetics and thus will help in defining parasite determinants involved in the biology of the Leishmania parasites.
* DNA markers for polymorphisms will be identified using different approaches: chromosomal size variability, variations in copy numbers, RFLP and sequence analysis. Newly identified markers will be submitted to extensive molecular analysis which will include mapping and sequences.
* Repeated coding sequences (gp63, PSA2, rDNA, miniexons) will be targeted to look for RFLPs and to study variations in copy numbers in relation to chromosomal size variability.
* PCR tests will be developed based on the gp63 gene family, minisatellites and microsatellites. A thorough screening for microsatellites on chromosome V will be made using a sequencing approach. Evaluation of these PCR tests will be performed on promastigote populations that will be the subject of this study and on the biological material that will be collected from patients and dogs in Tunisia and Lebanon.
* The study of the mechanisms underlying the genetic diversity in natural populations of parasites will be done on parasite populations collected in close sympatric. Intrachromosomic recombination will be studied on chromosome V. The chromosomal assortment will be studied by using unique markers to defined chromosomes (RFLP and/or PCR tools).
* Correlations between chromosomal size variability and variations in copy number of target genes will be investigated. These results will also be correlated to clinical outcome of the parasite infection: cutaneous leishmaniasis (CL) vs. visceral leishmaniasis (VL). To avoid biases which could be encountered while working on closely related parasite populations, this study will be conducted on groups of parasites from sympatric VL and CL cases, isolated in different geographical areas.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

INSTITUT PASTEUR DE TUNIS
Address
13,Place Pasteur 13
1002 Tunis
Tunisia

Participants (3)

American University of Beirut
Lebanon
Address
Bliss Street
8281 Beirut
Centre National de la Recherche Scientifique
France
Address
163,Rue Auguste Broussonet
34090 Montpellier
Instituut voor Tropische Geneeskunde Prins Leopold
Belgium
Address
155,Nationalestraat 155
2000 Antwerpen