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Gp63 gene polymorphism and population structure of Leishmania donovani complex: influence of the host selection
S Guerbouj1, K Victoir, I Guizani
1Institut Pasteur de Tunis, Laboratoire d'Epidémiologie et Ecologie Parasitaire, Tunis Belvédère, Tunisia.
Abstract:
The gp63 encoding genes were characterized by PCR-RFLP in 35 isolates representative of the Leishmania donovani complex (L. infantum, L. donovani, L. archibaldi and L. chagasi), with special attention to Mediterranean L. infantum from different geographical origins, and in separate groups from Old World Leishmania (L. major, L. tropica and L. aethiopica). The aim was to evaluate how the possible selective pressure by the host on these important surface proteins would influence structuring of our sample. Comparison was carried out with the structure obtained (i) from reported isoenzyme data, characters supposed to vary neutrally, and (ii) from PCR-RFLP analysis of gp63 inter-genic regions, containing nontranslated spacers and regulatory genes. Polymorphism within the gp63-encoding region, was much higher than in gp63 inter-genic regions. In the gp63 intra-genic dendrogram, the 4 species of L. donovani complex were discriminated and quite distinct from outgroups. Within L. infantum, geographical structuring was observed and did not overlap with the structure built-up from isoenzymes and inter-genic data. These results support the idea of a strong host-selection on gp63, at vector level but most of all at vertebrate (human or dog) immunological level. Furthermore, they illustrate how the nature of genetic characters may influence the perception of population structuring.
Insights
Host immune pressure shapes Leishmania gp63 surface proteins, influencing parasite population structure. This study reveals host selection impacts gp63 gene evolution differently than neutral markers.
Area of Science:
- Parasitology
- Molecular Biology
- Population Genetics
Background:
- The surface metalloproteinase gp63 is a key virulence factor in Leishmania parasites.
- Understanding gp63 evolution is crucial for deciphering Leishmania population dynamics and host-parasite interactions.
Purpose of the Study:
- To investigate the influence of host selective pressure on the genetic structuring of Leishmania populations, focusing on the gp63 gene.
- To compare the population structure derived from gp63-encoding genes with neutral markers (isoenzymes) and non-coding regions (gp63 intergenic regions).
Main Methods:
- Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to analyze gp63 encoding genes and intergenic regions in 35 Leishmania isolates.
- Comparative analysis with existing isoenzyme data was performed.
Main Results:
- The gp63 encoding region exhibited higher polymorphism than gp63 intergenic regions.
- The four species within the Leishmania donovani complex were clearly discriminated by gp63 intra-genic analysis.
- Geographical structuring was observed within Leishmania infantum based on gp63 data, distinct from isoenzyme and intergenic analyses.
Conclusions:
- Strong host selection, particularly at the vertebrate immunological level, significantly influences gp63 evolution.
- The choice of genetic markers (e.g., coding vs. non-coding regions) impacts the perceived population structure of Leishmania.