The taxonomic tree of the parasite that causes leishmaniasis

Through new analyzes of genetic material present in some infected patients, scientists have managed to identify different strains of the parasite responsible for leishmaniasis.

The new study has been carried out by a group from the Center for Biomedical Research in the Infectious Diseases Network (CIBERINFEC) at the National Microbiology Center of the Carlos III Health Institute and the Severo Ochoa Molecular Biology Center (attached to the Autonomous University of Madrid (UAM) and the Higher Council for Scientific Research (CSIC)), in Spain all these entities.

Parasites of great medical importance such as those of the Leishmania genus, protozoa responsible for the leishmaniasis disease; or the Trypanosoma, a protist that can cause sleeping sickness, are characterized by the presence of thousands of circular DNA molecules that form a structure known as a kinetoplast, within the mitochondria.

The study of these maxicircles, equivalent to the mitochondrial genome of other eukaryotes, is a promising phylogenetic marker and the new study has focused on it.

To carry out this study, using bioinformatic tools and reuse of existing genomic sequencing data in public repositories, the complete coding region of the maxicircles for 26 prototypic strains of trypanosomatid species has been assembled.

The phylogenetic analysis of them generated a robust taxonomic tree that allowed discerning even between different Leishmania species that are indistinguishable by classical methods. Likewise, the research team has provided a data set of the maxicircle sequences of 60 strains of Leishmania infantum isolated from patients in America, Western and Eastern Europe and North Africa.

Leishmaniasis is a parasitic disease spread by the bite of an infected insect. (Photo: James Gathany/CDC/Frank Collins)

“Consistent with previous studies, our data indicate that parasites from Brazil are highly homogeneous and related to European strains, which were transferred there during the discovery of America. But at the same time, we show the existence of different populations (clades) within the Mediterranean region, which we can differentiate on the basis of a maxicircle molecular signature that is characteristic for each clade”, explains José María Requena, member of CIBERINFEC at the Severo Ochoa Molecular Biology Center.

It should be noted that two populations of L. infantum were found coexisting in Spain, one similar to the American strains, called JPCM5, and another ‘non-JPC like’, which could be related to a major outbreak of leishmaniasis that occurred in Madrid, which had its peak in 2011.

Leishmaniasis is a parasitic disease, which can be cutaneous or visceral, spread by the bite of an infected sandfly. The cutaneous form is manifested by the appearance of sores on the skin, while the more serious visceral form produces systemic conditions that are more difficult to detect.

In summary, the maxicircle sequence emerges as a robust molecular marker for phylogenetic analysis and species typing within kinetoplastids, which also has the potential to discriminate intraspecific variability.

The study is titled “Assembly of a Large Collection of Maxicircle Sequences and Their Usefulness for Leishmania Taxonomy and Strain Typing.” And it has been published in the academic journal Genes. (Source: UAM)