The Montpellier Leishmania Collection, from a Laboratory Collection to a Biological Resource Center: A 39-Year-Long Story

We report the development of a laboratory collection of Leishmania that was initiated in 1975 and, after 39 years, has become an international Biological Resource Center (BRC-Leish, Montpellier, France, BioBank No. BB-0033-00052), which includes 6353 strains belonging to 36 Leishmania taxa. This is a retrospective analysis of the technical and organizational changes that have been adopted over time to take into account the technological advances and related modifications in the collection management and quality system. The technical improvements concerned the culture and cryopreservation techniques, strain identification by isoenzymatic and molecular techniques, data computerization and quality management to meet the changes in international standards, and in the cryogenic and microbiological safety procedures. The BRC is working toward obtaining the NF-S 96-900 certification in the coming years. Our long-term expertise in Leishmania storage and typing and collection maintenance should encourage field epidemiologists and clinical practitioners in endemic countries to secure their own strain collection with the help of the French BRC-Leish.

Single-molecule analysis of DNA replication reveals novel features in the divergent eukaryotes Leishmania and Trypanosoma brucei versus mammalian cells

Leishmania and Trypanosoma are unicellular parasites that possess markedly original biological features as compared to other eukaryotes. The Leishmania genome displays a constitutive 'mosaic aneuploidy', whereas in Trypanosoma brucei, the megabase-sized chromosomes are diploid. We accurately analysed DNA replication parameters in three Leishmania species and Trypanosoma brucei as well as mouse embryonic fibroblasts (MEF). Active replication origins were visualized at the single molecule level using DNA molecular combing. More than one active origin was found on most DNA fibres, showing that the chromosomes are replicated from multiple origins. Inter-origin distances (IODs) were measured and found very large in trypanosomatids: the mean IOD was 160 kb in T. brucei and 226 kb in L. mexicana. Moreover, the progression of replication forks was faster than in any other eukaryote analyzed so far (mean velocity 1.9 kb/min in T. brucei and 2.4-2.6 kb/min in Leishmania). The estimated total number of active DNA replication origins in trypanosomatids is ~170. Finally, 14.4% of unidirectional replication forks were observed in T. brucei, in contrast to 1.5-1.7% in Leishmania and 4% in MEF cells. The biological significance of these original features is discussed.

Global distribution maps of the leishmaniases

The leishmaniases are vector-borne diseases that have a broad global distribution throughout much of the Americas, Africa, and Asia. Despite representing a significant public health burden, our understanding of the global distribution of the leishmaniases remains vague, reliant upon expert opinion and limited to poor spatial resolution. A global assessment of the consensus of evidence for leishmaniasis was performed at a sub-national level by aggregating information from a variety of sources. A database of records of cutaneous and visceral leishmaniasis occurrence was compiled from published literature, online reports, strain archives, and GenBank accessions. These, with a suite of biologically relevant environmental covariates, were used in a boosted regression tree modelling framework to generate global environmental risk maps for the leishmaniases. These high-resolution evidence-based maps can help direct future surveillance activities, identify areas to target for disease control and inform future burden estimation efforts.