Abstract
Leishmania braziliensis, the main etiological agent of cutaneous leishmaniasis (CL) in Latin America, is characterized by major differences in basic biology in comparison with better-known Leishmania species. It is also associated with a high phenotypic and possibly genetic diversity that need to be more adequately defined. Here we used whole genome sequences to evaluate the genetic diversity of ten L. braziliensis isolates from a CL endemic area from Northeastern Brazil, previously classified by Multi Locus Enzyme Electrophoresis (MLEE) into ten distinct zymodemes. These sequences were first mapped using the L. braziliensis M2904 reference genome followed by identification of Single Nucleotide Polymorphisms (SNPs). A substantial level of diversity was observed when compared with the reference genome, with SNP counts ranging from ~95,000 to ~131,000 for the different isolates. When the genome data was used to infer relationship between isolates, those belonging to zymodemes Z72/Z75, recovered from forested environments, were found to cluster separately from the others, generally associated with more urban environments. Among the remaining isolates, those from zymodemes Z74/Z106 were also found to form a separate group. Phylogenetic analyses were also performed using Multi-Locus Sequence Analysis from genes coding for four metabolic enzymes used for MLEE as well as the gene sequence coding for the Hsp70 heat shock protein. All 10 isolates were firmly identified as L. braziliensis, including the zymodeme Z26 isolate previously classified as Leishmania shawi, with the clustering into three groups confirmed. Aneuploidy was also investigated but found in general restricted to chromosome 31, with a single isolate, from zymodeme Z27, characterized by extra copies for other chromosomes. Noteworthy, both Z72 and Z75 isolates are characterized by a much reduced heterozygosity. Our data is consistent with the existence of distinct evolutionary groups in the restricted area sampled and a substantial genetic diversity within L. braziliensis.
Highlights
Cutaneous Leishmaniasis (CL) is an infectious parasitic disease characterized by a very dynamic eco-epidemiology, which is associated with several cycles of transmission and involves a variety of reservoirs and competent vectors that vary according to different geographical regions
The genetic analysis clustered these isolates into three distinct phylogenetic groups, with those circulating in forested environments more related to each other (Z72 and Z75) and separated from the other eight isolates from more urbanized environments, but forming two further groups
All ten isolates were definitely identified as L. braziliensis, including one from zymodeme Z26, previously identified as L. shawi through Multi Locus Enzyme Electrophoresis (MLEE)
Summary
Cutaneous Leishmaniasis (CL) is an infectious parasitic disease characterized by a very dynamic eco-epidemiology, which is associated with several cycles of transmission and involves a variety of reservoirs and competent vectors that vary according to different geographical regions. It is known that L. braziliensis has some peculiarities in its genome that are absent from the Old World Leishmania species, such as transposable elements and genes encoding the RNA interference (RNAi) machinery [14,15,16,17]. In animal models, it has been demonstrated that the presence of double-stranded RNA that characterizes the virus stimulates an exacerbated immune response, with lesions characteristic of the mucosal form of the disease [18, 19]. Leishmania RNA viruses were identified and characterized for several years in L. (Viannia) braziliensis and L. guyanensis [20,21,22] as well as in a single L. major isolate [23]
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