A comprehensive phenotypic and genotypic taxonomic review of Leishmania (Leishmania) poncei n. sp. (Kinetoplastea: Trypanosomatidae): a novel agent of cutaneous (non-ulcerated) and visceral leishmaniasis in Honduras, Central America

Non-ulcerated cutaneous leishmaniasis (NUCL) is an atypical clinical form of leishmaniasis first described, in 1988, by Ponce and collaborators, in Honduras, Central America, characterized by isolated or disseminated closed skin lesions appearing as papules, nodules, or infiltrated plaques, primarily in adolescents and young adults. Leishmania (L.) chagasi was then identified as the causal agent of both NUCL and American visceral leishmaniasis (AVL) in Honduras, though NUCL has been reported as more prevalent. However, due to the uncertain taxonomic classification of the NUCL-causing parasite, especially since L. (L.) chagasi has not been associated to this form of the disease in South America, this study conducted a comprehensive taxonomic review incorporating phenotypic (biological and clinical-immunopathological) and genotypic (genomic/molecular) analyses. Biologically, Honduran parasite-LPG does not have Gal (β1,4) Man (α1)-PO4 side chains common to all Leishmania LPGs. From a clinical-pathogenic perspective, NUCL is unique, it does not ulcerate like cutaneous leishmaniasis due to L. (L.) chagasi or L. (L.) infantum. Molecular findings showed that the Honduran parasite is more ancestral than all known viscerotropic Leishmania species, exhibited an unprecedented structural variation on chromosome 17 with the highest frequency of genomic SNPs, formed a distinct phylogenetic lineage, and displayed a homozygous SNP profile typical of a parental (non-hybrid) parasite. Building on these findings, a new species, Leishmania (Leishmania) poncei n. sp. (Kinetoplastea: Trypanosomatidae), is proposed in honor of Professor Carlos Ponce, who first described NUCL in Honduras. This study formally classifies L. (L.) poncei n. sp. as a novel Leishmania species responsible for both NUCL and AVL in Honduras, Central America.