Análisis epidemiológico, genómico y proteómico de Leishmania infantum en Colombia

Resumen

Leishmaniasis, a vector-born disease (VBD), presents various clinical forms including cutaneous (CL), mucosal (LM), and visceral (VL). These parasitic illnesses are collectively categorized as neglected tropical diseases due to their association with poverty and lack of attention. Globally, the main causative agents of VL belong to the Leishmania donovani complex, with species of the L. enrietti complex playing a lesser role. In regions like Central and South America, the Mediterranean basin, and eastern Africa, L. infantum is the predominant species associated. Despite Colombia being one of the endemic countries for VL in South America, there remains limited research on the epidemiology of the disease, the biology of L. infantum, and the evolutionary patterns of this parasite within the country. Currently, VL presents several challenges, including: i) emergence of cases in new transmission areas, ii) coinfection with HIV and other pathogens, iii) lack of tools to identify potential coinfection events and iv) increasing therapeutic failures primarily due to the circulation of strains resistant to first-line treatments like Sodium Stibogluconate (Sb), Amphotericin B (AMB), and Miltefosine (MIL). Given the disease's severity, the vulnerability of affected populations, the spread of transmission foci, gaps in resistance knowledge, and the urgent need to identify new therapeutic targets, there's a growing interest in studying L. infantum locally. This aims to generate relevant data applicable not only at a regional but also at a global level. Considering the abovementioned context, our research aimed to address VL from four main perspectives, utilizing biostatistical, epidemiological, molecular, and bioinformatic tools. Firstly, we analyzed official data and scientific literature to describe the demographic characteristics of patients and examine changes in the spatial and temporal distribution patterns of VL cases in Colombia from 2007 to 2018, particularly focusing on incidence rates. Additionally, we investigated the correlation between the distribution of Lutzomyia spp. vectors and the incidence of cases nationwide. Secondly, we employed amplicon-based sequencing targeting a fragment of the HSP70 gene, enabling the detection of coinfection events involving various species of Leishmania and Trypanosoma spp. in samples from vectors, wild and domestic mammals, as well as patients with LC and VL. Moreover, we identified the circulation of previously undescribed Leishmania species in certain Colombian regions. Thirdly, through genome comparisons of four L. infantum isolates from Colombia with genomes from different global regions, we characterized the genetic diversity within and between geographic groups (America, Europe, Africa, Asia, and Colombia), identifying four distinct populations of the species and their geographic distributions. We also noted a closer phylogenetic relationship between Colombian genomes, Europe, and North Africa, compared to those from the local region and identified intriguing differences in nucleotide sequences of key parasite antigens used in VL diagnosis. Finally, employing high-depth proteomics, we qualitatively and quantitatively characterized protein changes in SbIII-induced resistant L. infantum. The resistant line's promastigotes exhibited altered growth kinetics, with a prolonged logarithmic phase compared to the wild type. Furthermore, we observed significant production of proteins related to transcription, translation, lipid and carbohydrate metabolism, energy compensation, and peroxisome biogenesis in the resistant line, alongside a reduction in proteins associated with iron and metal metabolism. The current thesis underscores the importance of addressing VL from multiple perspectives. Through the utilization of a wide array of methods and tools focusing not only on the parasite but also on its vectors and reservoirs, a better understanding of the disease at local and global levels has been achieved. On one hand, it has examined the impact of various factors on VL over time and space. On the other hand, the development of an effective strategy for the simultaneous identification of different Leishmania and Trypanosoma species in the same individual has shed light on the occurrence of coinfection events and their impact on disease severity and progression in endemic countries for both leishmaniasis and Chagas disease. Additionally, the study of the genetic diversity of autochthonous parasites has helped to better understand the genetic flow and phylogenetic relationships of the species on a global scale, providing genetic support for understanding the variation in sensitivity of certain antigens used in the diagnosis of this parasitic disease. Finally, but no less important, the understanding of L. infantum resistance to sodium stibogluconate has been expanded beyond what was previously known, elucidating a complex and multifactorial landscape that includes biological events not previously considered; while pinpointing new therapeutic targets is not feasible with certainty, we trust that this information can yield crucial insights for the development of new therapeutic proposals or the enhancement of existing ones.