Understanding the Role of Leishmania RNA Virus-1 (LRV-1) in the Pathogenesis of American Tegumentary Leishmaniasis (ATL)

American Tegumentary Leishmaniasis (ATL) comprises a spectrum of cutaneous leishmaniasis (CL) and mucosal or mucocutaneous leishmaniasis (ML/MCL) endemic to Latin America. Leishmania RNA Virus-1 (LRV-1) is a double stranded RNA virus identified in up to 25% of clinical isolates of the Leishmania Viannia subgenus. Approximately 1-15% of patients with healed CL will progress to ML/MCL on average 1-5 years later, the biological underpinnings of which could be related to LRV-1, given its ability to alter expression of certain proinflammatory cytokines and chemokines in both human and murine models. This doctoral thesis sets out to evaluate: 1) the prevalence of LRV-1 in ATL and its potential associations with clinical phenotype; 2) changes in proinflammatory biomarker expression from human macrophages infected with LRV-1 positive and negative strains of Leishmania Viannia braziliensis and L. V. panamensis and 3) virulence factor (VF) RNA transcript expression in previously infected human macrophages. LRV-1 was detected at a rate of 23%-26% and was not directly associated with clinical phenotype. Age was associated with clinical phenotype, whereby patients manifesting ML/MCL were, on average, 10 years older than patients manifesting localized CL (LCL). LRV-1 did not alter pro-inflammatory biomarker expression of TNF-α, IL-1β, IL-6, CXCL10 and SOD at 24- and 48- hours in strains of L. V. panamensis, regardless of isolate source. However, clinical L. V. braziliensis demonstrated significantly lower levels of TNF-α, IL-1β, IL-6 and CXCL10 at 24- and 48- hours compared to the ATCC® L. V. braziliensis strain. A direct comparison of clinical L. V. braziliensis strains, revealed LRV-1 to increase TNF-α and decrease CXCL10 at 48-hours. Analysis of VF RNA transcripts of heat shock protein 23 (HSP23), HSP70, HSP83, HSP100, mannose phosphate isomerase (MPI), cysteine proteinase B (CPB) and zinc metalloproteinase (GP63) revealed no difference in expression by LRV-1 status, however a marked increase at 24- and 48- hours post-macrophage infection was observed. In conclusion, LRV-1 status and causative species potentially represent a combined marker of immune responses as observed by differences in L. V. braziliensis and L. V. panamensis populations, possibly predictive of clinical phenotype.Ph.D