Transcriptional Blood Signatures for Active and Amphotericin B Treated Visceral Leishmaniasis in India

Abstract

31Amphotericin B provides improved therapy for visceral leishmaniasis (VL) caused by 32 Leishmania donovani, with single dose liposomal-encapsulated Ambisome providing the best 33 cure rates. The VL elimination program aims to reduce the incidence rate in the Indian 34 subcontinent to <1/10,000 population/year. Ability to predict which asymptomatic 35 individuals (e.g. anti-leishmanial IgG and/or Leishmania-specific modified Quantiferon 36 positive) will progress to clinical VL would help in monitoring disease outbreaks. Here we 37 examined whole blood transcriptional profiles associated with asymptomatic infection, active 38 disease, and in treated cases. Two independent microarray experiments were performed, with 39 analysis focussed primarily on differentially expressed genes (DEGs) concordant across both 40 experiments. No DEGs were identified for IgG or Quantiferon positive asymptomatic groups 41 compared to negative healthy endemic controls. We therefore concentrated on comparing 42 concordant DEGs from active cases with all healthy controls, and in examining differences in 43 the transcriptome following different regimens of drug treatment. In these comparisons 6 44 major themes emerged: (i) expression of genes and enrichment of gene sets associated with 45 erythrocyte function in active cases; (ii) strong evidence for enrichment of gene sets involved 46 in cell cycle in comparing active cases with healthy controls; (iii) identification of IFNG 47 encoding interferon- as the major hub gene in concordant gene expression patterns across 48 experiments comparing active cases with healthy controls or with treated cases; (iv) 49 enrichment for interleukin signalling (IL-1/3/4/6/7/8) and a prominent role for CXCL10/9/11 50 and chemokine signalling pathways in comparing active cases with treated cases; (v) the 51 novel identification of Aryl Hydrocarbon Receptor signalling as a significant canonical 52 pathway when comparing active cases with healthy controls or with treated cases; and (vi) 53 global expression profiling support for more effective cure at day 30 post-treatment with a 3 54 single dose of liposomal encapsulated amphotericin B compared to multi-dose non-liposomal 55 amphotericin B treatment over 30 days. (296 words; 300 words allowed) 56 57 Author Summary 58 Visceral leishmaniasis (VL), also known as kala-azar, is a potentially fatal disease caused by 59 intracellular parasites of the Leishmania donovani species complex. VL is a serious public 60 health problem in rural India, causing high morbidity and mortality, as well as major costs to 61 local and national health budgets. Amphotericin B provides improved therapy for VL with 62 single dose liposomal-encapsulated Ambisome, now affordable through WHO-negotiated 63price reductions, providing the best cure rates. The VL elimination program aims to reduce 64 the incidence rate in the Indian subcontinent to <1/10,000 population/year. By assessing 65 immune responses to parasites in people infected with L. donovani, but with different clinical 66 s...