Elimination of Leishmania RNA virus from Leishmania spp. via expression of homologous viral capsid proteins : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biological Sciences at Massey University, Palmerston North, New Zealand

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Massey University
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Leishmaniasis is a neglected tropical disease caused by the protozoan parasite Leishmania with complex pathology ranging from skin ulcers to fatal organ damage. There are no human vaccines for leishmaniasis, and resistance to the limited arsenal of drugs used for antileishmanial therapy emerges frequently among Leishmania parasites. Some strains of Leishmania have been found to harbour Leishmania RNA virus (LRV), which has been associated with higher rates of treatment failure, hyperinflammation, and relapse. Investigating the relationship between LRV and Leishmania may potentially reveal new targets or strategies for antileishmanial treatment. LRV has a dsRNA genome encoding two genes – capsid protein (CP) and RNA-dependent RNA polymerase (RDRP). Previous studies on the closely related L-A virus in Saccharomyces cerevisiae demonstrated that overexpression of full or truncated versions of the viral CP led to elimination of the virus from the host. This study aimed to test the specificity of CP-induced viral elimination. CPs from 5 strains of LRV – LRV1-4, LRV1- Lg2014, LRV1-LbrLEM2700, LRV1-1, and LRV2 – were integrated into the genomic SSU loci of two LRV-harbouring Leishmania strains, L. guyanensis M4147 and L. major T44g, bearing LRV1-4 and LRV2, respectively. The expression of exogenous CPs was confirmed via Western blotting and RT-qPCR. The effects of CP overexpression on viral copy numbers of resident LRVs were evaluated via RT-qPCR. All 5 CPs significantly reduced or eliminated LRV1-4 from L. guyanensis, whereas only LRV2 CP diminished LRV2 copy number in L. major. Thus, L. guyanensis and L. major appear to have disparate relationships with, and dissimilar mechanisms for maintenance of, their resident LRV.