Leishmania RNA Virus: Mere Endosymbiont or Major Player in Leishmania-Associated Disease?

SUMMARY Leishmaniasis is a vector-borne disease caused by various species of Leishmania parasites. They are transmitted by the bites of infected sand flies and go on to infect host macrophages. Approximately 12 million are currently infected with the disease worldwide, and there may be over 1 million new cases every year. Leishmaniasis has several clinical manifestations including cutaneous, mucocutaneous, and visceral disease. Current treatments involve chemotherapy and medications that directly act against the parasite, but are associated with adverse effects, disease relapse, and drug resistance. Without effective treatments for the disease, individuals can be left with debilitating skin and facial deformities, and can even lead to death if left untreated. Some parasite strains have been found to be infected with virus particles called Leishmania RNA virus (LRV). LRV is a small parasitic virus containing a dsRNA genome that encodes a capsid protein and RNA-dependent RNA polymerase, and resides exclusively in the cytoplasm of the parasite. Remarkably, LRV has been implicated with increased rates of disease relapse, drug treatment failure, and exacerbated disease symptoms. Investigating the role LRV plays in Leishmania-associated disease may open up novel alternative therapeutic avenues that can better treat Leishmaniasis and prevent future infections. This article provides an overview of the biological relationship between LRV and Leishmania parasites, what effects LRV has on Leishmania-associated disease, whether the virus can be specifically targeted as a therapeutic strategy and which components of the virus can be potential targets. Understanding LRV’s role and contribution to disease pathogenesis will not only increase our understanding of virally-infected parasites, but will also pave the way for considering LRV as a potential treatment target.