Toward an objective diagnostic for detection of Leishmania RNA virus (LRV) in clinical samples from cutaneous leishmaniasis patients.

Leishmania RNA virus (LRV) is a double strand RNA virus belonging to the Totiviridae family detected as cytoplasmic inclusions in some strains of the human parasite Leishmania spp. Experimental evidence supports the hypothesis that human co-infection with Leishmania spp-LRV triggers an exacerbated immune response in the host that can be responsible for the observed complicated outcomes in cutaneous leishmaniasis (CL), such as mucosal leishmaniasis (ML) and treatment failure of cutaneous leishmaniasis (TFCL). However, the reported frequencies of LRV associated to complicated outcomes in patients’ series are highly variable, diminishing the relevance on the virus presence in the pathogenesis of the disease. For determining if the apparent inconsistent information about the frequency of LRV associated to CL complicated outcomes could be connected with the virus detection approach, this study tested previously described methods for LRV detection in clinical samples of patients according with the type of sample. In 36 samples with diagnosis of complicated forms of CL (15 ML, 21 TFCL) and 6 samples with non-Leishmania spp infection, LRV presence was assessed by RT-PCR, RT-qPCR and nested-PCR. By combining methods, LRV1 presence was confirmed in 45% (9/20) of isolates and 75% (12/16) of biopsies. The predominant LRV1-infected Leishmania species in this study was Leishmania (Viannia) braziliensis and, for first time, Leishmania (Viannia) panamensis was found infected in clinical samples. In a number of cases, LRV1 was undetectable in the isolates but present in their respective biopsies, suggesting the possibility of underreporting of LRV1 presence in studies focused in parasites isolates exclusively.