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The present study investigated the possible role of Leishmania RNA virus 2 (LRV2) in the severity of dermal lesions and treatment failure due to Leishmania major. The drug susceptibility of 14 clinical isolates of L.major , including resistant (n = 7) and sensitive (n = 7) isolates, was checked in the J774A.1 macrophage cell line. The presence of LRV2 among isolates was investigated by the RdRp gene and semi-nested PCR. Moreover, 1 × 106 sensitive L. major LRV2+ and LRV2- promastigotes were inoculated subcutaneously into the base tails of the 40 BALB/c mice divided into 4 groups (n = 10 in each group), including clinical LRV2+, clinical LRV2-, positive control LRV2+ and negative control LRV2-. The groups were infected with a unique isolate. The lesion size and parasite burden were evaluated. Sensitive and resistant isolates were determined by the drug susceptibility method. A higher presence of LRV2 was observed among MA-resistant isolates (6/7) compared with susceptible isolates (4/7), which was not statistically significant (P = 0.237). On the other hand, a comparison of the lesion sizes between the LRV2+ and LRV2- BALB/c mice groups revealed that the mean size of the lesion in the LRV2+ groups was significantly higher than the LRV2- (P = 0.034). In the same direction, there was an increased parasite burden in mice inoculated with LRV2+ groups compared with the LRV2- BALB/c mice groups (P = 0.002). Our findings showed that the presence of LRV2 could be one of the factors contributing to exacerbating CL. Although we found a higher presence of LRV2 in the resistant isolates, it seems that further investigations are recommended to determine the detailed association between lesions' aggravation and being comparatively unresponsive to treatment. [Display omitted] • The presence of LRV2 among these isolates was detected by semi nested-PCR. • The presence of the LRV2 was observed more among Glucantime-resistant isolates (6/7) compared with susceptible isolates (4/7). • Comparison of the size of the lesions between the LRV2+ and LRV2- BALB/c mice groups revealed that the mean size of lesions in the LRV2+ groups was significantly higher than the LRV2-. [ABSTRACT FROM AUTHOR]

Cutaneous leishmaniasis (CL) is one of the most important infectious parasitic diseases in the world caused by the Leishmania parasite. In recent decades, the presence of a virus from the Totiviridae family has been proven in some Leishmania species. Although the existence of LRV2 in the Old world Leishmania species has been confirmed, almost no studies have been done to determine the potential impact of LRV2 on the immunopathogenicity of the Leishmania parasite. In this preliminary study, we measured the expression of target genes, including Glycoprotein 63 (gp63), Heat Shock Protein 70 (hsp70), Cysteine Protease b (cpb), Interleukin 1 beta (IL-1β), IL8 and IL-12 in LRV2 positive Leishmania major strain (LRV2+ L. major) and LRV2 negative L. major strain (LRV2- L. major). We exposed THP-1, a human leukemia monocytic cell line, to promastigotes of both strains. After the initial infection, RNA was extracted at different time points, and the relative gene expression was determined using a real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Findings showed that the presence of LRV2 in L. major was able to increase the expression of gp63, hsp70, and cpb genes; also, we observed lower levels of expression in cytokine genes of IL-1β, IL-8, IL-12 in the presence of LRV2+, which are critical factors in the host's immune response against leishmaniasis. These changes could suggest that the presence of LRV2 in L. major parasite may change the outcome of the disease and increase the probability of Leishmania survival; nevertheless, further studies are needed to confirm our results. • The presence of LRV2 in L. major parasite could increase the expression levels of GP63, HSP70, and CPb genes. • The expression of IL-1β, IL-8, and IL-12 genes was decreased in macrophage infected with LRV2+ L. major strain. [ABSTRACT FROM AUTHOR]