Abstract
BackgroundLeishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20–25% of Viannia—species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time. Our objective was to quantify known virulence factor (VF) RNA transcript expression according to LRV1 status, causative species, and isolate source.MethodsEight cultured isolates of Leishmania were used, four of which were LRV1-positive (Leishmania Viannia braziliensis [n = 1], L. (V.) guyanensis [n = 1], L. (V.) panamensis [n = 2]), and four were LRV1-negative (L. (V.) panamensis [n = 3], L. (V.) braziliensis [n = 1]). Promastigotes were inoculated into macrophage cultures, and harvested at 24 and 48 h. RNA transcript expression of hsp23, hsp70, hsp90, hsp100, mpi, cpb, and gp63 were quantified by qPCR.ResultsRNA transcript expression of hsp100 (p = 0.012), cpb (p = 0.016), and mpi (p = 0.022) showed significant increases from baseline pure culture expression to 24- and 48-h post-macrophage infection, whereas hsp70 (p = 0.004) was significantly decreased. A trend toward increased transcript expression of hsp100 at baseline in isolates of L. (V.) panamensis was noted. Pooled VF RNA transcript expression by L. (V.) panamensis isolates was lower than that of L. (V.) braziliensis and L. (V.) guyananesis at 24 h (p = 0.03). VF RNA transcript expression did not differ by LRV1 status, or source of cultured isolate at baseline, 24, or 48 h; however, a trend toward increased VF RNA transcript expression of 2.71- and 1.93-fold change of mpi (p = 0.11) and hsp90 (p = 0.11), respectively, in LRV1 negative isolates was noted. Similarly, a trend toward lower levels of overall VF RNA transcript expression in clinical isolates (1.15-fold change) compared to ATCC® strains at 24 h was noted (p = 0.07).ConclusionsOur findings suggest that known VF RNA transcript expression may be affected by the process of macrophage infection. We were unable to demonstrate definitively that LRV-1 presence affected VF RNA transcript expression in the species and isolates studied. L. (V.) guyanensis and L. (V.) braziliensis demonstrated higher pooled VF RNA transcript expression than L. (V.) panamensis; however, further analyses of protein expression to corroborate this finding are warranted.
Highlights
Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20–25% of Viannia—species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time
We evaluated the contribution of LRV1 to key Virulence factors (VFs) RNA transcript expression in the Viannia subgenus given its role as a mammalian host immunomodulator and potential influence on parasite itself, and did not demonstrate any change in relative abundance of VF RNA transcripts based on LRV1 status
Trends were identified suggesting that LRV1 may inversely correlate to VF RNA transcript expression, including mpi and hsp90, further studies focused on protein work post-macrophage infection are needed to corroborate this finding
Summary
Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20–25% of Viannia—species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time. Parasitological factors known to modulate the host immune response include Leishmania RNA virus-1 and endogenous virulence factors. A double-stranded RNA virus, Leishmania RNA virus-1 (LRV1), has been identified in certain strains of the Viannia species predominantly found in the Amazon basin of South America [7, 8]. LRV1 has been associated with an over-active immune response with increased expression of proinflammatory cytokines and chemokines including TNF-α, IL-6, CXCL10, CCL4, CCL5, and is believed to accelerate 10–15% of localized CL to either ML or MCL [11,12,13]. LRV1 has been documented in 20–58% of clinical isolates of L. (V.) guyanensis and L. (V.) braziliensis associated with first-line treatment failure and relapse [14, 15]
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