Further Evidence of an Association between the Presence of Leishmania RNA Virus 1 and the Mucosal Manifestations in Tegumentary Leishmaniasis Patients

Abstract

Tegumentary Leishmaniasis (TL) is endemic in Latin America, and Brazil contributes approximately 20 thousand cases per year. The pathogenesis of TL, however, is still not fully understood. Clinical manifestations vary from cutaneous leishmaniasis (CL) to more severe outcomes, such as disseminated leishmaniasis (DL), mucosal leishmaniasis (ML) and diffuse cutaneous leishmaniasis (DCL). Many factors have been associated with the severity of the disease and the development of lesions. Recent studies have reported that the presence of Leishmania RNA virus 1 infecting Leishmania (Leishmania RNA virus 1, LRV1) is an important factor associated with the severity of ML in experimental animal models. In the present study, 156 patients who attended Rondonia's Hospital of Tropical Medicine with both leishmaniasis clinical diagnoses (109 CL; 38 ML; 5 CL+ML; 3 DL and 1 DCL) and molecular diagnoses were investigated. The clinical diagnosis were confirmed by PCR by targeting hsp70 and kDNA DNA sequences and the species causing the infection were determined by HSP70 PCR-RFPL. The presence of LVR1 was tested by RT-PCR. Five Leishmania species were detected: 121 (77.6%) samples were positive for Leishmania (Viannia) braziliensis, 18 (11.5%) were positive for Leishmania (V.) guyanensis, 3 (1.8%) for Leishmania (V.) lainsoni, 2 (1.3%) for Leishmania (Leishmania) amazonensis and 2 (1.3%) for Leishmania (V.) shawi. Six (3.9%) samples were positive for Leishmania sp. but the species could not be determined, and 4 (2.6%) samples were suggestive of mixed infection by L. (V.) braziliensis and L. (V.) guyanensis. The virus was detected in L. braziliensis (N = 54), L. guyanensis (N = 5), L. amazonensis (N = 2), L. lainsoni (N = 1) and inconclusive samples (N = 6). Patients presenting with CL+ML, DL and DCL were excluded from further analysis. Association between the presence of the virus and the disease outcome were tested among the remaining 147 patients (CL = 109 and ML = 38). Of them, 71.1% (n = 27) mucosal lesions were positive for LRV1, and 28.9% (n = 11) were negative. In cutaneous lesions, 36.7% (n = 40) were positive and 63.3% (n = 69) were negative for LRV1. The ratio P(ML|LRV1+)/P(ML|LRV1-) was 2.93 (CI95% 1.57…5.46; p<0.001), thus corroborating the hypothesis of the association between LRV1 and the occurrence of mucosal leishmaniasis, as previously described in animal models; it also indicates that LRV1 is not the only factor contributing to the disease outcome.

Tilting the balance between RNA interference and replication eradicatesLeishmaniaRNA virus 1 and mitigates the inflammatory response

“…Our studies extend the generality of LRV1-dependent virulence to Lbr because LRV1 + Lbr likewise induces strong TLR3-dependent cytokine responses. These findings are especially important in light of published work on the association of LRV1 with MCL, with mixed results depending on the geographic region and methods used (6,(16)(17)(18)(19). Our data show that, in in vitro infections, LRV1 contributes strongly to the proinflammatory phenotype associated with elevated pathogenicity, as seen in Lgy, which suggests that, in human infections, it may be informative to seek for correlations between LRV1 and the severity of CL in Lbr infections.…”

“…Although in some studies LRV1 was not correlated with MCL (16,17), in others there was a strong association (6,18,19). Recent studies show that LRV1 in Lbr and Lgy clinical isolates correlates with drug treatment failure (16,20).…”

Type I interferons induced by endogenous or exogenous viral infections promote metastasis and relapse of leishmaniasis

“…These findings may explain why the tight correlation between disease severity and metastasis with LgyLRV1 + in animal models (5) may be more variable in humans (13,17,47,48). Potentially, coinfection with viruses or other pathogens inducing a sufficient amount of type I IFNs could increase the severity of Lgy infection, contributing to the development of more severe disease manifestations.…”

Antiviral screening identifies adenosine analogs targeting the endogenous dsRNALeishmaniaRNA virus 1 (LRV1) pathogenicity factor

“…There are now ample data suggesting that LRV1 contributes to the severity in human leishmaniasis (6,13,17,19,20,55), suggesting that anti-LRV1 inhibitors could be clinically useful, alone or in conjunction with existing antileishmanials. Unfortunately, pharmacokinetic studies of the two compounds studied here in mammals suggest that neither of these are good candidates for testing of this hypothesis just yet, as the concentration needed for LRV1 elimination (10 μM) is above the maximum achievable serum concentration in various mammalian models, typically less than 1 μM (38,49,56).…”

“…In lieu of such information, studies have focused on the association of LRV1 with MCL vs. CL, which is thought to reflect primarily immunopathology rather than parasite numbers (2,6,(14)(15)(16). Although in some studies LRV1 was not correlated with MCL clinical manifestations (17,18), in others there was a strong association (6,19,20). The basis for these discrepancies is of considerable interest, hypotheses for which include other parasite or host factors known to play a significant role in the development of MCL (13,21,22), or…”