Correlation between presence of Leishmania RNA virus 1 and clinical characteristics of nasal mucosal leishmaniosis

Epidemiology and Genetic Characterization of Leishmania RNA Virus in Leishmania (Viannia) spp. Isolates from Cutaneous Leishmaniasis Endemic Areas in Panama

Leishmania (Viannia) spp. can harbor a double-stranded RNA virus known as Leishmania RNA virus 1 (LRV-1), whose presence has been reported in nine countries across the Americas and seven Leishmania species. Here, we studied 100 Leishmania (Viannia) isolates from patients with cutaneous leishmaniasis collected from different endemic areas in Panama from 2016 to 2022. We identified L. (V.) panamensis, L. (V.) guyanensis, L. (V.) braziliensis/guyanensis hybrid, and L. (V.) panamensis sp.1. (genetic variant). LRV-1 was detected by RT-PCR in 9% of L. (Viannia) isolates (eight cases in L. (V.) panamensis, and one in L. (V.) guyanensis). Phylogenetic analysis based on sequencing data classified all LRV-1 isolates within genotype A, suggesting that LRV phylogenetic proximity is closely aligned with geographical distribution or to the phylogenetic proximity of the Leishmania host in the case of the L. (V.) panamensis and L. (V.) guyanensis in Panama.

Novel detection of Leishmania RNA virus-1 (LRV-1) in clinical isolates of Leishmania Viannia panamensis

American tegumentary leishmaniasis comprises a discrete set of clinical presentations endemic to Latin America. Leishmania RNA virus-1 (LRV-1) is a double-stranded RNA virus identified in 20–25% of the Leishmania Viannia braziliensis and L. V. guyanensis, however not in L. V. panamensis. This is the first report of LRV-1 in L. V. panamensis and its associations with clinical phenotypes of ATL. Unique surplus discard clinical isolates of L. V. panamensis were identified from the Public Health Ontario Laboratory (PHOL) and the Leishmania Clinic of the Instituto de Medicina Tropical ‘Alexander von Humboldt’ between 2012 and 2019 and screened for LRV-1 by real-time polymerase chain reaction. Patient isolates were stratified according to clinical phenotype. Of 30 patients with L. V. panamensis, 14 (47%) and 16 (53%) patients had severe and non-severe ATL, respectively. Five (36%) of 14 severe cases and 2 (12%) of 16 non-severe cases were positive for LRV-1, respectively. No differences in sex were observed for clinical phenotype and LRV-1 status. Although an association between LRV-1 status and clinical phenotype was not demonstrated, this is the first description of the novel detection of LRV-1 in L. V. panamensis, a species that has been documented predominantly in Central America.

Exploring Host-Specificity: Untangling the Relationship between Leishmania (Viannia) Species and Its Endosymbiont Leishmania RNA Virus 1

A relevant aspect in the epidemiology of Tegumentary Leishmaniasis (TL) are the Leishmania parasites carrying a viral endosymbiont, Leishmania RNA Virus 1 (LRV1), a dsRNA virus. Leishmania parasites carrying LRV1 are prone to causing more severe TL symptoms, increasing the likelihood of unfavorable clinical outcomes. LRV1 has been observed in the cultured strains of five L. (Viannia) species, and host specificity was suggested when studying the LRV1 from L. braziliensis and L. guyanensis strains. The coevolution hypothesis of LRV1 and Leishmania was based on phylogenetic analyses, implying an association between LRV1 genotypes, Leishmania species, and their geographic origins. This study aimed to investigate LRV1 specificity relative to Leishmania (Viannia) species hosts by analyzing LRV1 from L. (Viannia) species. To this end, LRV1 was screened in L. (Viannia) species other than L. braziliensis or L. guyanensis, and it was detected in 11 out of 15 L. naiffi and two out of four L. shawi. Phylogenetic analyses based on partial LRV1 genomic sequencing supported the hypothesis of host specificity, as LRV1 clustered according to their respective Leishmania species' hosts. These findings underscore the importance of investigating Leishmania and LRV1 coevolution and its impact on Leishmania (Viannia) species dispersion and pathogenesis in the American Continent.

Detection of Leishmania RNA Virus 1 in Leishmania (Viannia) panamensis Isolates, Panama

We detected Leishmania RNA virus 1 (LRV1) in 11 isolates of Leishmania (Viannia) panamensis collected during 2014-2019 from patients from different geographic areas in Panama. The distribution suggested a spread of LRV1 in L. (V.) panamensis parasites. We found no association between LRV1 and an increase in clinical pathology.

Pathological roles of macrophages in Leishmania infections

Macrophages are the major host cells for Leishmania parasites, and determine the fate of infection by either limiting or allowing growth of the parasites, resulting in development or control of leishmaniasis, respectively. They also play important roles in causing pathological outcomes during Leishmania infection. The pathophysiology is complex and include a wide variety of molecular and cellular responses including enhancement of inflammatory responses by releasing cytokines, causing damages to surrounding cells by reactive oxygen species, or disordered phagocytosis of other cells. It is of note that disease severity in leishmaniasis sometimes does not correlate with parasite burdens, indicating that pathological roles of macrophages are not necessarily linked to their parasite-killing activities that are often defined by M1/M2 status. Here, we review the roles of macrophages in leishmaniasis with a focus on their pathological mechanisms in disease development.

Oviedo M, K. Quintero Y, L. Fernández O, Gómez MA. Leishmania RNA Virus Is Not Detected in All Species of the Leishmania Viannia Subgenus: The Case of L. (V.) panamensis in Colombia

The endosymbiotic Leishmania RNA virus 1 (LRV1) has been associated with severity and clinical manifestations of American tegumentary leishmaniasis caused by species of the Leishmania (Viannia) subgenus. Between and within Leishmania species, and among endemic countries, the prevalence of LRV is highly variable. The LRV virus has not been detected in L. (V.) panamensis, the second-most prevalent species in Central America and Colombia. However, no systematic screening of LRV has been conducted in L. (V.) panamensis, and thus it is still controversial whether this virus is truly absent from the species. We sought to determine the prevalence of LRV1 in L. (V.) panamensis clinical strains isolated from patients with cutaneous leishmaniasis (CL), from different geographic areas of Colombia. We analyzed 219 clinical strains; 78% were L. (V.) panamensis, 18% were L. (V.) braziliensis, and 4% were L. (V.) guyanensis. Screening for LRV1 was performed by quantitative reverse transcription-polymerase chain reaction. The LRV1 was detected in 18% (7 of 40) of L. (V) braziliensis strains, and was not detected in any of the L. (V.) guyanensis or L. (V.) panamensis strains. The LRV1-positive L. (V). braziliensis strains came from the Amazon Basin. Of the seven LRV1-positive strains, two were isolated from patients with mucocutaneous leishmaniasis, and the remaining from patients with CL. Our results confirm the absence of LRV1 in L. (V.) panamensis in Colombia.

First report of Leishmania RNA virus 1 in Leishmania (Viannia) braziliensis clinical isolates from Rio de Janeiro State - Brazil

BACKGROUND

Leishmania parasites carry a double-stranded RNA virus (Leishmania RNA virus - LRV) that has been divided in LRV1 and LRV2.

OBJECTIVES

Leishmania (Viannia) braziliensis clinical isolates were assessed in order to determine LRV presence.

METHODS

Two-round polymerase chain reaction (PCR and nested PCR) was performed to detect LRV1 or LRV2 in L. (V.) braziliensis clinical isolates (n = 12).

FINDINGS

LRV1 was detected in three clinical isolates which was phylogenetically related to other sequences reported from other American tegumentary leishmaniasis (ATL) endemic areas of Brazil. Patients infected with L. (V.) braziliensis LRV-negative showed only cutaneous lesions while LRV-positive reported different manifestations.

MAIN CONCLUSION

Data presented here show for the first time that LRV1 is circulating in L. (V.) braziliensis clinical isolates from Rio de Janeiro State in Brazil.

Multiparametric analysis of host and parasite elements in new world tegumentary leishmaniasis

Tegumentary leishmaniasis is a tropical disease caused by protozoa of the genus Leishmania. Clinically, the disease presents a broad spectrum of symptoms, the mechanisms underlying the development of lesions remaining to be fully elucidated. In the present work, we performed a correlation and multiparametric analysis to evaluate how parasite- and host-related aspects associate with each other, and with the different clinical manifestations of tegumentary leishmaniasis. This cross-sectional study involved 75 individuals from endemic areas of Brazil, grouped according to their symptoms. Leishmania species were determined by DNA sequencing, and parasite load, antibody production, and cytokine profile were evaluated by kDNA qPCR, ELISA, and flow cytometry. Data were analyzed using the Chi-square test, principal component analysis, canonical discriminant analysis, and correlation analysis. Among the recruited patients, 23 (31%) were asymptomatic, 34 (45%) had primary cutaneous leishmaniasis, 10 (13%) presented recurrent cutaneous leishmaniasis, and eight (11%) had mucocutaneous leishmaniasis. Leishmania species identified included L. amazonensis, L. braziliensis, and L. guyanensis. Surprisingly, no Leishmania RNA virus infection was detected in any sample. In summary, our work showed that parasite load, antibody production, and cytokine levels alone are not determinants for tegumentary leishmaniasis symptoms. However, the correlation analysis allowed us to observe how these factors are correlated to each other within the groups, which revealed a unique network for each clinical manifestation. Our work reinforces the complexity of tegumentary leishmaniasis outcomes - which are associated with multiple host and parasite-related elements and provides a holistic model of the disease.

Prevalence of Leishmania RNA virus in Leishmania parasites in patients with tegumentary leishmaniasis: A systematic review and meta-analysis

Background

Cutaneous leishmaniasis is caused by different protozoan parasites of the genus Leishmania. Leishmania RNA virus (LRV) was identified as the first Leishmania infecting virus in 1998. Different studies showed the presence and role of the LRV in Leishmania parasites causing cutaneous leishmaniasis (CL). However, there is limited data on the pooled prevalence of LRV in Leishmania parasites causing CL. Therefore, the aim of this systematic review and meta-analysis was to determine the pooled prevalence of LRV in Leishmania parasite isolates and/or lesion biopsies in patients with CL from the available literature globally.

Methodology

We retrieved the studies from different electronic databases. The studies were screened and identified based on the inclusion and exclusion criteria. We excluded studies exclusively done in experimental animals and in vitro studies. The review was conducted in line with PRISMA guidelines. The meta-analysis was performed with Stata software version 14 with metan command. The forest plot with random-effect model was used to estimate the pooled prevalence with 95% confidence interval. Inverse variance index (I²) was used to assess the heterogeneity among the included articles.

Principal findings

A total of 1215 samples from 25 studies were included. Of these, 40.1% (487/1215) were positive for LRV. The overall pooled prevalence of LRV globally was 37.22% (95% CI: 27.54% - 46.90%). The pooled prevalence of LRV in the New World (NW) and Old World (OW) regions was 34.18% and 45.77%, respectively. Leishmania guyanensis, L. braziliensis, L. major, and L. tropica were the most studied species for the detection of LRV. The prevalence of LRV from Leishmania isolates and lesion biopsies was 42.9% (349/813) and 34.3% (138/402), respectively.

Conclusion

This systematic study revealed that there is high prevalence of LRV in Leishmania parasites isolated from patients with CL. More comprehensive studies would be required to investigate the presence of the LRV in other Leishmania species such as L. aethiopica to fully understand the role of LRV in different clinical manifestations and disease pathology presented in CL patients.

Cutaneous leishmaniasis (CL) is among the most neglected tropical diseases affecting a significant proportion of the world population, impacting mostly on the poorest communities. CL can present as localized, mucocutaneous or diffuse cutaneous. There are various reports on the prevalence of Leishmania RNA virus (LRV) in Leishmania parasites and/or lesion biopsies in patients with CL from both the Old World and New World regions. However, there is scarcity of comprehensive knowledge on the pooled prevalence of the virus in Leishmania parasites causing human CL. We searched different electronic databases and Google Scholar for published articles aimed to determine the presence of LRV in Leishmania parasites and/or lesion biopsies in patients with CL globally. The retrieved articles were screened according to the inclusion and exclusion parameters. Data was extracted based on the PRISMA guideline by reviewing the selected articles. Systematic review and meta-analysis would be one way to improve the level of evidence by providing pooled prevalence of the individual single studies regarding the presence of LRV in Leishmania parasites and/or lesion biopsies. This systematic review and meta-analysis revealed that a large proportion of the Leishmania parasites causing human CL harbour the endosymbiotic LRV. Further studies are needed to better understand the role of the virus in the clinical presentation of CL, as a potential target of treatment and vaccine development especially in Old World Leishmania parasites like L. aethiopica.

Sex-Biased Control of Inflammation and Metabolism by a Mitochondrial Nod-Like Receptor

Mitochondria regulate steroid hormone synthesis, and in turn sex hormones regulate mitochondrial function for maintaining cellular homeostasis and controlling inflammation. This crosstalk can explain sex differences observed in several pathologies such as in metabolic or inflammatory disorders. Nod-like receptor X1 (NLRX1) is a mitochondria-associated innate receptor that could modulate metabolic functions and attenuates inflammatory responses. Here, we showed that in an infectious model with the human protozoan parasite, Leishmania guyanensis, NLRX1 attenuated inflammation in females but not in male mice. Analysis of infected female and male bone marrow derived macrophages showed both sex- and genotype-specific differences in both inflammatory and metabolic profiles with increased type I interferon production, mitochondrial respiration, and glycolytic rate in Nlrx1-deficient female BMDMs in comparison to wild-type cells, while no differences were observed between males. Transcriptomics of female and male BMDMs revealed an altered steroid hormone signaling in Nlrx1-deficient cells, and a “masculinization” of Nlrx1-deficient female BMDMs. Thus, our findings suggest that NLRX1 prevents uncontrolled inflammation and metabolism in females and therefore may contribute to the sex differences observed in infectious and inflammatory diseases.

First Report of an Asymptomatic Leishmania (Viannia) shawi Infection Using a Nasal Swab in Amazon, Brazil

The state of Pará has recorded seven Leishmania species that cause tegumentary leishmaniasis (TL). Leishmania species induce distinct immunological responses from the host and exhibit resistance to Glucantime, the first-line drug treatment for TL in Brazil.

OBJECTIVE

Identify the etiology of TL in an Amazonian city in the state of Pará.

MATERIAL AND METHODS

Eleven patients with TL were recruited and nasal swabs, lesion swabs, and skin fragments samples were collected. In the control group (n = 6), only the nasal swabs were collected. Polymerase Chain Reaction (PCR) amplification of the gene region hsp70-234 was performed using the extracted DNA from the samples, from which nine patients with TL and five in the control group were positive. Products were sequenced, mounted in CAP3 software, aligned using MAFFT v.7.221, edited in Geneious software v.8.1.7, and compared and aligned with sequences available in GenBank using the BLAST tool.

RESULTS

For patients with TL, six molecular diagnosis at the species level (L. (Viannia) braziliensis (n = 5/9), L. (Viannia) shawi (n = 1/9)) and three at the genus level (Leishmania sp. (n = 3/9)) were obtained. In the control group, four individuals were infected with Leishmania sp. (n = 4/5) and L. (V.) shawi (n = 1/5).

CONCLUSION

This is the first report of L. (V.) shawi infection in the mucosal secretion of a healthy person in Brazil. Moreover, genetic variants were identified in the haplotypes of L. (V.) braziliensis in the gene sequence hsp70-234.

Leishmania RNA virus-1 is similarly detected among metastatic and non-metastatic phenotypes in a prospective cohort of American Tegumentary Leishmaniasis

American Tegumentary Leishmaniasis (ATL) is an endemic and neglected disease of South America. Here, mucosal leishmaniasis (ML) disproportionately affects up to 20% of subjects with current or previous localised cutaneous leishmaniasis (LCL). Preclinical and clinical reports have implicated the Leishmania RNA virus-1 (LRV1) as a possible determinant of progression to ML and other severe manifestations such as extensive cutaneous and mucosal disease and treatment failure and relapse. However, these associations were not consistently found in other observational studies and are exclusively based on cross-sectional designs. In the present study, 56 subjects with confirmed ATL were assessed and followed out for 24-months post-treatment. Lesion biopsy specimens were processed for molecular detection and quantification of Leishmania parasites, species identification, and LRV1 detection. Among individuals presenting LRV1 positive lesions, 40% harboured metastatic phenotypes; comparatively 58.1% of patients with LRV1 negative lesions harboured metastatic phenotypes (p = 0.299). We found treatment failure (p = 0.575) and frequency of severe metastatic phenotypes (p = 0.667) to be similarly independent of the LRV1. Parasite loads did not differ according to the LRV1 status (p = 0.330), nor did Leishmanin skin induration size (p = 0.907) or histopathologic patterns (p = 0.780). This study did not find clinical, parasitological, or immunological evidence supporting the hypothesis that LRV1 is a significant determinant of the pathobiology of ATL.

The Leishmania RNA virus-1 (LRV1) has been implicated as a possible modulator agent in the pathogenesis of leishmaniasis. In-vivo and in-vitro studies have depicted specific mechanisms of how LRV1 could lead to metastasis. Clinical studies and epidemiological evidence have both supported and rejected the hypothesis that LRV1 is a relevant determinant of progression, treatment failure and clinical severity of American Tegumentary Leishmaniasis (ATL). This lack of consistency between preclinical and clinical reports requires further longitudinal studies to clarify the role of LRV1 in ATL. Due to the complex nature of ATL, as other frequent human diseases, these studies should tackle multiple determinants of pathogenicity, including LRV1 status, parasite features, immune status, and prevalent comorbidities affecting individuals in endemic settings. Also, critical methodological aspects allowing for the reliable identification and quantification of LRV1 should be guaranteed.

The Geographical Distribution of Human Cutaneous and Visceral Leishmania Species Identified by Molecular Methods in Iran: A Systematic Review With Meta-Analysis

Leishmaniasis is one of the most common vector-borne parasitic diseases in Iran. Leishmania species identification is necessary for epidemiological aspects, precise prognosis, control and treatment of the disease. We systematically searched all the studies, reports, and documentation related to species identification and geographical distribution of causative agents of cutaneous (CL), mucosal (ML), and visceral leishmaniasis (VL) using DNA-based molecular diagnostic techniques in Iran. International databases including PubMed, ScienceDirect, Embase, Google Scholar, Scopus, and Web of Science were systemically searched for English articles and Iran's databases including SID, IranMedex and Magiran were searched for Persian reports and articles. Searches were performed from 1999 to 2019 (20 years). The current review was conducted using the keywords: cutaneous leishmaniasis, visceral leishmaniasis, Leishmania species, Human, Molecular, PCR, and Iran. The study quality was evaluated using the NOS checklist. This meta-analysis procedure was accomplished using STATA, version 2.7.9. Of the 3,426 records identified in the initial search, 154 articles met inclusion criteria and qualified for the systematic review and meta-analysis. In subgroup analysis, the pooled frequency of causative agents of CL isolates was 67.3% (95% CI: 59.51–74.67%) for L. major and 32.1% (95% CI: 24.72–39.87%) for L. tropica. In addition, the pooled frequency of causative agents of VL isolates was 97.1% (95% CI: 94.6–98.8%) for L. infantum and 2.9% (95% CI: 1.12–5.37%) for L. tropica. The findings of this study showed that the main causative agents of CL and VL in Iran are L. major and L. infantum, respectively. Moreover, kinetoplast DNA (kDNA) and internal transcriber spacer (ITS) were the most used markers for identifying Leishmania species. The current study provides valuable data to encourage and direct researchers as well as public health managers in the comprehensive leishmaniasis control and prevention planning in Iran.

Detection of Leishmania RNA Virus in Clinical Samples from Cutaneous Leishmaniasis Patients Varies according to the Type of Sample

Leishmania RNA virus (LRV) is a double-stranded 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 coinfection 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 CL. However, the reported frequencies of LRV associated with complicated outcomes in patient's series are highly variable, diminishing the relevance on the virus presence in the pathogenesis of the disease. To assess whether or not the inconsistent information about the frequency of LRV associated with CL complicated outcomes could be related to the virus detection approach, the present study evaluated the LRV presence in clinical samples using a diagnostic algorithm according to the type of the sample. In 36 samples with diagnosis of complicated forms of CL (15 of ML and 21 of CL antimony treatment failure) and six samples with non-Leishmania spp. infection, the LRV presence was assessed by RT-PCR, RT-qPCR, and nested RT-PCR. Viral load was estimated in parasite clinical isolates. By combining the methods, LRV1 presence was confirmed in 45% (9/20) of isolates and 37.5% (6/16) of the incisional biopsies. Remarkably, in some cases (4/8), LRV1 was undetectable in the isolates but present in their respective biopsies, and less frequently, the opposite was observed (1/8), suggesting the possibility of loss of parasites harboring LRV1 during the in vitro growth.

Viruses of protozoan parasites and viral therapy: Is the time now right?

Infections caused by protozoan parasites burden the world with huge costs in terms of human and animal health. Most parasitic diseases caused by protozoans are neglected, particularly those associated with poverty and tropical countries, but the paucity of drug treatments and vaccines combined with increasing problems of drug resistance are becoming major concerns for their control and eradication. In this climate, the discovery/repurposing of new drugs and increasing effort in vaccine development should be supplemented with an exploration of new alternative/synergic treatment strategies. Viruses, either native or engineered, have been employed successfully as highly effective and selective therapeutic approaches to treat cancer (oncolytic viruses) and antibiotic-resistant bacterial diseases (phage therapy). Increasing evidence is accumulating that many protozoan, but also helminth, parasites harbour a range of different classes of viruses that are mostly absent from humans. Although some of these viruses appear to have no effect on their parasite hosts, others either have a clear direct negative impact on the parasite or may, in fact, contribute to the virulence of parasites for humans. This review will focus mainly on the viruses identified in protozoan parasites that are of medical importance. Inspired and informed by the experience gained from the application of oncolytic virus- and phage-therapy, rationally-driven strategies to employ these viruses successfully against parasitic diseases will be presented and discussed in the light of the current knowledge of the virus biology and the complex interplay between the viruses, the parasite hosts and the human host. We also highlight knowledge gaps that should be addressed to advance the potential of virotherapy against parasitic diseases.

Genetic variability of molecules involved in the disease pathogenesis in Leishmania infection

Macrophages are the primary host cell for Leishmania parasites, by Toll like receptors (TLR-MyD88) that are central components of the innate and adaptive immunity against leishmania infection. The CD40/CD40L interaction has also been shown to be important in resistance to various protozoa. In this context, one of the most important properties of suppressors of cytokine signalling (SOCS) proteins, especially SOCS1 and SOCS3, is the regulation of macrophages cell for Leishmania parasites. In the present study we evaluated variants of molecules involved in activation and modulation of leishmanicidal signaling cascades and the possible associations between polymorphisms present in the TLR2, TLR4, MyD88, CD40, SOCS1, SOCS3 genes with susceptibility/resistent to Leishmania. The results suggest the absence of any association between TLR2 and TLR4 variants and susceptibility to Leishmaniasis. Analysis of the nucleotide sequence encoding the TIR recognition domain of the MyD88 molecule showed that it is highly conserved when compared to the reference sequences. In contrast, heterozygous rs 12953258, which reflects a decrease in the expression of SOCS3, suggesting that it may be involved in the leishmaniasis susceptibility. This study is a first advance in the analysis of polymorphisms of genes involved in the signaling pathway of the macrophage and their relationship with leishmaniases infection and disease progression.

Leishmania RNA Virus 1 (LRV-1) in Leishmania (Viannia) braziliensis Isolates from Peru: A Description of Demographic and Clinical Correlates

RNA virus 1-1 (LRV-1-1) is a dsRNA virus identified in isolates of Leishmania (Viannia) braziliensis and thought to advance localized cutaneous leishmaniasis (LCL) to mucocutaneous or mucosal leishmaniasis (MCL/ML). We examined the prevalence of LRV-1 and its correlation to phenotypes of American tegumentary leishmaniasis caused by L. (V.) braziliensis from Peru to better understand its epidemiology. Clinical isolates of L. (V.) braziliensis were screened for LRV-1 by real-time polymerase chain reaction (PCR) and stratified according to the phenotype: LCL (< 4 ulcers in number) MCL/ML; inflammatory ulcers (erythematous, purulent, painful ulcers with or without lymphatic involvement) or multifocal ulcers (≥ 4 in ≥ 2 anatomic sites). Proportionate LRV-1 positivity was compared across phenotypes. Of 78 L. (V.) braziliensis isolates, 26 (54.2%) had an inflammatory phenotype, 22 (28%) had the MCL/ML phenotype, whereas 30 (38.5%) had LCL. Mucocutaneous or mucosal leishmaniasis was found exclusively in adult male enrollees. Leishmania RNA virus 1 positivity by phenotype was as follows: 9/22 (41%) with MCL/ML; 5/26 (19%) with an inflammatory/multifocal cutaneous leishmaniasis phenotype; and 7/30 (23%) with LCL (P = 0.19). Leishmania RNA virus 1 positivity was not associated with age (P = 0.55) or gender (P = 0.49). Relative LRV-1 copy number was greater in those with MCL/ML than those with inflammatory/multifocal CL (P = 0.02). A direct association between LRV-1 status and clinical phenotype was not demonstrated; however, relative LRV-1 copy number was highest in those with MCL/ML. Future analyses to understand the relationship between viral burden and pathogenesis are required to determine if LRV-1 is truly a contributor to the MCL/ML phenotype.

Leishmaniavirus genetic diversity is not related to leishmaniasis treatment failure

OBJECTIVES

The outcome of American tegumentary leishmaniasis (ATL) may depend on the presence of the Leishmania RNA virus (LRV). This virus may be involved in treatment failure. We aimed to determine whether genetic clusters of LRV1 are involved in this therapeutic outcome.

METHODS

The presence of LRV1 was assessed in 129 Leishmania guyanensis isolates from patients treated with pentamidine in French Guiana. Among the 115 (89%) isolates found to carry LRV1, 96 were successfully genotyped. Patient clinical data were linked to the LRV data.

RESULTS

The rate of treatment failure for LRV1-positive isolates was 37% (15/41) versus 40% (2/5) among LRV1-negative isolates (p 0.88). Concerning LRV1 genotypes, two predominant LRV1 groups emerged, groups A (23% (22/96)) and B (70% (67/96)). The treatment failure rate was 37% (3/8) for group A and 45% (9/20) for group B (p 0.31).

DISCUSSION

Neither the presence nor genotype of LRV1 in patients with L. guyanensis seemed to correlate with pentamidine treatment failure.

Novel RNA viruses associated with Plasmodium vivax in human malaria and Leucocytozoon parasites in avian disease

Eukaryotes of the genus Plasmodium cause malaria, a parasitic disease responsible for substantial morbidity and mortality in humans. Yet, the nature and abundance of any viruses carried by these divergent eukaryotic parasites is unknown. We investigated the Plasmodium virome by performing a meta-transcriptomic analysis of blood samples taken from patients suffering from malaria and infected with P. vivax, P. falciparum or P. knowlesi. This resulted in the identification of a narnavirus-like sequence, encoding an RNA polymerase and restricted to P. vivax samples, as well as an associated viral segment of unknown function. These data, confirmed by PCR, are indicative of a novel RNA virus that we term Matryoshka RNA virus 1 (MaRNAV-1) to reflect its analogy to a "Russian doll": a virus, infecting a parasite, infecting an animal. Additional screening revealed that MaRNAV-1 was abundant in geographically diverse P. vivax derived from humans and mosquitoes, strongly supporting its association with this parasite, and not in any of the other Plasmodium samples analyzed here nor Anopheles mosquitoes in the absence of Plasmodium. Notably, related bi-segmented narnavirus-like sequences (MaRNAV-2) were retrieved from Australian birds infected with a Leucocytozoon—a genus of eukaryotic parasites that group with Plasmodium in the Apicomplexa subclass hematozoa. Together, these data support the establishment of two new phylogenetically divergent and genomically distinct viral species associated with protists, including the first virus likely infecting Plasmodium parasites. As well as broadening our understanding of the diversity and evolutionary history of the eukaryotic virosphere, the restriction to P. vivax may be of importance in understanding P. vivax-specific biology in humans and mosquitoes, and how viral co-infection might alter host responses at each stage of the P. vivax life-cycle.

While parasites are a major cause of human disease, they can themselves be infected by viruses. We asked whether three of the major malaria-causing parasites in humans—Plasmodium vivax, P. falciparum and P. knowlesi—were also infected by viruses. To this end we performed total RNA-Sequencing (“meta-transcriptomics”) on human blood samples infected with these Plasmodium species. This resulted in the discovery of an abundant bi-segmented virus—Matryoshka RNA virus 1 (MaRNAV-1)—in all P. vivax samples tested (but no other Plasmodium species) that contains a replicase segment related to those of narnaviruses, arguably the simplest type of RNA viruses discovered to date. By screening for MaRNAV-1 in a larger set of Plasmodium species we revealed a strong specificity between this virus and P. vivax, as well as the presence of a related virus—MaRNAV-2—in avian Leucocytozoon hematozoa parasites. This is the first discovery of a Plasmodium-associated virus and will assist in revealing the deep evolutionary history of RNA viruses and our understanding of Plasmodium biology and disease processes.

Protective or Detrimental? Understanding the Role of Host Immunity in Leishmaniasis

The intracellular protozoan parasites of the genus Leishmania are the causative agents of leishmaniasis, a vector-borne disease of major public health concern, estimated to affect 12 million people worldwide. The clinical manifestations of leishmaniasis are highly variable and can range from self-healing localized cutaneous lesions to life-threatening disseminated visceral disease. Once introduced into the skin by infected sandflies, Leishmania parasites interact with a variety of immune cells, such as neutrophils, monocytes, dendritic cells (DCs), and macrophages. The resolution of infection requires a finely tuned interplay between innate and adaptive immune cells, culminating with the activation of microbicidal functions and parasite clearance within host cells. However, several factors derived from the host, insect vector, and Leishmania spp., including the presence of a double-stranded RNA virus (LRV), can modulate the host immunity and influence the disease outcome. In this review, we discuss the immune mechanisms underlying the main forms of leishmaniasis, some of the factors involved with the establishment of infection and disease severity, and potential approaches for vaccine and drug development focused on host immunity.

What makes mucosal and anergic diffuse cutaneous leishmaniases so clinically and immunopathogically different? A review in Brazil

American cutaneous leishmaniasis (ACL) is a parasitic protozoan disease caused by different Leishmania species widely distributed throughout Latin America. Fifteen Leishmania species belonging to the subgenera Viannia, Leishmania and Mundinia are known to cause ACL. Seven of these species are found in Brazil, of which Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis have the highest potential to cause mucosal (ML) and anergic diffuse cutaneous leishmaniasis (DCL), respectively, the most severe forms of ACL. The clinical and immunopathological differences between these two clinical forms are reviewed here, taking into account their different physiopathogenic mechanisms of dissemination from cutaneous lesions to mucosal tissues in the case of ML and to almost all body surfaces in the case of anergic DCL. We also discuss some immunopathogenic mechanisms of species-specific Leishmania antigens (from the subgenera Viannia and Leishmania) that are most likely associated with the clinical and immunopathological differences between ML and anergic DCL. Those discussions emphasize the pivotal importance of some surface antigens of L. (V.) braziliensis and L. (L.) amazonensis, such as lipophosphoglycan, phosphatidylserine and CD200 (an immunoregulatory molecule that inhibits macrophage activation), that have been shown to exert strong influences on the clinical and immunopathological differences between ML and anergic DCL.

Global status of synchronizing Leishmania RNA virus in Leishmania parasites: A systematic review with meta-analysis

Leishmaniasis is one of the most neglected tropical diseases caused by protozoan parasites belonging to the genus Leishmania. There is much evidence regarding prevalence of Leishmania RNAvirus (LRV) causing Old World leishmaniasis (OWL) and New World leishmaniasis (NWL); however, a combined evidence-based knowledge on this topic is not still available. The purpose of this systematic review and meta-analysis was to address the global status of synchronizing LRV in Leishmania in the available literature. The data were systematically collected from the English electronic databases up to May 2018. Then, the studies were screened based on the inclusion and exclusion criteria. The random-effect model was used by forest plot with 95% confidence interval (CI). Overall, 877 samples from 17 articles were included in this study. Given species of Leishmania, the highest prevalence of LRV belonged to Leishmania (L.) Viannia (V.) guyanensis and L. V. braziliensis. Additionally, the virus was detected also in L. V. amazonensis, L. V. panamanensis, L. V. lainsoni, L. aethiopica, L. major and L. infantum. By random-effect model, the global prevalence of LRV was estimated to be 26.2% (95% CI: 14.4% - 40.1%). The high prevalence of LRV among causative agents of NWLisolated from the metastatic clinical forms suggests potential association of LRV with metastatic clinical forms in New World endemic regions. A comprehensive investigation on experimental and clinical aspects of LRV is needed to fully appraise the role of these viruses in pathogenicity of Leishmania parasites and their drug resistance.

Identification of divergent Leishmania (Viannia) braziliensis ecotypes derived from a geographically restricted area through whole genome analysis

Leishmania braziliensis, the main etiological agent of cutaneous leishmaniasis (CL) in Latin America, is characterized by major differences in basic biology in comparison with better-known Leishmania species. It is also associated with a high phenotypic and possibly genetic diversity that need to be more adequately defined. Here we used whole genome sequences to evaluate the genetic diversity of ten L. braziliensis isolates from a CL endemic area from Northeastern Brazil, previously classified by Multi Locus Enzyme Electrophoresis (MLEE) into ten distinct zymodemes. These sequences were first mapped using the L. braziliensis M2904 reference genome followed by identification of Single Nucleotide Polymorphisms (SNPs). A substantial level of diversity was observed when compared with the reference genome, with SNP counts ranging from ~95,000 to ~131,000 for the different isolates. When the genome data was used to infer relationship between isolates, those belonging to zymodemes Z72/Z75, recovered from forested environments, were found to cluster separately from the others, generally associated with more urban environments. Among the remaining isolates, those from zymodemes Z74/Z106 were also found to form a separate group. Phylogenetic analyses were also performed using Multi-Locus Sequence Analysis from genes coding for four metabolic enzymes used for MLEE as well as the gene sequence coding for the Hsp70 heat shock protein. All 10 isolates were firmly identified as L. braziliensis, including the zymodeme Z26 isolate previously classified as Leishmania shawi, with the clustering into three groups confirmed. Aneuploidy was also investigated but found in general restricted to chromosome 31, with a single isolate, from zymodeme Z27, characterized by extra copies for other chromosomes. Noteworthy, both Z72 and Z75 isolates are characterized by a much reduced heterozygosity. Our data is consistent with the existence of distinct evolutionary groups in the restricted area sampled and a substantial genetic diversity within L. braziliensis.

Phonotherapeutic Intervention in Patients With Mucosal Leishmaniasis Sequelae

PURPOSE

To characterize the voice before and after speech-language intervention, with Humming nasal sound in patients with sequelae Mucosal Leishmaniasis (ML) and Cutaneous Leishmaniasis (CL).

METHODS

Collection of phonation /a:/ from 44 patients with ML and CL for perceptual voice analysis and computed acoustic. The Wilcoxon nonparametric test and Fisher's exact test were used, with significance level of 5%.

RESULTS

It was observed, prespeech therapy, that 27.7% of participants with ML presented asthenic vocal quality, and for the acoustics characteristics there was a statistically significant result for measures of frequency, frequency disturbance, noise, and subharmonic measurements, indicating phonatory instability, weakness, and noise emission giving the emission a feeling of vocal weakness. After therapy, the subharmonic segment measurements for the group with ML, showing reduction noise emission. Patients with CL had more grade 1 instability (36.4%), indicating tremor in vocal tract structures. After speech therapy, this group presented a reduction in the degree of roughness and reduction of the frequency disturbance measures, indicating a decrease in tension in the larynx and pharynx.

CONCLUSION

Even after completing treatment for LM, patients may experience vocal changes due to the sequelae of the disease, like vocal alterations due to nasal lesions or in other locations that interfere in the correct vocal emission. As for participants with CL, no vocal changes would be expected, since these patients present thorax, leg and arm lesions that would not cause problems for the voice. Nevertheless, the two groups of participants presented vocal changes to different degrees before vocal therapy. However, it was observed that patients with ML present vocal alterations with more severe degrees. After the speech-language intervention, the participants of both groups showed vocal improvement, but the group with CL presented more vocal benefits, possibly due to the previous vocal alterations not being so severe.

Leishmania (Viannia) guyanensis in tegumentary leishmaniasis

Leishmania (Viannia) guyanensis is a causal agent of American tegumentary leishmaniasis (ATL). This protozoan has been poorly investigated; however, it can cause different clinical forms of ATL, ranging from a single cutaneous lesion to severe lesions that can lead to destruction of the nasopharyngeal mucosa. L. (V.) guyanensis and the disease caused by this species can present unique aspects revealing the need to better characterize this parasite species to improve our knowledge of the immunopathological mechanisms and treatment options for ATL. The mechanisms by which some patients develop a more severe form of ATL remain unclear. It is known that the host immune profile and parasite factors may influence the clinical manifestations of the disease. Besides intrinsic parasite factors, Leishmaniavirus RNA 1 (LRV1) infecting L. guyanensis can contribute to ATL immunopathogenesis. In this review, general aspects of L. guyanensis infection in humans and mouse models are presented.

Concentration of 2'C-methyladenosine triphosphate by Leishmania guyanensis enables specific inhibition of Leishmania RNA virus 1 via its RNA polymerase

Leishmania is a widespread trypanosomatid protozoan parasite causing significant morbidity and mortality in humans. The endobiont dsRNA virus Leishmania RNA virus 1 (LRV1) chronically infects some strains, where it increases parasite numbers and virulence in murine leishmaniasis models, and correlates with increased treatment failure in human disease. Previously, we reported that 2'-C-methyladenosine (2CMA) potently inhibited LRV1 in Leishmania guyanensis (Lgy) and Leishmania braziliensis, leading to viral eradication at concentrations above 10 μm Here we probed the cellular mechanisms of 2CMA inhibition, involving metabolism, accumulation, and inhibition of the viral RNA-dependent RNA polymerase (RDRP). Activation to 2CMA triphosphate (2CMA-TP) was required, as 2CMA showed no inhibition of RDRP activity from virions purified on cesium chloride gradients. In contrast, 2CMA-TP showed IC₅₀ values ranging from 150 to 910 μm, depending on the CsCl density of the virion (empty, ssRNA-, and dsRNA-containing). Lgy parasites incubated in vitro with 10 μm 2CMA accumulated 2CMA-TP to 410 μm, greater than the most sensitive RDRP IC₅₀ measured. Quantitative modeling showed good agreement between the degree of LRV1 RDRP inhibition and LRV1 levels. These results establish that 2CMA activity is due to its conversion to 2CMA-TP, which accumulates to levels that inhibit RDRP and cause LRV1 loss. This attests to the impact of the Leishmania purine uptake and metabolism pathways, which allow even a weak RDRP inhibitor to effectively eradicate LRV1 at micromolar concentrations. Future RDRP inhibitors with increased potency may have potential therapeutic applications for ameliorating the increased Leishmania pathogenicity conferred by LRV1.

Viral discovery and diversity in trypanosomatid protozoa with a focus on relatives of the human parasite Leishmania

Knowledge of viral diversity is expanding greatly, but many lineages remain underexplored. We surveyed RNA viruses in 52 cultured monoxenous relatives of the human parasite Leishmania (Crithidia and Leptomonas), as well as plant-infecting PhytomonasLeptomonas pyrrhocoris was a hotbed for viral discovery, carrying a virus (Leptomonas pyrrhocoris ostravirus 1) with a highly divergent RNA-dependent RNA polymerase missed by conventional BLAST searches, an emergent clade of tombus-like viruses, and an example of viral endogenization. A deep-branching clade of trypanosomatid narnaviruses was found, notable as Leptomonas seymouri bearing Narna-like virus 1 (LepseyNLV1) have been reported in cultures recovered from patients with visceral leishmaniasis. A deep-branching trypanosomatid viral lineage showing strong affinities to bunyaviruses was termed "Leishbunyavirus" (LBV) and judged sufficiently distinct to warrant assignment within a proposed family termed "Leishbunyaviridae" Numerous relatives of trypanosomatid viruses were found in insect metatranscriptomic surveys, which likely arise from trypanosomatid microbiota. Despite extensive sampling we found no relatives of the totivirus Leishmaniavirus (LRV1/2), implying that it was acquired at about the same time the Leishmania became able to parasitize vertebrates. As viruses were found in over a quarter of isolates tested, many more are likely to be found in the >600 unsurveyed trypanosomatid species. Viral loss was occasionally observed in culture, providing potentially isogenic virus-free lines enabling studies probing the biological role of trypanosomatid viruses. These data shed important insights on the emergence of viruses within an important trypanosomatid clade relevant to human disease.

An overview on Leishmania (Mundinia) enriettii: biology, immunopathology, LRV and extracellular vesicles during the host-parasite interaction

One of the Leishmania species known to be non-infective to humans is Leishmania (Mundinia) enriettii whose vertebrate host is the guinea pig Cavia porcellus. It is a good model for cutaneous leishmaniasis, chemotherapeutic and molecular studies. In the last years, an increased interest has emerged concerning the L. (Mundinia) subgenus after the finding of Leishmania (M.) macropodum in Australia and with the description of other new/putative species such as L. (M.) martiniquensis and 'L. (M.) siamensis'. This review focused on histopathology, glycoconjugates and innate immunity. The presence of Leishmania RNA virus and shedding of extracellular vesicles by the parasite were also evaluated.

Leptomonas seymouri narna-like virus 1 and not leishmaniaviruses detected in kala-azar samples from India

The great majority of kala-azar/visceral leishmaniasis (VL) cases, which are caused by Leishmania donovani (LD), are reported in Asia. We investigated whether leishmaniaviruses (LRVs) are present in LD isolates. These dsRNA viruses contribute to hyperpathogenicity, as observed in the case of other members of the genus Leishmania. However, LRVs could not be detected in 22 Indian LD isolates tested in the present study, while 70% of these original LD isolates harboured a virus that was not of LD but instead of Leptomonas seymouri (LS) origin. LS is another protozoon that parasitizes the sandfly vector of LD. Historically, LD clinical isolates from India often showed high incidence of LS coinfection. LS was detected in 20 out of the 22 (91%) above-mentioned LD isolates. Leptomonas seymouri narna-like virus 1 (Lepsey NLV1) was identified by whole-genome sequencing in an LD-LS coinfected sample, and its presence was confirmed by PCR and sequencing in 15 (75%) of the 20 LD-LS coinfected samples. The LS-negative LD samples were also virus negative by PCR. That the human host is exposed to an RNA virus in LS, another coinfecting parasite with LD, i.e., the "LD-LS-Lepsey NLV1 triple pathogen" phenomenon, unveils a new paradigm of research towards revisiting the mysteries of Indian leishmaniasis pathogenesis and management.

Unraveling the genetic diversity and phylogeny of Leishmania RNA virus 1 strains of infected Leishmania isolates circulating in French Guiana

Introduction

Leishmania RNA virus type 1 (LRV1) is an endosymbiont of some Leishmania (Vianna) species in South America. Presence of LRV1 in parasites exacerbates disease severity in animal models and humans, related to a disproportioned innate immune response, and is correlated with drug treatment failures in humans. Although the virus was identified decades ago, its genomic diversity has been overlooked until now.

Methodology/Principles findings

We subjected LRV1 strains from 19 L. (V.) guyanensis and one L. (V.) braziliensis isolates obtained from cutaneous leishmaniasis samples identified throughout French Guiana with next-generation sequencing and de novo sequence assembly. We generated and analyzed 24 unique LRV1 sequences over their full-length coding regions. Multiple alignment of these new sequences revealed variability (0.5%–23.5%) across the entire sequence except for highly conserved motifs within the 5’ untranslated region. Phylogenetic analyses showed that viral genomes of L. (V.) guyanensis grouped into five distinct clusters. They further showed a species-dependent clustering between viral genomes of L. (V.) guyanensis and L. (V.) braziliensis, confirming a long-term co-evolutionary history. Noteworthy, we identified cases of multiple LRV1 infections in three of the 20 Leishmania isolates.

Conclusions/Significance

Here, we present the first-ever estimate of LRV1 genomic diversity that exists in Leishmania (V.) guyanensis parasites. Genetic characterization and phylogenetic analyses of these viruses has shed light on their evolutionary relationships. To our knowledge, this study is also the first to report cases of multiple LRV1 infections in some parasites. Finally, this work has made it possible to develop molecular tools for adequate identification and genotyping of LRV1 strains for diagnostic purposes. Given the suspected worsening role of LRV1 infection in the pathogenesis of human leishmaniasis, these data have a major impact from a clinical viewpoint and for the management of Leishmania-infected patients.

Leishmaniasis is a well-known parasitosis due to an infection by the protozoan Leishmania parasites firmly established in South America. In French Guiana, where leishmaniasis is a public health problem, having an annual incidence of 5.6 cases/10,000 inhabitants, 80% of Leishmania spp. parasites are infected by an endosymbiotic virus, Leishmania RNA virus 1 (LRV1). The purpose of this study was to gain insights on the genetic variability and evolution of LRV1 at the genomic level. We subjected 20 Leishmania isolates obtained from cutaneous lesions with next generation sequencing and de novo sequence assembly. This allowed generating 24 LRV1 full-length coding sequences presenting among themselves a significant genetic diversity. The inferred phylogenetic relationships enabled to identify distinct well-supported genotypes and support the hypothesis of co-evolution between LRV1 strains and their parasite hosts. In addition, we identified multiple LRV1 infections in three parasite isolates. Based on these data, future characterization of new strains from other geographic areas and other parasite species should extend knowledge of LRV1 diversification processes. Finally, these results allowed us to identify genomic regions where best to allocate resources for subsequent analyses of LRV1 viral diversity and genotyping that could serve for accurate routine molecular diagnostic applications.

Viruses of parasites as actors in the parasite-host relationship: A "ménage à trois"

The complex parasite-host relationship involves multiple mechanisms. Moreover, parasites infected by viruses modify this relationship adding more complexity to the system that now comprises three partners. Viruses infecting parasites were described several decades ago. However, until recently little was known about the viruses involved and their impact on the resulting disease caused to the hosts. To clarify this situation, we have concentrated on parasitic diseases caused to humans and on how virus-infected parasites could alter the symptoms inflicted on the human host. It is clear that the effect caused to the human host depends on the virus and on the parasite it has infected. Consequently, the review is divided as follows: Viruses with a possible effect on the virulence of the parasite. This section reviews pertinent articles showing that infection of parasites by viruses might increase the detrimental effect of the tandem virus-parasite on the human host (hypervirulence) or decrease virulence of the parasite (hypovirulence). Parasites as vectors affecting the transmission of viruses. In some cases, the virus-infected parasite might facilitate the transfer of the virus to the human host. Parasites harboring viruses with unidentified effects on their host. In spite of recently renewed interest in parasites in connection with their viruses, there still remains a number of cases in which the effect of the virus of a given parasite on the human host remains ambiguous. The triangular relationship between the virus, the parasite and the host, and the modulation of the pathogenicity and virulence of the parasites by viruses should be taken into account in the rationale of fighting against parasites.

Antiviral screening identifies adenosine analogs targeting the endogenous dsRNA Leishmania RNA virus 1 (LRV1) pathogenicity factor

The endogenous double-stranded RNA (dsRNA) virus Leishmaniavirus (LRV1) has been implicated as a pathogenicity factor for leishmaniasis in rodent models and human disease, and associated with drug-treatment failures in Leishmania braziliensis and Leishmania guyanensis infections. Thus, methods targeting LRV1 could have therapeutic benefit. Here we screened a panel of antivirals for parasite and LRV1 inhibition, focusing on nucleoside analogs to capitalize on the highly active salvage pathways of Leishmania, which are purine auxotrophs. Applying a capsid flow cytometry assay, we identified two 2'-C-methyladenosine analogs showing selective inhibition of LRV1. Treatment resulted in loss of LRV1 with first-order kinetics, as expected for random virus segregation, and elimination within six cell doublings, consistent with a measured LRV1 copy number of about 15. Viral loss was specific to antiviral nucleoside treatment and not induced by growth inhibitors, in contrast to fungal dsRNA viruses. Comparisons of drug-treated LRV1⁺ and LRV1^- lines recapitulated LRV1-dependent pathology and parasite replication in mouse infections, and cytokine secretion in macrophage infections. Agents targeting Totiviridae have not been described previously, nor are there many examples of inhibitors acting against dsRNA viruses more generally. The compounds identified here provide a key proof-of-principle in support of further studies identifying efficacious antivirals for use in in vivo studies of LRV1-mediated virulence.

Atypical Manifestations of Cutaneous Leishmaniasis in a Region Endemic for Leishmania braziliensis: Clinical, Immunological and Parasitological Aspects

BACKGROUND

Atypical cutaneous leishmaniasis (ACL) has become progressively more frequent in Corte de Pedra, Northeast Brazil. Herein we characterize clinical presentation, antimony response, cytokine production and parasite strains prevailing in ACL.

METHODOLOGY/PRINCIPAL FINDINGS

Between 2005 and 2012, 51 ACL (cases) and 51 temporally matched cutaneous leishmaniasis (CL) subjects (controls) were enrolled and followed over time in Corte de Pedra. Clinical and therapeutic data were recorded for all subjects. Cytokine secretion by patients' peripheral blood mononuclear cells (PBMC) stimulated with soluble parasite antigen in vitro, and genotypes in a 600 base-pair locus in chromosome 28 (CHR28/425451) of the infecting L. (V.) braziliensis were compared between the two groups. ACL presented significantly more lesions in head and neck, and higher rate of antimony failure than CL. Cytosine-Adenine substitutions at CHR28/425451 positions 254 and 321 were highly associated with ACL (p<0.0001). In vitro stimulated ACL PBMCs produced lower levels of IFN-γ (p = 0.0002) and TNF (p <0.0001), and higher levels of IL-10 (p = 0.0006) and IL-17 (p = 0.0008) than CL PBMCs.

CONCLUSIONS/SIGNIFICANCE

ACL found in Northeast Brazil is caused by distinct genotypes of L. (V.) braziliensis and presents a cytokine profile that departs from that in classical CL patients. We think that differences in antigenic contents among parasites may be in part responsible for the variation in cytokine responses and possibly immunopathology between CL and ACL.

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

Many Leishmania (Viannia) parasites harbor the double-stranded RNA virus Leishmania RNA virus 1 (LRV1), which has been associated with increased disease severity in animal models and humans and with drug treatment failures in humans. Remarkably, LRV1 survives in the presence of an active RNAi pathway, which in many organisms controls RNA viruses. We found significant levels (0.4 to 2.5%) of small RNAs derived from LRV1 in both Leishmania braziliensis and Leishmania guyanensis, mapping across both strands and with properties consistent with Dicer-mediated cleavage of the dsRNA genome. LRV1 lacks cis- or trans-acting RNAi inhibitory activities, suggesting that virus retention must be maintained by a balance between RNAi activity and LRV1 replication. To tilt this balance toward elimination, we targeted LRV1 using long-hairpin/stem-loop constructs similar to those effective against chromosomal genes. LRV1 was completely eliminated, at high efficiency, accompanied by a massive overproduction of LRV1-specific siRNAs, representing as much as 87% of the total. For both L. braziliensis and L. guyanensis, RNAi-derived LRV1-negative lines were no longer able to induce a Toll-like receptor 3-dependent hyperinflammatory cytokine response in infected macrophages. We demonstrate in vitro a role for LRV1 in virulence of L. braziliensis, the Leishmania species responsible for the vast majority of mucocutaneous leishmaniasis cases. These findings establish a targeted method for elimination of LRV1, and potentially of other Leishmania viruses, which will facilitate mechanistic dissection of the role of LRV1-mediated virulence. Moreover, our data establish a third paradigm for RNAi-viral relationships in evolution: one of balance rather than elimination.

Low frequency of LRV1 in Leishmania braziliensis strains isolated from typical and atypical lesions in the State of Minas Gerais, Brazil

The double stranded RNA (dsRNA) virus Leishmaniavirus (Totiviridae) was first described in Leishmania guyanensis and L. braziliensis (LRV1), and more recently from L. major and L. aethiopica (LRV2). Parasites bearing LRV1 elicit a higher pro-inflammatory profile, arising through activation of Toll like receptor 3(TLR3) interacting with the viral dsRNA. LRV1 is most common in Leishmania from the Amazon region; however data for other regions of Brazil are more limited. Here we applied PCR tests with validated 'universal' LRV1 primers to search for LRV1 in 40 strains of cultured L. braziliensis from several locales within Minas Gerais State, including patients presenting with atypical lesion pathology. All strains were negative however. These data are in agreement with results from other areas of Southeastern Brazil that LRV1 is relatively uncommon.