Leishmania aethiopica field isolates bearing an endosymbiontic dsRNA virus induce pro-inflammatory cytokine response

Microbial Matryoshka: Addressing the Relationship between Pathogenic Flagellated Protozoans and Their RNA Viral Endosymbionts (Family Totiviridae)

Three genera of viruses of the family Totiviridae establish endosymbiotic associations with flagellated protozoa responsible for parasitic diseases of great impact in the context of One Health. Giardiavirus, Trichomonasvirus, and Leishmaniavirus infect the protozoa Giardia sp., Trichomonas vaginalis, and Leishmania sp., respectively. In the present work, we review the characteristics of the endosymbiotic relationships established, the advantages, and the consequences caused in mammalian hosts. Among the common characteristics of these double-stranded RNA viruses are that they do not integrate into the host genome, do not follow a lytic cycle, and do not cause cytopathic effects. However, in cases of endosymbiosis between Leishmaniavirus and Leishmania species from the Americas, and between Trichomonasvirus and Trichomonas vaginalis, it seems that it can alter their virulence (degree of pathogenicity). In a mammalian host, due to TLR3 activation of immune cells upon the recognition of viral RNA, uncontrolled inflammatory signaling responses are triggered, increasing pathological damage and the risk of failure of conventional standard treatment. Endosymbiosis with Giardiavirus can cause the loss of intestinal adherence of the protozoan, resulting in a benign disease. The current knowledge about viruses infecting flagellated protozoans is still fragmentary, and more research is required to unravel the intricacies of this three-way relationship. We need to develop early and effective diagnostic methods for further development in the field of translational medicine. Taking advantage of promising biotechnological advances, the aim is to develop ad hoc therapeutic strategies that focus not only on the disease-causing protozoan but also on the virus.

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.

Diversity and dissemination of viruses in pathogenic protozoa

Viruses are the most abundant biological entities on Earth and play a significant role in the evolution of many organisms and ecosystems. In pathogenic protozoa, the presence of viruses has been linked to an increased risk of treatment failure and severe clinical outcome. Here, we studied the molecular epidemiology of the zoonotic disease cutaneous leishmaniasis in Peru and Bolivia through a joint evolutionary analysis of Leishmania braziliensis and their dsRNA Leishmania virus 1. We show that parasite populations circulate in tropical rainforests and are associated with single viral lineages that appear in low prevalence. In contrast, groups of hybrid parasites are geographically and ecologically more dispersed and associated with an increased prevalence, diversity and spread of viruses. Our results suggest that parasite gene flow and hybridization increased the frequency of parasite-virus symbioses, a process that may change the epidemiology of leishmaniasis in the region.

The effects of Leishmania RNA virus 2 (LRV2) on the virulence factors of L. major and pro-inflammatory biomarkers: an in vitro study on human monocyte cell line (THP-1)

BACKGROUND

Cutaneous Leishmaniasis (CL) is a parasitic disease with diverse outcomes. Clinical diversity is influenced by various factors such as Leishmania species and host genetic background. The role of Leishmania RNA virus (LRV), as an endosymbiont, is suggested to not only affect the pathogenesis of Leishmania, but also impact host immune responses. This study aimed to investigate the influence of LRV2 on the expression of a number of virulence factors (VFs) of Leishmania and pro-inflammatory biomarkers.

MATERIALS AND METHODS

Sample were obtained from CL patients from Golestan province. Leishmania species were identified by PCR (LIN 4, 17), and the presence of LRV2 was checked using the semi-nested PCR (RdRp gene). Human monocyte cell line (THP-1) was treated with three isolates of L. major with LRV2 and one isolate of L. major without LRV2. The treatments with four isolates were administered for the time points: zero, 12, 24, 36, and 48 h after co-infection. The expression levels of Leishmania VFs genes including GP63, HSP83, and MPI, as well as pro-inflammatory biomarkers genes including NLRP3, IL18, and IL1β, were measured using quantitative real-time PCR.

RESULTS

The expression of GP63, HSP83, and MPI revealed up-regulation in LRV2 + isolates compared to LRV2- isolates. The expression of the pro-inflammatory biomarkers including NLRP3, IL1β, and IL18 genes in LRV2- were higher than LRV2 + isolates.

CONCLUSION

This finding suggests that LRV2 + may have a probable effect on the Leishmania VFs and pro-inflammatory biomarkers in the human macrophage model.

Evolution of RNA viruses in trypanosomatids: new insights from the analysis of Sauroleishmania

RNA viruses play an important role in Leishmania biology and virulence. Their presence was documented in three (out of four) Leishmania subgenera. Sauroleishmania of reptiles remained the only underinvestigated group. In this work, we analyzed the viral occurrence in Sauroleishmania spp. and detected RNA viruses in three out of seven isolates under study. These viruses were of two families-Narnaviridae and Totiviridae. Phylogenetic inferences demonstrated that totiviruses from L. adleri and L. tarentolae group together within a larger cluster of LRV2s, while a narnavirus of L. gymnodactyli appeared as a phylogenetic relative of narnaviruses of Blechomonas spp. Taken together, our work not only expanded the range of trypanosomatids that can host RNA viruses but also shed new light on the evolution and potential routes of viral transmission in these flagellates.

First report of putative Leishmania RNA virus 2 (LRV2) in Leishmania infantum strains from canine and human visceral leishmaniasis cases in the southeast of Brazil

BACKGROUND

Leishmania RNA virus 1 (LRV1) is commonly found in South American Leishmania parasites belonging to the subgenus Viannia, whereas Leishmania RNA virus 2 (LRV2) was previously thought to be restricted to the Old-World pathogens of the subgenus Leishmania.

OBJECTIVES

In this study, we investigated the presence of LRV2 in strains of Leishmania (L.) infantum, the causative agent of visceral leishmaniasis (VL), originating from different hosts, clinical forms, and geographical regions.

METHODS

A total of seventy-one isolates were screened for LRV2 using semi-nested reverse transcription-polymerase chain reaction (RT-PCR) targeting the RNA-dependent RNA polymerase (RdRp) gene.

FINDINGS

We detected LRV2 in two L. infantum isolates (CUR268 and HP-EMO) from canine and human cases, respectively.

MAIN CONCLUSIONS

To the best of our knowledge, this is the first detection of LRV2 in the New World.

Diversity of RNA viruses in the cosmopolitan monoxenous trypanosomatid Leptomonas pyrrhocoris

BACKGROUND

Trypanosomatids are parasitic flagellates well known because of some representatives infecting humans, domestic animals, and cultural plants. Many trypanosomatid species bear RNA viruses, which, in the case of human pathogens Leishmania spp., influence the course of the disease. One of the close relatives of leishmaniae, Leptomonas pyrrhocoris, has been previously shown to harbor viruses of the groups not documented in other trypanosomatids. At the same time, this species has a worldwide distribution and high prevalence in the natural populations of its cosmopolitan firebug host. It therefore represents an attractive model to study the diversity of RNA viruses.

RESULTS

We surveyed 106 axenic cultures of L. pyrrhocoris and found that 64 (60%) of these displayed 2-12 double-stranded RNA fragments. The analysis of next-generation sequencing data revealed four viral groups with seven species, of which up to five were simultaneously detected in a single trypanosomatid isolate. Only two of these species, a tombus-like virus and an Ostravirus, were earlier documented in L. pyrrhocoris. In addition, there were four new species of Leishbuviridae, the family encompassing trypanosomatid-specific viruses, and a new species of Qinviridae, the family previously known only from metatranscriptomes of invertebrates. Currently, this is the only qinvirus with an unambiguously determined host. Our phylogenetic inferences suggest reassortment in the tombus-like virus owing to the interaction of different trypanosomatid strains. Two of the new Leishbuviridae members branch early on the phylogenetic tree of this family and display intermediate stages of genomic segment reduction between insect Phenuiviridae and crown Leishbuviridae.

CONCLUSIONS

The unprecedented wide range of viruses in one protist species and the simultaneous presence of up to five viral species in a single Leptomonas pyrrhocoris isolate indicate the uniqueness of this flagellate. This is likely determined by the peculiarity of its firebug host, a highly abundant cosmopolitan species with several habits ensuring wide distribution and profuseness of L. pyrrhocoris, as well as its exposure to a wider spectrum of viruses compared to other trypanosomatids combined with a limited ability to transmit these viruses to its relatives. Thus, L. pyrrhocoris represents a suitable model to study the adoption of new viruses and their relationships with a protist host.

A Diverse Virome Is Identified in Parasitic Flatworms of Domestic Animals in Xinjiang, China

Parasitic flatworms infect diverse vertebrates and are major threats to animal and even human health; however, little is known about the virome of these lower life forms. Using viral metagenomic sequencing, we characterized the virome of the parasitic flatworms collected from major domestic animals, including Dicrocoelium lanceatum and Taenia hydatigena, Echinococcus granulosus sensu stricto and Echinococcus multilocularis. Seven and three different viruses were discovered from D. lanceatum and T. hydatigena, respectively, and no viral sequences were found in adult tapeworms and protoscoleces of E. granulosus sensu stricto and E. multilocularis. Two out of the five parasitic flatworm species carry viruses, showing a host specificity of these viruses. These viruses belong to the Parvoviridae, Circoviridae, unclassified circular, Rep-encoding single-stranded (CRESS) DNA virus, Rhabdoviridae, Endornaviridae, and unclassified RNA viruses. The presence of multiple highly divergent RNA viruses, especially those that cluster with viruses found in marine animals, implies a deep evolutionary history of parasite-associated viruses. In addition, we found viruses with high identity to common pathogens in dogs, including canine circovirus and canine parvovirus 2. The presence of these viruses in the parasites implies that they may infect parasitic flatworms but does not completely exclude the possibility of contamination from host intestinal contents. Furthermore, we demonstrated that certain viruses, such as CRESS DNA virus may integrate into the genome of their host. Our results expand the knowledge of viral diversity in parasites of important domestic animals, highlighting the need for further investigations of their prevalence among other parasites of key animals. IMPORTANCE Characterizing the virome of parasites is important for unveiling the viral diversity, evolution, and ecology and will help to understand the "Russian doll" pattern among viruses, parasites, and host animals. Our data indicate that diverse viruses are present in specific parasitic flatworms, including viruses that may have an ancient evolutionary history and viruses currently circulating in parasite-infected host animals. These data also raise the question of whether parasitic flatworms acquire and/or carry some viruses that may have transmission potential to animals. In addition, through the study of virus-parasite-host interactions, including the influence of viral infection on the life cycle of the parasite, as well as its fitness and pathogenicity to the host, we could find new strategies to prevent and control parasitic diseases.

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.

Parasite hybridization promotes spreading of endosymbiotic viruses

Viruses are the most abundant biological entities on Earth and play a significant role in the evolution of many organisms and ecosystems. In pathogenic protozoa, the presence of endosymbiotic viruses has been linked to an increased risk of treatment failure and severe clinical outcome. Here, we studied the molecular epidemiology of the zoonotic disease cutaneous leishmaniasis in Peru and Bolivia through a joint evolutionary analysis of Leishmania braziliensis parasites and their endosymbiotic Leishmania RNA virus. We show that parasite populations circulate in isolated pockets of suitable habitat and are associated with single viral lineages that appear in low prevalence. In contrast, groups of hybrid parasites were geographically and ecologically dispersed, and commonly infected from a pool of genetically diverse viruses. Our results suggest that parasite hybridization, likely due to increased human migration and ecological perturbations, increased the frequency of endosymbiotic interactions known to play a key role in disease severity.

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.

Multiple Regulations of Parasitic Protozoan Viruses: A Double-Edged Sword for Protozoa

Parasite infections affect human and animal health significantly and contribute to a major burden on the global economy. Parasitic protozoan viruses (PPVs) affect the protozoan parasites' morphology, phenotypes, pathogenicity, and growth rates. This discovery provides an opportunity to develop a novel preventive and therapeutic strategy for parasitic protozoan diseases (PPDs). Currently, there is greater awareness regarding PPVs; however, knowledge of viruses and their associations with host diseases remains limited. Parasite-host interactions become more complex owing to PPVs; however, few studies have investigated underlying viral regulatory mechanisms in parasites. In this study, we reviewed relevant studies to identify studies that investigated PPV development and life cycles, the triangular association between viruses, parasites, and hosts, and the effects of viruses on protozoan pathogenicity. This study highlights that viruses can alter parasite biology, and viral infection of parasites may exacerbate the adverse effects of virus-containing parasites on hosts or reduce parasite virulence. PPVs should be considered in the prevention of parasitic epidemics and outbreaks, although their effects on the host and the complexity of the triangular association between PPVs, protozoans, and hosts remain unclear. IMPORTANCE PPVs-based regulation of parasitic protozoa can provide a theoretical basis and direction for PPD prevention and control, although PPVs and PPV regulatory mechanisms remain unclear. In this review, we investigated the differences between PPVs and the unique properties of each virus regarding virus discovery, structures, and life cycles, focused on the Trichomonas vaginalis virus, Giardia lamblia virus, Leishmania RNA virus, and the Cryptosporidium parvum virus 1. The triangular association between PPVs, parasitic protozoa, and hosts reveals the "double-edged sword" property of PPVs, which maintains a balance between parasitic protozoa and hosts in both positive and negative respects. These studies discuss the complexity of parasitic protozoa and their co-existence with hosts and suggest novel pathways for using PPVs as tools to gain a deeper understanding of protozoal infection and treatment.

Identification of Leishmania species and frequency distribution of LRV1 and LRV2 viruses on cutaneous leishmaniasis patients in Isfahan Province, Iran

PURPOSE

Leishmaniasis is one of the most serious health problems in developing countries. Iran is one of the endemic regions of cutaneous leishmaniasis. Leishmania RNA virus (LRV) is a dsRNA virus member of the Totiviridae family, which was first detected in the promastigotes of Leishmania braziliensis guyanensis. Our study aimed to investigate possible changes in the predominant and causative strains of CL and screening the LRV1 and LRV2 species genome from Leishmania species isolated from the lesions of patients.

MATERIALS AND METHODS

Direct smear samples obtained from 62 patients with leishmaniasis referring to the Skin Diseases and Leishmaniasis Research Center in Isfahan province during 2021-2022 were examined. Total DNA extraction procedures and conservation of site-specific multiplex PCR and nested PCR were performed for detecting Leishmania species. The molecular identification of LRV1 and LRV2 viruses, samples were used for total RNA extraction and real-time (RT)-PCR analysis, followed by conducting a restriction enzyme assay to confirm the PCR products.

RESULTS

Of the total Leishmania isolates, 54 and 8 isolates were identified as L. major and L. tropica, respectively. LRV2 was identified in 18 samples affected by L. major, while LRV1 was only detected in one of the samples with L. tropica. No LRV2 was found in any samples with L. tropica. The results showed that there was a significant relationship between LRV1 and the type of leishmaniasis (Sig. ​= ​0.009, P ​≤ ​0.05), while this relationship was not observed between LRV2 and the type of leishmaniasis.

CONCLUSIONS

The presence of a significant number of LRV2 in isolated samples, as well as the recognition of LRV1 in one of the Old World leishmaniasis species, which is a new result, could pave the way for investigating further aspects of this disease and successful treatment strategies in future studies.

First report of Leishmania (Mundinia) martiniquensis in South American territory and confirmation of Leishbunyavirus infecting this parasite in a mare

BACKGROUND

Epidemiological data related to leishmaniases or Leishmania infection in horses are scarce. However, studies carried out in different regions in the world showed equids parasitised by Leishmania braziliensis, L. infantum and L. martiniquensis.

OBJECTIVES

Identify the Leishmania species causing cutaneous leishmaniasis in a mare, living in Rio de Janeiro State (Brazil), and search the presence of Leishmania viruses in the isolated parasite.

METHODS

Isoenzymes and polymerase chain reaction (PCR) targeting ITSrDNA region followed by sequencing were conducted for typing the isolated parasite. A search for Leishmania virus infection was also performed.

FINDINGS

The mare presented skin nodules and ulcers in the left pinna caused by Leishmania spp. that was detected by culture and PCR. The parasite was identified as Leishmania (Mundinia) martiniquensis, infected by Leishbunyavirus (LBV), representing the first description of this species in South America. The animal travelled to different Brazilian regions, but not to outside the country.

MAIN CONCLUSIONS

The worldwide distribution of L. martiniquensis and its infection by LBV were confirmed in this study, indicating the autochthonous transmission cycle in Brazil. The clinical profile of the disease in the mare, showing fast spontaneous healing of cutaneous lesions, may indicate that skin lesions related to L. martiniquensis infection in horses might be underdiagnosed.

Genome diversity of Leishmania aethiopica

Leishmania aethiopica is a zoonotic Old World parasite transmitted by Phlebotomine sand flies and causing cutaneous leishmaniasis in Ethiopia and Kenya. Despite a range of clinical manifestations and a high prevalence of treatment failure, L. aethiopica is one of the most neglected species of the Leishmania genus in terms of scientific attention. Here, we explored the genome diversity of L. aethiopica by analyzing the genomes of twenty isolates from Ethiopia. Phylogenomic analyses identified two strains as interspecific hybrids involving L. aethiopica as one parent and L. donovani and L. tropica respectively as the other parent. High levels of genome-wide heterozygosity suggest that these two hybrids are equivalent to F1 progeny that propagated mitotically since the initial hybridization event. Analyses of allelic read depths further revealed that the L. aethiopica - L. tropica hybrid was diploid and the L. aethiopica - L. donovani hybrid was triploid, as has been described for other interspecific Leishmania hybrids. When focusing on L. aethiopica, we show that this species is genetically highly diverse and consists of both asexually evolving strains and groups of recombining parasites. A remarkable observation is that some L. aethiopica strains showed an extensive loss of heterozygosity across large regions of the nuclear genome, which likely arose from gene conversion/mitotic recombination. Hence, our prospection of L. aethiopica genomics revealed new insights into the genomic consequences of both meiotic and mitotic recombination in Leishmania.

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.

Detection of Leptomonas seymouri narna-like virus in serum samples of visceral leishmaniasis patients and its possible role in disease pathogenesis

Kala-azar/Visceral Leishmaniasis (VL) caused by Leishmania donovani (LD) is often associated with Leptomonas seymouri (LS) co-infection in India. Leptomonas seymouri narna-like virus 1 (Lepsey NLV1) has been reported in multi-passaged laboratory isolates of VL samples which showed LD-LS co-infection. A pertinent question was whether this virus of LS is detectable in direct clinical samples. DNA from the serum of twenty-eight LD diagnosed patients was subjected to LD-specific and LS-specific PCR to reconfirm the presence of LD parasites and to detect LD-LS co-infections. RNA extracted from same samples was subjected to RT-PCR, qRT-PCR and sequencing using virus-specific primers to detect/identify and quantify the virus. The presence of the virus was confirmed in thirteen of eighteen (72%) recently collected VL and PKDL samples. Cytokine profiling showed significantly elevated IL-18 in only LD infected patients compared to the virus-positive LD and control samples. IL-18 is crucial for Th1 and macrophage activation which eventually clears the parasite. The Lepsey NLV1 interaction with the immune system results in reduced IL-18 which favors LD survival and increased parasitic burden. The study emphasizes the need to revisit LD pathogenesis in the light of the association and persistence of a protozoan virus in kala-azar and PKDL patients.

In and out: Leishmania metastasis by hijacking lymphatic system and migrating immune cells

The lymphatic system plays a crucial role in mounting immune response against intracellular pathogens, and recent studies have documented its role in facilitating tumor dissemination linked largely with cancer cells. However, in mucocutaneous leishmaniasis (MCL) caused by Leishmania Viannia subgenus showing infectious metastasis and resulting in severe distant secondary lesions, the route of escape of these parasites to secondary sites has not yet been investigated in detail. Our results demonstrated that when infection was associated with inflammation and additionally exacerbated by the presence of dsRNA viral endosymbiont (LRV1), lymphatic vessels could serve as efficient routes for infected cells to egress from the primary site and colonize distant organs. We challenged this hypothesis by using the intracellular Leishmania protozoan parasites Leishmania guyanensis (Lgy) associated with or without a dsRNA viral endosymbiont, exacerbating the infection and responsible for a strong inflammatory response, and favoring metastasis of the infection. We analyzed possible cargo cells and the routes of dissemination through flow cytometry, histological analysis, and in vivo imaging in our metastatic model to show that parasites disseminated not only intracellularly but also as free extracellular parasites using migrating immune cells, lymph nodes (LNs), and lymph vessels, and followed intricate connections of draining and non-draining lymph node to finally end up in the blood and in distant skin, causing new lesions.

Elimination of LRVs Elicits Different Responses in Leishmania spp

Leishmaniaviruses (LRVs) have been demonstrated to enhance progression of leishmaniasis, a vector-transmitted disease with a wide range of clinical manifestations that is caused by flagellates of the genus Leishmania. Here, we used two previously proposed strategies of the LRV ablation to shed light on the relationships of two Leishmania spp. with their respective viral species (L. guyanensis, LRV1 and L. major, LRV2) and demonstrated considerable difference between two studied systems. LRV1 could be easily eliminated by the expression of exogenous capsids regardless of their origin (the same or distantly related LRV1 strains, or even LRV2), while LRV2 was only partially depleted in the case of the native capsid overexpression. The striking differences were also observed in the effects of complete viral elimination with 2'C-methyladenosine (2-CMA) on the transcriptional profiles of these two Leishmania spp. While virtually no differentially expressed genes were detected after the LRV1 removal from L. guyanensis, the response of L. major after ablation of LRV2 involved 87 genes, the analysis of which suggested a considerable stress experienced even after several passages following the treatment. This effect on L. major was also reflected in a significant decrease of the proliferation rate, not documented in L. guyanensis and naturally virus-free strain of L. major. Our findings suggest that integration of L. major with LRV2 is deeper compared with that of L. guyanensis with LRV1. We presume this determines different effects of the viral presence on the Leishmania spp. infections.

IMPORTANCELeishmania spp. represent human pathogens that cause leishmaniasis, a widespread parasitic disease with mild to fatal clinical manifestations. Some strains of leishmaniae bear leishmaniaviruses (LRVs), and this has been shown to aggravate disease course. We investigated the relationships of two distally related Leishmania spp. with their respective LRVs using different strategies of virus removal. Our results suggest the South American L. guyanensis easily loses its virus with no important consequences for the parasite in the laboratory culture. Conversely, the Old-World L. major is refractory to virus removal and experiences a prominent stress if this removal is nonetheless completed. The drastically different levels of integration between the studied Leishmania spp. and their viruses suggest distinct effects of the viral presence on infections in these species of parasites.

Successful Isolation of Leishmania RNA Virus (LRV) from Leishmania major in a Cutaneous Leishmaniasis Focus in Central Iran: An Update on Cases

Purpose

Cutaneous leishmaniasis (CL) is a major vector-borne disease that affects people globally, including Iran. Different factors are associated with leishmaniasis pathogenicity; recently, a link of the possible relationship between Leishmania RNA Virus (LRV) and disease severity was proposed, especially in the New World leishmaniasis (NWL). This study was aimed to investigate the presence of LRV2 in Leishmania isolates in Aran o Bidgol, Isfahan province.

Methods

Samples were collected from 110 CL-suspected patients referred to the health center. In this study, we aimed to investigate CL cases (parasitologically and clinically), identify Leishmania species (by ITS1-PCR–RFLP), and finally detection of LRV2 (by RdRp-semi-nested PCR).

Results

Parasitological methods showed 60 positive cases, based on the HaeIII enzyme restriction profile, 59 cases were caused by L. major and 1 case by L. tropica. Our project is the first study on LRV2 isolation in Aran o Bidgol city and the LRV was successfully detected from a single L. major isolated in a women’s hand lesion. Using BLAST, 94.8–100% similarity was observed in the RdRp sequence of current LRV isolate with those available in GenBank from Iran or overseas.

Conclusion

L. major was the main cause of CL in Aran o Bidgol, although L. tropica is also present in a much lower proportion in the area. This is the first report on the presence of LRV2 in Aran o Bidgol and the fifth in Iran.

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.

Leishmania guyanensis M4147 as a new LRV1-bearing model parasite: Phosphatidate phosphatase 2-like protein controls cell cycle progression and intracellular lipid content

Leishmaniasis is a parasitic vector-borne disease caused by the protistan flagellates of the genus Leishmania. Leishmania (Viannia) guyanensis is one of the most common causative agents of the American tegumentary leishmaniasis. It has previously been shown that L. guyanensis strains that carry the endosymbiotic Leishmania RNA virus 1 (LRV1) cause more severe form of the disease in a mouse model than those that do not. The presence of the virus was implicated into the parasite's replication and spreading. In this respect, studying the molecular mechanisms of cellular control of viral infection is of great medical importance. Here, we report ~30.5 Mb high-quality genome assembly of the LRV1-positive L. guyanensis M4147. This strain was turned into a model by establishing the CRISPR-Cas9 system and ablating the gene encoding phosphatidate phosphatase 2-like (PAP2L) protein. The orthologue of this gene is conspicuously absent from the genome of an unusual member of the family Trypanosomatidae, Vickermania ingenoplastis, a species with mostly bi-flagellated cells. Our analysis of the PAP2L-null L. guyanensis showed an increase in the number of cells strikingly resembling the bi-flagellated V. ingenoplastis, likely as a result of the disruption of the cell cycle, significant accumulation of phosphatidic acid, and increased virulence compared to the wild type cells.

Increasing the Sensitivity of Leishmania RNA Virus 2 (LRV2) Detection with a Modification in cDNA Synthesis

OBJECTIVE

Leishmania RNA virus was detected the first time in the New World Leishmania species. Recent studies were also showed the presence of Leishmania RNA virus 2 (LRV2) in Old Word Leishmania species including Turkish L. major and L. tropica isolates. This study aimed to increase the sensitivity of qPCR with a modification in the denaturation step of cDNA preparation protocol.

METHODS

In this study, LRV2+ three L. major, two L. tropica strains and L. major control strain (MHOM/SU/73/5-ASKH) were included. Total RNA isolation was done using different numbers of Leishmania promastigotes (10⁸, 10⁵ and 10³). Before cDNA synthesis, samples were denatured at 95 °C for 2 min, as a modification of the kit procedure. qPCR was undertaken using 0.5 mM primers (LRV F-HR/LRV R-HR) diluted in SYBR Green Master mix.

RESULTS

We observed lower Ct values in amplicons with the modified version than with the classical kit protocol for cDNA synthesis, in all of the strains used in the study. The addition of pre-denaturation step at 95 °C showed lower Ct values meaning the sensitivity increased. Different parasite dilutions showed similar results.

CONCLUSION

It is important to increase the sensitivity especially with the aim for detecting LRV in clinical samples obtained from patients probably have less number of parasites. The presence and burden of the virus can help to understand the relationship between the clinical findings and the pathogenicity of the parasite which may lead to changes in the course of treatment.

The Dangerous Liaisons in the Oxidative Stress Response to Leishmania Infection

Leishmania parasites preferentially invade macrophages, the professional phagocytic cells, at the site of infection. Macrophages play conflicting roles in Leishmania infection either by the destruction of internalized parasites or by providing a safe shelter for parasite replication. In response to invading pathogens, however, macrophages induce an oxidative burst as a mechanism of defense to promote pathogen removal and contribute to signaling pathways involving inflammation and the immune response. Thus, oxidative stress plays a dual role in infection whereby free radicals protect against invading pathogens but can also cause inflammation resulting in tissue damage. The induced oxidative stress in parasitic infections triggers the activation in the host of the antioxidant response to counteract the damaging oxidative burst. Consequently, macrophages are crucial for disease progression or control. The ultimate outcome depends on dangerous liaisons between the infecting Leishmania spp. and the type and strength of the host immune response.

Molecular identification of Leishmania RNA virus in cutaneous leishmaniasis patients and rodent reservoirs in Isfahan province, Iran

Leishmania RNA virus (LRV) is a double-strand RNA virus that was first detected in members of the Leishmania viannia in the New World. The present study aimed to investigate the presence of LRV in the Leishmania species isolated from cutaneous leishmaniasis (CL) patients and rodents as reservoirs in Isfahan province an old zoonotic CL focus, center of Iran. Totally, 85 samples were collected from CL patients (n = 80) and rodent reservoirs (n = 5) from different regions of Isfahan province. Species identification was determined using the PCR-RFLP method. Viral dsRNA was extracted and for observation of 5.3 kb dsRNA on an agarose gel. The presence of LRV was surveyed using the Semi-nested PCR method. For phylogenetic analyzes, 6 samples of 13 isolates were sequenced and a phylogenetic tree was drawn by MEGA7 version 7.0.26. Of 80 Leishmania isolates recovered from the patients with CL, 79 and only one were identified as L. major and L. tropica, respectively. Also, the PCR assays detected four L. major and one L. turanica in five assessed Rhombomys opimus as the rodent reservoirs. LRV was detected only in Leishmania species isolated from 13 species of 85 (15.3%) CL including (L. major, n = 12) and (L. tropica, n = 1). Phylogenetic analysis showed that they were belonged to LRV2 and had the highest similarity with Iranian reference LRV2 in GenBank. Our results showed that the LRV2 was present in cutaneous Leishmania species in Isfahan province is the most historical and touristic province of Iran. In the study LRV was not reported from rodent reservoirs, it may be due to the small sample size. Phylogenetic analysis of current sequences demonstrated that these isolates belong to the registered LRV2 of the Old World.

Analyses of Leishmania-LRV Co-Phylogenetic Patterns and Evolutionary Variability of Viral Proteins

Leishmania spp. are important pathogens causing a vector-borne disease with a broad range of clinical manifestations from self-healing ulcers to the life-threatening visceral forms. Presence of Leishmania RNA virus (LRV) confers survival advantage to these parasites by suppressing anti-leishmanial immunity in the vertebrate host. The two viral species, LRV1 and LRV2 infect species of the subgenera Viannia and Leishmania, respectively. In this work we investigated co-phylogenetic patterns of leishmaniae and their viruses on a small scale (LRV2 in L. major) and demonstrated their predominant coevolution, occasionally broken by intraspecific host switches. Our analysis of the two viral genes, encoding the capsid and RNA-dependent RNA polymerase (RDRP), revealed them to be under the pressure of purifying selection, which was considerably stronger for the former gene across the whole tree. The selective pressure also differs between the LRV clades and correlates with the frequency of interspecific host switches. In addition, using experimental (capsid) and predicted (RDRP) models we demonstrated that the evolutionary variability across the structure is strikingly different in these two viral proteins.

Giardia duodenalis Induces Proinflammatory Cytokine Production in Mouse Macrophages via TLR9-Mediated p38 and ERK Signaling Pathways

Giardia duodenalis, also known as Giardia lamblia or Giardia intestinalis, is an important opportunistic, pathogenic, zoonotic, protozoan parasite that infects the small intestines of humans and animals, causing giardiasis. Several studies have demonstrated that innate immunity-associated Toll-like receptors (TLRs) are critical for the elimination of G. duodenalis; however, whether TLR9 has a role in innate immune responses against Giardia infection remains unknown. In the present study, various methods, including reverse transcriptase–quantitative polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, immunofluorescence, inhibitor assays, and small-interfering RNA interference, were utilized to probe the role of TLR9 in mouse macrophage-mediated defenses against G. lamblia virus (GLV)–free or GLV-containing Giardia trophozoites. The results revealed that in G. duodenalis–stimulated mouse macrophages, the secretion of proinflammatory cytokines, including interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and IL-12 p40, was enhanced, concomitant with the significant activation of TLR9, whereas silencing TLR9 attenuated the host inflammatory response. Notably, the presence of GLV exacerbated the secretion of host proinflammatory cytokines. Moreover, G. duodenalis stimulation activated multiple signaling pathways, including the nuclear factor κB p65 (NF-κB p65), p38, ERK, and AKT pathways, the latter three in a TLR9-dependent manner. Additionally, inhibiting the p38 or ERK pathway downregulated the G. duodenalis–induced inflammatory response, whereas AKT inhibition aggravated this process. Taken together, these results indicated that G. duodenalis may induce the secretion of proinflammatory cytokines by activating the p38 and ERK signaling pathways in a TLR9-dependent manner in mouse macrophages. Our in vitro findings on the mechanism underlying the TLR9-mediated host inflammatory response may help establish the foundation for an in-depth investigation of the role of TLR9 in the pathogenicity of G. duodenalis.

The Maze Pathway of Coevolution: A Critical Review over the Leishmania and Its Endosymbiotic History

The description of the genus Leishmania as the causative agent of leishmaniasis occurred in the modern age. However, evolutionary studies suggest that the origin of Leishmania can be traced back to the Mesozoic era. Subsequently, during its evolutionary process, it achieved worldwide dispersion predating the breakup of the Gondwana supercontinent. It is assumed that this parasite evolved from monoxenic Trypanosomatidae. Phylogenetic studies locate dixenous Leishmania in a well-supported clade, in the recently named subfamily Leishmaniinae, which also includes monoxenous trypanosomatids. Virus-like particles have been reported in many species of this family. To date, several Leishmania species have been reported to be infected by Leishmania RNA virus (LRV) and Leishbunyavirus (LBV). Since the first descriptions of LRVs decades ago, differences in their genomic structures have been highlighted, leading to the designation of LRV1 in L. (Viannia) species and LRV2 in L. (Leishmania) species. There are strong indications that viruses that infect Leishmania spp. have the ability to enhance parasitic survival in humans as well as in experimental infections, through highly complex and specialized mechanisms. Phylogenetic analyses of these viruses have shown that their genomic differences correlate with the parasite species infected, suggesting a coevolutionary process. Herein, we will explore what has been described in the literature regarding the relationship between Leishmania and endosymbiotic Leishmania viruses and what is known about this association that could contribute to discussions about the worldwide dispersion of Leishmania.

The antioxidant response favors Leishmania parasites survival, limits inflammation and reprograms the host cell metabolism

The oxidative burst generated by the host immune system can restrict intracellular parasite entry and growth. While this burst leads to the induction of antioxidative enzymes, the molecular mechanisms and the consequences of this counter-response on the life of intracellular human parasites are largely unknown. The transcription factor NF-E2-related factor (NRF2) could be a key mediator of antioxidant signaling during infection due to the entry of parasites. Here, we showed that NRF2 was strongly upregulated in infection with the human Leishmania protozoan parasites, its activation was dependent on a NADPH oxidase 2 (NOX2) and SRC family of protein tyrosine kinases (SFKs) signaling pathway and it reprogrammed host cell metabolism. In inflammatory leishmaniasis caused by a viral endosymbiont inducing TNF-α in chronic leishmaniasis, NRF2 activation promoted parasite persistence but limited TNF-α production and tissue destruction. These data provided evidence of the dual role of NRF2 in protecting both the invading pathogen from reactive oxygen species and the host from an excess of the TNF-α destructive pro-inflammatory cytokine.

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.

Presence and diversity of Leishmania RNA virus in an old zoonotic cutaneous leishmaniasis focus, northeastern Iran: haplotype and phylogenetic based approach

OBJECTIVE

Leishmania RNA virus (LRV) is a double-stranded RNA (dsRNA) virus that circulates within many species of the Leishmania parasite. In this study, we aimed to investigate the presence of LRV2 circulating in Leishmania isolates in an old focus of ZCL located in northeastern of Iran.

METHODS

Leishmania isolates were collected from 85 patients that confirmed to have cutaneous leishmaniasis (CL) based on parasitological examination. To identify the Leishmania isolates, species-specific primer sets were applied for molecular identification. The presence of LRV2 was performed by RdRp-semi nested-PCR. The genetic diversity were calculated using MEGA and DnaSP. To assess haplotype diversity, 31 LRV2 strains in different regions were surveyed using analysis a 292-bp section of the RdRp sequences.

RESULTS

Out of 85 patients, 83 (97.6 %) were diagnosed with L. major and 2 (2.4 %) with L. tropica. LRV2 virus was detected in 59 (69.4%) of the CL cases. For the first time, LRV2 was reported in one L. tropica strain in Iran. The current LRV2 sequences indicated the highest similarities to an Old World LRV2. Moreover, 10 unique haplotypes were identified based on the analyzed sequences of the RdRp gene.

CONCLUSIONS

Our results indicated the highest occurrence of Leishmania/LRV2 co-circulation in this known ZCL focus from northeastern Iran. Phylogenetic analyses of LRV2 sequences confirmed that these isolates belong to the order of LRV2 from the Old World. This study offered an insight into LRV2 haplotype that the informative issue can be used for genetic research of LRV2 in other regions.

Cutaneous leishmaniasis in the 21st century: from the laboratory to the bedside

PURPOSE OF REVIEW

Despite modern advances in molecular diagnostic tools and a better understanding of its complex pathophysiology, cutaneous leishmaniasis, a neglected tropical disease, remains a major global health problem. Laboratory methods to inform prognosis and treatment are not widely available, the therapeutic options are limited and have significant adverse effects, and emergence of drug resistance is a further complication. New advances in the understanding of the role of Leishmania RNA virus (LRV) as a prognostic factor, speciation methods and antimicrobial resistance testing and their limitations will be discussed.

RECENT FINDINGS

LRV, an intracytoplasmic endosymbiont found mostly in Leishmania spp. associated with more severe disease, appears to play a role in modulating the host immune response and has been associated with treatment failure in some Viannia subgenus species. Proper speciation is an important guide to management. However, recent findings have demonstrated significant heterogeneity of results related to differences in genotyping methods.

SUMMARY

Recognition of the role of LRV in immune modulation and response to treatment along with more accessible tools for its detection to guide management at the bedside should allow a better individualized approach. Improving accessibility and standardization of speciation methods and antimicrobial susceptibility testing should be major goals to improve cutaneous leishmaniasis management in the 21st century.

Viral Double-Stranded RNA Detection by DNase I and Nuclease S1 digestions in Leishmania parasites

Many RNA viruses are found in protozoan parasites. They can be responsible for more serious pathology or treatment failure. For the detection of viral double-stranded RNA (dsRNA), sequence-dependent and -independent methods are available, such as quantitative real-time PCR and immunofluorescence, dot blot, ELISA or sequencing. The technique presented here is sequence-independent and is well detailed in the following protocol, taking the example of Leishmania RNA virus (LRV) in Leishmania guyanensis (Lgy) species. To summarise, the protocol is divided into four major steps: RNA extraction from the parasites, RNA purification, enzymatic digestions with DNase I and Nuclease S1, and visualization by gel electrophoresis. This method can be used to detect other viral dsRNA in other parasites. It provides an additional tool, complementary to other techniques previously cited and it is easy and quite fast to achieve.

Relationship of Leishmania RNA Virus (LRV) and treatment failure in clinical isolates of Leishmania major

OBJECTIVE

Leishmaniasis is caused by different Leishmania spp. Treatment failure (TF) of cutaneous leishmaniasis (CL) is a serious issue that may be due to various reasons, previous studies suggested Leishmania RNA virus (LRV) as a potential cause of TF. Two variant groups of LRV1 and LRV2 are reported. In this study, the presence of LRV1/LRV2 was compared in TF with treatment response (TR) isolates of L. major. Clinical isolates of 15 TF and 15 TR were collected from CL patients referred to the Health Centers of Isfahan. Genomic DNA was extracted to identify Leishmania spp. using ITS1-PCR-RFLP. Identification of LRV1/LRV2 was performed using SYBR Green Real-Time PCR. The statistical analysis to test relationship between the treatment response with Glucantime and the presence of LRV were performed using SPSS 16.0 with Fisher's Exact test. P value of less than 0.05 was considered significant.

RESULTS

ITS1-PCR-RFLP results showed that every isolate was identified as L. major. The results showed no LRV1 in any of the samples but 7 TR isolates and 2 TF isolates showed positive for LRV2. Statistical analysis showed no significant difference between the presence of LRV2 and response to Glucantime (p-value = 0.1086). Therefore, other mechanisms might be responsible for TF.

The First Non-LRV RNA Virus in Leishmania

In this work, we describe the first Leishmania-infecting leishbunyavirus-the first virus other than Leishmania RNA virus (LRV) found in trypanosomatid parasites. Its host is Leishmania martiniquensis, a human pathogen causing infections with a wide range of manifestations from asymptomatic to severe visceral disease. This virus (LmarLBV1) possesses many characteristic features of leishbunyaviruses, such as tripartite organization of its RNA genome, with ORFs encoding RNA-dependent RNA polymerase, surface glycoprotein, and nucleoprotein on L, M, and S segments, respectively. Our phylogenetic analyses suggest that LmarLBV1 originated from leishbunyaviruses of monoxenous trypanosomatids and, probably, is a result of genomic re-assortment. The LmarLBV1 facilitates parasites' infectivity in vitro in primary murine macrophages model. The discovery of a virus in L. martiniquensis poses the question of whether it influences pathogenicity of this parasite in vivo, similarly to the LRV in other Leishmania species.

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.

Molecular Characterization of Leishmania RNA virus 2 in Leishmania major from Uzbekistan

Here we report sequence and phylogenetic analysis of two new isolates of Leishmania RNA virus 2 (LRV2) found in Leishmania major isolated from human patients with cutaneous leishmaniasis in south Uzbekistan. These new virus-infected flagellates were isolated in the same region of Uzbekistan and the viral sequences differed by only nineteen SNPs, all except one being silent mutations. Therefore, we concluded that they belong to a single LRV2 species. New viruses are closely related to the LRV2-Lmj-ASKH documented in Turkmenistan in 1995, which is congruent with their shared host (L. major) and common geographical origin.

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.

An NFκB Activity Calculator to Delineate Signaling Crosstalk: Type I and II Interferons Enhance NFκB via Distinct Mechanisms

Nuclear factor kappa B (NFκB) is a transcription factor that controls inflammation and cell survival. In clinical histology, elevated NFκB activity is a hallmark of poor prognosis in inflammatory disease and cancer, and may be the result of a combination of diverse micro-environmental constituents. While previous quantitative studies of NFκB focused on its signaling dynamics in single cells, we address here how multiple stimuli may combine to control tissue level NFκB activity. We present a novel, simplified model of NFκB (SiMoN) that functions as an NFκB activity calculator. We demonstrate its utility by exploring how type I and type II interferons modulate NFκB activity in macrophages. Whereas, type I IFNs potentiate NFκB activity by inhibiting translation of IκBα and by elevating viral RNA sensor (RIG-I) expression, type II IFN amplifies NFκB activity by increasing the degradation of free IκB through transcriptional induction of proteasomal cap components (PA28). Both cross-regulatory mechanisms amplify NFκB activation in response to weaker (viral) inducers, while responses to stronger (bacterial or cytokine) inducers remain largely unaffected. Our work demonstrates how the NFκB calculator can reveal distinct mechanisms of crosstalk on NFκB activity in interferon-containing microenvironments.

How to master the host immune system? Leishmania parasites have the solutions!

Infection by protozoan parasites of the genus Leishmania results in the development of leishmaniasis, an increasingly prevalent group of diseases affecting over 12 million people worldwide. Leishmaniasis can have very different outcomes ranging from cutaneous lesions, mucosal lesions to visceralization depending on the species of the infecting parasite and on the immune response developed by the host. As an obligate intracellular parasite, residing within macrophages, Leishmania evolved in strict contact with the host immune system, developing different mechanisms to evade or modulate the immune response. Various types of immune responses are observed during different Leishmania spp. infections, resulting in parasite clearance but also contributing to the pathogenesis, thus increasing the complexity of the course of the disease. Interestingly, depending on the type of leishmaniasis developed, opposite treatment strategies, which either boost or inhibit the inflammatory response, have shown efficacy. In this review, we summarize the contribution of different immune cell types to the development of the anti-leishmanial immune response and the parasite strategies to evade and modulate host immunity. Further, we discuss the involvement of co-infecting pathogens in the determination of the outcome of leishmaniasis and on the effectiveness of treatment and the implication of the immune response for treatment and vaccine development.

Cutaneous Leishmaniasis Due to Leishmania aethiopica

Leishmania aethiopica is the main causative species for cutaneous leishmaniasis (CL) in Ethiopia. Despite its considerable burden, L. aethiopica has been one of the most neglected Leishmania species. In this review, published evidence on L. aethiopica history, geography, vector, reservoir, epidemiology, parasitology, and immunology is discussed and knowledge gaps are outlined. L. aethiopica endemic regions are limited to the highland areas, although nationwide studies on CL prevalence are lacking. Phlebotomus pedifer and P. longipes are the sandfly vectors and hyraxes are considered to be the main reservoir, but the role of other sandfly species and other potential reservoirs requires further investigation. Where and how transmission occurs exactly are also still unknown. Most CL patients in Ethiopia are children and young adults. Lesions are most commonly on the face, in contrast to CL caused by other Leishmania species which may more frequently affect other body parts. CL lesions caused by L. aethiopica seem atypical and more severe in their presentation as compared to other Leishmania species. Mucocutaneous leishmaniasis and diffuse cutaneous leishmaniasis are relatively common, and healing of lesions caused by L. aethiopica seems to take longer than that of other species. A thorough documentation of the natural evolution of L. aethiopica as well as in depth studies into the immunological and parasitological characteristics that underpin the atypical and severe clinical presentation are needed. Better understanding of CL caused by this parasite species will contribute to interventions related to transmission, prevention, and treatment.

RNA Viruses in Blechomonas (Trypanosomatidae) and Evolution of Leishmaniavirus

In this work, we analyzed viral prevalence in trypanosomatid parasites (Blechomonas spp.) infecting Siphonaptera and discovered nine species of viruses from three different groups (leishbunyaviruses, narnaviruses, and leishmaniaviruses). Most of the flagellate isolates bore two or three viral types (mixed infections). Although no new viral groups were documented in Blechomonas spp., our findings are important for the comprehension of viral evolution. The discovery of bunyaviruses in blechomonads was anticipated, since these viruses have envelopes facilitating their interspecific transmission and have already been found in various trypanosomatids and metatranscriptomes with trypanosomatid signatures. In this work, we also provided evidence that even representatives of the family Narnaviridae are capable of host switching and evidently have accomplished switches multiple times in the course of their evolution. The most unexpected finding was the presence of leishmaniaviruses, a group previously solely confined to the human pathogens Leishmania spp. From phylogenetic inferences and analyses of the life cycles of Leishmania and Blechomonas, we concluded that a common ancestor of leishmaniaviruses most likely infected Leishmania first and was acquired by Blechomonas by horizontal transfer. Our findings demonstrate that evolution of leishmaniaviruses is more complex than previously thought and includes occasional host switching.IMPORTANCE Flagellates belonging to the genus Leishmania are important human parasites. Some strains of different Leishmania species harbor viruses (leishmaniaviruses), which facilitate metastatic spread of the parasites, thus aggravating the disease. Up until now, these viruses were known to be hosted only by Leishmania Here, we analyzed viral distribution in Blechomonas, a related group of flagellates parasitizing fleas, and revealed that they also bear leishmaniaviruses. Our findings shed light on the entangled evolution of these viruses. In addition, we documented that Blechomonas can be also infected by leishbunyaviruses and narnaviruses, viral groups known from other insects' flagellates.

Evolutionary origin of 2A-like sequences in Totiviridae genomes

In recent years there has been a significant increase in the number of new species potentially belonging to the Totiviridae family. Most of these new viruses have not yet been covered by the Committee on Taxonomy of Viruses (ICTV) official classification. In this study, a phylogenetic analysis including new sequences of Totiviridae candidates revealed a clade including Giardiavirus and a great diversity of new totiviruses, which infect arthropods, protozoa and mollusc. This expanded Giardiavirus clade comprises two monophyletic groups, one of them including Giardia lamblia virus (GLV) grouped with viruses that infect arthropods and vertebrates (GLV-like group), and the other includes the previously proposed Artivirus group (IMNV-like group). A screening of the members of the GLV-like group in search of genomic elements already described in IMNV-like group revealed the existence of sites with a high propensity to become 2 A-like oligopeptides, mainly in a specific subgroup of arthropod viruses, suggesting that these viruses preserved ancestral characteristics. The existence of these "pseudo 2 A-sites" associated to phylogenetic reconstruction indicates that these sequences appear at a decisive stage for viral evolution. If they are changed to functional 2 A-like sequences, an irreversible route to increase the genome complexity will be initiated.

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.

The criminal association of Leishmania parasites and viruses

In nature, humans infected with protozoan parasites can encounter viruses, which could alter their host immune response. The impact of viruses on human parasitic diseases remains largely unexplored due to the highly sterilized environment in experimental studies and the difficulty to draw a correlation between co-infection and pathology. Recent studies show that viral infections exacerbate pathology and promote dissemination of some Leishmania infections, based on a hyper-inflammatory reaction driven by type I interferons. Thus, not only the infecting parasite species, but also bystander viral infections could be a major determinant of the outcome of Leishmania infection. In this review, we focus on the contribution of viral co-infection to the exacerbation of leishmaniasis's pathology and its possible impact on treatment and vaccination strategies.

The Binomial Parasite-Host Immunity in the Healing Process and in Reactivation of Human Tegumentary Leishmaniasis

Leishmaniasis is a vector-borne infectious disease caused by different species of protozoa from the Leishmania genus. Classically, the disease can be classified into two main clinical forms: Visceral (VL) and Tegumentary (TL) leishmaniasis. TL is a skin/mucosal granulomatous disease that manifests mainly as cutaneous localized or disseminated ulcers, papules diffusely distributed, mucosal lesions or atypical lesions. Once the etiology of the infection is confirmed, treatment can take place, and different drugs can be administered. It has already been shown that, even when the scar is clinically evident, inflammation is still present in the native tissue, and the decrease of the inflammatory process occurs slowly during the 1st years after clinical healing. The maintenance of residual parasites in the scar tissue is also well documented. Therefore, it is no longer a surprise that, under some circumstances, therapeutic failure and/or lesion reactivation occurs. All over the years, an impressive amount of data on relapses, treatment resistance and lesion reactivation after healing has been collected, and several factors have been pointed out as having a role in the process. Different factors such as Leishmania species, parasite variability, Leishmania RNA virus 1, parasite load, parasite persistence, age, nutritional status, gender, co-morbidities, co-infection, pregnancy, immunosuppression, lesion duration, number and localization of lesions, drug metabolism, irregular treatment and individual host cellular immune response were described and discussed in the present review. Unfortunately, despite this amount of information, a conclusive understanding remains under construction. In addition, multifactorial influence cannot be discarded. In this context, knowing why leishmaniasis has been difficult to treat and control can help the development of new approaches, such as drugs and immunotherapy in order to improve healing maintenance. In this sense, we would like to highlight some of the findings that may influence the course of Leishmania infection and the therapeutic response, with an emphasis on TL.

New insights into the genetic diversity of Leishmania RNA Virus 1 and its species-specific relationship with Leishmania parasites

Cutaneous leishmaniasis is a neglected parasitic disease that manifests in infected individuals under different phenotypes, with a range of factors contributing to its broad clinical spectrum. One factor, Leishmania RNA Virus 1 (LRV1), has been described as an endosymbiont present in different species of Leishmania. LRV1 significantly worsens the lesion, exacerbating the immune response in both experimentally infected animals and infected individuals. Little is known about the composition and genetic diversity of these viruses. Here, we investigated the relationship between the genetic composition of LRV1 detected in strains of Leishmania (Viannia) braziliensis and L. (V.) guyanensis and the interaction between the endosymbiont and the parasitic species, analyzing an approximately 850 base pair region of the viral genome. We also included one LRV1 sequence detected in L. (V.) shawi, representing the first report of LRV1 in a species other than L. braziliensis and L. guyanensis. The results illustrate the genetic diversity of the LRV1 strains analyzed here, with smaller divergences detected among viral sequences from the same parasite species. Phylogenetic analyses showed that the LRV1 sequences are grouped according to the parasite species and possibly according to the population of the parasite in which the virus was detected, corroborating the hypothesis of joint evolution of the viruses with the speciation of Leishmania parasites.

PD-L1 May Mediate T-Cell Exhaustion in a Case of Early Diffuse Leishmaniasis Caused by Leishmania (L.) amazonensis

Introduction

Diffuse cutaneous leishmaniasis (DCL) is a rare disease form associated with Leishmania (L.) amazonensis in South America. It represents the “anergic” pole of American Tegumentary Leishmaniasis, and the explanation for its resistance to treatment remains elusive. We aimed to study some possible immunological mechanisms involved in the poor DCL treatment response by evaluating some cell surface molecules obtained from a patient with DCL by flow cytometry.

Case presentation

A 65-year-old DCL patient who initially failed to respond to the standard treatment for the disease showed vacuolated macrophages filled with amastigotes in lesion biopsy, and L. (L.) amazonensis was identified through ITS1PCR amplification. The Leishmania skin test and indirect immunofluorescence analysis revealed negative results. Peripheral blood from the patient was collected after a few months of treatment, when the patient presented with no lesion. Peripheral blood mononuclear cells were analyzed ex vivo and in vitro after 48 h of stimulation with soluble L. (L.) amazonensis antigen (SLA). Cell death, surface molecules, and intracellular molecules, such as IFN-γ and granzyme B, were analyzed in the cells using flow cytometry. Analysis of the surface markers showed an increased expression of the inhibitory molecule programmed death ligand 1 (PD-L1) in the monocytes restimulated with SLA (approximately 65%), whereas the negative controls were 35% positive for PD-L1. Conversely, compared with the negative controls, we observed a decrease in CD4⁺IFN-γ⁺ T cells (8.32 versus 1.7%) and CD8⁺IFN-γ⁺ T cells (14% versus 1%). We also observed a relevant decrease in the granzyme B levels in the CD8⁺ T cells, from 31% in the negative controls to 5% after SLA restimulation.

Conclusion

The dysfunctional activation of PD-L1 inhibitory pathway after Leishmania antigen stimulation and reduced levels of IFN-gamma and granzyme B-producing cells could be closely related to unresponssiveness to standard drug treatment of DCL patient.