Leishmania RNA virus: when the host pays the toll

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.

Proteome profiling of cutaneous leishmaniasis lesions due to dermotropic Leishmania donovani in Sri Lanka

BACKGROUND

Characterization of the host response in cutaneous leishmaniasis (CL) through proteome profiling has gained limited insights into leishmaniasis research compared to that of the parasite. The primary objective of this study was to comprehensively analyze the proteomic profile of the skin lesions tissues in patients with CL, by mass spectrometry, and subsequent validation of these findings through immunohistochemical methods.

METHODS

Eight lesion specimens from leishmaniasis-confirmed patients and eight control skin biopsies were processed for proteomic profiling by mass spectrometry. Formalin-fixed paraffin-embedded lesion specimens from thirty patients and six control skin specimens were used for Immunohistochemistry (IHC) staining. Statistical analyses were carried out using SPSS software. The chi-square test was used to assess the association between the degree of staining for each marker and the clinical and pathological features.

RESULTS

Sixty-seven proteins exhibited significant differential expression between tissues of CL lesions and healthy controls (p < 0.01), representing numerous enriched biological processes within the lesion tissue, as evident by both the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Reactome databases. Among these, the integrated endoplasmic reticulum stress response (IERSR) emerges as a pathway characterized by the up-regulated proteins in CL tissues compared to healthy skin. Expression of endoplasmic reticulum (ER) stress sensors, inositol-requiring enzyme-1 (IRE1), protein kinase RNA-like ER kinase (PERK) and activating transcription factor 6 (ATF6) in lesion tissue was validated by immunohistochemistry.

CONCLUSIONS

In conclusion, proteomic profiling of skin lesions carried out as a discovery phase study revealed a multitude of probable immunological and pathological mechanisms operating in patients with CL in Sri Lanka, which needs to be further elaborated using more in-depth and targeted investigations. Further research exploring the intricate interplay between ER stress and CL pathophysiology may offer promising avenues for the development of novel diagnostic tools and therapeutic strategies in combating this disease.

Revolutionizing Leishmaniasis Treatment with Cutting Edge Drug Delivery Systems and Nanovaccines: An Updated Review

Leishmaniasis, one of the most overlooked tropical diseases, is a life-threatening illness caused by the parasite Leishmania donovani that is prevalent in underdeveloped nations. Over 350 million individuals in more than 90 different nations worldwide are at risk of contracting the disease, which has a current fatality rate of 50 000 mortalities each year. The administration of liposomal Amp B, pentavalent antimonials, and miltefosine are still considered integral components of the chemotherapy regimen. Antileishmanial medications fail to treat leishmaniasis because of their numerous drawbacks. These include inadequate effectiveness, toxicity, undesired side effects, drug resistance, treatment duration, and cost. Consequently, there is a need to overcome the limitations of conventional therapeutics. Nanotechnology has demonstrated promising outcomes in addressing these issues because of its small size and distinctive characteristics, such as enhanced bioavailability, lower toxicity, biodegradability, and targeted drug delivery. This review is an effort to highlight the recent progress in various nanodrug delivery systems (nDDSs) over the past five years for treating leishmaniasis. Although the preclinical outcomes of nDDSs have shown promising treatment for leishmaniasis, further research is needed for their clinical translation. Advancement in three primary priority domains─molecular diagnostics, clinical investigation, and knowledge dissemination and standardization─is imperative to propel the leishmaniasis field toward translational outcomes.

Visceral Leishmaniasis in a Twin Pregnancy: A Case Report and Review of the Literature

Visceral leishmaniasis (VL), often referred to as kala-azar, is quite rare in developed countries during pregnancy. Only few studies have evaluated its impact on perinatal outcome. It is caused primarily by Leishmania donovani or Leishmania infantum and presents with a wide spectrum of clinical manifestations from cutaneous ulcers to multisystem disease. Differential diagnosis is challenging as symptoms and signs are insidious, mimicking other diseases. Misdiagnosis can result in severe adverse perinatal outcomes, even maternal/neonatal death. Early treatment with liposomal amphotericin-B (LAmB) is currently the first choice with adequate effectiveness. We report a rare case of VL in a twin pregnancy with onset at the second trimester, presenting with periodic fever with rigors, right flank pain, and gradual dysregulation of all three cell lines. The positive rK39 enzyme-linked immunosorbent assay test confirmed the diagnosis. Treatment with LAmB resulted in clinical improvement within 48 h and in the delivery of two late-preterm healthy neonates with no symptoms or signs of vertical transmission. The one-year follow-up, of the mother and the neonates, was negative for recurrence. To our knowledge, this is the first reported case of VL in a twin pregnancy, and consequently treatment and perinatal outcome are of great importance.

Live attenuated-nonpathogenic Leishmania and DNA structures as promising vaccine platforms against leishmaniasis: innovations can make waves

Leishmaniasis is a vector-borne disease caused by the protozoan parasite of Leishmania genus and is a complex disease affecting mostly tropical regions of the world. Unfortunately, despite the extensive effort made, there is no vaccine available for human use. Undoubtedly, a comprehensive understanding of the host-vector-parasite interaction is substantial for developing an effective prophylactic vaccine. Recently the role of sandfly saliva on disease progression has been uncovered which can make a substantial contribution in vaccine design. In this review we try to focus on the strategies that most probably meet the prerequisites of vaccine development (based on the current understandings) including live attenuated/non-pathogenic and subunit DNA vaccines. Innovative approaches such as reverse genetics, CRISP/R-Cas9 and antibiotic-free selection are now available to promisingly compensate for intrinsic drawbacks associated with these platforms. Our main goal is to call more attention toward the prerequisites of effective vaccine development while controlling the disease outspread is a substantial need.

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.

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.

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.

Factors associated with mucosal involvement in tegumentary leishmaniasis: a nation-based study using surveillance data from Brazil

This study aimed to assess the factors associated with mucosal leishmaniasis (ML) within the scope of tegumentary leishmaniasis (TL) cases reported in Brazil. Surveillance data were assessed, and comparisons were made between ML and cutaneous leishmaniasis (CL) cases. Additionally, ML incidence rates for municipalities were depicted through a geographic information system. From 2007 to 2017, 235,489 TL cases were reported, of which 235,232 were classified as follows: 14,204 (6%) were ML cases and 221,028 (94%) were CL cases. Multivariate analysis showed that the proportion of ML cases reached 16.8% among individuals >75 years (adjusted OR = 2.77; 95% CI = 2.41-3.19; p < 0.001), and ML was also more frequent among males (aOR = 1.28; 95% CI = 1.20-1.38; p < 0.001), HIV-positive patients (aOR = 2.15; 95% CI = 1.80-2.56; p < 0.001), patients residing in urban areas (aOR = 1.52; 95% CI = 1.43-1.62; p < 0.001), and imported cases (with respect to county) when compared to autochthonous cases (aOR = 1.84; 95% CI = 1.71-1.98; p < 0.001). A lower proportion of positive results in direct parasitological examinations was observed in ML cases (32.6% vs. 60.8%; p < 0.001). The leishmanin skin test results were more often positive in ML cases (41.7% vs. 25.9%; p < 0.001). In ML, compatible changes in histopathology were more frequent (14.6% vs. 3.9%; p < 0.001). A greater proportion of ML cases were treated with amphotericin B (6.9% vs. 0.9%; p < 0.001). The case-fatality rate was higher in ML (0.6% vs. 0.1%; p < 0.001). A higher incidence of ML was observed in a geographical band extending across the Amazon region from the southern Para State to the Acre State. ML exhibited varying frequencies within specific populations. The definition of predictable factors predisposing Leishmania-infected subjects to develop ML is important for defining strategies to mitigate the mucosal damage caused by leishmaniasis.

Systematic Review of Treatment Failure and Clinical Relapses in Leishmaniasis from a Multifactorial Perspective: Clinical Aspects, Factors Associated with the Parasite and Host

Leishmaniasis is a disease caused by protozoa of the genus Leishmania. Treatment options are limited, and there are frequent cases of treatment failure and clinical relapse. To understand these phenomena better, a systematic review was conducted, considering studies published between 1990 and 2021 in Portuguese, English, and Spanish. The review included 64 articles divided into three categories. Case reports (26 articles) focused on treatment failure and clinical relapse in cutaneous leishmaniasis patients (47.6%), primarily affecting males (74%) and children (67%), regardless of the clinical manifestation. Experimental studies on the parasite (19 articles), particularly with L. major (25%), indicated that alterations in DNA and genic expression (44.82%) played a significant role in treatment failure and clinical relapse. Population data on the human host (19 articles) identified immunological characteristics as the most associated factor (36%) with treatment failure and clinical relapse. Each clinical manifestation of the disease presented specificities in these phenomena, suggesting a multifactorial nature. Additionally, the parasites were found to adapt to the drugs used in treatment. In summary, the systematic review revealed that treatment failure and clinical relapse in leishmaniasis are complex processes influenced by various factors, including host immunology and parasite adaptation.

Clinical and immunological spectra of human cutaneous leishmaniasis in North Africa and French Guiana

Cutaneous leishmaniasis (CL) caused by infection with the parasite Leishmania exhibits a large spectrum of clinical manifestations ranging from single healing to severe chronic lesions with the manifestation of resistance or not to treatment. Depending on the specie and multiple environmental parameters, the evolution of lesions is determined by a complex interaction between parasite factors and the early immune responses triggered, including innate and adaptive mechanisms. Moreover, lesion resolution requires parasite control as well as modulation of the pathologic local inflammation responses and the initiation of wound healing responses. Here, we have summarized recent advances in understanding the in situ immune response to cutaneous leishmaniasis: i) in North Africa caused by Leishmania (L.) major, L. tropica, and L. infantum, which caused in most cases localized autoresolutives forms, and ii) in French Guiana resulting from L. guyanensis and L. braziliensis, two of the most prevalent strains that may induce potentially mucosal forms of the disease. This review will allow a better understanding of local immune parameters, including cellular and cytokines release in the lesion, that controls infection and/or protect against the pathogenesis in new world compared to old world CL.

Field-Deployable Treatments For Leishmaniasis: Intrinsic Challenges, Recent Developments and Next Steps

Leishmaniasis is a neglected tropical disease endemic primarily to low- and middle-income countries, for which there has been inadequate development of affordable, safe, and efficacious therapies. Clinical manifestations of leishmaniasis range from self-healing skin lesions to lethal visceral infection with chances of relapse. Although treatments are available, secondary effects limit their use outside the clinic and negatively impact the quality of life of patients in endemic areas. Other non-medicinal treatments, such as thermotherapies, are limited to use in patients with cutaneous leishmaniasis but not with visceral infection. Recent studies shed light to mechanisms through which Leishmania can persist by hiding in cellular safe havens, even after chemotherapies. This review focuses on exploring the cellular niches that Leishmania parasites may be leveraging to persist within the host. Also, the cellular, metabolic, and molecular implications of Leishmania infection and how those could be targeted for therapeutic purposes are discussed. Other therapies, such as those developed against cancer or for manipulation of the ferroptosis pathway, are proposed as possible treatments against leishmaniasis due to their mechanisms of action. In particular, treatments that target hematopoietic stem cells and monocytes, which have recently been found to be necessary components to sustain the infection and provide a safe niche for the parasites are discussed in this review as potential field-deployable treatments against leishmaniasis.

Dosing implications for liposomal amphotericin B in pregnancy

Liposomal amphotericin B (LAmB) is used in the treatment of opportunistic fungal and parasitic infections, including leishmaniasis. Given its lack of known teratogenicity in pregnancy, LAmB is a preferred agent for treatment for these patients. However, significant gaps remain in determining optimal dosing regimens for LAmB in pregnancy. We describe the use of LAmB for a pregnant patient with mucocutaneous leishmaniasis (MCL) using a dosing strategy of 5 mg/kg/day for days 1-7 using ideal body weight followed by 4 mg/kg weekly using adjusted body weight. We reviewed the literature for LAmB dosing strategies, particularly dosing weight, in pregnancy. Of the 143 cases identified in 17 studies, only one reported a dosing weight, in which ideal body weight was used. Five Infectious Diseases Society of America guidelines in total discussed the use of amphotericin B in pregnancy but no guidelines included recommendations for dosing weight. This review describes our experience in using ideal body weight for dosing LAmB in pregnancy for the treatment of MCL. Use of ideal body weight may minimize risk of adverse effects to the fetus compared to the use of total body weight while maintaining efficacy for treatment of MCL in pregnancy.

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.

Cryptosporidium uses CSpV1 to activate host type I interferon and attenuate antiparasitic defenses

Cryptosporidium infects gastrointestinal epithelium and is a leading cause of infectious diarrhea and diarrheal-related death in children worldwide. There are no vaccines and no fully effective therapy available for the infection. Type II and III interferon (IFN) responses are important determinants of susceptibility to infection but the role for type I IFN response remains obscure. Cryptosporidium parvum virus 1 (CSpV1) is a double-stranded RNA (dsRNA) virus harbored by Cryptosporidium spp. Here we show that intestinal epithelial conditional Ifnar1^-/- mice (deficient in type I IFN receptor) are resistant to C. parvum infection. CSpV1-dsRNAs are delivered into host cells and trigger type I IFN response in infected cells. Whereas C. parvum infection attenuates epithelial response to IFN-γ, loss of type I IFN signaling or inhibition of CSpV1-dsRNA delivery can restore IFN-γ-mediated protective response. Our findings demonstrate that type I IFN signaling in intestinal epithelial cells is detrimental to intestinal anti-C. parvum defense and Cryptosporidium uses CSpV1 to activate type I IFN signaling to evade epithelial antiparasitic response.

In vitro miltefosine and amphotericin B susceptibility of strains and clinical isolates of Leishmania species endemic in Brazil that cause tegumentary leishmaniasis

Tegumentary leishmaniasis encompasses a spectrum of clinical manifestations caused by the parasitic protozoa of the genus Leishmania. In Brazil, there are at least seven Leishmania species that are endemic and responsible for this set of clinical manifestations of the disease. Current treatment is limited to a restricted number of drugs that in general have several drawbacks including parenteral use, toxicity, and severe side effects. Amphotericin B is considered a second-line drug for tegumentary leishmaniasis in Brazil, while miltefosine was recently approved for clinical use in the treatment of this disease. In this study, we investigated the in vitro susceptibility of Leishmania strains representative of the species endemic to Brazil, as well as a panel of thirteen clinical isolates of tegumentary leishmaniasis, to both amphotericin B and miltefosine. A moderate variation in the susceptibility to both drugs was found, where the EC₅₀ values varied from 11.43 to 52.67 μM for miltefosine and from 12.89 to 62.36 nM for amphotericin B in promastigotes, while for the intracellular amastigotes, values ranged from 1.08 to 9.60 μM and from 1.69 to 22.71 nM for miltefosine and amphotericin B respectively. Furthermore, the clinical isolates and strains of the subgenus Viannia were evaluated for the presence of Leishmania RNA virus 1 (LRV1), as this is an important factor associated with disease severity and treatment outcome. These findings provide a preclinical dataset of the activity of these drugs against the causative species of tegumentary leishmaniasis in Brazil.

Effect of Leishmania RNA virus 2 on virulence factors and cytokines gene expression in a human macrophage infected with Leishmania major: A preliminary study

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

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.

Raising the suspicion of a non-autochthonous infection: identification of Leishmania guyanensis from Costa Rica exhibits a Leishmaniavirus related to Brazilian north-east and French Guiana viral genotypes

BACKGROUND

Costa Rica has a history of neglecting prevention, control and research of leishmaniasis, including limited understanding on Leishmania species causing human disease across the country and a complete lack of knowledge on the Leishmania RNA virus, described as a factor linked to the worsening and metastasis of leishmanial lesions.

OBJECTIVES

The aim of this work was to describe a case of cutaneous leishmaniasis by Leishmania (Viannia) guyanensis, bearing infection with Leishmaniavirus 1 (LRV1) in Costa Rica, raising the suspicion of imported parasites in the region.

METHODS

The Leishmania strain was previously identified by routine hsp70 polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in Costa Rica and subsequently characterised by isoenzyme electrophoresis and Sanger sequencing in Brazil. Screening for LRV1 was conducted with a dual RT-PCR approach and sequencing of the fragment obtained.

FINDINGS

Since 2016 Costa Rica performs Leishmania isolation and typing as part of its epidemiological surveillance activities. Amongst 113 strains typed until 2019, only one was characterised as a L. (V.) guyanensis, corresponding to the first confirmed report of this species in the country. Interestingly, the same strain tested positive for LRV1. Sequencing of the viral orf1 and 2, clustered this sample with other LRV1 genotypes of South American origin, from the Northeast of Brazil and French Guiana.

MAIN CONCLUSION

The unique characteristics of this finding raised the suspicion that it was not an autochthonous strain. Notwithstanding its presumed origin, this report points to the occurrence of said endosymbiont in Central American Leishmania strains. The possibility of its local dispersion represents one more challenge faced by regional health authorities in preventing and controlling leishmaniasis.

An RNA Interference (RNAi) Toolkit and Its Utility for Functional Genetic Analysis of Leishmania (Viannia)

RNA interference (RNAi) is a powerful tool whose efficacy against a broad range of targets enables functional genetic tests individually or systematically. However, the RNAi pathway has been lost in evolution by a variety of eukaryotes including most Leishmania sp. RNAi was retained in species of the Leishmania subgenus Viannia, and here we describe the development, optimization, and application of RNAi tools to the study of L. (Viannia) braziliensis (Lbr). We developed vectors facilitating generation of long-hairpin or "stem-loop" (StL) RNAi knockdown constructs, using Gateway^TM site-specific recombinase technology. A survey of applications of RNAi in L. braziliensis included genes interspersed within multigene tandem arrays such as quinonoid dihydropteridine reductase (QDPR), a potential target or modulator of antifolate sensitivity. Other tests include genes involved in cell differentiation and amastigote proliferation (A600), and essential genes of the intraflagellar transport (IFT) pathway. We tested a range of stem lengths targeting the L. braziliensis hypoxanthine-guanine phosphoribosyl transferase (HGPRT) and reporter firefly luciferase (LUC) genes and found that the efficacy of RNAi increased with stem length, and fell off greatly below about 128 nt. We used the StL length dependency to establish a useful 'hypomorphic' approach not possible with other gene ablation strategies, with shorter IFT140 stems yielding viable cells with compromised flagellar morphology. We showed that co-selection for RNAi against adenine phosphoryl transferase (APRT1) using 4-aminopyrazolpyrimidine (APP) could increase the efficacy of RNAi against reporter constructs, a finding that may facilitate improvements in future work. Thus, for many genes, RNAi provides a useful tool for studying Leishmania gene function with some unique advantages.

Virion structure of Leishmania RNA virus 1

The presence of Leishmania RNA virus 1 (LRV1) enables Leishmania protozoan parasites to cause more severe disease than the virus-free strains. The structure of LRV1 virus-like particles has been determined previously, however, the structure of the LRV1 virion has not been characterized. Here we used cryo-electron microscopy and single-particle reconstruction to determine the structures of the LRV1 virion and empty particle isolated from Leishmania guyanensis to resolutions of 4.0 Å and 3.6 Å, respectively. The capsid of LRV1 is built from sixty dimers of capsid proteins organized with icosahedral symmetry. RNA genomes of totiviruses are replicated inside the virions by RNA polymerases expressed as C-terminal extensions of a sub-population of capsid proteins. Most of the virions probably contain one or two copies of the RNA polymerase, however, the location of the polymerase domains in LRV1 capsid could not be identified, indicating that it varies among particles. Importance. Every year over 200 000 people contract leishmaniasis and more than five hundred people die of the disease. The mucocutaneous form of leishmaniasis produces lesions that can destroy the mucous membranes of the nose, mouth, and throat. Leishmania parasites carrying Leishmania RNA virus 1 (LRV1) are predisposed to cause aggravated symptoms in the mucocutaneous form of leishmaniasis. Here, we present the structure of the LRV1 virion determined using cryo-electron microscopy.

Characterisation of Trichomonas vaginalis Isolates Collected from Patients in Vienna between 2019 and 2021

Trichomonas vaginalis (TV) is the causative agent of trichomoniasis, the most common nonviral sexually transmitted disease. TV can carry symbionts such as Trichomonas vaginalis virus (TVV) or Mycoplasma hominis. Four distinct strains of TV are known: TVV1, TVV2, TVV3, and TVV4. The aim of the current study was to characterise TV isolates from Austrian patients for the presence of symbionts, and to determine their effect on metronidazole susceptibility and cytotoxicity against HeLa cells. We collected 82 TV isolates and detected presence of TVV (TVV1, TVV2, or TVV3) in 29 of them (35%); no TVV4 was detected. M. hominis was detected in vaginal/urethral swabs by culture in 37% of the TV-positive patients; M. hominis DNA was found in 28% of the TV isolates by PCR. In 15% of the patients, M. hominis was detected in the clinical samples as well as within the respective TV isolates. In 22% of the patients, M. hominis was detected by culture only. In 11 patients, M. hominis was detected only within the respective cultured TV isolates (13%), while the swab samples were negative for M. hominis. Our results provide a first insight into the distribution of symbionts in TV isolates from Austrian patients. We did not observe significant effects of the symbionts on metronidazole susceptibility, cytotoxicity, or severity of symptoms.

Diverse RNA Viruses Associated with Diatom, Eustigmatophyte, Dinoflagellate, and Rhodophyte Microalgae Cultures

Unicellular microalgae are of immense ecological importance with growing commercial potential in industries such as renewable energy, food, and pharmacology. Viral infections can have a profound impact on the growth and evolution of their hosts. However, very little is known of the diversity within, and the effect of, unicellular microalgal RNA viruses. In addition, identifying RNA viruses in these organisms that could have originated more than a billion years ago constitutes a robust data set to dissect molecular events and address fundamental questions in virus evolution. We assessed the diversity of RNA viruses in eight microalgal cultures, including representatives from the diatom, eustigmatophyte, dinoflagellate, red algae, and euglenid groups. Using metatranscriptomic sequencing combined with bioinformatic approaches optimized to detect highly divergent RNA viruses, we identified 10 RNA virus sequences, with nine constituting new viral species. Most of the newly identified RNA viruses belonged to the double-stranded Totiviridae, Endornaviridae, and Partitiviridae, greatly expanding the reported host range for these families. Two new species belonging to the single-stranded RNA viral clade Marnaviridae, commonly associated with microalgal hosts, were also identified. This study highlights that a substantial diversity of RNA viruses likely exists undetected within the unicellular microalgae. It also highlights the necessity for RNA viral characterization and for investigation of the effects of viral infections on microalgal physiology, biology, and growth, considering their environmental and industrial roles. IMPORTANCE Our knowledge of the diversity of RNA viruses infecting microbial algae-the microalgae-is minimal. However, describing the RNA viruses infecting these organisms is of primary importance at both the ecological and economic scales because of the fundamental roles these organisms play in aquatic environments and their growing value across a range of industrial fields. Using metatranscriptomic sequencing, we aimed to reveal the RNA viruses present in cultures of eight microalgae species belonging to the diatom, dinoflagellate, eustigmatophyte, rhodophyte, and euglena major clades of algae. Accordingly, we identified 10 new divergent RNA virus species belonging to RNA virus families as diverse as the double-stranded Totiviridae, Endornaviridae, and Partitiviridae and the single-stranded Marnaviridae. By expanding the known diversity of RNA viruses infecting unicellular eukaryotes, this study contributes to a better understanding of the early evolution of the virosphere and will inform the use of microalgae in industrial applications.

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.

Dissection of the macrophage response towards infection by the Leishmania-viral endosymbiont duo and dynamics of the type I interferon response

Leishmania RNA virus 1 (LRV1) is a double-stranded RNA virus found in some strains of the human protozoan parasite Leishmania, the causative agent of leishmaniasis, a neglected tropical disease. Interestingly, the presence of LRV1 inside Leishmania constitutes an important virulence factor that worsens the leishmaniasis outcome in a type I interferon (IFN)–dependent manner and contributes to treatment failure. Understanding how macrophages respond toward Leishmania alone or in combination with LRV1 as well as the role that type I IFNs may play during infection is fundamental to oversee new therapeutic strategies. To dissect the macrophage response toward infection, RNA sequencing was performed on murine wild-type and Ifnar-deficient bone marrow–derived macrophages infected with Leishmania guyanensis (Lgy) devoid or not of LRV1. Additionally, macrophages were treated with poly I:C (mimetic virus) or with type I IFNs. By implementing a weighted gene correlation network analysis, the groups of genes (modules) with similar expression patterns, for example, functionally related, coregulated, or the members of the same functional pathway, were identified. These modules followed patterns dependent on Leishmania, LRV1, or Leishmania exacerbated by the presence of LRV1. Not only the visualization of how individual genes were embedded to form modules but also how different modules were related to each other were observed. Thus, in the context of the observed hyperinflammatory phenotype associated to the presence of LRV1, it was noted that the biomarkers tumor-necrosis factor α (TNF-α) and the interleukin 6 (IL-6) belonged to different modules and that their regulating specific Src-family kinases were segregated oppositely. In addition, this network approach revealed the strong and sustained effect of LRV1 on the macrophage response and genes that had an early, late, or sustained impact during infection, uncovering the dynamics of the IFN response. Overall, this study contributed to shed light and dissect the intricate macrophage response toward infection by the Leishmania-LRV1 duo and revealed the crosstalk between modules made of coregulated genes and provided a new resource that can be further explored to study the impact of Leishmania on the macrophage response.

Development of an Indirect Fluorescent Antibody (IFA) Assay for the Detection of Leishmania RNA Virus 2 (LRV2) in Leishmania Parasites

BACKGROUND

Detection of Leishmania RNA virus (LRV) in Old World Leishmania species and their possible role in the disease prognosis requires sensitive and specific methods, preferably independent of the viral genome. We aimed to develop an indirect immunofluorescence antibody (IFA) assay to detect LRV in the Old World Leishmania parasites.

METHODS

Clinical samples were collected from 86 cutaneous leishmaniasis (CL) patients in different endemic areas of CL in Iran, during 2017-2019. For antibody preparation, the viruses were obtained from sediment of an LRV-infected L. major culture-using freeze and thaw cycles followed by gradient cesium chloride centrifugation. The purified viruses were used to immunize a male 3-4 months rabbit. Various dilutions of the LRV-immunized rabbit's serum and a conjugated antibody were deployed to detect LRV in 48 isolates by IFA assay.

RESULTS

LRV virus was detected in four of the 48 CL cases using IFA method. Amplification of a partial fragment of RNA-dependent RNA polymerase (RdRp) gene from the isolates confirmed the IFA results. In phylogeny, the generated RdRp sequences from four isolates were grouped with the other Old World LRVs, but separate from L. aethiopica LRVs, which appeared as a highly supported distinct clade.

CONCLUSION

Further optimization of this approach to detect the LRV directly in lesion scrapings can make it a more reliable tool for field studies and disclosing the virus's possible role in disseminating and unusual clinical features.

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.

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.

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.

Vaccines against leishmaniasis: using controlled human infection models to accelerate development

INTRODUCTION

Leishmaniasis is a neglected tropical disease that is defined by the World Health Organization as vaccine preventable. Although several new candidate vaccines are in development, no vaccine has successfully reached the market for human use. Several species of Leishmania cause human disease and have co-evolved with their respective sand fly vectors. These unique relationships have implications for initiation of infection and vaccine development. An approach to vaccine development for many infectious diseases is the use of controlled human infection models (CHIMs).

AREAS COVERED

We describe the history and recent development of experimental and deliberate infection using Leishmania in humans and the rationale for developing a new sand fly-initiated CHIM to progress leishmaniasis vaccine development. Examples from other infectious diseases are discussed in the context of the development of a new leishmaniasis CHIM. We also reflect upon the manufacture of the challenge agent, practical considerations, safety, ethics, and regulatory issues.

EXPERT OPINION

A new cutaneous Leishmania CHIM is being developed to enable testing of vaccines in the development pipeline. Questions remain about the use of such CHIMs to determine effectiveness of vaccines against visceral leishmaniasis. However, such a CHIM will be invaluable in expediting time to market for vaccines.

A Combination Extract of Gardeniae Fructus and Perillae Folium Exerts Anti-Inflammatory Effects on LPS-Activated RAW 264.7 Mouse Macrophages via an ER Stress-Induced CHOP Pathway

The aim of this study is to investigate the effects of a combination extract of Gardeniae Fructus and Perillae Folium (GP) on inflammatory reactions in lipopolysaccharide (LPS)-activated mouse macrophages RAW 264.7 cells. Multiplex cytokine assay, Fluo-4 calcium assay, Flow cytometry assay for phospho-P38 MAPK, and quantitative PCR were carried out. GP significantly reduced LPS-induced productions of macrophage inflammatory protein (MIP)-1α and monokine induced by gamma interferon (MIG) and release of intracellular calcium in LPS-activated RAW 264.7 cells. GP also significantly inhibited P38 MAPK phosphorylation and mRNA levels of Chop, Camk2a, Stat1, Stat3, Jak2, Fas, Nos2, and Ptgs2 in LPS-activated RAW 264.7 cells. Taken together, this study represents that GP exerts anti-inflammatory effects on LPS-activated RAW 264.7 cells via ER stress-induced CHOP pathway.

Production, Quantitation, and Infection of Amazonian Icoaraci Phlebovirus (Bunyaviridae)

Phlebotomine vectors, sand flies of the order Diptera, are known to transmit Leishmania parasites as well as RNA viruses (arboviruses) to humans. The arbovirus, Icoaraci Phlebovirus (BeAN 24262 - ICOV), used in this study was isolated from Nectomys rodents, a mammalian species that is the same natural sylvatic reservoir of Leishmania (Leishmania) amazonensis. This Leishmania species is distributed in primary and secondary forests in Brazil and other countries in America and causes localized and diffuse anergic skin lesions. In our recent studies, we observed an aggravation of the protozoan infection by ICOV through the modulation of cytokine expression, such as IL-10 and IFN-β, enhancing the parasite load and possibly the pathogenesis. Efficient viral production and quantitation had to be developed and standardized to ensure that immuno-molecular assays provide consistent and reproducible viral infection results. The standardization of these procedures becomes a particularly useful tool in research, with several applications in understanding the interaction between the host cell and Phlebovirus, as well as co-infections, allowing the study of intracellular signaling pathways. Here, we detail a protocol that allows the production and quantitation of the Icoaraci Phlebovirus using BHK-21 cells (baby hamster kidney cells) and subsequent infection of peritoneal macrophages from C57BL/6 mice.

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.

A Review of Leishmaniasis: Current Knowledge and Future Directions

Purpose of Review

The goal of this review is to summarize the current knowledge of the epidemiology, clinical manifestations, diagnosis, and treatment of cutaneous, mucosal, and visceral leishmaniasis. We will describe the most recent findings and suggest areas of further research in the leishmaniasis field.

Recent Findings

This article reviews newer leishmaniasis tests (including rapid diagnostic tests using rK39 antibodies), vaccine candidates, and updated treatment recommendations.

Summary

While leishmaniasis is a complex disease, learning the prominent clinical manifestations and major parasite species can guide the recommendations for diagnosis and treatment.

Cryo-EM reveals a previously unrecognized structural protein of a dsRNA virus implicated in its extracellular transmission

Mosquito viruses cause unpredictable outbreaks of disease. Recently, several unassigned viruses isolated from mosquitoes, including the Omono River virus (OmRV), were identified as totivirus-like viruses, with features similar to those of the Totiviridae family. Most reported members of this family infect fungi or protozoans and lack an extracellular life cycle stage. Here, we identified a new strain of OmRV and determined high-resolution structures for this virus using single-particle cryo-electron microscopy. The structures feature an unexpected protrusion at the five-fold vertex of the capsid. Disassociation of the protrusion could result in several conformational changes in the major capsid. All these structures, together with some biological results, suggest the protrusions’ associations with the extracellular transmission of OmRV.

Mosquito is a reservoir of viruses, with a large amount of them perform significant research value. Omono River virus (OmRV) has been isolated from Culex mosquito and is closely related to the family Totiviridae. However, current researches have reported the extracellular transmission ability of OmRV, which is lacked in most members of Totiviridae. In the current study, we isolated a new strain, OmRV-LZ, and obtained its high-resolution cryo-electron microscopy (cryo-EM) structure. Unexpectedly, a protrusion structure has been found located at the five-fold vertex, which is unrecognized in the previous studies. Structural and molecular biological experiments were applied to try to investigate its functions. The results may be helpful to understand the extracellular transmission ability of OmRV-LZ and similar double-stranded RNA (dsRNA) viruses.

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.

Capsid Structure of Leishmania RNA Virus 1

Twelve million people worldwide suffer from leishmaniasis, resulting in more than 30 thousand deaths annually. The disease has several variants that differ in their symptoms.

Leishmania parasites cause a variety of symptoms, including mucocutaneous leishmaniasis, which results in the destruction of the mucous membranes of the nose, mouth, and throat. The species of Leishmania carrying Leishmania RNA virus 1 (LRV1), from the family Totiviridae, are more likely to cause severe disease and are less sensitive to treatment than those that do not contain the virus. Although the importance of LRV1 for the severity of leishmaniasis was discovered a long time ago, the structure of the virus remained unknown. Here, we present a cryo-electron microscopy reconstruction of the virus-like particle of LRV1 determined to a resolution of 3.65 Å. The capsid has icosahedral symmetry and is formed by 120 copies of a capsid protein assembled in asymmetric dimers. RNA genomes of viruses from the family Totiviridae are synthetized, but not capped at the 5′ end, by virus RNA polymerases. To protect viral RNAs from degradation, capsid proteins of the L-A totivirus cleave the 5′ caps of host mRNAs, creating decoys to overload the cellular RNA quality control system. Capsid proteins of LRV1 form positively charged clefts, which may be the cleavage sites for the 5′ cap of Leishmania mRNAs. The putative RNA binding site of LRV1 is distinct from that of the related L-A virus. The structure of the LRV1 capsid enables the rational design of compounds targeting the putative decapping site. Such inhibitors may be developed into a treatment for mucocutaneous leishmaniasis caused by LRV1-positive species of Leishmania.

IMPORTANCE Twelve million people worldwide suffer from leishmaniasis, resulting in more than 30 thousand deaths annually. The disease has several variants that differ in their symptoms. The mucocutaneous form, which leads to disintegration of the nasal septum, lips, and palate, is caused predominantly by Leishmania parasites carrying Leishmania RNA virus 1 (LRV1). Here, we present the structure of the LRV1 capsid determined using cryo-electron microscopy. Capsid proteins of a related totivirus, L-A virus, protect viral RNAs from degradation by cleaving the 5′ caps of host mRNAs. Capsid proteins of LRV1 may have the same function. We show that the LRV1 capsid contains positively charged clefts that may be sites for the cleavage of mRNAs of Leishmania cells. The structure of the LRV1 capsid enables the rational design of compounds targeting the putative mRNA cleavage site. Such inhibitors may be used as treatments for mucocutaneous leishmaniasis.

Plasmodium yoelii Uses a TLR3-Dependent Pathway to Achieve Mammalian Host Parasitism

Malaria is associated with complicated immunopathogenesis. In this study, we provide evidence for an unexpected role of TLR3 in promoting the establishment of Plasmodium yoelii infection through delayed clearance of parasitemia in wild type C57BL/6jRj (B6) compared with TLR3 knockout mice. In this study, we confirmed an increased expression of Tlr3, Trif, Tbk1, and Irf7/Irf3 in the liver 42 h postinfection and the initiation of an early burst of proinflammatory response such as Ifng, NF-kB, and Tnfa in B6 mice that may promote parasite fitness. Interestingly, in the absence of TLR3, we showed the involvement of high IFN-γ and lower type I IFN response in the early clearance of parasitemia. In parallel, we observed an increase in splenic NK and NKT cells expressing TLR3 in infected B6 mice, suggesting a role for TLR sensing in the innate immune response. Finally, we find evidence that the increase in the frequency of CD19⁺TLR3⁺ B cells along with reduced levels of total IgG in B6 mice possibly suggests the initiation of TLR3-dependent pathway early during P. yoelii infection. Our results thus reveal a new mechanism in which a parasite-activated TLR3 pathway promotes blood stage infection along with quantitative and qualitative differences in Ab responses.

Case Report: Cutaneous Leishmaniasis due to Leishmania (Viannia) panamensis in Two Travelers Successfully Treated with Miltefosine

We present two cases of Leishmania (V) panamensis in returning travelers from Central America successfully treated with miltefosine. The couple presented with ulcerative skin lesions nonresponsive to antibiotics. Skin biopsy with polymerase chain reaction (PCR) revealed L. (V) panamensis. To prevent the development of mucosal disease and avoid the inconvenience of parental therapy, we treated both patients with oral miltefosine. We suggest that miltefosine represents an important therapeutic alternative in the treatment of cutaneous lesions caused by L. panamensis and in preventing mucosal involvement.

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.

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.

Entamoeba and Giardia parasites implicated as hosts of CRESS viruses

Metagenomic techniques have enabled genome sequencing of unknown viruses without isolation in cell culture, but information on the virus host is often lacking, preventing viral characterisation. High-throughput methods capable of identifying virus hosts based on genomic data alone would aid evaluation of their medical or biological relevance. Here, we address this by linking metagenomic discovery of three virus families in human stool samples with determination of probable hosts. Recombination between viruses provides evidence of a shared host, in which genetic exchange occurs. We utilise networks of viral recombination to delimit virus-host clusters, which are then anchored to specific hosts using (1) statistical association to a host organism in clinical samples, (2) endogenous viral elements in host genomes, and (3) evidence of host small RNA responses to these elements. This analysis suggests two CRESS virus families (Naryaviridae and Nenyaviridae) infect Entamoeba parasites, while a third (Vilyaviridae) infects Giardia duodenalis. The trio supplements five CRESS virus families already known to infect eukaryotes, extending the CRESS virus host range to protozoa. Phylogenetic analysis implies CRESS viruses infecting multicellular life have evolved independently on at least three occasions.

A Novel Virus Alters Gene Expression and Vacuolar Morphology in Malassezia Cells and Induces a TLR3-Mediated Inflammatory Immune Response

Malassezia is the most dominant fungal genus on the human skin surface and is associated with various skin diseases including dandruff and seborrheic dermatitis. Among Malassezia species, Malassezia restricta is the most widely observed species on the human skin. In the current study, we identified a novel dsRNA virus, named MrV40, in M. restricta and characterized the sequence and structure of the viral genome along with an independent satellite dsRNA viral segment. Moreover, expression of genes involved in ribosomal synthesis and programmed cell death was altered, indicating that virus infection affected the physiology of the fungal host cells. Our data also showed that the viral nucleic acid from MrV40 induces a TLR3-mediated inflammatory immune response in bone marrow-derived dendritic cells, indicating that a viral element likely contributes to the pathogenicity of Malassezia. This is the first study to identify and characterize a novel mycovirus in Malassezia.

Most fungal viruses have been identified in plant pathogens, whereas the presence of viral particles in human-pathogenic fungi is less well studied. In the present study, we observed extrachromosomal double-stranded RNA (dsRNA) segments in various clinical isolates of Malassezia species. Malassezia is the most dominant fungal genus on the human skin surface, and species in this group are considered etiological factors of various skin diseases including dandruff, seborrheic dermatitis, and atopic dermatitis. We identified novel dsRNA segments, and our sequencing results revealed that the virus, named MrV40, belongs to the Totiviridae family and contains an additional satellite dsRNA segment encoding a novel protein. The transcriptome of virus-infected Malassezia restricta cells was compared to that of virus-cured cells, and the results showed that transcripts involved in ribosomal biosynthesis were downregulated and those involved in energy production and programmed cell death were upregulated. Moreover, transmission electron microscopy revealed significantly larger vacuoles in virus-infected M. restricta cells, indicating that MrV40 infection dramatically altered M. restricta physiology. Our analysis also revealed that viral nucleic acid from MrV40 induced a TLR3 (Toll-like receptor 3)-mediated inflammatory immune response in bone marrow-derived dendritic cells, suggesting that a viral element contributes to the pathogenicity of Malassezia.

Leishmania naiffi and lainsoni in French Guiana: Clinical features and phylogenetic variability

In French Guiana, five species are associated with Cutaneous Leishmaniasis (CL). Though infections with Leishmania guyanensis, L. (V.) braziliensis and L. (L.) amazonensis have been extensively described, there are few available clinical and genetic data on L. (V.) lainsoni and L. (V.) naiffi. We determined the clinical and epidemiological features of all cases of CL due to L. (V.) naiffi and L. (V.) lainsoni diagnosed in French Guiana between 2003 and 2019. Phylogenetic analysis was performed by sequencing a portion of HSP70 and cyt b genes. Five cases of L. naiffi and 25 cases of L. lainsoni were reported. Patients infected by L. (V.) lainsoni were usually infected on gold camps, mostly along the Maroni river (60%), while L. naiffi was observed in French patients infected on the coast (100%). A high number of pediatric cases (n = 5; 20%) was observed for L. (V.) lainsoni. A mild clinical course was observed for all cases of L. (V.) naiffi. HSP70 and cyt b partial nucleotide sequence analysis revealed different geographical clusters within L. (V.) naiffi and L. (V.) lainsoni but no association were found between phylogenetic and clinical features. Our data suggest distinct socio-epidemiological features for these two Leishmania species. Patients seem to get infected with L. (V.) naiffi during leisure activities in anthropized coastal areas, while L. (V.) lainsoni shares common features with L. (V.) guyanensis and braziliensis and seems to be acquired during professional activities in primary forest regions. Phylogenetic analysis has provided information on the intraspecific genetic variability of L. (V.) naiffi and L. (V.) lainsoni and how these genotypes are distributed at the geographic level.

Review on the Role of Host Immune Response in Protection and Immunopathogenesis during Cutaneous Leishmaniasis Infection

Cutaneous leishmaniasis (CL) is a major public health problem worldwide and spreads to human via the bite of sand flies during blood meal. Following its inoculation, the promastigotes are immediately taken up by phagocytic cells and these leishmania-infected host cells produce proinflammatory cytokines that activate other immune cells and these infected host cells produce more cytokines and reactive nitrogen and oxygen species for efficient control of leishmania infection. Many experimental studies showed that resistance to infection with leishmania paraites is associated with the production of proinflammatory cytokines and activation of CD4⁺ Th1 response. On the other hand, vulnerability to this parasitic infection is correlated to production of T helper 2 cytokines that facilitate persistence of parasites and disease progression. In addition, some studies have also indicated that CD8⁺ T cells play a vital role in immune defense through cytokine production and their cytotoxic activity and excessive production of proinflammatory mediators promote amplified recruitment of cells. This could be correlated with excessive inflammatory reaction and ultimately resulted in tissue destruction and development of immunopathogenesis. Thus, there are contradictions regarding the role of immune responses in protection and immunopathogenesis of CL disease. Therefore, the aim of this paper was to review the role of host immune response in protection and its contribution to disease severity for CL infection. In order to obtain more meaningful data regarding the nature of immune response to leishmania, further in-depth studies focused on immune modulation should be conducted to develop better therapeutic strategies.

Interferon Alpha Favors Macrophage Infection by Visceral Leishmania Species Through Upregulation of Sialoadhesin Expression

Type I interferons (IFNs) induced by an endogenous Leishmania RNA virus or exogenous viral infections have been shown to exacerbate infections with New World Cutaneous Leishmania parasites, however, the impact of type I IFNs in visceral Leishmania infections and implicated mechanisms remain to be unraveled. This study assessed the impact of type I IFN on macrophage infection with L. infantum and L. donovani and the implication of sialoadhesin (Siglec-1/CD169, Sn) as an IFN-inducible surface receptor. Stimulation of bone marrow-derived macrophages with type I IFN (IFN-α) significantly enhanced susceptibility to infection of reference laboratory strains and a set of recent clinical isolates. IFN-α particularly enhanced promastigote uptake. Enhanced macrophage susceptibility was linked to upregulated Sn surface expression as a major contributing factor to the infection exacerbating effect of IFN-α. Stimulation experiments in Sn-deficient macrophages, macrophage pretreatment with a monoclonal anti-Sn antibody or a novel bivalent anti-Sn nanobody and blocking of parasites with soluble Sn restored normal susceptibility levels. Infection of Sn-deficient mice with bioluminescent L. infantum promastigotes revealed a moderate, strain-dependent role for Sn during visceral infection under the used experimental conditions. These data indicate that IFN-responsive Sn expression can enhance the susceptibility of macrophages to infection with visceral Leishmania promastigotes and that targeting of Sn may have some protective effects in early infection.

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.