Downregulation of IRF7-mediated type-I interferon response by LmCen parasites is necessary for protective immunity.

Leishmaniasis is a tropical disease caused by Leishmania parasites and currently has no licensed vaccines. We developed a dermotropic Leishmania major centrin gene-deleted strain (LmCen) as a live attenuated vaccine. Recent studies have shown that type I interferons (IFNs) play important roles in immunity to parasitic and viral pathogens.

Manufacturing and preclinical toxicity of GLP grade gene deleted attenuated Leishmania donovani parasite vaccine.

Centrin1 gene deleted Leishmania donovani parasite (LdCen1) was developed and extensively tested experimentally as an intracellular stage-specific attenuated and immunoprotective live parasite vaccine candidate ex vivo using human PBMCs and in vivo in animals. Here we report manufacturing and pre-clinical evaluation of current Good-Laboratory Practice (cGLP) grade LdCen1 parasites, as a prerequisite before proceeding with clinical trials. We screened three batches of LdCen1 parasites manufactured in bioreactors under cGLP conditions, for their consistency in genetic stability, attenuation, and safety.

Immunization with -Deficient Does Not Protect against Homologous Challenge.

Immunization with various species lacking induces robust immunity against a homologous and heterologous virulent challenge, making mutants a putative candidate for a leishmaniasis vaccine. Centrin is a calcium-binding cytoskeletal protein involved in centrosome duplication in higher eukaryotes and spp. lacking centrin are unable to replicate and are non-pathogenic.

The Preclinical Validation of 405 nm Light Parasiticidal Efficacy on in Ex Vivo Platelets in a Rag2 Mouse Model.

Violet-blue light of 405 nm in the visible spectrum at a dose of 270 J/cm alone has been shown to be an effective microbicidal tool for inactivating several bacteria, HIV-1, and in ex vivo plasma and platelets. Unlike chemical- and ultraviolet (UV)-based pathogen inactivation methods for plasma and platelet safety, 405 nm light is shown to be less toxic to host cells at light doses that are microbicidal. In this report, we evaluated the parasiticidal activity of a 405 nm light treatment on platelets spiked with the parasite.

promotes pain-reducing metabolomic reprogramming in cutaneous lesions.

Cutaneous leishmaniasis (CL) is characterized by extensive skin lesions, which are usually painless despite being associated with extensive inflammation. The molecular mechanisms responsible for this analgesia have not been identified. Through untargeted metabolomics, we found enriched anti-nociceptive metabolic pathways in -infected mice.

Production of leishmanin skin test antigen from Leishmania donovani for future reintroduction in the field.

The leishmanin skin test was used for almost a century to detect exposure and immunity to Leishmania, the causative agent of leishmaniasis, a major neglected tropical disease. Due to a lack of antigen used for the intradermal injection, the leishmanin skin test is no longer available. As leishmaniasis control programs are advancing and new vaccines are entering clinical trials, it is essential to re-introduce the leishmanin skin test.

knockout parasites promote M1-polarizing metabolic changes.

Leishmaniasis is a tropical disease prevalent in 90 countries. Presently, there is no approved vaccine for human use. We developed a live attenuated strain as a vaccine candidate that showed excellent efficacy, characterized by reduced Th2 and enhanced Th1 responses in C57BL/6 and BALB/c mice, respectively, compared to wild-type WT infection.

knock-out parasites reprogram tryptophan metabolism to induce a pro-inflammatory response.

Leishmaniasis is a parasitic disease that is prevalent in 90 countries, and yet no licensed human vaccine exists against it. Toward control of leishmaniasis, we have developed gene deletion mutant strains () as a live attenuated vaccine, which induces a strong IFN-γ-mediated protection to the host. However, the immune mechanisms of such protection remain to be understood.

Dual-scRNA-seq analysis reveals rare and uncommon parasitized cell populations in chronic L. donovani infection.

Although phagocytic cells are documented targets of Leishmania parasites, it is unclear whether other cell types can be infected. Here, we use unbiased single-cell RNA sequencing (scRNA-seq) to simultaneously analyze host cell and Leishmania donovani transcriptomes to identify and annotate parasitized cells in spleen and bone marrow in chronically infected mice. Our dual-scRNA-seq methodology allows the detection of heterogeneous parasitized populations.

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.

Deletion of MIF gene from live attenuated LdCen parasites enhances protective CD4 T cell immunity.

Vaccination with live attenuated Leishmania parasites such as centrin deleted Leishmania donovani (LdCen) against visceral leishmaniasis has been reported extensively. The protection induced by LdCen parasites was mediated by both CD4 and CD8 T cells. While the host immune mediators of protection are known, parasite determinants that affect the CD4 and CD8 T cell populations remain unknown.

Toll-like Receptor-9 (TLR-9) Signaling Is Crucial for Inducing Protective Immunity following Immunization with Genetically Modified Live Attenuated Parasites.

No human vaccine is available for visceral leishmaniasis (VL). Live attenuated centrin gene-deleted () parasite vaccine has been shown to induce robust innate immunity and provide protection in animal models. Toll-like receptors (TLRs) are expressed in innate immune cells and are essential for the early stages of infection.

Centrin-deficient Leishmania mexicana confers protection against Old World visceral leishmaniasis.

Leishmaniasis is one of the top neglected tropical diseases with significant morbidity and mortality in low and middle-income countries (LMIC). However, this disease is also spreading in the developed world. Currently, there is a lack of effective strategies to control this disease.

The History of Live Attenuated Gene-Deleted Vaccine Candidates.

Leishmaniasis, caused by an infection of the protozoa, is a neglected tropical disease and a major health problem in tropical and subtropical regions of the world, with approximately 350 million people worldwide at risk and 2 million new cases occurring annually. Current treatments for leishmaniasis are not highly efficacious and are associated with high costs, especially in low- and middle-income endemic countries, and high toxicity. Due to a surge in the incidence of leishmaniases worldwide, the development of new strategies such as a prophylactic vaccine has become a high priority.

Centrin Gene-Deleted Parasites Generate Skin Resident Memory T-Cell Immune Response Analogous to Leishmanization.

Leishmaniasis is a vector-borne parasitic disease transmitted through the bite of a sand fly with no available vaccine for humans. Recently, we have developed a live attenuated gene-deleted parasite strain ( ) that induced protection against homologous and heterologous challenges. We demonstrated that the protection is mediated by IFN (Interferon) γ-secreting CD4 T-effector cells and multifunctional T cells, which is analogous to leishmanization.

Centrin-deficient Leishmania mexicana confers protection against New World cutaneous leishmaniasis.

Leishmaniasis is a neglected protozoan disease affecting over 12 million people globally with no approved vaccines for human use. New World cutaneous leishmaniasis (CL) caused by L. mexicana is characterized by the development of chronic non-healing skin lesions.

Neutrophil-dendritic cell interaction plays an important role in live attenuated Leishmania vaccine induced immunity.

Background: Neutrophils are involved in the initial host responses to pathogens. Neutrophils can activate T cell responses either independently or through indirect involvement of Dendritic cells (DCs). Recently we have demonstrated direct neutrophil-T cell interactions that initiate adaptive immune responses following immunization with live attenuated Leishmania donovani centrin deleted parasite vaccine (LdCen-/-).

Determinants of Innate Immunity in Visceral Leishmaniasis and Their Implication in Vaccine Development.

Leishmaniasis is endemic to the tropical and subtropical regions of the world and is transmitted by the bite of an infected sand fly. The multifaceted interactions between , the host innate immune cells, and the adaptive immunity determine the severity of pathogenesis and disease development. parasites establish a chronic infection by subversion and attenuation of the microbicidal functions of phagocytic innate immune cells such as neutrophils, macrophages and dendritic cells (DCs).

From infection to vaccination: reviewing the global burden, history of vaccine development, and recurring challenges in global leishmaniasis protection.

Introduction: Leishmaniasis is a major public health problem and the second most lethal parasitic disease in the world due to the lack of effective treatments and vaccines. Even when not lethal, leishmaniasis significantly affects individuals and communities through life-long disabilities, psycho-sociological trauma, poverty, and gender disparity in treatment.

Areas Covered: This review discusses the most relevant and recent research available on Pubmed and GoogleScholar highlighting leishmaniasis' global impact, pathogenesis, treatment options, and lack of effective control strategies.

MicroRNA-21 Deficiency Promotes the Early Th1 Immune Response and Resistance toward Visceral Leishmaniasis.

MicroRNA-21 (miR-21) inhibits IL-12 expression and impairs the Th1 response necessary for control of infection. Recent studies have shown that infection induces miR-21 expression in dendritic cells and macrophages, and inhibition of miR-21 restores IL-12 expression. Because miR-21 is known to be expressed due to inflammatory stimuli in a wide range of hematopoietic cells, we investigated the role of miR-21 in regulating immune responses during visceral leishmaniasis (VL) caused by infection.

Preclinical validation of a live attenuated dermotropic Leishmania vaccine against vector transmitted fatal visceral leishmaniasis.

Visceral Leishmaniasis (VL), a potentially fatal disease is caused by Leishmania donovani parasites with no vaccine available. Here we produced a dermotropic live attenuated centrin gene deleted Leishmania major (LmCen) vaccine under Good Laboratory Practices and demonstrated that a single intradermal injection confers robust and durable protection against lethal VL transmitted naturally via bites of L. donovani-infected sand flies and prevents mortality.

Revival of Leishmanization and Leishmanin.

Leishmaniasis includes a spectrum of diseases ranging from debilitating cutaneous to fatal visceral infections. This disease is caused by the parasitic protozoa of the genus that is transmitted by infected sandflies. Over 1 billion people are at risk of leishmaniasis with an annual incidence of over 2 million cases throughout tropical and subtropical regions in close to 100 countries.

Essential Role of Neutrophils in the Protective Immune Response Induced by a Live Attenuated Vaccine.

No licensed vaccine exists against visceral leishmaniasis (VL), a disease caused by the parasite. We have previously reported both macrophages and dendritic cells play important role in the protection induced by a live attenuated centrin gene-deleted ( ) parasite vaccine. The role of neutrophils in orchestrating the initial innate response to pathogens is widely recognized.

A second generation leishmanization vaccine with a markerless attenuated Leishmania major strain using CRISPR gene editing.

Leishmaniasis is a neglected tropical disease caused by Leishmania protozoa transmitted by infected sand flies. Vaccination through leishmanization with live Leishmania major has been used successfully but is no longer practiced because it resulted in occasional skin lesions. A second generation leishmanization is described here using a CRISPR genome edited L.

miR-21 Expression Determines the Early Vaccine Immunity Induced by Immunization.

Unlabelled: No vaccine exists against visceral leishmaniasis. Toward developing vaccines against VL, we have reported previously on the immunogenicity of live attenuated parasites in animal models. Immunization with parasites has been shown to induce durable protective immunity in pre-clinical animal models.