lipid-a and Leishmaniasis

Lipopolysaccharide (LPS) is a well-defined agonist of Toll-like receptor (TLR) 4 that activates innate immune responses and influences the development of the adaptive response during infection with Gram-negative bacteria. Many years ago, Dr. Edgar Ribi separated the adjuvant activity of LPS from its toxic effects, an effort that led to the development of monophosphoryl lipid A (MPL). MPL, derived from Salmonella minnesota R595, has progressed through clinical development and is now used in various product-enabling formulations to support the generation of antigen-specific responses in several commercial and preclinical vaccines. We have generated several synthetic lipid A molecules, foremost glucopyranosyl lipid adjuvant (GLA) and second-generation lipid adjuvant (SLA), and have advanced these to clinical trial for various indications. In this review we summarize the potential and current positioning of TLR4-based adjuvant formulations in approved and emerging vaccines.

Topics: Adjuvants, Immunologic; Alum Compounds; Animals; Glucosides; HIV Infections; Humans; Immunity, Cellular; Immunity, Humoral; Immunogenicity, Vaccine; Leishmaniasis; Leprosy; Lipid A; Liposomes; Malaria; Mice; Schistosomiasis; T-Lymphocytes, Helper-Inducer; Toll-Like Receptor 4; Tuberculosis; Vaccines

The parasite Leishmania has been used for pioneering work to define T-cell subsets and cytokine patterns mediating susceptibility or resistance to infectious pathogens. This understanding has been essential for the development of a new generation of candidate vaccines for major diseases, such as leishmaniases themselves, tuberculosis and others. It is clear that effective vaccines can be developed through a combination of both antigen and adjuvant selection. Until recently, no adjuvants acceptable for use in human T-cell vaccines were available. However, one such adjuvant, monophosphoryl lipid A, has been shown to be safe and effective. Just as the understanding of T-cell responses has been necessary for the development of a new generation of vaccines, an understanding of signaling by antigen-presenting cells has been essential for adjuvant selection. A combination of antigens and an adjuvant that is effective at promoting durable T-helper 1 responses and is safe for human use comprise a promising vaccine candidate, Leish-111f. This vaccine has potential application in both the prevention and treatment of leishmaniasis.

Topics: Adjuvants, Immunologic; Animals; Antigens, Protozoan; Humans; Leishmania; Leishmaniasis; Lipid A; Mice; Protozoan Vaccines; T-Lymphocytes

Vaccine adjuvants based on the structure of lipid A, such as monophosphoryl lipid A (MLA), have proven to be safe and effective in inducing immune responses to heterologous proteins in animal and human vaccines. Recent work on the development of a recombinant vaccine for leishmaniasis has demonstrated that a clinical grade MLA formulation - MPL(R) adjuvant - is essential in the development of a protective response. Preliminary evidence suggests that MLA and a chemically distinct family of lipid A mimetics - the aminoalkyl glucosaminide 4-phosphates - act on Toll-like receptor 4 (TLR4). As TLR4 agonists, they have potent immunomodulatory effects when used both as vaccine adjuvants and as stand-alone products. Novel approaches to vaccine development could benefit from taking full advantage of the effects of these compounds on innate and adaptive responses.

Topics: Adjuvants, Immunologic; Animals; Drosophila Proteins; Female; Immunity, Innate; Leishmaniasis; Lipid A; Membrane Glycoproteins; Mice; Molecular Mimicry; Molecular Structure; Mucous Membrane; Receptors, Cell Surface; Toll-Like Receptor 4; Toll-Like Receptors; Vaccination

The aim of this study was to evaluate, in terms of dog macrophage killing ability in vitro, a vaccine based on Leishmania infantum promastigote soluble antigen (LSA) formulated with three different adjuvants (BCG, AdjuPrime, MPL/TDM/CWS). A significant increase of the macrophage killing ability was observed in dogs vaccinated with LSA+MPL/TDM/CWS after 1 month from vaccination. A similar increase of macrophage parasitocidal ability was present only after 5 months in dogs vaccinated with LSA+BCG or LSA+AdjuPrime. In all dogs the augmented killing percentage was still present after 12 months from vaccination. Therefore, in particular LSA+MPL/TDM/CWS vaccine seems promising for further studies in dogs.

Topics: Adjuvants, Immunologic; Animals; Antigens, Protozoan; BCG Vaccine; Cell Wall Skeleton; Cord Factors; Dog Diseases; Dogs; Female; Humans; Leishmania infantum; Leishmaniasis; Leishmaniasis Vaccines; Leukocytes, Mononuclear; Lipid A; Macrophages; Male; Time Factors

One strategy to control leishmaniasis is vaccination with potent antigens alongside suitable adjuvants. The use of toll-like receptor (TLR) agonists as adjuvants is a promising approach in Leishmania vaccine research. Leishmania (L.) tropica is among the less-investigated Leishmania species and a causative agent of cutaneous and sometimes visceral leishmaniasis with no approved vaccine against it. In the present study, we assessed the adjuvant effects of a TLR4 agonist, monophosphoryl lipid A (MPL) and a TLR7/8 agonist, R848 beside two different types of Leishmania vaccine candidates; namely, whole-cell soluble L. tropica antigen (SLA) and recombinant L. tropica stress-inducible protein-1 (LtSTI1). BALB/c mice were vaccinated three times by the antigens (SLA or LtSTI1) with MPL or R848 and then were challenged by L. tropica. Delayed-type hypersensitivity (DTH), parasite load, disease progression and cytokines (IL-10 and IFN-γ) responses were assessed. In general compared to SLA, application of LtSTI1 resulted in higher DTH, higher IFN-γ response and lower lymph node parasite load. Also compared to R848, MPL as an adjuvant resulted in higher DTH and lower lymph node parasite load. Although, no outstanding ability for SLA and R848 in evoking immune responses of BALB/c mice against L. tropica infection could be observed, our data suggest that LtSTI1 and MPL have a better potential to control L. tropica infection and could be pursued for the development of effective vaccination strategies.

Topics: Adjuvants, Immunologic; Animals; Antigens, Protozoan; Cytokines; Disease Models, Animal; Female; Imidazoles; Leishmania tropica; Leishmaniasis; Leishmaniasis Vaccines; Lipid A; Mice, Inbred BALB C; Parasite Load; Protozoan Proteins; Random Allocation; Recombinant Proteins; Toll-Like Receptors; Vaccination; Vaccines, Inactivated

With the paucity of new drugs and HIV co-infection, vaccination remains an unmet research priority to combat visceral leishmaniasis (VL) requiring strong cellular immunity. Protein vaccination often suffers from low immunogenicity and poor generation of memory T cells for long-lasting protection. Cysteine proteases (CPs) are immunogenic proteins and key mediators of cellular functions in Leishmania. Here, we evaluated the vaccine efficacies of CPs against VL, using cationic liposomes with Toll like receptor agonists for stimulating host immunity against L. donovani in a hamster model.. Recombinant CPs type I (cpb), II (cpa) and III (cpc) of L. donovani were tested singly and in combination as a triple antigen cocktail for antileishmanial vaccination in hamsters. We found the antigens to be highly immunoreactive and persistent anti-CPA, anti-CPB and anti-CPC antibodies were detected in VL patients even after cure. The liposome-entrapped CPs with monophosphoryl lipid A-Trehalose dicorynomycolate (MPL-TDM) induced significantly high nitric oxide (up to 4 fold higher than controls) mediated antileishmanial activity in vitro, and resulted in strong in vivo protection. Among the three CPs, CPC emerged as the most potent vaccine candidate in combating the disease. Interestingly, a synergistic increase in protection was observed with liposomal CPA, CPB and CPC antigenic cocktail which reduced the organ parasite burden by 1013-1016 folds, and increased the disease-free survival of >80% animals at least up to 6 months post infection. Robust secretion of IFN-γ and IL-12, along with concomitant downregulation of Th2 cytokines, was observed in cocktail vaccinates, even after 3 months post infection.. The present study is the first report of a comparative efficacy of leishmanial CPs and their cocktail using liposomal formulation with MPL-TDM against L. donovani. The level of protection attained has not been reported for any other subcutaneous single or polyprotein vaccination against VL.

Topics: Animals; Antigens, Protozoan; Cations; Cord Factors; Cricetinae; Cysteine Proteases; Disease Models, Animal; Drug Delivery Systems; Leishmania donovani; Leishmaniasis; Lipid A; Liposomes; Mesocricetus; Protozoan Vaccines

A synthetic lipid A analog (ONO-4007) exhibits antileishmanial activity by activating Leishmania-infected macrophages in experimental leishmaniasis. In the present in vitro study, ONO-4007 at concentrations between 0.01 and 1.00 mg/mL markedly inhibited the proliferation of Leishmania major and L. amazonensis promastigotes. Ultrastructurally, L. major-infected macrophages showed degenerated intracellular amastigotes after exposure to ONO-4007. Leishmania-infected macrophages treated with ONO-4007 showed poorly developed parasitophorous vacuoles. High levels of tumor necrosis factor-alpha were induced by ONO-4007 in Leishmania-infected macrophages. In this in vivo study, L. amazonensis-infected BALB/c mice were treated with a dose of 30 mg/kg of ONO-4007 by perilesional and peritoneal injections. The skin lesion size was assessed before treatment with ONO-4007 and at eight weeks after injection. The lesion size was significantly suppressed in mice perilesionally injected with ONO-4007 (P < 0.01) compared with the controls. The data from our present in vitro and in vivo studies indicate that ONO-4007 has an antileishmanial effect.

Topics: Animals; Antiprotozoal Agents; Cell Line; Enzyme-Linked Immunosorbent Assay; Female; Gene Expression Regulation; Leishmania; Leishmania major; Leishmaniasis; Lipid A; Macrophages; Mice; Mice, Inbred BALB C; Specific Pathogen-Free Organisms; Time Factors; Tumor Necrosis Factor-alpha