BALB/c Mice Infected with Antimony Treatment Refractory Isolate of Leishmania braziliensis Present Severe Lesions due to IL-4 Production

Leishmaniasis is a neglected disease that affects more than 12 million people worldwide. In Brazil, the cutaneous disease is more prevalent with about 28,000 new cases reported each year, and L. braziliensis is the main causative agent. The interesting data about the infection with this parasite is the wide variety of clinical manifestations that ranges from single ulcerated lesions to mucocutaneous and disseminated disease. However, experimental models to study the infection with this parasite are difficult to develop due to high resistance of most mouse strains to the infection, and the mechanisms underlying the distinct manifestations remain poorly understood. Here, the authors use a mouse experimental model of infection with different L. braziliensis isolates, known to induce diseases with distinct severity in the human hosts, to elucidate immune mechanisms that may be involved in the different manifestations. They showed that distinct parasite isolates may modulate host response, and increased IL-4 production and Arg I expression was related to more severe disease, resulting in longer length of disease with larger lesions and reduced parasite clearance. These findings may be useful in the identification of immunological targets to control L. braziliensis infection and potential clinical markers of disease progression

Extracellular nucleotide metabolism in Leishmania: influence of adenosine in the establishment of infection

Leishmaniasis is a parasitic disease with a variety of clinical forms, which are related to the Leishmania species involved. In the murine model, Leishmania amazonensis causes chronic non-healing lesions in Leishmania braziliensis- or Leishmania major-resistant mouse strains. In this study, we investigated the involvement of the pathway of extracellular nucleotide hydrolysis, with special focus on the role of extracellular adenosine, in the establishment of Leishmania infection. Our results show that the more virulent parasite—L. amazonensis—hydrolyzes higher amounts of ATP, ADP and AMP than the two other species, probably due to the higher expression of membrane NTPDase. Corroborating the idea that increased production of adenosine is important to lesion development and establishment of tissue parasitism, we observed that increased 5′-nucleotidase activity in L. braziliensis or addition of adenosine at the moment of infection with this parasite resulted in an increase in lesion size and parasitism as well as a delay in lesion healing. Furthermore, inhibition of adenosine receptor A2B led to decreased lesion size and parasitism. Thus, our results suggest that the conversion of ATP, a molecule with pro-inflammatory activity, into adenosine, which possesses immunomodulatory properties, may contribute to the establishment of infection by Leishmania

Extracellular nucleotide metabolism in Leishmania: influence of adenosine in the establishment of infection.

Leishmaniasis is a parasitic disease with a variety of clinical forms, which are related to the Leishmania species involved. In the murine model, Leishmania amazonensis causes chronic non-healing lesions in Leishmania braziliensis- or Leishmania major-resistant mouse strains. In this study, we investigated the involvement of the pathway of extracellular nucleotide hydrolysis, with special focus on the role of extracellular adenosine, in the establishment of Leishmania infection. Our results show that the more virulent parasitedL. Amazonensisdhydrolyzes higher amounts of ATP, ADP and AMP than the two other species, probably due to the higher expression of membrane NTPDase. Corroborating the idea that increased production of adenosine is important to lesion development and establishment of tissue parasitism, we observed that increased 50-nucleotidase activity in L. braziliensis or addition of adenosine at the moment of infection with this parasite resulted in an increase in lesion size and parasitism as well as a delay in lesion healing. Furthermore, inhibition of adenosine receptor A2B led to decreased lesion size and parasitism. Thus, our results suggest that the conversion of ATP, a molecule with pro-inflammatory activity, into adenosine, which possesses immunomodulatory properties, may contribute to the establishment of infection by Leishmania

The pattern recognition receptors Nod1 and Nod2 account for neutrophil recruitment to the lungs of mice infected with Legionella pneumophila

The intracellular bacterium Legionella pneumophila induces a severe form of pneumonia called Legionnaires diseases, which is characterized by a strong neutrophil (NE) infiltrate to the lungs of infected individuals. Although the participation of pattern recognition receptors, such as Toll-like receptors, was recently demonstrated, there is no information on the role of nod-like receptors (NLRs) for bacterial recognition in vivo and for NE recruitment to the lungs. Here, we employed a murine model of Legionnaires disease to evaluate host and bacterial factors involved in NE recruitment to the mice lungs. We found that L. pneumophila type four secretion system, known as Dot/Icm, was required for NE recruitment as dot/icm mutants fail to trigger NE recruitment in a process independent of bacterial multiplication. By using mice deficient for Nod1, Nod2, and Rip2, we found that these receptors accounted for NE recruitment to the lungs of infected mice. In addition, Rip2-dependent responses were important for cytokine production and bacterial clearance. Collectively, these studies show that Nod1, Nod2, and Rip2 account for generation of innate immune responses in vivo, which are important for NE recruitment and bacterial clearance in a murine model of Legionnaires diseases. (C) 2010 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.PEW Latin America Program in Biomedical SciencesINCTV/CNPqFAPESP[06/52867-4

Leishmania Lipophosphoglycan Triggers Caspase-11 and the Non-canonical Activation of the NLRP3 Inflammasome

Submitted by Nuzia Santos ([email protected]) on 2019-10-18T17:46:51Z No. of bitstreams: 1 Leishmania Lipophosphoglycan Triggers.pdf: 6570102 bytes, checksum: 1cc17d11c4468270e12be56a2360905e (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2019-10-18T17:51:32Z (GMT) No. of bitstreams: 1 Leishmania Lipophosphoglycan Triggers.pdf: 6570102 bytes, checksum: 1cc17d11c4468270e12be56a2360905e (MD5)Made available in DSpace on 2019-10-18T17:51:32Z (GMT). No. of bitstreams: 1 Leishmania Lipophosphoglycan Triggers.pdf: 6570102 bytes, checksum: 1cc17d11c4468270e12be56a2360905e (MD5) Previous issue date: 2019Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.National Institute of Biological Sciences. Beijing, China.Fundação Oswaldo Cruz. Instituto René Rachou. Belo Horizonte, MG, Brasil.Fundação Oswaldo Cruz. Instituto René Rachou. Belo Horizonte, MG, Brasil.Fundação Oswaldo Cruz. Instituto René Rachou. Belo Horizonte, MG, Brasil.Department of Molecular Microbiology. Washington University School of Medicine. Saint Louis, MO, USA.National Institute of Biological Sciences. Beijing, China.Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos. Ribeirão Preto, SP, Brasil.Activation of the NLRP3 inflammasome by Leishmania parasites is critical for the outcome of leishmaniasis, a disease that affects millions of people worldwide. We investigate the mechanisms involved in NLRP3 activation and demonstrate that caspase-11 (CASP11) is activated in response to infection by Leishmania species and triggers the non-canonical activation of NLRP3. This process accounts for host resistance to infection in macrophages and in vivo. We identify the parasite membrane glycoconjugate lipophosphoglycan (LPG) as the molecule involved in CASP11 activation. Cytosolic delivery of LPG in macrophages triggers CASP11 activation, and infections performed with Lpg1(-/-) parasites reduce CASP11/NLRP3 activation. Unlike bacterial LPS, purified LPG does not activate mouse CASP11 (or human Casp4) in vitro, suggesting the participation of additional molecules for LPG-mediated CASP11 activation. Our data identify a parasite molecule involved in CASP11 activation, thereby establishing the mechanisms underlying inflammasome activation in response to Leishmania species