Effect of phospholipase A2 inhibitors during infection caused by Leishmania (Leishmania) amazonensis

Background: Lipid metabolites play an important role in parasite differentiation and virulence. Studies have revealed that Leishmania sp. uses prostaglandins to evade innate barriers, thus enabling the parasites to survive inside immune cells. Despite the role of the enzyme Phospholipase A2 (PLA2) in prostaglandins production, few studies have investigated the role of parasite PLA2 during the interaction between L. (L.) amazonensis and the host (in vitro and in vivo) immune cells. Methods: In the present work, the leishmanicidal effect of PLA2 inhibitors, methyl arachidonyl fluorophosphonate (MAFP), bromoenol lactone (BEL) and aristolochic acid (AA) were investigated in vitro (promastigote and intracellular amastigote forms of L. (L.) amazonensis) and during in vivo infection using BALB/c mice. Results: The aforementioned inhibitors were deleterious to promastigote and amastigote forms of the L. (L.) amazonensis and were non-toxic to peritoneal macrophages from BALB/c mice. L. (L.) amazonensis-infected BALB/c mice treated with the inhibitor BEL presented decreased lesion size and skin parasitism; however, BEL treatment induced hepatotoxicity in BALB/c mice. Conclusions: Results presented herein suggested that PLA2 inhibitors altered L. (L.) amazonensis viability. In spite of liver toxicity, treatment with BEL was the most selective compound in vitro, as well in vivo, resulting in lower skin parasitism in the infected mice. These findings corroborate the role of PLA2 in parasite virulence and maintenance in vertebrate hosts, and suggest that molecules structurally related to BEL should be considered when planning compounds against Leishmania sp.

Effect of phospholipase A2 inhibitors during infection caused by Leishmania (Leishmania) amazonensis

Lipid metabolites play an important role in parasite differentiation and virulence. Studies have revealed that Leishmania sp. uses prostaglandins to evade innate barriers, thus enabling the parasites to survive inside immune cells. Despite the role of the enzyme Phospholipase A2 (PLA2) in prostaglandins production, few studies have investigated the role of parasite PLA2 during the interaction between L. (L.) amazonensis and the host (in vitro and in vivo) immune cells. Methods: In the present work, the leishmanicidal effect of PLA2 inhibitors, methyl arachidonyl fluorophosphonate (MAFP), bromoenol lactone (BEL) and aristolochic acid (AA) were investigated in vitro (promastigote and intracellular amastigote forms of L. (L.) amazonensis) and during in vivo infection using BALB/c mice. Results: The aforementioned inhibitors were deleterious to promastigote and amastigote forms of the L. (L.) amazonensis and were non-toxic to peritoneal macrophages from BALB/c mice. L. (L.) amazonensis-infected BALB/c mice treated with the inhibitor BEL presented decreased lesion size and skin parasitism; however, BEL treatment induced hepatotoxicity in BALB/c mice. Conclusions: Results presented herein suggested that PLA2 inhibitors altered L. (L.) amazonensis viability. In spite of liver toxicity, treatment with BEL was the most selective compound in vitro, as well in vivo, resulting in lower skin parasitism in the infected mice. These findings corroborate the role of PLA2 in parasite virulence and maintenance in vertebrate hosts, and suggest that molecules structurally related to BEL should be considered when planning compounds against Leishmania sp.(AU)

Co-administration of plasmid-encoded granulocyte-macrophage colony-stimulating factor increases human immunodeficiency virus-1 DNA vaccine-induced polyfunctional CD4+ T-cell responses

T-cell based vaccines against human immunodeficiency virus (HIV) generate specific responses that may limit both transmission and disease progression by controlling viral load. Broad, polyfunctional, and cytotoxic CD4+T-cell responses have been associated with control of simian immunodeficiency virus/HIV-1 replication, supporting the inclusion of CD4+ T-cell epitopes in vaccine formulations. Plasmid-encoded granulocyte-macrophage colony-stimulating factor (pGM-CSF) co-administration has been shown to induce potent CD4+ T-cell responses and to promote accelerated priming and increased migration of antigen-specific CD4+ T-cells. However, no study has shown whether co-immunisation with pGM-CSF enhances the number of vaccine-induced polyfunctional CD4+ T-cells. Our group has previously developed a DNA vaccine encoding conserved, multiple human leukocyte antigen (HLA)-DR binding HIV-1 subtype B peptides, which elicited broad, polyfunctional and long-lived CD4+ T-cell responses. Here, we show that pGM-CSF co-immunisation improved both magnitude and quality of vaccine-induced T-cell responses, particularly by increasing proliferating CD4+ T-cells that produce simultaneously interferon-γ, tumour necrosis factor-α and interleukin-2. Thus, we believe that the use of pGM-CSF may be helpful for vaccine strategies focused on the activation of anti-HIV CD4+ T-cell immunity.

Análise da imunogenicidade de uma vacina de DNA codificando epitopos CD4 promíscuos e conservados do HIV-1 em camundongos BALB/c e transgênicos para moléculas de HLA classe II / Immunogenicity analysis of a DNA vaccine encoding promiscuous and conserved HIV-1 CD4 epitopes in BALB/c and HLA class II transgenic mice

Abordagens atuais no desenho de vacinas contra o HIV-1 estão focadas em imunógenos que codificam proteínas inteiras do HIV-1 e visam induzir respostas citotóxicas específicas. É concebível que vacinas bem-sucedidas devem induzir respostas contra múltiplos epitopos do HIV-1, coincidindo com seqüências das cepas circulantes do vírus, conhecido por sua grande variabilidade genética. Sabe-se que células T CD4+ são necessárias para indução de respostas efetivas de linfócitos T CD8+ citotóxicos. Neste trabalho, nós avaliamos a imunogenicidade de uma vacina de DNA codificando 18 epitopos para linfócitos T CD4+, conservados e ligadores de múltiplas moléculas HLA-DR em camundongos BALB/c e em quatro linhagens de camundongos transgênicos para moléculas de HLA classe II. Os camundongos imunizados apresentaram respostas de amplitude e magnitude significativas com proliferação e secreção de citocinas por linfócitos T CD4+ e T CD8+. Onze dos 18 epitopos para linfócitos T CD4+ presentes na vacina foram reconhecidos pelas linhagens de camundongos transgênicos para moléculas de HLA classe II. Em suma, 17 dos 18 epitopos codificados pela vacina foram reconhecidos. As células induzidas pela vacina apresentaram um perfil polifuncional com tipo 1 de citocinas, incluindo produção de IFN- , TNF- e IL-2. A vacina também induziu células T CD4+ de memória central de longa duração, capazes de fornecer auxílio contínuo para células T CD8 +. Pela capacidade da vacina HIVBr18 de induzir respostas contra múltiplos epitopos de linfócitos T CD4+ conservados que podem ser reconhecidos no contexto de múltiplas moléculas de HLA classe II, esse conceito vacinal pode solucionar o problema da variabilidade genética viral assim como aumentar a cobertura populacional. Portanto, essa vacina, pode ser útil se utilizada isoladamente ou como fonte de auxílio cognato para células T CD8+ HIV-específicas induzidas por outros imunógenos gerando resposta em uma grande proporção dos vacinados.

Current HIV vaccine approaches are focused on immunogens encoding whole HIV antigenic proteins that elicit cytotoxic CD8+ responses. It is conceivable that successful vaccines have to elicit responses to multiple epitopes, to match circulating strains of HIV, a virus known for its high genetic variability. It is known that CD4+ T cell responses are necessary for effective CD8+ antiviral responses. Here we assessed the immunogenicity of a DNA vaccine encoding 18 conserved, multiple HLA-DR-binding HIV CD4 epitopes in BALB/c and four strains of HLA class II-transgenic mice. Immunized mice displayed CD4+ and CD8+ proliferative and cytokine T cell responses of significant breadth and magnitude. Eleven out of the 18 encoded epitopes were recognized by CD4+ T cells from HLA class IItransgenic strain. Overall, 17 out of the 18 encoded peptides were recognized. The induced T cell response had a polyfunctional type 1 cytokine profile, including IFN- , TNF- and IL-2. The vaccine also induced long-lived central memory CD4+ T cells, which might provide sustained help for CD8+ T cells. By virtue of inducing broad responses against conserved CD4+ T cell epitopes that can be recognized in the context of widely diverse, common HLA class II alleles, this vaccine concept may cope both with HIV genetic variability and increased population coverage. The vaccine may thus be usefull either as a standalone approach or as a source of cognate help for HIV-specific CD8+ T cells elicited by conventional immunogens, eliciting responses in a wide proportion of vaccinees.