Non-clinical toxicity and immunogenicity evaluation of a Plasmodium vivax malaria vaccine using Poly-ICLC (Hiltonol®) as adjuvant.

Malaria caused byPlasmodium vivaxis a pressing public health problem in tropical and subtropical areas.However, little progress has been made toward developing a P. vivaxvaccine, with only three candidates being tested in clinical studies. We previously reported that one chimeric recombinant protein (PvCSP-All epitopes) containing the conserved C-terminus of the P. vivax Circumsporozoite Protein (PvCSP), the three variant repeat domains, and aToll-like receptor-3 agonist,Poly(I:C), as an adjuvant (polyinosinic-polycytidylic acid, a dsRNA analog mimicking viral RNA), elicits strong antibody-mediated immune responses in mice to each of the three allelic forms of PvCSP. In the present study, a pre-clinical safety evaluation was performed to identify potential local and systemic toxic effects of the PvCSP-All epitopes combined with the Poly-ICLC (Poly I:C plus poly-L-lysine, Hiltonol®) or Poly-ICLC when subcutaneously injected into C57BL/6 mice and New Zealand White Rabbits followed by a 21-day recovery period. Overall, all observations were considered non-adverse and were consistent with the expected inflammatory response and immune stimulation following vaccine administration. High levels of vaccine-induced specific antibodies were detected both in mice and rabbits. Furthermore, mice that received the vaccine formulation were protected after the challenge with Plasmodium berghei sporozoites expressing CSP repeats from P. vivax sporozoites (Pb/Pv-VK210). In conclusion, in these non-clinical models, repeated dose administrations of the PvCSP-All epitopes vaccine adjuvanted with a Poly-ICLC were immunogenic, safe, and well tolerated.

The IRAK1/IRF5 axis initiates IL-12 response by dendritic cells and control of Toxoplasma gondii infection.

Activation of endosomal Toll-like receptor (TLR) 7, TLR9, and TLR11/12 is a key event in the resistance against the parasite Toxoplasma gondii. Endosomal TLR engagement leads to expression of interleukin (IL)-12 via the myddosome, a protein complex containing MyD88 and IL-1 receptor-associated kinase (IRAK) 4 in addition to IRAK1 or IRAK2. In murine macrophages, IRAK2 is essential for IL-12 production via endosomal TLRs but, surprisingly, Irak2-/- mice are only slightly susceptible to T. gondii infection, similar to Irak1-/- mice. Here, we report that upon T. gondii infection IL-12 production by different cell populations requires either IRAK1 or IRAK2, with conventional dendritic cells (DCs) requiring IRAK1 and monocyte-derived DCs (MO-DCs) requiring IRAK2. In both populations, we identify interferon regulatory factor 5 as the main transcription factor driving the myddosome-dependent IL-12 production during T. gondii infection. Consistent with a redundant role of DCs and MO-DCs, mutations that affect IL-12 production in both cell populations show high susceptibility to infection in vivo.

Itaconate impairs immune control of Plasmodium by enhancing mtDNA-mediated PD-L1 expression in monocyte-derived dendritic cells.

Severe forms of malaria are associated with systemic inflammation and host metabolism disorders; however, the interplay between these outcomes is poorly understood. Using a Plasmodium chabaudi model of malaria, we demonstrate that interferon (IFN) γ boosts glycolysis in splenic monocyte-derived dendritic cells (MODCs), leading to itaconate accumulation and disruption in the TCA cycle. Increased itaconate levels reduce mitochondrial functionality, which associates with organellar nucleic acid release and MODC restraint. We hypothesize that dysfunctional mitochondria release degraded DNA into the cytosol. Once mitochondrial DNA is sensitized, the activation of IRF3 and IRF7 promotes the expression of IFN-stimulated genes and checkpoint markers. Indeed, depletion of the STING-IRF3/IRF7 axis reduces PD-L1 expression, enabling activation of CD8+ T cells that control parasite proliferation. In summary, mitochondrial disruption caused by itaconate in MODCs leads to a suppressive effect in CD8+ T cells, which enhances parasitemia. We provide evidence that ACOD1 and itaconate are potential targets for adjunct antimalarial therapy.

The role of MHC haplotypes H2d/H2b in mouse resistance/susceptibility to cyst formation is influenced by the lineage of infective Toxoplasma gondii strain

Toxoplasma gondii strains displaying the Type I/III genotype are associated with acquired ocular toxoplasmosis in humans. Here, we used a mice model to characterize some immunological mechanisms involved in host resistance to infection with such strains. We have chosen the Type I/III strains D8, G2 and P-Br, which cause a chronic infection in mice that resembles human toxoplamosis. Mice deficient of molecules MyD88, IFN-gamma, and IL-12 were susceptible to all three parasite strains. This finding indicates the importance of innate mechanisms in controlling infection. On the other hand, MHC haplotype did not influenced resistance/susceptibility; since mice lineages displaying a same genetic background but different MHC haplotypes (H2b or H2d) developed similar mortality and cyst numbers after infection with those strains. In contrast, the C57BL/6 genetic background, and not MHC haplotype, was critical for development of intestinal inflammation caused by any of the studied strains. Finally, regarding effector mechanisms, weobserved that B and CD8+ T lymphocytes controlled survival,whereas the inducible nitric oxide synthase influenced cyst numbers in brains of mice infected with Type I/III strains. These findings are relevant to further understanding of the immunologic mechanisms involved in host protection and pathogenesis during infection with T. gondii.

Cepas de Toxoplasma gondii que apresentam o genótipo I/III são associadas a toxoplasmose ocular adquirida em humanos. No presente trabalho, nós utilizamos um modelo da doença em camundongos para caracterizar mecanismos imunológicos envolvidos na resistência do hospedeiro à infecção por aquelas cepas. Escolhemos as cepas D8, G2 e P-Br, que causam infecção crônica em camundongos, semelhante à toxoplasmose humana. Camundongos deficientes em MyD88, IFN-G e IL-12 foram susceptíveis a infecções com todas as três linhagens do parasita. Esses dados indicam a importância de mecanismos inatos no controle da infecção. Por outro lado, o haplótipo do MHC não influenciou na resistência/susceptibilidade, na medida em que linhagens de camundongos com um mesmo "background'' genético, mas diferentes haplótipos de MHC (H2b e H2d) apresentam o índice de mortalidade e número de cistos semelhantes após a infecção com aquelas cepas do parasita. Em contraste, o "background'' genético de C57BL/6, mas não o haplótipo de MHC, foi crítico para o desenvolvimento de inflamação intestinal causada pelas cepas estudadas. Finalmente, com relação aos mecanismos efetores, observamos que linfócitos B e T CD8+ controlam a sobrevivência após infecção. Por outro lado, a ativação da enzima óxido nítrico sintase induzida foi um fator importante para controle do número de cistos cerebrais em camundongos infectados com cepas do Tipo I/III. Esses achados são relevantes para o melhor entendimento dos mecanismos imunológicos envolvidos na proteção e patogênese durante infecção com T. gondii.

Immune responses induced by a Leishmania (Leishmania) amazonensis recombinant antigen in mice and lymphocytes from vaccinated subjects

A resposta imune induzida por uma proteina recombinante de Leishmania (Leishmania) amazonensis de 33 kD (Larp33) foi avaliada em linfocitos de individuos vacinados com a Leishvacin e em camundongos atraves de vacinacao. Larp33 foi expressa em Escherichia coli apos clonagem de um fragmento genomico de L. (L.) amazonensis de 2,2 kb no vetor pDS56-6His. Larp33 foi reconhecida por anticorpos IgG presentes no soro de individuos vacinados com Leishvacin e induziu proliferacao em linfocitos desses individuos em niveis comparaveis ao antigeno total de Leishmania...

Role of parasite surface glycoconjugates on induction/regulation of immune responses and inflammation, elicited during Trypanosoma cruzi infection: potential implications on pathophysiology of Chagas" disease

To understand the interaction of Trypanosoma cruzi and the immune system of the vertebrate host, and therefore the pathophysiology of Chagas' disease, different research groups have focused their attention on the identification and characterization of parasite molecules involved in the activation of either innate or adaptive immune responses. The parasite surface molecules that serve as targets of the vertebrate host immune system have also been studied and identified. These studies have revealed that the quatitatively dominant complex of glycosylphosphatidylinositol (GPI)-anchored molecules (GIPLs, mucins and TS) present on the surface of T. cruzi trypomastigotes are essential to control activation of the innate immune system and promote initiation of acquired immune responses in the vertebrate host. Two major families of surface glycoproteins (mucin-like glycoproteins and transialidases) have also been shown to be important targets of parasite specific humoral and cellular immune responses. They are, thus, important candidates for vaccine development as determined in studies using experimental models. Studies regarding the molecular cloning and/or biochemical characterization of the above mentioned T. cruzi surface molecules, and their ability to influence the outcome of T. cruzi infection in the vertebrate host through the stimulation and/or control of the immune system are presently reviewed. A proposition is made that such molecules may have evolved and been selectively conserved to establish an equilibrium between the parasite and its vertebrate host, limiting parasite replication, but allowing parasite persistence and host survival, thus favoring the maintenance of T. cruzi life cycle.