RESUMO
BACKGROUND: Visceral leishmaniasis (VL) is a severe vector-born disease of humans and dogs caused by Leishmania donovani complex parasites. Approximately 0.2 to 0.4 million new human VL cases occur annually worldwide. In the new world, these alarming numbers are primarily due to the impracticality of current control methods based on vector reduction and dog euthanasia. Thus, a prophylactic vaccine appears to be essential for VL control. The current efforts to develop an efficacious vaccine include the use of animal models that are as close to human VL. We have previously reported a L. infantum-macaque infection model that is reliable to determine which vaccine candidates are most worthy for further development. Among the few amastigote antigens tested so far, one of specific interest is the recombinant A2 (rA2) protein that protects against experimental L. infantum infections in mice and dogs. METHODOLOGY/PRINCIPAL FINDINGS: Primates were vaccinated using three rA2-based prime-boost immunization regimes: three doses of rA2 plus recombinant human interleukin-12 (rhIL-12) adsorbed in alum (rA2/rhIL-12/alum); two doses of non-replicative adenovirus recombinant vector encoding A2 (Ad5-A2) followed by two boosts with rA2/rhIL-12/alum (Ad5-A2+rA2/rhIL12/alum); and plasmid DNA encoding A2 gene (DNA-A2) boosted with two doses of Ad5-A2 (DNA-A2+Ad5-A2). Primates received a subsequent infectious challenge with L. infantum. Vaccines, apart from being safe, were immunogenic as animals responded with increased pre-challenge production of anti-A2-specific IgG antibodies, though with some variability in the response, depending on the vaccine formulation/protocol. The relative parasite load in the liver was significantly lower in immunized macaques as compared to controls. Protection correlated with hepatic granuloma resolution, and reduction of clinical symptoms, particularly when primates were vaccinated with the Ad5-A2+rA2/rhIL12/alum protocol. CONCLUSIONS/SIGNIFICANCE: The remarkable clinical protection induced by A2 in an animal model that is evolutionary close to humans qualifies this antigen as a suitable vaccine candidate against human VL.
Assuntos
Antígenos de Protozoários/imunologia , Portadores de Fármacos , Leishmania infantum/imunologia , Leishmaniose/prevenção & controle , Vacinas Protozoárias/imunologia , Vacinação/métodos , Adenovírus Humanos/genética , Adjuvantes Imunológicos/administração & dosagem , Animais , Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/genética , Modelos Animais de Doenças , Feminino , Vetores Genéticos , Imunoglobulina G/sangue , Leishmania infantum/genética , Leishmaniose/imunologia , Fígado/parasitologia , Fígado/patologia , Macaca , Masculino , Carga Parasitária , Vacinas Protozoárias/administração & dosagem , Vacinas Protozoárias/genética , Vacinas Sintéticas/administração & dosagem , Vacinas Sintéticas/genética , Vacinas Sintéticas/imunologiaRESUMO
Retinochoroiditis manifests in patients infected with Toxoplasma gondii. Here, we assessed 30 sibships and 89 parent/case trios of presumed ocular toxoplasmosis (POT) to evaluate associations with polymorphisms in the NOD2 gene. Three haplotype-tagging single-nucleotide polymorphisms (tag-SNPs) within the NOD2 gene were genotyped. The family-based association test showed that the tag-SNP rs3135499 is associated with retinochoroiditis (P = .039). We then characterized the cellular immune response of 59 cases of POT and 4 cases of active ocular toxoplasmosis (AOT). We found no differences in levels of interferon γ (IFN-γ) and interleukin 2 produced by T-helper 1 cells when comparing patients with AOT or POT to asymptomatic individuals. Unexpectedly, we found an increased interleukin 17A (IL-17A) production in patients with POT or OAT. In patients with POT or AOT, the main cellular source of IL-17A was CD4(+)CD45RO(+)T-bet(-)IFN-γ(-) T-helper 17 cells. Altogether, our results suggest that NOD2 influences the production of IL-17A by CD4(+) T lymphocytes and might contribute to the development of ocular toxoplasmosis.
Assuntos
Interleucina-17/metabolismo , Proteína Adaptadora de Sinalização NOD2/genética , Polimorfismo de Nucleotídeo Único/genética , Toxoplasmose Ocular/genética , Adulto , Alelos , Brasil , Linfócitos T CD4-Positivos/imunologia , Proliferação de Células , Estudos de Coortes , Citocinas/análise , Haplótipos , Humanos , Imunofenotipagem , Interleucina-17/imunologia , Proteína Adaptadora de Sinalização NOD2/imunologia , Fenótipo , Polimorfismo de Nucleotídeo Único/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Células Th1/imunologia , Células Th17/imunologia , Toxoplasmose Ocular/imunologiaRESUMO
Interleukin-1 receptor (IL1R)-associated kinase 4 (IRAK4) is a member of the IRAK family and has an important role in inducing the production of inflammatory mediators. This kinase is downstream of MyD88, an adaptor protein essential for Toll-like receptor (TLR) function. We investigated the role of this kinase in IRAK4-deficient mice orally infected with the cystogenic ME49 strain of Toxoplasma gondii. IRAK4(-/-) mice displayed higher morbidity, tissue parasitism, and accelerated mortality than the control mice. The lymphoid follicles and germinal centers from infected IRAK4(-/-) mice were significantly smaller. We consistently found that IRAK4(-/-) mice showed a defect in splenic B cell activation and expansion as well as diminished production of gamma interferon (IFN-γ) by T lymphocytes. The myeloid compartment was also affected. Both the frequency and ability of dendritic cells (DCs) and monocytes/macrophages to produce IL-12 were significantly decreased, and resistance to infection with Toxoplasma was rescued by treating IRAK4(-/-) mice with recombinant IL-12 (rIL-12). Additionally, we report the association of IRAK4 haplotype-tagging single nucleotide polymorphisms (tag-SNPs) with congenital toxoplasmosis in infected individuals (rs1461567 and rs4251513, P < 0.023 and P < 0.045, respectively). Thus, signaling via IRAK4 is essential for the activation of innate immune cells, development of parasite-specific acquired immunity, and host resistance to infection with T. gondii.
Assuntos
Quinases Associadas a Receptores de Interleucina-1/deficiência , Toxoplasma/patogenicidade , Toxoplasmose Congênita/genética , Toxoplasmose/imunologia , Adulto , Animais , Linfócitos B/imunologia , Criança , Pré-Escolar , Suscetibilidade a Doenças , Feminino , Genótipo , Humanos , Imunidade Inata , Quinases Associadas a Receptores de Interleucina-1/genética , Ativação Linfocitária , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Th1/imunologia , Toxoplasma/imunologia , Toxoplasmose/genética , Toxoplasmose/parasitologia , Toxoplasmose/patologia , Toxoplasmose Congênita/imunologia , Toxoplasmose Congênita/parasitologia , Toxoplasmose Congênita/patologiaRESUMO
A2 was identified as an amastigote virulence factor of Leishmania (Leishmania) donovani and as a candidate antigen for vaccine development against visceral leishmaniasis. Here, predicted hydrophilic, class I and II MHC-binding synthetic peptides were used to define epitopes recognized by A2-specific antibodies, CD8+ T and CD4+ T cells, respectively. Immunization of BALB/c mice with adenovirus expressing A2 (AdA2) resulted in low antibody response, contrasting with high levels of IFN-gamma producing CD4+ T and CD8+ T cells specific for A2. Further, A2-specific CD8+ T cells from immunized mice were capable of lysing sensitized target cells in vivo. Finally, we demonstrated an association of A2-specific T cell responses and reduced parasitism in both liver and spleen from mice immunized with AdA2 and challenged with L. (L.) chagasi.