RESUMEN
In leishmaniasis, the protective immunity is largely mediated by proinflammatory cytokine producing abilities of T cells and an efficient parasite killing by phagocytic cells. Notwithstanding a substantial progress that has been made during last decades, the mechanisms or factors involved in establishing protective immunity against Leishmania are not identified. In ancient Indian literature, metallic "bhasma," particularly that of "swarna" or gold (fine gold particles), is indicated as one of the most prominent metal-based therapeutic medicine, which is known to impart protective and curative properties in various health issues. In this work, we elucidated the potential of swarna bhasma (SB) on the effector properties of phagocytes and antigen-activated CD4+ T cells in augmenting the immunogenicity of L. donovani antigens. The characterization of SB revealing its shape, size, composition, and measurement of cytotoxicity established the physiochemical potential for its utilization as an immunomodulator. The activation of macrophages with SB enhanced their capacity to produce nitric oxide and proinflammatory cytokines, which eventually resulted in reduced uptake of parasites and their proliferation in infected cells. Further, in Leishmania-infected animals, SB administration reduced the generation of IL-10, an anti-inflammatory cytokine, and enhanced pro-inflammatory cytokine generation by antigen activated CD4+ T cells with increased frequency of double (IFNγ+/TNFα+) and triple (IFNγ+TNFα+IL-2+) positive cells and abrogated disease pathogeneses at the early days of infection. Our results also suggested that cow-ghee (A2) emulsified preparation of SB, either alone or with yashtimadhu, a known natural immune modulator which enhances the SB's potential in enhancing the immunogenicity of parasitic antigens. These findings suggested a definite potential of SB in enhancing the effector functions of phagocytes and CD4+ T cells against L. donovani antigens. Therefore, more studies are needed to elucidate the mechanistic details of SB and its potential in enhancing vaccine-induced immunity.
Asunto(s)
Presentación de Antígeno , Antígenos de Protozoos , Linfocitos T CD4-Positivos , Calotropis , Oro , Látex , Leishmania donovani , Macrófagos , Medicina Ayurvédica , Células TH1 , Arsénico , Combinación de Medicamentos , Oro/administración & dosificación , Oro/farmacología , Látex/administración & dosificación , Látex/farmacología , Plomo , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Linfocitos T CD4-Positivos/inmunología , Fagocitos/efectos de los fármacos , Fagocitos/inmunología , Leishmaniasis/inmunología , Leishmaniasis/parasitología , Leishmania donovani/efectos de los fármacos , Leishmania donovani/crecimiento & desarrollo , Leishmania donovani/inmunología , Antígenos de Protozoos/inmunología , Células TH1/inmunología , Animales , Ratones , Células RAW 264.7 , Femenino , Ratones Endogámicos BALB CRESUMEN
One of the major reasons behind the limited success of vaccine candidates against all forms of leishmaniasis is the inability of parasitic antigens to induce robust cell-mediated immunity and immunological memory. Here we find, for the first time, that the adjuvantation of whole-killed Leishmania vaccine (Leishvacc) with anti-CD200 and anti-CD300a antibodies enhances CD4+ T cells mediated immunity in vaccinated mice and provides protection against wild-type parasites. The antibody adjuvantation, either alone or with a TLR4 agonist monophosphoryl A (MPL-A), induced the production of pro-inflammatory cytokines viz., IFN-γ, TNF-α, and IL-2 by antigen experienced CD4+ T cells, and also enhanced their rate of conversion into their memory phenotypes against Leishvacc antigens. The antibody adjuvanted vaccine also promoted the generation of IgG2a-mediated protective humoral immunity in vaccinated mice. Further, the mice vaccinated with antibodies adjuvanted vaccine showed strong resilience against metacyclic forms of L. donovani parasites as we observed reduced clinical features such as splenomegaly, hepatomegaly, granulomatous tissues in the liver, and parasitic load in their spleen. The findings of this study demonstrate that the anti-CD200 and anti-CD300a antibodies have potential to increase the protective efficacy of the whole-killed Leishmania vaccine, and opens up a new gateway to diversify the roles of immune checkpoints in vaccine development against leishmaniasis.
Asunto(s)
Leishmania donovani , Leishmania , Vacunas contra la Leishmaniasis , Leishmaniasis Visceral , Leishmaniasis , Parásitos , Animales , Ratones , Vacunas de Productos Inactivados , Adyuvantes Inmunológicos/farmacología , Leishmaniasis/prevención & control , Ratones Endogámicos BALB C , Antígenos de ProtozoosRESUMEN
CD8+ T cells are an important regiment of adaptive immunity that play a decisive role in elimination of many species of Leishmania parasite from the host. In visceral leishmaniasis, caused by L. donovani, the loss of CD8+ T cells function has been found associated with augmented pathogenesis. The factors determining CD8+ T cells activation and function against Leishmania antigens are largely unknown. In this study, we investigated the role of an immune inhibitory receptor, CD300a, on the effector properties of dendritic cells and CD8+ T cells. We observed that the Leishmania regulates the effectors function of CD8+ T cells by increasing CD300a expression on CD11c+ dendritic cells. The abrogation of CD300a signaling in parasites infected animals induced CD8+ T cell abilities to produce IFN-γ, TNF-α and also helped them to acquire desired multifunctionality. The CD300a receptor blocking also enhanced the number of CD8+ T cells memory phenotypes at the early days of infection, suggesting its potential beneficial role in vaccine induced immunity. We also observed significantly enhanced levels of pro-inflammatory cytokines in the spleen of CD300a blocked infected animals with concomitant reduced spleen parasite load. Additionally, the abrogation of CD300a signals in the infected animals helped in establishing Th1 type protective humoral immunity with significantly elevated levels of IgG2a antibodies. Since CD8+ T cells are an important determinant of vaccine induced immunity against leishmaniasis, the findings corroborate the potential of CD300a in vaccine induced immunity and thus require further attention.
Asunto(s)
Leishmania donovani , Leishmaniasis Visceral , Animales , Ratones , Leishmania donovani/genética , Linfocitos T CD8-positivos , Leishmaniasis Visceral/parasitología , Citocinas , Activación de Linfocitos , Ratones Endogámicos BALB CRESUMEN
The parasites of the genus Leishmania survive and proliferate in the host phagocytic cells by taking control over their microbicidal functions. The parasite also promotes differentiation of antigen-specific anti-inflammatory cytokines producing effector T cells, which eventually results in disease pathogenesis. The mechanisms that parasites employ to dominate host adaptive immunity are largely unknown. For the first time, we report that L. donovani, which causes visceral leishmaniasis in the Indian subcontinent, upregulates the expression of an immune inhibitory receptor i.e., CD300a on antigen presenting and phagocytic cells to dampen their effector functions. The blocking of CD300a signals in leishmania antigens activated macrophages and dendritic cells enhanced the production of nitric oxide, pro-inflammatory cytokines along with MHCI/II genes expression, and reduced parasitic uptake. Further, the abrogation of CD300a signals in Leishmania infected mice benefited antigen-experienced, i.e., CD4+CD44+ and CD8+CD44+ T cells to acquire more pro-inflammatory cytokines producing phenotypes and helped in the early clearance of parasites from their visceral organs. The CD300a receptor blocking also enhanced the conversion of CD4+ T effectors cells to their memory phenotypes i.e., CCR7high CD62Lhigh up to 1.6 and 1.9 fold after 14 and 21 days post-infection, respectively. These findings implicate that CD300a is an important determinant of host phagocytic cells functions and T cells differentiation against Leishmania antigens.