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- Arama, Charles, et al.
(författare)
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A recombinant Bacille Calmette-Guerin construct expressing the Plasmodium falciparum circumsporozoite protein enhances dendritic cell activation and primes for circumsporozoite-specific memory cells in BALB/c mice
- 2012
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Ingår i: Vaccine. - : Elsevier. - 0264-410X .- 1873-2518. ; 30:37, s. 5578-5584
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Tidskriftsartikel (refereegranskat)abstract
- A protective malaria vaccine may induce both high levels of neutralising antibodies and strong T-cell responses. The Plasmodium falciparum circumsporozoite protein (CSp) is a leading pre-erythrocytic vaccine candidate. CSp is a week immunogen per se, but Mycobacterium bovis Bacille Calmette-Guérin (BCG) has excellent adjuvant activity and has been utilized as a vector to deliver heterologous vaccine candidate antigens. It is safe in immunocompetent individuals and inexpensive to produce. We assessed in vitro and in vivo a recombinant BCG-expressing CSp (BCG-CS) as malaria vaccine candidate. Immunisation of BALB/c mice with BCG-CS augmented numbers of dendritic cells (DCs) in draining lymph nodes and in the spleen. The activation markers MHC-class-II, CD40, CD80 and CD86 on DCs were significantly upregulated by BCG-CS as compared to wild-type BCG (wt-BCG). In vitro stimulation of bone marrow-derived DCs and macrophages with BCG-CS induced IL-12 and TNF-α production. BCG-CS induced higher phagocytic activity in macrophages as compared to wt-BCG. Immunogenicity studies show that BCG-CS induced CS-specific antibodies and IFN-γ-producing memory cells. In conclusion, BCG-CS is highly efficient in activating antigen-presenting cells (APCs) for priming of adaptive immunity. Implications for the rational design of novel vaccines against malaria and TB, the two major devastating poverty-related diseases, are discussed.
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- Arama, Charles, et al.
(författare)
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Epigenetics and Malaria Susceptibility/Protection : A Missing Piece of the Puzzle
- 2018
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 9
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Forskningsöversikt (refereegranskat)abstract
- A better understanding of stable changes in regulation of gene expression that result from epigenetic events is of great relevance in the development of strategies to prevent and treat infectious diseases. Histone modification and DNA methylation are key epigenetic mechanisms that can be regarded as marks, which ensure an accurate transmission of the chromatin states and gene expression profiles over generations of cells. There is an increasing list of these modifications, and the complexity of their action is just beginning to be understood. It is clear that the epigenetic landscape plays a fundamental role in most biological processes that involve the manipulation and expression of DNA. Although the molecular mechanism of gene regulation is relatively well understood, the hierarchical order of events and dependencies that lead to protection against infection remain largely unknown. In this review, we propose that host epigenetics is an essential, though relatively under studied, factor in the protection or susceptibility to malaria.
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- Arama, Charles, et al.
(författare)
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Heterologous prime-boost regimen adenovector 35-circumsporozoite protein vaccine/recombinant Bacillus Calmette-Guerin expressing the Plasmodium falciparum circumsporozoite induces enhanced long-term memory immunity in BALB/c mice
- 2012
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Ingår i: Vaccine. - : Elsevier BV. - 0264-410X .- 1873-2518. ; 30:27, s. 4040-4045
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sustained antibody levels are a hallmark of immunity against many pathogens, and induction of long-term durable antibody titers is an essential feature of effective vaccines. Heterologous prime-boost approaches with vectors are optimal strategies to improve a broad and prolonged immunogenicity of malaria vaccines. Results: In this study, we demonstrate that the heterologous prime-boost regimen Ad35-CS/BCG-CS induces stronger immune responses by enhancing type 1 cellular producing-cells with high levels of CSp-specific IFN-gamma and cytophilic IgG2a antibodies as compared to a homologous BCG-CS and a heterologous BCG-CS/CSp prime-boost regimen. Moreover, the heterologous prime-boost regimen elicits the highest level of LLPC-mediated immune responses. Conclusion: The increased IFN-gamma-producing cell responses induced by the combination of Ad35-CS/BCG-CS and sustained type 1 antibody profile together with high levels of LLPCs may be essential for the development of long-term protective immunity against liver-stage parasites.
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- Lyke, Kirsten E., et al.
(författare)
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Antigen-Specific B Memory Cell Responses to Plasmodium falciparum Malaria Antigens and Schistosoma haematobium Antigens in Co-Infected Malian Children
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:6, s. e37868-
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Tidskriftsartikel (refereegranskat)abstract
- Polyparasitism is common in the developing world. We have previously demonstrated that schistosomiasis-positive (SP) Malian children have age-dependent protection from malaria compared to matched schistosomiasis-negative (SN) children. Evidence of durable immunologic memory to malaria antigens is conflicting, particularly in young children and the effect of concomitant schistomiasis upon acquisition of memory is unknown. We examined antigen-specific B memory cell (MBC) frequencies (expressed as percentage of total number of IgG-secreting cells) in 84 Malian children aged 4-14 to malaria blood-stage antigens, apical membrane antigen 1 (AMA-1) and merozoite surface protein 1 (MSP-1) and to schistosomal antigens, Soluble Worm Antigenic Preparation (SWAP) and Schistosoma Egg Antigen (SEA), at a time point during the malaria transmission season and a follow-up dry season visit. We demonstrate, for the first time, MBC responses to S. haematobium antigens in Malian children with urinary egg excretion and provide evidence of seasonal acquisition of immunologic memory, age-associated differences in MBC acquisition, and correlation with circulating S. haematobium antibody. Moreover, the presence of a parasitic co-infection resulted in older children, aged 9-14 years, with underlying S. haematobium infection having significantly more MBC response to malaria antigens (AMA1 and MSP1) than their age-matched SN counterparts. We conclude that detectable MBC response can be measured against both malaria and schistosomal antigens and that the presence of S. haematobium may be associated with enhanced MBC induction in an age-specific manner.
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- Lyke, Kirsten E., et al.
(författare)
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Reduced T Regulatory Cell Response during Acute Plasmodium falciparum Infection in Malian Children Co-Infected with Schistosoma haematobium
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:2, s. e31647-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Regulatory T cells (Tregs) suppress host immune responses and participate in immune homeostasis. In co-infection, secondary parasite infections may disrupt the immunologic responses induced by a pre-existing parasitic infection. We previously demonstrated that schistosomiasis-positive (SP) Malian children, aged 4-8 years, are protected against the acquisition of malaria compared to matched schistosomiasis-negative (SN) children. Methods and Findings: To determine if Tregs contribute to this protection, we performed immunologic and Treg depletion in vitro studies using PBMC acquired from children with and without S. haematobium infection followed longitudinally for the acquisition of malaria. Levels of Tregs were lower in children with dual infections compared to children with malaria alone (0.49 versus 1.37%, respectively, P = 0.004) but were similar months later, during a period with negligible malaria transmission. The increased levels of Tregs in SN subjects were associated with suppressed serum Th1 cytokine levels, as well as elevated parasitemia compared to co-infected counterparts. Conclusions: These results suggest that lower levels of Tregs in helminth-infected children correlate with altered circulating cytokine and parasitologic results which may play a partial role in mediating protection against falciparum malaria.
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