A whodunit: an appointment with death.
ABSTRACT This is the tale of murder, suicide, evolution, and resurrection, taking place in four parts, and all in the name of antigen cross-priming. We invite you to explore the dark mysteries lurking within each of us as you are guided through circuitous cellular pathways in a merciless fight for survival... with viral immunity being the grand finale?!
SourceAvailable from: Pierre-Emmanuel Joubert[Show abstract] [Hide abstract]
ABSTRACT: Phagocytosis of dying cells constitutes an important mechanism of antigen capture for the cross-priming of CD8(+) T cells. This process has been shown to be critical for achieving tumor and viral immunity. While most studies have focused on the mechanisms inherent in the dendritic cell that account for exogenous antigen accessing MHC I, several recent reports have highlighted the important contribution made by the antigen donor cell. Specifically, the cell stress and cell death pathways that precede antigen transfer are now known to impact cross-presentation and cross-priming. Herein, we review the current literature regarding a role for macroautophagy within the antigen donor cell. Further examination of this point of immune regulation is warranted and may contribute to a better understanding of how to optimize immunotherapy for treatment of cancer and chronic infectious disease.Frontiers in Immunology 03/2012; 3:61. DOI:10.3389/fimmu.2012.00061
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ABSTRACT: Antigen processing involves many proteolytic enzymes such as proteasomes and cathepsins. The processed antigen is then presented on the cell surface bound to either MHC class I or class II molecules and induces/interacts with antigen-specific CD8+ and CD4+ T-cells, respectively. Preliminary immunological data from the RV144 phase III trial indicated that the immune responses were biased towards the Env antigen with a dominant CD4+ T-cell response. In this study, we examined the susceptibility of HIV-1 Env-A244 gp120 protein, one of the protein boost subunits of the RV144 Phase III vaccine trial, to proteasomes and cathepsins and identified the generated peptide epitope repertoire by mass spectrometry. The peptide fragments were tested for cytokine production in CD4(+) T-cell lines derived from RV144 volunteers. Env-A244 was resistant to proteasomes, thus diminishing the possibility of the generation of class I epitopes by the classical MHC class I pathway. However, Env-A244 was efficiently cleaved by cathepsins generating peptide arrays identified by mass spectrometry that contained both MHC class I and class II epitopes as reported in the Los Alamos database. Each of the cathepsins generated distinct degradation patterns containing regions of light and dense epitope clusters. The sequence DKKQKVHALF that is part of the V2 loop of gp120 produced by cathepsins induced a polyfunctional cytokine response including the generation of IFN-γ from CD4(+) T-cell lines-derived from RV144 vaccinees. This sequence is significant since antibodies to the V1/V2-loop region correlated inversely with HIV-1 infection in the RV144 trial. Based on our results, the susceptibility of Env-A244 to cathepsins and not to proteasomes suggests a possible mechanism for the generation of Env-specific CD4(+)T cell and antibody responses in the RV144 vaccinees.PLoS ONE 08/2012; 7(8):e42579. DOI:10.1371/journal.pone.0042579 · 3.53 Impact Factor
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ABSTRACT: Manipulation of cell death pathways has been identified as a common feature of host-microbe interactions. We examine two examples: influenza A as a representative acute infection and cytomegalovirus as an example of chronic infection. From the perspective of viral entry, replication, and transmission, we identify points of interconnection with the host response to infection, namely the induction of host cell death, inflammation, and immunity. Following from this analysis, we argue that the evolution and fine-tuned regulation of death-associated genes may result from constant microbial pressure--past and present--that helped to support and coordinate cell death programs within the host. Interestingly, the delay in host cell death allows time for the virus to replicate while perturbations in cell death allow the host cell to initiate an immune response. This may represent a genetically encoded trade-off ensuring survival of both host and virus, or it may be a part of the complex agenda of infectious microbes.Immunity 10/2011; 35(4):478-90. DOI:10.1016/j.immuni.2011.10.010 · 19.75 Impact Factor