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Virologie

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Dendritic cells and HIV infection Volume 3, issue 2, Mars - Avril 1999

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Dendritic cells are leukocytes which present antigens to T lymphocytes. They are the only antigen presenting cells able to activate naive T cells in the course of a primary immunisation, and they activate memory T cells optimally. Dendritic cells are infected in vivo by HIV, but with a low frequency, as well as Langerhans cells, which are the epithelial dendritic cells from the skin and pluristratified mucosa. In these mucosa, they represent a very likely port of entry for the virus. Then they transport it to the draining lymph node T cell areas, where they confer infection to T lymphocytes. The coreceptors they express in addition to CD4 and their ability to replicate and transmit the virus depend on their maturation stage. When immature, they are mostly permissive to R5 (monocytotropic) strain penetration, replication and transmission to T cells, which in turn induce their maturation. When mature, they are permissive to R5 and X4 (T-tropic) strains and transfer infection to T cells while activating them optimally, thereby inducing viral transcription in T cells ; however, they only replicate HIV in the presence of activated T cells, particularly in syncytia formed during an antigen-specific stimulation. This differential coreceptor expression might explain the bias towards R5 strains during primary infection. It opens therapeutic avenues using chemokine analogs. Therefore, dendritic cells are a port of entry and an important factor in the propagation of HIV infection, and at the same time a key-factor for the induction of the immune response which fights this infection. In that respect, they must be triggered by the new preventive and therapeutic vaccination strategies.