Vaccines at work

Vaccines that elicit a CD8⁺ T cell response have the potential to prevent or treat a number of infectious diseases and malignancies, but little is known about how vaccine encoded proteins are presented to the immune system. In February 4 online Nature Immunology, Christopher Norbury and colleagues from National Institutes of Health, Bethesda, USA, show how antigen-presenting cells (APC) infected with a vector virus prime naïve CD8⁺ T cells in vivo.

Norbury et al. used confocal microscopy to visualize the mouse CD8⁺ T cell response to a well-defined antigen expressed by a recombinant vaccinia virus (rVV). They found infected macrophages and dendritic cells in the draining lymph nodes but only the dendritic cells (DC) presented antigen to naïve CD8⁺ T cells. Presentation was swift — as rapidly as 6 h after inoculation — and then quickly declined in parallel with the number of infected cells present in the nodes (Nat Immunol 2002, DOI: 10.1038/ni762).

"The creation of optimal CD8⁺ T cell vaccines will require the development of a vector that, like VV, induces the abundant synthesis of the nominal antigen in DCs and creates the danger signals necessary to induce and maintain CD8⁺ T cell activation, but does so without expressing other foreign proteins", suggested the authors.