Effector Memory Th1 CD4 T Cells Are Maintained in a Mouse Model of Chronic Malaria

Protection against malaria often decays in the absence of infection, suggesting that protective immunological memory depends on stimulation. Here we have used CD4+ T cells from a transgenic mouse carrying a T cell receptor specific for a malaria protein, Merozoite Surface Protein-1, to investigate memory in a Plasmodium chabaudi infection. CD4+ memory T cells (CD44hiIL-7Rα+) developed during the chronic infection, and were readily distinguishable from effector (CD62LloIL-7Rα−) cells in acute infection. On the basis of cell surface phenotype, we classified memory CD4+ T cells into three subsets: central memory, and early and late effector memory cells, and found that early effector memory cells (CD62LloCD27+) dominated the chronic infection. We demonstrate a linear pathway of differentiation from central memory to early and then late effector memory cells. In adoptive transfer, CD44hi memory cells from chronically infected mice were more effective at delaying and reducing parasitemia and pathology than memory cells from drug-treated mice without chronic infection, and contained a greater proportion of effector cells producing IFN-γ and TNFα, which may have contributed to the enhanced protection. These findings may explain the observation that in humans with chronic malaria, activated effector memory cells are best maintained in conditions of repeated exposure

Anatomically restricted synergistic antiviral activities of innate and adaptive immune cells in the skin.

Despite extensive ex vivo investigation, the spatiotemporal organization of immune cells interacting with virus-infected cells in tissues remains uncertain. To address this, we used intravital multiphoton microscopy to visualize immune cell interactions with virus-infected cells following epicutaneous vaccinia virus (VV) infection of mice. VV infects keratinocytes in epidermal foci and numerous migratory dermal inflammatory monocytes that outlie the foci. We observed Ly6G(+) innate immune cells infiltrating and controlling foci, while CD8(+) T cells remained on the periphery killing infected monocytes. Most antigen-specific CD8(+) T cells in the skin did not interact with virus-infected cells. Blocking the generation of reactive nitrogen species relocated CD8(+) T cells into foci, modestly reducing viral titers. Depletion of Ly6G(+) and CD8(+) cells dramatically increased viral titers, consistent with their synergistic but spatially segregated viral clearance activities. These findings highlight previously unappreciated differences in the anatomic specialization of antiviral immune cell subsets. Comment in: Getting in front and behind the enemy lines to counter virus infection. [Cell Host Microbe. 2013

Vaccinia virus hijacks EGFR signalling to enhance virus spread through rapid and directed infected cell motility

Cell motility is essential for viral dissemination1. Vaccinia virus (VACV), a close relative of smallpox virus, is thought to exploit cell motility as a means to enhance the spread of infection1. A single viral protein, F11L, contributes to this by blocking RhoA signalling to facilitate cell retraction2. However, F11L alone is not sufficient for VACV-induced cell motility, indicating that additional viral factors must be involved. Here, we show that the VACV epidermal growth factor homologue, VGF, promotes infected cell motility and the spread of viral infection. We found that VGF secreted from early infected cells is cleaved by ADAM10, after which it acts largely in a paracrine manner to direct cell motility at the leading edge of infection. Real-time tracking of cells infected in the presence of EGFR, MAPK, FAK and ADAM10 inhibitors or with VGF-deleted and F11-deleted viruses revealed defects in radial velocity and directional migration efficiency, leading to impaired cell-to-cell spread of infection. Furthermore, intravital imaging showed that virus spread and lesion formation are attenuated in the absence of VGF. Our results demonstrate how poxviruses hijack epidermal growth factor receptor-induced cell motility to promote rapid and efficient spread of infection in vitro and in vivo