The efficiency of antigen (Ag) processing by dendritic cells (DCs) is vital for the strength of the ensuing T-cell responses. Previously, we and others have shown that in comparison to protein vaccines, vaccination with synthetic long peptides (SLPs) has shown more promising (pre-)clinical results. Here, we studied the unknown mechanisms underlying the observed vaccine efficacy of SLPs. We report an in vitro processing analysis of SLPs for MHC class I and class II presentation by murine DCs and human monocyte-derived DCs. Compared to protein, SLPs were rapidly and much more efficiently processed by DCs, resulting in an increased presentation to CD4 + and CD8 + T cells. The mechanism of access to MHC class I loading appeared to differ between the two forms of Ag. Whereas whole soluble protein Ag ended up largely in endolysosomes, SLPs were detected very rapidly outside the endolysosomes after internalization by DCs, followed by proteasomeand transporter associated with Ag processing-dependent MHC class I presentation. Compared to the slower processing route taken by whole protein Ags, our results indicate that the efficient internalization of SLPs, accomplished by DCs but not by B or T cells and characterized by a different and faster intracellular routing, leads to enhanced CD8 + T-cell activation.Keywords: Antigen presentation/processing r Cellular immunology r CD8 + T cells r Dendritic cells Additional supporting information may be found in the online version of this article at the publisher's web-site lower efficiency compared to SLP-loaded DCs (Fig. 1B). Prestimulation of DCs with the TLR4 ligand LPS had no effect on the MHC class I presentation of OVA-protein but improved Ag presentation of SSP-OVA 8aa (data not shown) and long peptide Ag (Fig. 1C). HLA-B7-restricted presentation by human monocyte-derived DCs (MoDCs) of HIV-derived protein and SLPs was also studied. We were unable to detect cytokine production by CD8 + T cells cocultured with GAG-protein-loaded DCs. In contrast, SLP-GAG 22aa induced significant CD8 + T-cell activation (see Fig. 2 and below).Together, these data show that cross-presentation of SLPs is superior to that of proteins as examined with both mouse and human DCs. Rapid Ag presentation of SLPs by murine and human DCsThe efficiency of SLP-processing was assessed by studying the time required for DCs to present Ag on MHC class I (H2-K b )molecules. Murine DCs were incubated with a single concentration of SLPs, synthetic short peptides (SSPs) or protein for the indicated time periods. The minimal peptide, SSPs, was rapidly presented to CD8 + T cells resulting in strong activation already after 1 h. DCs loaded with SLP also activated CD8 + T cells 1 h after Ag loading but with lower potency. We excluded that SLPs were cleaved extracellularly, processed, and loaded on MHC class I and II molecules by incubating paraformaldehyde (PFA) fixed cells with the peptide Ag and observed no cross-presentation (data not shown). DCs loaded with 10 μM OVA-protein failed to induce significant CD8 + T-ce...

Memory T-cell inflation develops during certain persistent viral infections and is char-Keywords: CD8 + T cells r CMV r Memory T-cell inflation r T-cell activation r Viral immunity Additional supporting information may be found in the online version of this article at the publisher's web-site

f Cytomegaloviruses (CMVs) establish lifelong infections that are controlled in part by CD4؉ and CD8 ؉ T cells. To promote persistence, CMVs utilize multiple strategies to evade host immunity, including modulation of costimulatory molecules on infected antigen-presenting cells. In humans, CMV-specific memory T cells are characterized by the loss of CD27 expression, which suggests a critical role of the costimulatory receptor-ligand pair CD27-CD70 for the development of CMV-specific T cell immunity. In this study, the in vivo role of CD27-CD70 costimulation during mouse CMV infection was examined. During the acute phase of infection, the magnitudes of CMV-specific CD4؉ and CD8 ؉ T cell responses were decreased in mice with abrogated CD27-CD70 costimulation. Moreover, the accumulation of inflationary memory T cells during the persistent phase of infection and the ability to undergo secondary expansion required CD27-CD70 interactions. The downmodulation of CD27 expression, however, which occurs gradually and exclusively on inflationary memory T cells, is ligand independent. Furthermore, the IL-2 production in both noninflationary and inflationary CMV-specific T cells was dependent on CD27-CD70 costimulation. Collectively, these results highlight the importance of the CD27-CD70 costimulation pathway for the development of CMV-specific T cell immunity during acute and persistent infection.

CD8+ T cells have the potential to attack and eradicate cancer cells. The efficacy of therapeutic vaccines against cancer, however, lacks defined immune correlates of tumor eradication after (therapeutic) vaccination based on features of Ag-specific T cell responses. In this study, we examined CD8+ T cell responses elicited by various peptide and TLR agonist-based vaccine formulations in nontumor settings and show that the formation of CD62L−KLRG1+ effector-memory CD8+ T cells producing the effector cytokines IFN-γ and TNF predicts the degree of therapeutic efficacy of these vaccines against established s.c. tumors. Thus, characteristics of vaccine-induced CD8+ T cell responses instill a predictive determinant for the efficacy of vaccines during tumor therapy.

Objective: T-cells are central to the immune response responsible for native atherosclerosis. The objective of this study is to investigate T-cell contribution to post-interventional accelerated atherosclerosis development, as well as the role of the CD28-CD80/86 co-stimulatory and Cytotoxic T-Lymphocyte Antigen (CTLA)-4 co-inhibitory pathways controlling T-cell activation status in this process. Methods and results: The role of T-cells and the CD28-CD80/86 co-stimulatory and CTLA-4 co-inhibitory pathways were investigated in a femoral artery cuff mouse model for post-interventional remodeling, with notable intravascular CTLA-4+ T-cell infiltration. Reduced intimal lesions developed in CD4 −/− and CD80 −/− CD86 −/− mice compared to normal C57Bl/6J controls. Systemic abatacept-treatment, a soluble CTLA-4Ig fusion protein that prevents CD28-CD80/86 co-stimulatory T-cell activation, prevented intimal thickening by 58.5% (p = 0.029). Next, hypercholesterolemic ApoE3*Leiden mice received abatacept-treatment which reduced accelerated atherosclerosis development by 78.1% (p = 0.040) and prevented CD4 T-cell activation, indicated by reduced splenic fractions of activated KLRG1 +, PD1 +, CD69+ and CTLA-4+ T-cells. This correlated with reduced plasma interferon-γ and elevated interleukin-10 levels. The role of CTLA-4 was confirmed using CTLA-4 blocking antibodies, which strongly increased vascular lesion size by 66.7% (p=0.008), compared to isotype-treated controls. Conclusions: T-cell CD28-CD80/86 co-stimulation is vital for post-interventional accelerated atherosclerosis development and is regulated by CTLA-4 co-inhibition, indicating promising clinical potential for prevention of post-interventional remodeling by abatacept.