Maintenance of T cell function in the face of chronic antigen stimulation and repeated reactivation for a latent virus infection

Persisting infections are often associated with chronic T cell activation. For certain pathogens, this can lead to T cell exhaustion and survival of what is otherwise a cleared infection. In contrast, for herpesviruses, T cells never eliminate infection once it is established. Instead, effective immunity appears to maintain these pathogens in a state of latency. We used infection with HSV to examine whether effector-type T cells undergoing chronic stimulation retained functional and proliferative capacity during latency and subsequent reactivation. We found that latency-associated T cells exhibited a polyfunctional phenotype and could secrete a range of effector cytokines. These T cells were also capable of mounting a recall proliferative response on HSV reactivation and could do so repeatedly. Thus, for this latent infection, T cells subjected to chronic Ag stimulation and periodic reactivation retain the ability to respond to local virus challenge.

T cell retargeting with MHC class I-restricted antibodies: the CD28 costimulatory domain enhances antigen-specific cytotoxicity and cytokine production

T cells require both primary and costimulatory signals for optimal activation. The primary Ag-specific signal is delivered by engagement of the TCR. The second Ag-independent costimulatory signal is mediated by engagement of the T cell surface costimulatory molecule CD28 with its target cell ligand B7. However, many tumor cells do not express these costimulatory molecules. We previously constructed phage display derived F(AB), G8, and Hyb3, Ab-based receptors with identical specificity but distinct affinities for HLA-A1/MAGE-A1, i.e., "TCR-like" specificity. These chimeric receptors comprised the FcepsilonRI-gamma signaling element. We analyzed whether linking the CD28 costimulation structure to it (gamma + CD28) could affect the levels of MHC-restricted cytolysis and/or cytokine production. Human scFv-G8(POS) T lymphocytes comprising the gamma + CD28 vs the gamma signaling element alone produced substantially more IL-2, TNF-alpha, and IFN-gamma in response to HLA-A1/MAGE-A1(POS) melanoma cells. Also a drastic increase in cytolytic capacity of scFv-G8(POS) T cells, equipped with gamma + CD28 vs the gamma-chain alone was observed.

Transfer of myelin-specific cells deviated in vitro towards IL-4 production ameliorates ongoing experimental allergic neuritis

A causal role of IL-4 (Th2) production for recovery in experimental allergic neuritis (EAN) was indicated by experiments where Th1-like autoreactive cell populations, taken from the induction phase of the disease, were deviated to extensive secretion of IL-4 in a selective fashion, by ex vivo stimulation with autoantigen in the presence of IL-4. The deviated cells were adoptively transferred to EAN rats at a time just prior to the onset of clinical signs. This treatment ameliorated EAN compared with sham treatment. This therapeutic approach, with generation of autoreactive IL-4-secreting cells ex vivo followed by subsequent adoptive transfer, may become a new selective treatment of organ-specific autoimmune diseases since, in contrast to previous attempts, it is done in a physiological and technically easy way.