Endogenous costimulatory molecules on T cells such as 4-1BB (CD137) can be leveraged for cancer immunotherapy. Systemic administration of agonistic anti–4-1BB antibodies, although effective preclinically, has not advanced to phase 3 trials because they have been hampered by both dependency on Fcγ receptor–mediated hyperclustering and hepatotoxicity. To overcome these issues, we engineered proteins simultaneously targeting 4-1BB and a tumor stroma or tumor antigen: FAP–4-1BBL (RG7826) and CD19–4-1BBL. In the presence of a T cell receptor signal, they provide potent T cell costimulation strictly dependent on tumor antigen–mediated hyperclustering without systemic activation by FcγR binding. We could show targeting of FAP–4-1BBL to FAP-expressing tumor stroma and lymph nodes in a colorectal cancer–bearing rhesus monkey. Combination of FAP–4-1BBL with tumor antigen–targeted T cell bispecific (TCB) molecules in human tumor samples led to increased IFN-γ and granzyme B secretion. Further, combination of FAP– or CD19–4-1BBL with CEA-TCB (RG7802) or CD20-TCB (RG6026), respectively, resulted in tumor remission in mouse models, accompanied by intratumoral accumulation of activated effector CD8+T cells. FAP– and CD19–4-1BBL thus represent an off-the-shelf combination immunotherapy without requiring genetic modification of effector cells for the treatment of solid and hematological malignancies.

Lymphocytic choriomeningitis virus (LCMV) exhibits natural tropism for dendritic cells and represents the prototypic infection that elicits protective CD8+ T cell (cytotoxic T lymphocyte (CTL)) immunity. Here we have harnessed the immunobiology of this arenavirus for vaccine delivery. By using producer cells constitutively synthesizing the viral glycoprotein (GP), it was possible to replace the gene encoding LCMV GP with vaccine antigens to create replication-defective vaccine vectors. These rLCMV vaccines elicited CTL responses that were equivalent to or greater than those elicited by recombinant adenovirus 5 or recombinant vaccinia virus in their magnitude and cytokine profiles, and they exhibited more effective protection in several models. In contrast to recombinant adenovirus 5, rLCMV failed to elicit vector-specific antibody immunity, which facilitated re-administration of the same vector for booster vaccination. In addition, rLCMV elicited T helper type 1 CD4+ T cell responses and protective neutralizing antibodies to vaccine antigens. These features, together with low seroprevalence in humans, suggest that rLCMV may show utility as a vaccine platform against infectious diseases and cancer.

Photosynthetic organisms respond to changes in ambient light by modulating the size and composition of their lightharvesting complexes, which in the case of the green alga Chlamydomonas reinhardtii consists of >15 members of a large extended family of chlorophyll binding subunits. How their expression is coordinated is unclear. Here, we describe the analysis of an insertion mutant, state transitions mutant3 (stm3), which we show has increased levels of LHCBM subunits associated with the light-harvesting antenna of photosystem II. The mutated nuclear gene in stm3 encodes the RNA binding protein NAB1 (for putative nucleic acid binding protein). In vitro and in vivo RNA binding and protein expression studies have confirmed that NAB1 differentially binds to LHCBM mRNA in a subpolysomal high molecular weight RNA-protein complex. Binding of NAB1 stabilizes LHCBM mRNA at the preinitiation level via sequestration and thereby represses translation. The specificity and affinity of binding are determined by an RNA sequence motif similar to that used by the Xenopus laevis translation repressor FRGY2, which is conserved to varying degrees in the LHCBM gene family. We conclude from our results that NAB1 plays an important role in controlling the expression of the light-harvesting antenna of photosystem II at the posttranscriptional level. The similarity of NAB1 and FRGY2 of Xenopus implies the existence of similar RNA-masking systems in animals and plants.

Signaling of the TNF receptor superfamily member CD27 activates costimulatory pathways to elicit T-and B-cell responses. CD27 signaling is regulated by the expression of its ligand CD70 on subsets of dendritic cells and lymphocytes. Here, we analyzed the role of the CD27-CD70 interaction in the immunologic control of solid tumors in Cd27-deficient mice. In tumor-bearing wild-type mice, the CD27-CD70 interaction increased the frequency of regulatory T cells (Tregs), reduced tumor-specific T-cell responses, increased angiogenesis, and promoted tumor growth. CD27 signaling reduced apoptosis of Tregs in vivo and induced CD4 þ effector T cells (Teffs) to produce interleukin-2, a key survival factor for Tregs. Consequently, the frequency of Tregs and growth of solid tumors were reduced in Cd27-deficient mice or in wild-type mice treated with monoclonal antibody to block CD27 signaling. Our findings, therefore, provide a novel mechanism by which the adaptive immune system enhances tumor growth and may offer an attractive strategy to treat solid tumors. Cancer Res; 72 (14); 3664-76. Ó2012 AACR.