Tumor-infiltrating T cells, particularly CD45RO þ CD8þ memory T cells, confer a positive prognostic value in human cancers. However, the mechanisms that promote a protective T-cell response in the tumor microenvironment remain unclear. In chronic inflammatory settings such as the tumor microenvironment, lymphoid neogenesis can occur to create local lymph node-like structures known as tertiary lymphoid structures (TLS). These structures can exacerbate a local immune response, such that TLS formation in tumors may help promote an efficacious immune contexture. However, the role of TLS in tumors has yet to be investigated carefully. In lung tumors, mature dendritic cells (DC) present in tumor-associated TLS can provide a specific marker of these structures. In this study, we evaluated the influence of TLS on the characteristics of the immune infiltrate in cohorts of prospective and retrospective human primary lung tumors (n ¼ 458). We found that a high density of mature DC correlated closely to a strong infiltration of T cells that are predominantly of the effector-memory phenotype. Moreover, mature DC density correlated with expression of genes related to T-cell activation, T-helper 1 (Th1) phenotype, and cytotoxic orientation. Lastly, a high density of TLS-associated DC correlated with long-term survival, which also allowed a distinction of patients with high CD8 þ T-cell infiltration but a high risk of death. Taken together, our results show how tumors infiltrated by TLS-associated mature DC generate a specific immune contexture characterized by a strong Th1 and cytotoxic orientation that confers the lowest risk of death. Furthermore, our findings highlight the pivotal function of TLS in shaping the immune character of the tumor microenvironment, in promoting a protective immune response mediated by T cells against cancer. Cancer Res; 74(3); 705-15. Ó2013 AACR.

Programmed cell-death 1 ligand 1 (PD-L1) is a member of the B7/CD28 family of proteins that control T-cell activation. Many tumors can upregulate expression of PD-L1, inhibiting antitumor T-cell responses and avoiding immune surveillance and elimination. We have identified and characterized MEDI4736, a human IgG1 monoclonal antibody that binds with high affinity and specificity to PD-L1 and is uniquely engineered to prevent antibody-dependent cell-mediated cytotoxicity. In vitro assays demonstrate that MEDI4736 is a potent antagonist of PD-L1 function, blocking interaction with PD-1 and CD80 to overcome inhibition of primary human T-cell activation. In vivo MEDI4736 significantly inhibits the growth of human tumors in a novel xenograft model containing coimplanted human T cells. This activity is entirely dependent on the presence of transplanted T cells, supporting the immunological mechanism of action for MEDI4736. To further determine the utility of PD-L1 blockade, an anti-mouse PD-L1 antibody was investigated in immunocompetent mice. Here, anti-mouse PD-L1 significantly improved survival of mice implanted with CT26 colorectal cancer cells. The antitumor activity of anti-PD-L1 was enhanced by combination with oxaliplatin, which resulted in increased release of HMGB1 within CT26 tumors. Taken together, our results demonstrate that inhibition of PD-L1 function can have potent antitumor activity when used as monotherapy or in combination in preclinical models, and suggest it may be a promising therapeutic approach for the treatment of cancer. MEDI4736 is currently in several clinical trials both alone and in combination with other agents, including anti-CTLA-4, anti-PD-1, and inhibitors of IDO, MEK, BRAF, and EGFR.

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MEDI9447 is a human monoclonal antibody that is specific for the ectoenzyme CD73 and currently undergoing Phase I clinical trials. Here we show that MEDI9447 is a potent inhibitor of CD73 ectonucleotidase activity, with wide ranging immune regulatory consequences. MEDI9447 results in relief from adenosine monophosphate (AMP)-mediated lymphocyte suppression in vitro and inhibition of mouse syngeneic tumor growth in vivo. In contrast with other cancer immunotherapy agents such as checkpoint inhibitors or T-cell agonists, MEDI9447 drives changes in both myeloid and lymphoid infiltrating leukocyte populations within the tumor microenvironment of mouse models. Changes include significant alterations in a number of tumor micro-environmental subpopulations including increases in CD8+ effector cells and activated macrophages. Furthermore, these changes correlate directly with responder and non-responder subpopulations within animal studies using syngeneic tumors. Combination data showing additive activity between MEDI9447 and anti-PD-1 antibodies using human cells in vitro and mouse tumor models further demonstrate the potential value of relieving adenosine-mediated immunosuppression. Based on these data, a Phase I study to test the safety, tolerability, and clinical activity of MEDI9447 in cancer patients was initiated (NCT02503774).

The skin is an attractive target for vaccine delivery. Topical application of adjuvants results in potent immune responses and good safety profiles. Adjuvants can be coadministered in a patch with vaccine antigens (transcutaneous immunization) or similar delivery format, or administered separately with an injection or IS patch (Iomai), leading to enhanced immune responses. These observations have moved into the clinic, highlighting the likelihood that skin delivery of vaccines will play an important future role in vaccine applications.

Bispecific antibodies have been extensively studied in vitro and in vivo for their use in redirected tumor cell lysis. A particular challenge of bispecific antibody constructs that recognize the invariant CD3 signaling complex is a controlled polyclonal activation of T cells that, ideally, is exquisitely dependent on the presence of target cells. Otherwise, overt production of inflammatory cytokines and secondary reactions may occur as side effects, as can be observed with constitutively T-cell activating monoclonal antibodies to CD3 or CD28, and with bispecific antibodies bearing Fc gamma portions. Here we analyzed 2 distinct bispecific single-chain antibody constructs of the BiTE class, called MT110 and MT103 (or MEDI-538), for conditional T-cell activation. In the presence of target-expressing cell lines, low picomolar concentrations of the BiTE molecules were sufficient to stimulate a high percentage of peripheral human T cells to express cytokines and surface activation markers, enter into cell cycle, and induce redirected lysis of target cells. However, in the absence of target cells, the 2 BiTE molecules even at high concentrations did not detectably activate T cells. Our data show that T cell activation by monomeric forms of MT110 and MT103 is highly conditional in that it is strictly dependent on the presence of cells expressing the proper target antigen. BiTE molecules therefore qualify for a highly controlled polyclonal T-cell therapy of cancer.

Persistent infection of equids by equine infectious anemia virus (EIAV)is typically characterized by a progression during the first year postinfection from chronic disease with recurring disease cycles to a long-term asymptomatic infection that is maintained indefinitely. The goal of the current study was to perform a comprehensive longitudinal analysis of the course of virus infection and development of host immunity in experimentally infected horses as they progressed from chronic disease to long-term inapparent carriage. We previously described the evolution of EIAV genomic quasispecies (C. Equine infectious anemia virus (EIAV) infection of horses provides a novel system in which to examine the natural immunological control of lentivirus replication and disease (reviewed in reference 27). Horses infected in the field or experimentally with EIAV typically develop within the first month postinfection acute disease (fever, diarrhea, lethargy, anemia, and thrombocytopenia) and an associated high level of infectious plasma viremia. Following this initial clinical episode that lasts 3 to 5 days, most infected horses experience recurring disease episodes and associated waves of viremia at irregular intervals. This cyclic disease is designated chronic EIA. The frequency of disease episodes and the severity of clinical symptoms typically decrease with time and are usually completely resolved by 1 year postinfection. At this time, persistently infected horses become clinically asymptomatic for EIA and negative for infectious plasma viremia, indicating a highly effective control of virus replication and disease. In fact, most horses infected by EIAV are inapparent carriers that will remain asymptomatic for the remainder of their life span of up to 20 years. Thus, the EIAV system offers a uniquely dynamic model in which to examine changes in viral replication and host immune responses during the clearly demarcated progression from chronic disease to a long-term inapparent infection.LerouxA number of studies indicate that the eventual control of EIAV replication and disease in horses is mediated by host immune responses that control virus infection to subclinical levels and not by the attenuation of the virus during persistent infection. For example, transfer of whole blood from long-term inapparent carriers to naive horses reproducibly causes infection and disease (11), and experimental immune suppression of inapparent carriers can cause recrudescence of disease and associated viremia (19,43). Recent analyses of EIAV infection in long-term apparent carriers by genetic (8, 40) and in situ (29) methods demonstrate persistent low levels of virus infection and replication predominantly in tissue macrophages, with negligible virus detectable in plasma or peripheral blood cells. These studies indicate that the progression from chronic EIA to inapparent infection is associated with the evolution of highly effective and enduring host immune responses that are able to suppress EIAV replication, despite the array of persis-* Corre...

Cancer vaccine development has been vigorously pursued for 40 years. Immunity to tumor antigens can be elicited by most vaccines tested, but their clinical efficacy remains modest. We argue that a concerted international effort is necessary to understand the human antitumor immune response and achieve clinically effective cancer vaccines.