InVivoPlus polyclonal Armenian hamster IgG

Clinical responses to immunotherapy have been associated with augmentation of preexisting immune responses, manifested by heightened inflammation in the tumor microenvironment. However, many tumors have a noninflamed microenvironment, and response rates to immunotherapy in melanoma have been <50%. We approached this problem by utilizing immunotherapy (CTLA-4 blockade) combined with chemotherapy to induce local inflammation. In murine models of melanoma and prostate cancer, the combination of chemotherapy and CTLA-4 blockade induced a shift in the cellular composition of the tumor microenvironment, with infiltrating CD8(+) and CD4(+) T cells increasing the CD8/Foxp3 T-cell ratio. These changes were associated with improved survival of the mice. To translate these findings into a clinical setting, 26 patients with advanced melanoma were treated locally by isolated limb infusion with the nitrogen mustard alkylating agent melphalan followed by systemic administration of CTLA-4 blocking antibody (ipilimumab) in a phase II trial. This combination of local chemotherapy with systemic checkpoint blockade inhibitor resulted in a response rate of 85% at 3 months (62% complete and 23% partial response rate) and a 58% progression-free survival at 1 year. The clinical response was associated with increased T-cell infiltration, similar to that seen in the murine models. Together, our findings suggest that local chemotherapy combined with checkpoint blockade-based immunotherapy results in a durable response to cancer therapy.

PU.1 is an ETS family transcription factor that is important for the development of multiple hematopoietic cell lineages. Previous work demonstrated a critical role for PU.1 in promoting Th9 development and in limiting Th2 cytokine production. Whether PU.1 has functions in other Th lineages is not clear. In this study, we examined the effects of ectopic expression of PU.1 in CD4+ T cells and observed decreased expression of genes involved with the function of T follicular helper (Tfh) cells, including Il21 and Tnfsf5 (encoding CD40L). T cells from conditional mutant mice that lack expression of PU.1 in T cells (Sfpi1lck-/-) demonstrated increased production of CD40L and IL-21 in vitro. Following adjuvant-dependent or adjuvant-independent immunization, we observed that Sfpi1lck-/- mice had increased numbers of Tfh cells, increased germinal center B cells (GCB cells), and increased Ab production in vivo. This correlated with increased expression of IL-21 and CD40L in Tfh cells from Sfpi1lck-/- mice compared with control mice. Finally, although blockade of IL-21 did not affect GCB cells in Sfpi1lck-/- mice, anti-CD40L treatment of immunized Sfpi1lck-/- mice decreased GCB cell numbers and Ag-specific Ig concentrations. Together, these data indicate an inhibitory role for PU.1 in the function of Tfh cells, germinal centers, and Tfh-dependent humoral immunity.

Programmed cell death 1 (PD-1) is a key regulatory molecule that has been targeted in human cancers, including melanoma. In clinical testing, Abs against PD-1 have resulted in psoriasiform dermatitis (PsD). To determine whether PD-1 regulates PsD, we compared skin responses of PD-1-deficient (PD-1KO) mice and wild-type (WT) controls in an imiquimod (IMQ)-induced murine model of psoriasis. PD-1KO mice showed severe epidermal hyperplasia, greater neutrophilic infiltration, and higher expression of Th17 cytokines (versus WT mice). IMQ exposure increased PD-1 expression by skin gammadelta-low (GDL) T cells and enhanced expression of PD-L1 by keratinocytes. Three-fold increases in the percentage of IL-17A(+) GDL T cells were observed in skin cell suspensions derived from IMQ-treated PD-1KO mice (versus WT controls), suggesting that the lack of PD-1 has a functional effect not only on alphabeta T cells, but also on GDL T cells, and that PD-1 may play a regulatory role in PsD.

PD-1 negatively regulates CD8(+) cytotoxic T lymphocytes (CTL) cytotoxicity and anti-tumor immunity. However, it is not fully understood how PD-1 expression on CD8(+) CTL is regulated during anti-tumor immunotherapy. In this study, we have identified that the ADAP-SKAP55 signaling module reduced CD8(+) CTL cytotoxicity and enhanced PD-1 expression in a Fyn-, Ca(2+)-, and NFATc1-dependent manner. In DC vaccine-based tumor prevention and therapeutic models, knockout of SKAP55 or ADAP showed a heightened protection from tumor formation or metastases in mice and reduced PD-1 expression in CD8(+) effector cells. Interestingly, CTLA-4 levels and the percentages of tumor infiltrating CD4(+)Foxp3(+) Tregs remained unchanged. Furthermore, adoptive transfer of SKAP55-deficient or ADAP-deficient CD8(+) CTLs significantly blocked tumor growth and increased anti-tumor immunity. Pretreatment of wild-type CD8(+) CTLs with the NFATc1 inhibitor CsA could also downregulate PD-1 expression and enhance anti-tumor therapeutic efficacy. Together, we propose that targeting the unrecognized ADAP-SKAP55-NFATc1-PD-1 pathway might increase efficacy of anti-tumor immunotherapy.