Potent Immune Modulation by MEDI6383, an Engineered Human OX40 Ligand IgG4P Fc Fusion Protein.

Ligation of OX40 (CD134, TNFRSF4) on activated T cells by its natural ligand (OX40L, CD252, TNFSF4) enhances cellular survival, proliferation, and effector functions such as cytokine release and cellular cytotoxicity. We engineered a recombinant human OX40L IgG4P Fc fusion protein termed MEDI6383 that assembles into a hexameric structure and exerts potent agonist activity following engagement of OX40. MEDI6383 displayed solution-phase agonist activity that was enhanced when the fusion protein was clustered by Fc gamma receptors (FcγRs) on the surface of adjacent cells. The resulting costimulation of OX40 on T cells induced NFκB promoter activity in OX40-expressing T cells and induced Th1-type cytokine production, proliferation, and resistance to regulatory T cell (Treg)-mediated suppression. MEDI6383 enhanced the cytolytic activity of tumor-reactive T cells and reduced tumor growth in the context of an alloreactive human T cell:tumor cell admix model in immunocompromised mice. Consistent with the role of OX40 costimulation in the expansion of memory T cells, MEDI6383 administered to healthy nonhuman primates elicited peripheral blood CD4 and CD8 central and effector memory T-cell proliferation as well as B-cell proliferation. Together, these results suggest that OX40 agonism has the potential to enhance antitumor immunity in human malignancies. Mol Cancer Ther; 17(5); 1024-38. ©2018 AACR.

Predominant type 1 CMV-specific memory T-helper response in humans: evidence for gender differences in cytokine secretion.

Cell-mediated memory immune responses to viral antigens are important for protection against viruses causing persistent or acute infections. This study compared the cytokine profile of memory T-helper cells specific for cytomegalovirus (CMV) in healthy CMV-seropositive men and women. The cytokine response reflected T(H)1 bias, with dominant secretion of interferon (IFN)-gamma along with moderate levels of tumor necrosis factor-alpha, interleukin (IL)-10, and IL-2. Analyzed by gender, women had higher and significant spontaneous release of IFN-gamma and CMV-specific IL-2 secretion. Similar analysis with herpes simplex virus-1 showed a trend toward higher cytokine responsiveness in women, but the differences were not statistically significant. In contrast, men had statistically significant higher influenza virus-specific tumor necrosis factor-alpha secretion. IL-4 and IL-5, both T(H)2 cytokines, were low for all three viruses. The results show a predominant T(H)1 antiviral cytokine T-help memory response with significant differences linked to gender. Such differences may have an impact in the design of immunization strategies against CMV.

Relevance of peptide avidity to the T cell receptor for cytomegalovirus-specific ex vivo CD8 T cell cytotoxicity.

CD8(+) T cells contribute to the control of viral infection by several effector mechanisms, including lysis of virally infected cells and interferon (IFN)-gamma secretion. Ex vivo cytotoxicity and potent secretion of IFN-gamma in response to cytomegalovirus (CMV) epitope peptides was seen in freshly prepared unstimulated peripheral blood mononuclear cells from human immunodeficiency virus-infected patients with high T cell receptor (TCR)/peptide avidity. Lymphocytes with low TCR/peptide avidity had no ex vivo cytotoxicity, secreted minimal IFN-gamma, and could not recognize autologous infected targets. Despite this, ex vivo responding and nonresponding patients had substantial frequencies of tetramer-positive and IFN-gamma-secreting lymphocytes. Levels of activation and memory markers were also similar in tetramer-positive populations of both groups. However, cytolytic capacity remained in nonresponders; their lymphocytes regained cytotoxicity after in vitro stimulation with peptide without coactivators or interleukin-2. High-avidity CD8(+) T cells are likely important in viral control, and their generation should be a goal of therapeutic vaccination.

Intranasal administration of a synthetic lipopeptide without adjuvant induces systemic immune responses.

Parenteral injection of a lipopeptide containing a human leucocyte antigen (HLA)-A*0201-restricted cytotoxic T-lymphocyte (CTL) epitope from the human cytomegalovirus (HCMV) immunodominant matrix protein pp65 efficiently induces systemic CTL responses in HLA-A*0201 transgenic mice. In this study, we demonstrate that intranasal (i.n.) administration of this lipopeptide, covalently linked to a universal T helper (Th) epitope (PADRE), also induces potent systemic CTL responses. Immune responses were substantially reduced when the unlipidated peptide analogue was used (P<0.01). The induced CTL were CD8+, major histocompatibility complex (MHC) class I-restricted and CMV specific. Moreover, i.n. administration of this lipidated peptide elicited both systemic and local mucosal CD4+ T-cell proliferative responses, as well as antigen-specific delayed type hypersensitivity (DTH) immune responses. In contrast, mice receiving the unlipidated peptide analogue developed substantially reduced Th or DTH responses (P<0.05). These results highlight the usefulness and potential of lipopeptides delivered via mucosal routes as painless, safe, and non-invasive vaccines.