Agonistic antibodies targeting co-stimulating receptor OX40 on T cells are considered as important as (or complementary to) the immune checkpoint blockers in cancer treatment. However, none of these agonistic antibodies have reached the late stage of clinical development partially due to the lack of intrinsic potency with the correlation between binding epitope and activity of the antibody not well understood. Here, we identified a novel anti-OX40 agonistic antibody DF004, which stimulated the proliferation of human CD4+ T cells in vitro and inhibited tumor growth in a mouse model. Our crystallography structural studies showed that DF004 binds to the CRD2 region of OX40 while RG7888, an OX40 agonist antibody developed by Roche, binds to CRD3 of OX40 to the diametrically opposite position of DF004. This suggests that the agonistic activities of the antibodies are not necessarily epitope dependent. As their agonistic activities critically depend on clustering or cross-linking, our structural modeling indicates that the agonistic activity requires the optimal positioning of three Fc receptor/antibody/OX40 complexes on the cell membrane to facilitate the formation of one intracellular hexameric TRAF complex for downstream signal transduction, which is relatively inefficient. This may explain the lack of sufficient potency of these OX40 antibodies in a therapeutic setting and sheds light on the development of cross-linking-independent agonistic antibodies.

Pulmonary fibrosis is a chronic interstitial lung disease that causes irreversible and progressive lung scarring and respiratory failure. Activation of fibroblasts plays a central role in the progression of pulmonary fibrosis. Here we show that platelet endothelial aggregation receptor 1 (PEAR1) in fibroblasts may serve as a target for pulmonary fibrosis therapy. Pear1 deficiency in aged mice spontaneously causes alveolar collagens accumulation. Mesenchyme-specific Pear1 deficiency aggravates bleomycin-induced pulmonary fibrosis, confirming that PEAR1 potentially modulates pulmonary fibrosis progression via regulation of mesenchymal cell function. Moreover, single cell and bulk tissue RNA-seq analysis of pulmonary fibroblast reveals the expansion of Activated-fibroblast cluster and enrichment of marker genes in extracellular matrix development in Pear1 −/− fibrotic lungs. We further show that PEAR1 associates with Protein Phosphatase 1 to suppress fibrotic factors-induced intracellular signalling and fibroblast activation. Intratracheal aerosolization of monoclonal antibodies activating PEAR1 greatly ameliorates pulmonary fibrosis in both WT and Pear1 -humanized mice, significantly improving their survival rate.

Antibodies targeting CTLA-4 are emerging as an important class of cancer therapeutics. It is assumed that these antibodies cause tumor rejection by blocking negative signaling from the CTLA-4-B7 interactions to enhance the priming of naïve T cells in lymphoid organs. However, recent findings have shown that the effectiveness of CTLA-4 antibody critically depends on the Fc domain and the host Fc receptors. It remains unclear if the blocking function of CTLA-4 antibody is required for its anti-tumor activity. To address this, here we have selected a non-blocking anti-CTLA-4 antibody (D138) and assessed its binding property and antitumor activity in comparison with the therapeutic CTLA-4 antibody ipilimumab. Crystal structures of CTLA-4 complexed with these antibodies show that D138 binds to a distinctly different site to that of ipilimumab on the CTLA-4 surface. D138 binding did not block the association of cells expressing CTLA-4 and B7 whereas ipilimumab did. Subsequent antitumor assay revealed that D138 was similarly effective as ipilimumab in inhibiting tumor growth in mice. This antitumor activity required Fc function for efficacy and was correlated with selective reduction of intratumor regulatory T (T reg ) cells, resulting in a significant increase in the ratio of CD8 + over T reg cells. Overall these data clearly demonstrate that blocking CTLA-4-B7 interaction is not required for CTLA-4 antibody mediated antitumor activity, opening prospects of developing non-blocking CTLA-4 antibodies or simple binders towards other T reg surface markers for T reg -targeted immunotherapy.

Unicellular organisms live under diverse stressful conditions and must respond and adapt quickly to these stresses. When these stresses persist, cells favor a transition to quiescence. There are changes to many processes when cells begin their entry into quiescence. It has been reported that Hsp82 plays an important role in several such processes, and its distribution and activity change according to nutrient conditions. In this study, we found that the subcellular distribution of Hsp82 is regulated by its co-chaperone Ppt1. Under starvation conditions, Ppt1 expression was significantly reduced by a TOR-independent pathway. Furthermore, we found that Ppt1 regulates Hsp82 distribution in the cytoplasm and nucleus by dephosphorylating the S485 residue on Hsp82. The Hsp82S485A strain has impaired membrane-related protein transport, and its cell size did not become larger in quiescence compared to log phase, resulting in failure to survive during starvation.