Combination gemcitabine and PD-L1xCD3 bispecific T cell engager (BiTE) enhances T lymphocyte cytotoxicity against cholangiocarcinoma cells.

Cholangiocarcinoma (CCA) is a lethal cancer with rapid progression and poor survival. Novel and more effective therapies than those currently available are, therefore, urgently needed. Our research group previously reported the combination of gemcitabine and cytotoxic T lymphocytes to be more effective than single-agent treatment for the elimination of CCA cells. However, gemcitabine treatment of CCA cells upregulates the expression of an immune checkpoint protein (programmed death-ligand 1 [PD-L1]) that consequently inhibits the cytotoxicity of T lymphocytes. To overcome this challenge and take advantage of PD-L1 upregulation upon gemcitabine treatment, we generated recombinant PD-L1xCD3 bispecific T cell engagers (BiTEs) to simultaneously block PD-1/PD-L1 signaling and recruit T lymphocytes to eliminate CCA cells. Two recombinant PD-L1xCD3 BiTEs (mBiTE and sBiTE contain anti-PD-L1 scFv region from atezolizumab and from a published sequence, respectively) were able to specifically bind to both CD3 on T lymphocytes, and to PD-L1 overexpressed after gemcitabine treatment on CCA (KKU213A, KKU055, and KKU100) cells. mBiTE and sBiTE significantly enhanced T lymphocyte cytotoxicity against CCA cells, especially after gemcitabine treatment, and their magnitudes of cytotoxicity were positively associated with the levels of PD-L1 expression. Our findings suggest combination gemcitabine and PD-L1xCD3 BiTE as a potential alternative therapy for CCA.

A Synthetic Bioactive Peptide Derived from the Asian Medicinal Plant Acacia catechu Binds to Dengue Virus and Inhibits Cell Entry.

Dengue virus (DENV) infection has become a critically important globally prevalent infectious disease, especially in tropical and subtropical countries. Since neither currently exists, there is an urgent need for an effective vaccine to prevent, and a specific drug to treat DENV infection. Therapeutic peptides represent an attractive alternative for development into anti-DENV drugs due to their safety and their diverse biological and chemical properties. We recently reported novel bioactive peptides extracted from the Asian medicinal plant Acacia catechu that efficiently inhibited all four DENV serotypes. In this study, we investigated the anti-DENV activity of a synthetic bioactive peptide derived from this plant. The most effective peptide (designated Pep-RTYM) inhibited DENV infection with a half-maximal inhibition concentration value of 7.9 µM. Time-of-addition study demonstrated that Pep-RTYM interacted with DENV particles and inhibited cellular entry. Pep-RTYM at 50 µM significantly reduced DENV production in Vero-kidney epithelial cells about 1000-fold, but it could decrease the virus production in Huh7 hepatocyte cells approximately 40-fold. Binding of Pep-RTYM to DENV particles may prevent virus interaction with cellular receptor and subsequent virus entry. This finding suggests a potential role of Pep-RTYM in the development of a novel anti-DENV drug.