NK cells require immune checkpoint receptor LILRB4/gp49B to control neurotropic Zika virus infections in mice.

Immune cells express an array of inhibitory checkpoint receptors that are upregulated upon activation and limit tissue damage associated with excessive response to pathogens or allergens. Mouse leukocyte immunoglobulin like receptor B4 (LILRB4), also known as glycoprotein 49B (gp49B), is an inhibitory checkpoint receptor constitutively expressed in myeloid cells and upregulated in B cells, T cells, and NK cells upon activation. Here, we report that expression of LILRB4, which binds Zika virus (ZIKV), was increased in microglia and myeloid cells infiltrating the brains of neonatal mice with ZIKV-associated meningoencephalitis. Importantly, while C57BL/6 mice developed transient neurological symptoms but survived infection, mice lacking LILRB4/gp49B (LILRB4 KO) exhibited more severe signs of neurological disease and succumbed to disease. Their brains showed increased cellular infiltration but reduced control of viral burden. The reduced viral clearance was associated with altered NK cell function in the absence of LILRB4/gp49B. In naive animals, this manifested as reduced granzyme B responses to stimulation, but in ZIKV-infected animals, NK cells showed phenotypic changes that suggested altered maturation, diminished glucose consumption, reduced IFN-γ and granzyme B production, and impaired cytotoxicity. Together, our data reveal LILRB4/gp49B as an important regulator of NK cell function during viral infections.

BRAF and MEK inhibitors differentially affect nivolumab-induced T cell activation by modulating the TCR and AKT signaling pathways.

Immune checkpoint inhibitors (ICIs) such as the anti-PD-1 antibody Nivolumab, achieve remarkable clinical efficacy in patients with late stage cancers. However, only a small subset of patients benefit from this therapy. Numerous clinical trials are underway testing whether combining ICIs with other anti-cancer therapies can increase this response rate. For example, anti-PD-1/PD-L1 therapy combined with MAP kinase inhibition using BRAF inhibitors (BRAFi) and/or MEK inhibitors (MEKi) are in development for treatment of late stage melanomas. However, the benefits and underlying mechanisms of these combinatorial therapies remain unclear. In the current study, we assess the effects of MAPK inhibition on Nivolumab-induced T cell responses. Using an in vitro mixed lymphocyte reaction assay, we demonstrate that Nivolumab-induced T cell activation is highly heterogeneous. While BRAFi inhibits Nivolumab-induced cytokine production, T cell proliferation, activation markers (CD69, CD25), and Granzyme B in a substantial proportion of donor pairs, a small subset of donor pairs shows an additive effect. MEKi alone significantly inhibits Nivolumab-induced T cell activation; the addition of BRAFi significantly enhances this inhibitory effect. Mechanistically, the effects of BRAFi and/or MEKi on Nivolumab-induced T cell activation may be due to alteration of the activation of the AKT and T cell receptor (TCR) signaling pathways. Our results suggest that MAPK inhibition may not provide a clinical benefit for most melanoma patients being treated with anti-PD-1 therapy.

In vitro evaluation of a targeted and sustained release system for retinoblastoma cells using Doxorubicin as a model drug.

PURPOSE: The objective of this study was to develop a novel folate receptor-targeted drug delivery system for retinoblastoma cells using doxorubicin (DOX) as a model drug. METHODS: Biodegradable DOX-loaded poly(d,l-lactide-co-glycolide)-poly(ethylene glycol)-folate (PLGA-PEG-FOL) micelles (DOXM) were prepared with various solvents (dimethylsulfoxide, acetone, and dimethylformamide). The effects of solvents on entrapment efficiency, particle size, and polydispersity were examined. The effects of thermosensitive gel structure on the release of DOX from the DOXM were also studied. Qualitative and quantitative uptake studies of DOX and DOXM were carried out in Y-79 cell line. Cytotoxicity studies of DOXM were performed on Y-79 cells. RESULTS: Based on size, polydispersity, and entrapment efficiency, dimethylformamide was found to be the most suitable solvent for the preparation of DOXM. Dispersion of DOXM in PLGA-PEG-PLGA gel sustained drug release for a period of 2 weeks. Uptake of DOX was ∼4 times higher with DOXM than DOX in Y-79 cells overexpressing folate receptors. This was further confirmed from the quantitative uptake studies. DOXM exhibited higher cytotoxicity in Y-79 cells when compared with pure DOX. CONCLUSION: These polymeric micellar systems suspended in thermosensitive gels may provide sustained and targeted delivery of anticancer agents to retinoblastoma cells following intravitreal administration.