Macrophages Mediate the Antitumor Effects of the Oncolytic Virus HSV1716 in Mammary Tumors.

Oncolytic viruses (OV) have been shown to activate the antitumor functions of specific immune cells like T cells. Here, we show OV can also reprogram tumor-associated macrophage (TAM) to a less immunosuppressive phenotype. Syngeneic, immunocompetent mouse models of primary breast cancer were established using PyMT-TS1, 4T1, and E0771 cell lines, and a metastatic model of breast cancer was established using the 4T1 cell line. Tumor growth and overall survival was assessed following intravenous administration of the OV, HSV1716 (a modified herpes simplex virus). Infiltration and function of various immune effector cells was assessed by NanoString, flow cytometry of dispersed tumors, and immunofluorescence analysis of tumor sections. HSV1716 administration led to marked tumor shrinkage in primary mammary tumors and a decrease in metastases. This was associated with a significant increase in the recruitment/activation of cytotoxic T cells, a reduction in the presence of regulatory T cells and the reprograming of TAMs towards a pro-inflammatory, less immunosuppressive phenotype. These findings were supported by in vitro data demonstrating that human monocyte-derived macrophages host HSV1716 replication, and that this led to immunogenic macrophage lysis. These events were dependent on macrophage expression of proliferating cell nuclear antigen (PCNA). Finally, the antitumor effect of OV was markedly diminished when TAMs were depleted using clodronate liposomes. Together, our results show that TAMs play an essential role in support of the tumoricidal effect of the OV, HSV1716-they both host viral replication via a novel, PCNA-dependent mechanism and are reprogramed to express a less immunosuppressive phenotype.

Publisher Correction: Blocking elevated p38 MAPK restores efferocytosis and inflammatory resolution in the elderly.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Blocking elevated p38 MAPK restores efferocytosis and inflammatory resolution in the elderly.

Increasing age alters innate immune-mediated responses; however, the mechanisms underpinning these changes in humans are not fully understood. Using a human dermal model of acute inflammation, we found that, although inflammatory onset is similar between young and elderly individuals, the resolution phase was substantially impaired in elderly individuals. This arose from a reduction in T cell immunoglobulin mucin receptor-4 (TIM-4), a phosphatidylserine receptor expressed on macrophages that enables the engulfment of apoptotic bodies, so-called efferocytosis. Reduced TIM-4 in elderly individuals was caused by an elevation in macrophage p38 mitogen-activated protein kinase (MAPK) activity. Administering an orally active p38 inhibitor to elderly individuals rescued TIM-4 expression, cleared apoptotic bodies and restored a macrophage resolution phenotype. Thus, inhibiting p38 in elderly individuals rejuvenated their resolution response to be more similar to that of younger people. This is the first resolution defect identified in humans that has been successfully reversed, thereby highlighting the tractability of targeting pro-resolution biology to treat diseases driven by chronic inflammation.

Impaired LXRα Phosphorylation Attenuates Progression of Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is a very common indication for liver transplantation. How fat-rich diets promote progression from fatty liver to more damaging inflammatory and fibrotic stages is poorly understood. Here, we show that disrupting phosphorylation at Ser196 (S196A) in the liver X receptor alpha (LXRα, NR1H3) retards NAFLD progression in mice on a high-fat-high-cholesterol diet. Mechanistically, this is explained by key histone acetylation (H3K27) and transcriptional changes in pro-fibrotic and pro-inflammatory genes. Furthermore, S196A-LXRα expression reveals the regulation of novel diet-specific LXRα-responsive genes, including the induction of Ces1f, implicated in the breakdown of hepatic lipids. This involves induced H3K27 acetylation and altered LXR and TBLR1 cofactor occupancy at the Ces1f gene in S196A fatty livers. Overall, impaired Ser196-LXRα phosphorylation acts as a novel nutritional molecular sensor that profoundly alters the hepatic H3K27 acetylome and transcriptome during NAFLD progression placing LXRα phosphorylation as an alternative anti-inflammatory or anti-fibrotic therapeutic target.