Neutrophils in viral infection.

Neutrophils are the first wave of recruited immune cells to sites of injury or infection and are crucial players in controlling bacterial and fungal infections. Although the role of neutrophils during bacterial or fungal infections is well understood, their impact on antiviral immunity is much less studied. Furthermore, neutrophil function in tumor pathogenesis and cancer treatment has recently received much attention, particularly within the context of oncolytic virus infection where neutrophils produce antitumor cytokines and enhance oncolysis. In this review, multiple functions of neutrophils in viral infections and immunity are discussed. Understanding the role of neutrophils during viral infection may provide insight into the pathogenesis of virus infections and the outcome of virus-based therapies.

Utilising the intrinsic fluorescence of pomalidomide for imaging applications.

Optimisation of protein degraders requires balancing multiple factors including potency, cell permeability and solubility. Here we show that the fluorescence of pomalidomide can be used in high-throughput screening assays to rapidly assess cellular penetration of degrader candidates. In addition, this technique can be paired with endocytosis inhibitors to gain insight into potential mechanisms of candidates entering a target cell. A model library of pomalidomide conjugates was synthesised and evaluated using high-throughput fluorescence microscopy. This technique based on intrinsic fluorescence can be used to guide rational design of pomalidomide conjugates without the need for additional labels or tags.

Intravital Microscopy Techniques to Image Wound Healing in Mouse Skin.

The ability to visualize biological phenomenon has driven scientific interest and advancement over the centuries. Although many methods and assays provide a detailed snapshot of a physiology, the ability to track such processes in real time has expanded the breadth of questions that can be interrogated in the laboratory. Intravital Microscopy (IVM) is a dynamic and powerful way to investigate both the homeostatic and host response to either therapeutic or pathological intervention using live animals. In this technique, animal models, (often mice) are anesthetized, and the organ of interest surgically exteriorized. The animal containing fluorescent labels (either endogenous, or conjugated to antibodies/proteins) will then be placed on a high-powered laser scanning microscope, where the labeled cells or structures can be observed in their natural environment. Complex behavioral data and interactions can be captured in a temporal manner, providing a plethora of information that will help researchers make conclusions on a more systemic level, rather than isolating only part the response. As the technology advances, a greater number of imaging modality options can be utilized, and more diverse research questions can be addressed. The goal of this chapter is to highlight IVM as a technique and help instruct new users on how to choose the proper modalities, and by using imaging of a skin wound in mice as a model, provide troubleshooting strategies, technical advice, and considerations.

Repeated dosing improves oncolytic rhabdovirus therapy in mice via interactions with intravascular monocytes.

There is debate in the field of oncolytic virus (OV) therapy, whether a single viral dose, or multiple administrations, is better for tumor control. Using intravital microscopy, we describe the fate of vesicular stomatitis virus (VSV) delivered systemically as a first or a second dose. Following primary administration, VSV binds to the endothelium, initiates tumor infection and activates a proinflammatory response. This initial OV dose induces neutrophil migration into the tumor and limits viral replication. OV administered as a second dose fails to infect the tumor and is captured by intravascular monocytes. Despite a lack of direct infection, this second viral dose, in a monocyte-dependent fashion, enhances and sustains infection by the first viral dose, promotes CD8 T cell recruitment, delays tumor growth and improves survival in multi-dosing OV therapy. Thus, repeated VSV dosing engages monocytes to post-condition the tumor microenvironment for improved infection and anticancer T cell responses. Understanding the complex interactions between the subsequent viral doses is crucial for improving the efficiency of OV therapy and virus-based vaccines.

Platelet-Mediated NET Release Amplifies Coagulopathy and Drives Lung Pathology During Severe Influenza Infection.

The influenza A virus (IAV) causes a respiratory tract infection with approximately 10% of the population infected by the virus each year. Severe IAV infection is characterized by excessive inflammation and tissue pathology in the lungs. Platelet and neutrophil recruitment to the lung are involved in the pathogenesis of IAV, but the specific mechanisms involved have not been clarified. Using confocal intravital microscopy in a mouse model of IAV infection, we observed profound neutrophil recruitment, platelet aggregation, neutrophil extracellular trap (NET) production and thrombin activation within the lung microvasculature in vivo. Importantly, deficiency or antagonism of the protease-activated receptor 4 (PAR4) reduced platelet aggregation, NET production, and neutrophil recruitment. Critically, inhibition of thrombin or PAR4 protected mice from virus-induced lung tissue damage and edema. Together, these data imply thrombin-stimulated platelets play a critical role in the activation/recruitment of neutrophils, NET release and directly contribute to IAV pathogenesis in the lung.

Optimization of In vivo Imaging Provides a First Look at Mouse Model of Non-Alcoholic Fatty Liver Disease (NAFLD) Using Intravital Microscopy.

Non-alcoholic fatty liver disease is a spectrum of liver pathology ranging from simple steatosis to steatohepatitis and can progress to diseases associated with poor outcomes including cirrhosis and hepatocellular carcinoma (HCC). NAFLD research has typically focused on the pathophysiology associated with lipid metabolism, using traditional measures such as histology and serum transaminase assessment; these methods have provided key information regarding NAFLD progression. Although valuable, these techniques are limited in providing further insight into the mechanistic details of inflammation associated with NAFLD. Intravital microscopy (IVM) is an advanced tool that allows for real-time visualization of cellular behavior and interaction in a living animal. Extensive IVM imaging has been conducted in liver, but, in the context of NAFLD, this technique has been regularly avoided due to significant tissue autofluorescence, a phenomenon that is exacerbated with steatosis. Here, we demonstrate that, using multiple imaging platforms and optimization techniques to minimize autofluorescence, IVM in fatty liver is possible. Successful fatty liver intravital imaging provides details on cell trafficking, recruitment, function, and behavior in addition to information about blood flow and vessel dynamics, information which was previously difficult to obtain. As more than 30% of the global population is overweight/obese, there is a significant proportion of the population at risk for NAFLD and complications due to NAFLD (liver decompensation, cirrhosis, HCC). IVM has the potential to elucidate the poorly understood mechanisms surrounding liver inflammation and NAFLD progression and possesses the potential to identify key processes that may be targeted for future therapeutic interventions in NAFLD patients.

Tracking Cell Recruitment and Behavior within the Tumor Microenvironment Using Advanced Intravital Imaging Approaches.

Recent advances in imaging technology have made it possible to track cellular recruitment and behavior within the vasculature of living animals in real-time. Using approaches such as resonant scanning confocal and multiphoton intravital microscopy (IVM), we are now able to observe cells within the intact tumor microenvironment of a mouse. We are able to follow these cells for extended periods of time (hours) and can characterize how specific cell types (T cells, neutrophils, monocytes) interact with the tumor vasculature and cancer cells. This approach provides greater insight into specific cellular behaviors and cell⁻cell interactions than conventional techniques such as histology and flow cytometry. In this report, we describe the surgical preparation of animals to expose the tumor and both resonant scanning confocal and multiphoton imaging approaches used to track leukocyte recruitment, adhesion, and behavior within the tumor microenvironment. We present techniques for the measurement and quantification of leukocyte behavior within the bloodstream and tumor interstitium. The use of IVM to study leukocyte behavior within the tumor microenvironment provides key information not attainable with other approaches, that will help shape the development of better, more effective anticancer drugs and therapeutic approaches.