Positron emission tomography imaging with 89Zr-labeled anti-CD8 cys-diabody reveals CD8+ cell infiltration during oncolytic virus therapy in a glioma murine model.

Determination of treatment response to immunotherapy in glioblastoma multiforme (GBM) is a process which can take months. Detection of CD8+ T cell recruitment to the tumor with a noninvasive imaging modality such as positron emission tomography (PET) may allow for tumor characterization and early evaluation of therapeutic response to immunotherapy. In this study, we utilized 89Zr-labeled anti-CD8 cys-diabody-PET to provide proof-of-concept to detect CD8+ T cell immune response to oncolytic herpes simplex virus (oHSV) M002 immunotherapy in a syngeneic GBM model. Immunocompetent mice (n = 16) were implanted intracranially with GSC005 GBM tumors, and treated with intratumoral injection of oHSV M002 or saline control. An additional non-tumor bearing cohort (n = 4) receiving oHSV M002 treatment was also evaluated. Mice were injected with 89Zr-labeled anti-CD8 cys-diabody seven days post oHSV administration and imaged with a preclinical PET scanner. Standardized uptake value (SUV) was quantified. Ex vivo tissue analyses included autoradiography and immunohistochemistry. PET imaging showed significantly higher SUV in tumors which had been treated with M002 compared to those without M002 treatment (p = 0.0207) and the non-tumor bearing M002 treated group (p = 0.0021). Accumulation in target areas, especially the spleen, was significantly reduced by blocking with the non-labeled diabody (p < 0.001). Radioactive probe accumulation in brains was consistent with CD8+ cell trafficking patterns after oHSV treatment. This PET imaging strategy could aid in distinguishing responders from non-responders during immunotherapy of GBM.

A Prototype QSP Model of the Immune Response to SARS-CoV-2 for Community Development.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic requires the rapid development of efficacious treatments for patients with life-threatening coronavirus disease 2019 (COVID-19). Quantitative systems pharmacology (QSP) models are mathematical representations of pathophysiology for simulating and predicting the effects of existing or putative therapies. The application of model-based approaches, including QSP, have accelerated the development of some novel therapeutics. Nevertheless, the development of disease-scale mechanistic models can be a slow process, often taking years to be validated and considered mature. Furthermore, emerging data may make any QSP model quickly obsolete. We present a prototype QSP model to facilitate further development by the scientific community. The model accounts for the interactions between viral dynamics, the major host immune response mediators and tissue damage and regeneration. The immune response is determined by viral activation of innate and adaptive immune processes that regulate viral clearance and cell damage. The prototype model captures two physiologically relevant outcomes following infection: a "healthy" immune response that appropriately defends against the virus, and an uncontrolled alveolar inflammatory response that is characteristic of acute respiratory distress syndrome. We aim to significantly shorten the typical QSP model development and validation timeline by encouraging community use, testing, and refinement of this prototype model. It is our expectation that the model will be further advanced in an open science approach (i.e., by multiple contributions toward a validated quantitative platform in an open forum), with the ultimate goal of informing and accelerating the development of safe and effective treatment options for patients.

Specific ablation of CD4+ T-cells promotes heart regeneration in juvenile mice.

Unlike adult cardiomyocytes, neonatal cardiomyocytes can readily proliferate that contributes to a transient regenerative potential after myocardial injury in mice. We have recently reported that CD4+ regulatory T-cells promote this process; however, the role of other CD4+ T-cell subsets as well as CD8+ T-cells in postnatal heart regeneration has been less studied. Methods: by comparing the regenerating postnatal day (P) 3 and the non-regenerating P8 heart after injury, we revealed the heterogeneity of CD4+ and CD8+ T-cells in the myocardium through single cell analysis. We also specifically ablated CD4+ and CD8+ T-cells using the lytic anti-CD4 and -CD8 monoclonal antibodies, respectively, in juvenile mice at P8 after myocardial injury. Results: we observe significantly more CD4+FOXP3- conventional T-cells in the P8 heart when compared to that of the P3 heart within a week after injury. Surprisingly, such a difference is not seen in CD8+ T-cells that appear to have no function as their depletion does not reactivate heart regeneration. On the other hand, specific ablation of CD4+ T-cells contributes to mitigated cardiac fibrosis and increased cardiomyocyte proliferation after injury in juvenile mice. Single-cell transcriptomic profiling reveals a pro-fibrotic CD4+ T-cell subset in the P8 but not P3 heart. Moreover, there are likely more Th1 and Th17 cells in the P8 than P3 heart. We further demonstrate that cytokines of Th1 and Th17 cells can directly reduce the proliferation and increase the apoptosis of neonatal cardiomyocytes. Moreover, ablation of CD4+ T-cells can directly or indirectly facilitate the polarization of macrophages away from the pro-fibrotic M2-like signature in the juvenile heart. Nevertheless, ablation of CD4+ T-cells alone does not offer the same protection in the adult heart after myocardial infarction, suggesting a developmental change of immune cells including CD4+ T-cells in the regulation of age-related mammalian heart repair. Conclusions: our results demonstrate that ablation of CD4+ but not CD8+ T-cells promotes heart regeneration in juvenile mice; and CD4+ T-cells play a distinct role in the regulation of heart regeneration and repair during development.

Diet Reversal and Immune Modulation Show Key Role for Liver and Adipose Tissue T Cells in Murine Nonalcoholic Steatohepatitis.

BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH) is a multisystem condition, implicating liver and adipose tissue. Although the general involvement of the innate and adaptive immune system has been established, we aimed to define the exact role of the functionally diverse T-cell subsets in NASH pathogenesis through diet reversal and immunologic modulation. METHODS: Multiple experimental set-ups were used in 8-week-old C57BL/6J mice, including prolonged high-fat high-fructose diet (HFHFD) feeding, diet reversal from HFHFD to control diet, and administration of anti-CD8a and anti-interleukin 17A antibodies. Plasma alanine aminotransferase, glucose, and lipid levels were determined. Liver and adipose tissue were assessed histologically. Cytotoxic T (Tc), regulatory T, T helper (Th) 1, and Th17 cells were characterized in liver and visceral adipose tissue (VAT) via flow cytometry and RNA analysis. RESULTS: HFHFD feeding induced the metabolic syndrome and NASH, which coincided with an increase in hepatic Th17, VAT Tc, and VAT Th17 cells, and a decrease in VAT regulatory T cells. Although diet reversal induced a phenotypical metabolic and hepatic normalization, the observed T-cell disruptions persisted. Treatment with anti-CD8a antibodies decreased Tc cell numbers in all investigated tissues and induced a biochemical and histologic attenuation of the HFHFD-induced NASH. Conversely, anti-interleukin 17A antibodies decreased hepatic inflammation without affecting other features of NASH or the metabolic syndrome. CONCLUSIONS: HFHFD feeding induces important immune disruptions in multiple hepatic and VAT T-cell subsets, refractory to diet reversal. In particular, VAT Tc cells are critically involved in NASH pathogenesis, linking adipose tissue inflammation to liver disease.