CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

Th1/Th17 was also addressed by immunofluorescence in lung tissue from n=3 deceased critical COVID-19 patients. Induction of SARS-CoV-2 specific Th1 and Th17 cells in response to S1 peptides or S1-primed Mo was analyzed in PB and BAL from critical COVID-19 patients. Correlation network between immune, functional and clinical parameters from BAL samples was also assessed. Results: SARS-CoV-2 S1 induced Mo differentiation into NC-Mo in BAL and PB samples from critical COVID-19 patients and required NFκB activation. In addition, activation of NC-Mo in response to S1 was associated with higher ability to induce IFNγ+ and IL-17+ CD4+ T cells (p=0.0156) and was dependent on NLRP3 inflammasome. Importantly, NLRP3+Caspase1+ Mo, IFNγ+ and IL-17+ T cells were detected in in highly infiltrated areas from the lung of deceased COVID-19 patients. Consistently, higher levels of the inflammasome target ferritin correlated with increased detection of Th17 cells in these individuals (p=0.037). Additionally, memory NKG2C+ NK cells were enriched in BAL and PB in critical COVID-19 patients and increased expression of TRAIL on this population significantly correlated with higher frequencies of NC-Mo in the lung (p=0.016) and increased levels of systemic inflammation biomarkers such as procalcitonin (p=0.017), C-reactive protein (p=0.0027) and ferritin (p=0.016) in these subjects. Conclusion: Interconnection between inflammasome activation in Mo, induction of Th1/Th17 and NKG2C+ memory NK cells feed pathogenic immune cell environments during critical COVID-19 and may represent promising therapeutic cellular targets. The figure, table, or graphic for this abstract has been removed. Complement-Driven Type-I IFN Response Enhances mTOR Activation and T-Cell Immunity Marta Bermejo Jambrina 1 , John L. van Hamme 2 , Lieve van der Donk 2 , Doris Wilflingseder 1 , Teunis B. Geijtenbeek 2 1 Innsbruck Medical University, Innsbrusk, Austria, 2 Academic Medical Center, Amsterdam, Netherlands Background: Uncontrolled SARS-CoV-2 infection is associated with disorders of the innate immune and delayed adaptive immune systems. Yet, it remains unclear how SARS-CoV-2 causes local and systemic dysregulation. The role of the complement system in SARS-CoV-2 pathogenesis is well established, in particular as a driver of systemic inflammation which is characteristic of severe COVID-19. Although complement is traditionally known as a central arm of innate immunity, it has equally important roles in the regulation of adaptive immunity. However, how mechanistic complement affects dendritic cell (DC) functionality and T cell- priming upon SARS-CoV-2 infection, is still poorly defined. Methods: Effects of differently opsonized SARS-CoV-2-loaded primary DCs were measured by RT-PCR, ELISA, PathScan and flow cytometry. Co-culture with naïve CD4+ and CD8+ T cells, T-cell activation, cytotoxic T-cells GRZB/PRF production and SARS-CoV-2–specific cytokine-producing T-cells were measured by flow cytometry and ELISpot. Results: DC were not susceptible to SARS-CoV-2 infection, and exposure to SARS-CoV-2 triggered neither induction nor secretion of type-I IFN and inflammatory cytokines. Notably, complement-opsonized-SARS-CoV- 2 loaded DCs displayed enhanced maturation and efficient type-I IFN and IL-1β responses, suggesting that complement is crucial for mediating immunity against SARS-CoV-2. Here, we describe that IL-1β secretion occurs following intracellular caspase-1 activation by inflammasome activation, revealing a mechanistic link between complement and IL-1β secretion in human DCs. Strikingly, complement-triggered IL-1β production was mediated by the mammalian target of rapamycin (mTOR). NLRP3 inhibition resulted in impaired priming of IFN-gamma-producing CD4+ and CD8+ T cells, suggesting an essential role of complement in increasing antigen-specific T-cell responses. Conclusion: The potential for myeloid cells to act as bona fide targets of SARS CoV-2 infection remains unclear. Here, we show that complement-opsonized SARS-CoV-2 induces type I IFN secretion, upregulates the mTOR pathway and directly activates NLRP3, which leads to IL-1ß secretion. The role of IL-1 β as part of the bridge between innate and adaptive immunity may be clinically translated into therapeutic strategies to empower the formation of T cell immunity. Our data demonstrate distinct immunological functions for DCs and consider the role of complement and mTOR activation in regulating immune system responses in SARS-CoV-2 infection.

Therefore, our data provide a basis for understanding tissue responses during infection and potentially some mechanistic basis on developing PASC once confirmed in human subjects. Further, this information will be valuable for developing/refining mucosal vaccines against emerging SARS-CoV-2 variants. Markers of Microbial Translocation and Inflammatory Cytokines Are Predictive of Severe COVID-19 Ty Schroeder 1 , Christopher Basting 1 , Kathie G. Ferbas 2 , Adrian Velez 1 , Courtney A. Broedlow 1 , Erik Swanson 1 , Melisa Bailey 1 , Robert Langat 1 , Luca Schifanella 3 , Grace M. Aldrovandi 2 , Nicole H. Tobin 2 , Otto Yang 2 , Jennifer Fulcher 2 , Nichole R. Klatt 1 1 University of Minnesota, Minneapolis, MN, USA, 2 University of California Los Angeles, Los Angeles, CA, USA, 3 National Institutes of Health, Bethesda, MD, USA Background: The novel SARS-CoV-2 virus caused the global COVID-19 pandemic resulting in approximately 770 million global cases and 7 million deaths to date. Several factors predict severe COVID-19 including comorbidities such as age, cardiovascular disease and diabetes. Furthermore, gastrointestinal symptoms and microbial dysbiosis are commonly observed in COVID-19 and may therefore be indicators of severe disease. In this study, we aimed to understand the differences in markers of microbial translocation and circulating cytokines between healthy individuals and patients with severe COVID-19. We then investigated the accuracy of these biological factors in predicting whether an individual was healthy or had severe COVID-19. Methods: A cohort of California-based participants were entered into the study, consisting of 62 patients hospitalized with COVID-19 and 115 healthy individuals. Plasma samples were used to measure circulating concentrations of cytokines by Luminex and markers of microbial translocation including LPS binding protein (LBP), soluble CD14 (sCD14), intestinal fatty acid binding protein (I-FABP), and Zonulin were measured by ELISA. Results: Hospitalized COVID-19 patients had significantly higher plasma concentrations of markers of microbial translocation including LBP and sCD14 compared to healthy individuals (p=1.4-17, p=9.35-5). Hospitalized patients also had elevated inflammatory plasma cytokine concentrations, most notably IL-6, TNF-α, IFN-γ, and IL-18. Spearman correlation analysis showed that IL-6 was significantly positive correlated with markers of microbial translocation including LBP and sCD14 (p=1.42-25, p=1.455-4). A random forest model showed the best accuracy in predicting healthy versus hospitalized individuals with a true positive percent (TPP) of 94%. LBP and IL-6 were the greatest drivers of prediction. This model was further tested on two other COVID-19 datasets with varying accuracy: 81% TPP and 75% TPP. Conclusion: Hospitalized individuals were characterized by elevated inflammatory cytokines (especially IL-6) and microbial translocation measured by sCD14 and LBP. The correlation between inflammatory cytokines and markers of microbial translocation suggests a relationship between gut barrier integrity and systemic inflammation in COVID-19, which may better predict whether an individual is healthy or has severe COVID-19, with IL-6 and LBP being the most important variables in the prediction. Pathogenic Monocyte, Th17, and NK Cell Immune Networks in the Lung From Critical COVID-19 Patients Ilya Tsukalov 1 , Ildefonso Sanchez-Cerrillo 1 , Olga Rajas 2 , María Buzón 3 , Meritxell Genescà 3 , Noa Martín-Cófreces 2 , Ignacio Santos 2 , María Jose Calzada 1 , Isidoro González-Álvaro 2 , Jose Palacios 4 , Arantzazu Alfranca 2 , Julio Ancochea 2 , Francisco Sánchez-Madrid 2 , Enrique Martín-Gayo 1 1 Universidad Autónoma de Madrid, Madrid, Spain, 2 Hospital Universitario de La Princesa, Madrid, Spain, 3 Vall d'Hebron Research Institute, Barcelona, Spain, 4 Hospital Ramón y Cajal, Madrid, Spain Background: Pathogenic inflammation in the lung has been connected to non-classical monocytes (NC-Mo), Natural Killer (NK) cells and Th1/Th17 cell immune responses in critical COVID-19 patients. However, the pathogenic inflammatory networks in the pulmonary tissue of these patients, including interactions between specific innate immune cell subsets, the underlying molecular mechanisms involved in their activation and the functional impact on pathogenic Th1/Th17 cells is not completely understood and may lead to new therapeutic targets. Methods: Frequency, activation and functional maturation of NC-Mo and memory NK cell subsets from n=17 Bronchoalveolar lavage (BAL) and n=16 peripheral blood (PB) samples from critical COVID-19 patients and n=9 healthy controls were assessed at baseline or after in vitro stimulation with SARS-CoV-2 Spike (S1) peptide pools. Histological distribution and activation of Mo and

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CROI 2024