Multi-organ Failure in SARS-CoV2: Identifying Mechanisms and Potential Therapeutic Targets

COVID-19 is a highly contagious virus, causing a global health emergency. A significant number (~17%) of hospitalised patients become severely unwell and require admission to an intensive care unit (ICU) due to lung failure (acute respiratory distress syndrome (ARDS)) and multi-organ failure (MOF). Sadly, 51.8% of COVID-ARDS patients develop kidney failure, which has a markedly increased risk of dying (61%). We have learned that kidney failure starts several days after lung failure, which suggest an initial viral "attack" on the lungs followed by kidney involvement several days later.

Cytokines are "signalling" molecules made by cells, which in healthy individuals help fight disease. It was initially thought that in COVID-19, lung cells release excessive cytokines (i.e. cytokine storm), which then cause kidney injury and MOF. However, research has demonstrated that cytokine levels in blood are actually very low and not enough to explain the extent of organ injury in COVID-19. This perhaps explains why treatment strategies aimed at specifically damping down the action of these particular cytokines in COVID-19 have failed. Consequently, there remains no cure for COVID-19 MOF, and whilst treatments such as steroids, manage symptoms, have a general anti-inflammatory effect and improve mortality, 30% of intensive care patients still die. Therefore, urgent research is needed to improve scientific knowledge of this condition and identify new therapies.

Microvesicles (MVs) are extremely small particles released by cells and carry various chemicals including cytokines, from inside the cell, packaged securely and safely within membranes (cellular envelopes). These vesicles act as 'postmen' delivering chemical messengers (e.g. cytokines) between cells and are important in various diseases where inflammation is implicated. The investigators have demonstrated that MVs have a fundamental role in the development of organ failure in laboratory models of non-COVID ARDS but the investigators do not yet know the role of these vesicles in the development of ARDS/MOF in COVID-19.

The investigators hypothesise that during COVID-19 infection of the lung, significant numbers of MVs are released within the lung (especially in severe COVID-19), which then "transmit" signals and inflammation to other organs via the bloodstream, causing organs to fail. Furthermore, as chemical messengers (e.g. cytokines) are hidden inside these vesicles, they are not measured by standard laboratory techniques and may explain why there are low cytokine levels in blood. This may also clarify why treatments inhibiting circulating cytokines (not hidden in vesicle membranes) have failed.

To explore these ideas, the group aim to investigate MVs in blood and urine of ICU patients with severe COVID-19 (20mls blood (1 1/3 tablespoons); 10ml urine (3/4 tablespoon)). The investigators intend to examine which chemicals are present in these tiny vesicles and to relate this information to the clinical progress or otherwise of patients. These data will help the scientific community understand the chemical systems involved in severe COVID-19, tell us the significance of MVs and whether blocking MV signalling could lead to new treatments for COVID-19. Furthermore, analysis of these MVs may allow the investigators to identify patients who are likely to become seriously ill, which would help in planning treatment.