- A recent publication in Immunity used IsoPlexis’ low volume bulk highly multiplexed solution to demonstrate markedly elevated monocyte/macrophage and T cell-derived cytokines in airways (tracheal lavage) of COVID-19 patients leading to inflammatory immune cells congregating in the lungs–particularly the monocyte chemoattractants MCP-1 (CCL2) and MIP-1α (CCL3).
- IsoPlexis’ highly multiplexed CodePlex secretome proteomics provides the qualitative and quantitative measurements in paired airway and plasma samples from COVID-19 patients and demonstrates MCP-1, MIP-1α, and MIP-1β, granzyme B, IL-7, and TNF-β were significantly increased in airways compared to blood.
- The detected excessive levels of MCP-1, MIP-1α and MIP-1β proteins in the airways but not in blood further support a role of airway monocytes/macrophages in perpetuating pulmonary inflammatory responses in severe COVID-19 and resulting in COVID-19-related acute respiratory distress syndrome (ARDS), which was associated with older age and mortality.
- IsoPlexis’ CodePlex Secretome reveals hyper inflammatory immune responses predominantly in airways and provide additional evidence that targeting airway-derived cytokines such as CCL2 through CCR2 antagonists or other airway-specific mediators may be more effective in reducing lung damage or promoting recovery from ARDS in severe COVID-19.
Analysis of Dynamic Immune Processes Fills Gaps in Understanding of Severe COVID-19 Pathogenesis
In a recent publication in Immunity, researchers Szabo, et al. used IsoPlexis’ low volume highly multiplexed bulk proteomics (CodePlex) to investigate the role of airway and plasma immune cells in the pathogenesis of severe COVID-19. About 5-10% of patients with SARS-CoV-2 develop severe respiratory disease which is marked by lung infiltrates and low oxygen saturation and can result in acute respiratory distress syndrome (ARDS) and death. Previous research shows that immune responses to respiratory viruses are focused in the lungs, where the production of proinflammatory cytokines can lead to damage.
Macrophages and infiltrating monocytes mediate the innate immune response at the same time as the adaptive immune response mobilizes effector T cells to the lung to clear out infected cells.1 Some of these lung effector T cells remain in the lung long-term as tissue-resident memory T cells (TRMs). TRMs are the predominant T cell subset in adult lungs throughout many decades of life, suggesting they play a critical role in protecting the lungs from respiratory pathogens. However, the role of these resident immune cells, including alveolar macrophages and lung TRMs, and other immune responses in dictating COVID-19 pathogenesis is unclear. Understanding immune responses to COVID-19 is necessary to improve treatment and prevention of the disease. Szabo, et al. thus aimed to “define the dynamic immune processes involved in pathogenesis of severe COVID-19” using phenotypic, transcriptomic, and functional profiling.1
The researchers obtained paired airway and blood samples from 15 patients ages 14-84 with severe COVID-19, all of whom required ventilation and intubation. The samples were collected starting 24-36 hours after intubation and continued daily for up to 10 days.1 The researchers used IsoPlexis’ highly-multiplexed functional proteomics to characterize the cytokine and chemokine content of these samples and compare them to samples from healthy subjects.
Highly Multiplexed Bulk Proteomics Identifies Elevated Inflammatory Mediators in Airway Samples of Severe COVID-19
IsoPlexis’ Human Adaptive Immune panel for the CodePlex Secretome chip identified significant differences in the cytokine and chemokine content of severe COVID-19 airway and blood cell samples. Several analytes were elevated in the airways, including monocyte/macrophage chemoattractants MCP-1 (CCL2), MIP-1α (CCL3), and MIP1β (CCL4), and T cell-associated cytokines granzyme B, IL-7, and TNF-β. In the blood, MCP-1 (CCL2), MIP-1α (CCL3), granzyme B, IL-7, and TNF-β were not detected, while MIP-1β (CCL4) was present at variable levels across patients.1 In the patients with severe COVID-19, both plasma and airway samples contained low or variable levels of molecules associated with T cell effector function, as well as cytokines IL-6, IL-8, and TGF-β.1 The results showed that proinflammatory chemokines and cytokines were prominent in the airways, with only some of these proteins present in the blood.1
The researchers also observed an accumulation of monocytes/macrophages in the lungs of severe COVID-19 patients, hypothesizing that the production of airway monocyte chemoattractants resulted in the infiltration of dysregulated monocytes from the blood into the lung. “Overall, the results suggested that the airways of severe COVID-19 patients are a highly inflammatory environment and a play a significant role in recruiting immune cells from circulation to the site of infection.”1 The researchers concluded that the results “strongly implicate myeloid cell recruitment as a major mechanism perpetuating inflammation and pathogenesis of severe COVID-19.”1
IsoPlexis’ Walk-Away Proteomics Reveals Critical Therapeutic Targets and Predictive Biomarkers
While previous studies have investigated patient’s innate and adaptive immune responses to COVID-19, the role of these COVID-19-specific immune responses in disease pathogenesis has still been unclear. Immune responses to respiratory viruses are localized to the lungs and respiratory tract, but improved understanding of how airway and blood immune cells function together to drive COVID-19 pathogenesis is needed. The study published in Immunity found protective T cell signatures in the respiratory tract that were associated with younger age and survival from severe COVID-19. Conversely, the researchers identified airway myeloid cells, primarily macrophages and monocytes, that drove immune cell recruitment and lung inflammation, and were associated with older age and mortality. CCL2 was noted as a potential therapeutic target due to its role in recruiting monocytes into the lung. Furthermore, the identification of elevated airway chemotactic mediators suggests that targeting these attractors of circulating monocytes and macrophages may help improve COVID-19 outcomes. Finally, airway T cell frequencies, which correlated with younger age and survival, may be useful as a predictive biomarker for monitoring patients and stratifying risk.1
Overall, the study by Szabo, et al. elucidates the roles of airway and blood immune cells in both protective and inflammatory responses to COVID-19, providing novel insights which enable the development of improved methods for monitoring and treating COVID-19. IsoPlexis’ highly multiplexed functional proteomics characterized the cytokine/chemokine content of severe COVID-19 airway cells and plasma, providing data that correlates with in vivo function. Obtaining these insights were uniquely possible with IsoPlexis’ platform which multiplexes 30+ analytes with walk-away automation, drastically reducing hands-on time. Unlike traditional methods which estimate function or analyze only a few cytokines at a time, IsoPlexis provides key functional insights in a fraction of the time, on one integrated proteomics hub.
To learn more about how IsoPlexis’ highly multiplexed bulk proteomics uncovers underlying mechanisms of disease pathogenesis in other research areas, such as cancer metastasis, read our Nature Communications paper summary.
- Szabo PA, et al. Longitudinal profiling of respiratory and systemic immune responses reveals myeloid cell-driven lung inflammation in severe COVID-19. Immunity, 54: 1-18, 2021.