SARS-CoV-2, a novel coronavirus emerging in late 2019, presents in patients with fever, sore throat, malaise and dry cough after infection. Severely ill patients tend to develop respiratory distress and/or hypoxemia a week after onset, and severe cases can rapidly progress to acute respiratory distress syndrome, septic shock, uncorrectable metabolic acidosis, and bleeding and clotting dysfunction. As of March 3, 2020, the cumulative number of diagnosed cases nationwide has reached 80,270, with 2,981 deaths. A large number of recent studies have shown that IL-6-mediated immune response with cytokine storm syndrome plays an important role in the progression of the disease in mild and severe patients.
IL-6-mediated immune and inflammatory responses
The Jak/Stat signaling pathway is a key part of many regulatory cell growth, survival and pathogen resistance signaling, and IL-6 plays an early activation role in this pathway, which in turn initiates the regulation of B-cell differentiation, plasminogenesis and a series of acute phase responses. Thus, the early appearance of IL-1, TNF-α and IL-6 in early inflammation promotes hepatocyte synthesis of acute phase proteins, such as C-reactive protein (CRP), serum amyloid A protein (SAA), calcitoninogen (PCT), and alpha acidic glycoprotein, which facilitate the body's defense against viral infection.
IL-6 is an important cytokine expressed by the immune system in the initial response to injury and infection. IL-6 is central in the acute inflammatory response, and elevated IL-6 is at the very early stage of cytokine initiation and lasts for a long time, so it can be used to assist in the early diagnosis of acute infection. IL-6 is also used to evaluate the severity of infection and to determine prognosis, and dynamic observation of IL-6 levels can help to understand the progression of infectious disease and response to treatment.
IL-6 expression in patients with neocoronary pneumonia
Multiple studies of viral infections after the twentieth century found elevated IL-6 levels following SARS-CoV, MERS-CoV, H5N1, and H7N9 infections. Following SARS-CoV-2 infection, various research teams have also investigated cytokine changes after SARS-CoV-2 infection. in January 2020, a joint study by Wang Jianwei's team at Peking Union Medical College and Cao Bin's team at Beijing China-Japan Friendship Hospital was published in Lancet, which examined 27 cytokines, including IL-6, and found that ICU patients had higher IL-6 levels than the control group.
In an article published in medRxiv on February 12, 2020, by researchers from Chongqing Three Gorges Central Hospital, the cytokine profile of 123 patients with new coronary pneumonia (NCP) was analyzed, in which the percentage of IL-6 levels higher than normal in the mild group (30.39%) was significantly lower than in the severe group (76.19%), and the difference in IL-6 between mild and severe patients compared to each other was statistically significant.
Also the differences in CD4+T, CD8+T, and IL-10 were statistically significant, indicating that the immunosuppression (caused by excessive release of cytokines) of neocoronavirus infection was more pronounced in severely ill patients, which is consistent with many experts' opinions.
In the "Notice on the issuance of the Treatment Plan for Heavy and Critical Cases of Novel Coronavirus Pneumonia (Trial Version 2)" jointly issued by the General Office of the National Health and Wellness Commission and the Office of the State Administration of Traditional Chinese Medicine on February 14, a progressive rise in IL-6 has been clearly identified as a clinical warning indicator of worsening disease and the need for timely monitoring of critically ill Patients should be monitored promptly.
New Coronary Pneumonia and Cytokine Storm
In February 2020, Zhong Ming, Zhou Zheng, and other experts from China, said that although most patients with novel coronavirus infection have mild symptoms, some patients may have mild disease in the early stage and suddenly worsen in the later stage, and eventually die of multi-organ failure, and the cause of the worsening is mainly the "inflammatory factor storm". This is consistent with the concept of "cytokine storm" emphasized by academician Lanjuan Li of the Chinese Academy of Engineering, in which patients with mild cases of NCCP may experience sudden deterioration due to cytokine storm.
Cytokine storms have also been an important cause of death in many patients (especially young patients) in the current NCCP outbreak. As the epidemic continues to develop, many studies have mentioned that neo-coronavirus infection triggers cytokine storms that release multiple cytokines, including IL-6, causing acute respiratory distress syndrome and multi-organ organ failure.
The analysis of 30 immunological parameters of blood from 33 patients with neocoronavirus pneumonia by Prof. Hai-Ming Wei's team at the Chinese University of Science and Technology suggested a key mechanism for the novel coronavirus infection causing severe pneumonia and cytokine storm: the novel coronavirus infection rapidly activates pathogenic T cells and produces factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-6. GM-CSF further activates CD14+ and CD16+ inflammatory monocytes to produce even greater amounts of IL-6 and other cytokines, resulting in a cytokine storm that causes severe immune damage to the lungs and other organs. This provides further evidence that IL-6 is a key factor in triggering the inflammatory storm in patients with neocrown pneumonia.
As mentioned earlier, IL-6 plays a key role in the early initiation of important signaling pathways in the body's immune and inflammatory response. By triggering the trans signaling pathway (one of the three transduction pathways of IL-6, the remaining two being classical conduction and trans presentation), high concentrations of IL-6 can induce various pathological functions associated with thrombogenesis, vascular leakage and myocardial dysfunction, leading to tissue hypoxia, hypotension, multi-organ dysfunction and DIC (diffuse intravascular coagulation). Therefore IL-6 has the potential to be an early warning, monitoring and prognostic biomarker in cytokine storms.
Drug therapy targeting IL-6 receptors
In addition to the above-mentioned applications, IL-6 also has a very high potential value in the strategic determination of drug therapy and in the concomitant diagnostic role of drug efficacy monitoring.
Tocilizumab (Actemra), a drug previously used in clinical practice for rheumatic diseases, is an anti-IL-6 receptor monoclonal antibody that blocks the IL-6 pathway. The drug is also approved by the FDA for the treatment of cytokine storms caused by CAR-T cell therapy, an emerging approach to treating tumors.
In order to suppress the cytokine storm in patients with neoclonal pneumonia, the research team at the First Affiliated Hospital of China University of Science and Technology has brought "tolimumab" to the clinical trial stage. Based on available clinical data, this new treatment option is likely to reduce mortality by blocking the cytokine storm and thus preventing patients from progressing to severe and critical illnesses.
On February 13, 2020, the Chinese Clinical Trials Registry officially accepted tolimumab, a monoclonal antibody targeting the IL-6 receptor (IL-6R), for a multicenter, randomized, controlled clinical study on the efficacy and safety of tolimumab in novel coronavirus pneumonia.
Figure 4. tolimumab initiation clinical trial (image from China Clinical Trials Registry website)
The level of IL-6 in the patient's blood is the key indication for treatment with anti-IL-6 receptor monoclonal antibodies. Therefore, once the clinical trial of this drug is successful, the demand for IL-6 serum level testing is bound to increase significantly in the future for a large number of treatment decisions and efficacy monitoring.
Laboratory testing for IL-6
In summary, IL-6 can be used as a marker for early infection in this new pneumonia epidemic in combination with PCT for infection determination, as a basis for monitoring disease control and progression in patients with confirmed disease, and as a biomarker for cytokine storm warning, and as a concomitant diagnostic tool for tolimumab treatment strategy and efficacy monitoring. It also has the potential to become a biomarker for early warning of cytokine storms.
Therefore, the importance of IL-6 detection and treatment has become increasingly important. The current methods for IL-6 detection in the aforementioned publications include ELISA (2004), RT-PCR (2005), and flow-through microsphere technology (2020), which have the disadvantages of high manual effort, low efficiency, and low throughput as well as low prevalence and high cost, respectively. In contrast, chemiluminescence immunoassay has long been popular in hospitals, and the sensitivity of IL-6 detection can reach pg/mL level, so the promotion of chemiluminescence method for IL-6 detection is particularly important.
DIRUI Medical's chemiluminescence immunoassay platform for the detection of IL-6 has received good results since its clinical application in the past year. Clinical performance evaluation shows that: the sensitivity is very high, the lowest detection limit of the test batch can be as low as 0.34pg/mL; linear range 0pg/mL ~ 7160.58pg/mL, linear correlation coefficient r is 0.9999; specificity: IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-8 and INF-r are non-interfering (interference rate is less than The specificity of IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-8 and INF-r were free of interference (interference rate less than 0.02%); in addition, the performance indexes such as repeatability and inter-batch variation were much higher than the industry standard. In this new crown pneumonia test, DIRUI's chemiluminescent immunoassay series have also been widely used in clinical practice.
