The new definition of sepsis is as life-threatening organ dysfunction caused by a dysregulated host response to infection more closely fits severe COVID-19. It abandons use of host inflammatory response syndrome criteria (SIRS) in identification of sepsis and eliminated the term severe sepsis. It is usually associated with bacterial rather than viral infections, but this new definition fits severe COVID better than cytokine storm. This latter description suggests a simple positive correlation and causation with pro-inflammatory cytokines. One should expect as their systemic levels go up, the symptoms get worse. The measurable level should correlate with the severity. The alternative is, if this doesn’t happen, the severity must be related to direct viral effects and immunosuppression, allowing the virus to greatly increase in number and spread to many organs, reeking havoc. At first glance these mechanisms may appear diametrically opposed. However, measurements can reflect the dynamics of cytokine levels verses progression of symptoms and exhaustion of the immune system not being synchronized. A recent study illustrates this paradox. https://www.thelancet.com/action/showPdf?pii=S2213-2600%2820%2930404-5. In spite of clinically resembling other classic syndromes associated with cytokine storms, meta-analysis of COVID-19 studies, published or posted preprints, between Nov 1, 2019, and April 14, 2020, in which interleukin-6 concentrations in patients with severe or critical disease were determined (25 COVID-19 studies of 1245 patients were included) showed lower than expected cytokine levels measured. The study groups included four each in sepsis (n=5320), cytokine release syndrome (n=72), and acute respiratory distress syndrome unrelated to COVID-19 (n=2767). Cytokine release syndrome may occur after treatment with some types of immunotherapy, such as monoclonal antibodies and CAR-T cells. Cytokine release syndrome is caused by a large, rapid release of cytokines into the blood from immune cells affected by the immunotherapy. I had seen this with intraperitoneally injected immobilized oxidase-peroxidase causing the rapid experimental destruction of large Novikoff abdominal hepatocarcinoma cancers in rats. In patients with severe or critical COVID-19, the pooled mean serum interleukin-6 concentration was 36.7 pg/ml. Mean interleukin-6 concentrations were nearly 100 times higher in patients with cytokine release syndrome (3110.5 pg/mL), 27 times higher in patients with sepsis (983.6 pg/mL), and 12 times higher in patients with acute respiratory distress syndrome unrelated to COVID-19 (460 pg/ml). Other cytokines gave similar levels with a mean TNFα (tumor necrosis factor alpha) concentration of 5.0 pg/mL (2.3–10.7 pg/mL) in patients with COVID-19, mean concentration of 34.6 pg/mL (20.0–59.9 pg/mL) in patients with sepsis and 52.2 pg/mL (2.0–1390 pg/mL) in patients with cytokine release syndrome. All but one COVID-19 study of the studies analyzed had mean TNFα concentrations lower than 10 pg/mL. IFNγ (gamma interferon) concentrations were not elevated in patients with COVID-19, at an average of 10.8 pg/mL, but were highly elevated in patients with cytokine release syndrome, averaging 3722.1 pg/mL (624–21838 pg/ml). Mean sIL-2R (serum soluble interleukin 2 receptor) was elevated in patients with COVID-19, but much less than in patients with cytokine release syndrome comparison (506 pg/mL vs 12396 pg/ml). The disparity between studies in TNF alpha level reported in an earlier post suggests that when it is measured in the course of the disease is important, but where it is measured is also important. Innate immunity is often very localized, and therefore, not measurable accurately in the serum. CRP (C reactive protein) concentrations were similar in COVID-19 and sepsis patients, and higher in patients with cytokine release syndrome. The studies examined indicated that patients with COVID-19 had higher D-dimer elevations (local fibrin formation and lysis are part of the inflammatory response, and fibrin degradation products, including D-dimer, have been shown to have diverse effects on inflammatory processes and acute phase responses, including hepatic synthesis of acute-phase proteins, such as CRP and fibrinogen) than did patients with sepsis. Mean ferritin and lactate dehydrogenase (measures of cell damage) concentrations were much higher in patients with cytokine release syndrome than in those with COVID-19, but still highly elevated in patients with COVID-19. Again, this indicates that pro-inflammatory processes were in play somewhere other than reflected in the blood measurements. In other highly lethal infectious disease which should resemble sepsis and septic shock syndrome, surprises have been found in cytokine stochastic measurements https://www.ncbi.nlm.nih.gov/pmc/articles/PMC303127/. Edema toxin (ET) of anthrax bacteria and lipopolysaccharide of Gram negative bacteria (LPS) each induced human monocytes to secrete approximately the same amounts of IL-6. ET did not inhibit and, in most experiments, modestly enhanced LPS-induced IL-6 production. In contrast to this stimulation of IL-6 production, ET yielded little or no TNF-alpha production, which is associated with septic shock. Moreover, ET profoundly inhibited LPS-induced TNF-alpha synthesis. Monocytes treated with dibutyryl cAMP, an active analog agonist of cAMP, produced cytokines in a pattern identical to that of cells treated with ET. The disruption of cytokine networks as a consequence of unregulated, ET-mediated cAMP accumulation in human monocytes may impair cellular antimicrobial responses and contribute to clinical signs and symptoms of anthrax. Lethal toxin of anthrax proteolytically inhibits MAP kinase kinase, an essential enzyme in the activation pathways of lymphocytes (MAPKK1 and MAPKK2 are cleaved which inactivates MAPKK1 and inhibits the MAPK signal transduction pathway). Another study with anthrax, that I was involved in, examined these two toxins that cause an intense systemic inflammatory response, edema, shock, and eventually death and showed similar dysfunction and dysregulation of the immune system not expected based on the effects on cytokine function. https://europepmc.org/article/med/11890668. Parent strain mice and knockouts were challenged with LD95 of anthrax spores (5 x 10exp6). administered subcutaneously. The results showed that all genetic knockouts succumbed to anthrax infection as frequently as the parent. TNF antibody delayed death but TNF receptor 1 knockout genetic modification had no effect. IL-1 receptor or iNOS (inducible nitric oxide synthase) knockouts died sooner. Anthrax was more abundant in the injection site of TNF-alpha and iNOS knockouts compared to parent suggesting that localized attenuated inflammatory cellular response increased the disease progression. The deaths were so rapid that, with the exception of edema and necrosis at the injection sites, no pathological changes were observed in internal organs, indicating a lethal per acute shock syndrome. Therefore, the dysregulation leading to dysfunction of the immune system in severe COVID-19 is not unheard of. The general distribution of an otherwise localized response may be the real culprit in severe COVID-19. As mentioned in a previous post, when anti-parasitic immune responses are suddenly generalized, shock and death can rapidly and irreversibly ensue. This is seen with crushing of parasitic fly larvae in a wound (myiasis) or rapid disintegration of filarial or other parasitic worms in a host.
To summarize. the possible sequence of events in COVID-19 are to first infect nasal and oral epithelial cells, trigger interferon and mucosal immunity; if this does not clear the virus, it descends into the lungs, widely infecting pneumocytes, leading to low grade pneumonitis that may trigger an effective adaptive response or not. If the adaptive response fails or results in autoantibody to interferons, then viremia spreads the virus systemically and causes lymphocytopenia (decrease in lymphocyte counts in blood, with removal of lymphocyte regulation of the immune response, typical of viremia). Multi-organ infection and generalized infection of the lungs, followed by immune-mediated cellular (antibody-dependent) inflammatory response against all the infected sites leading to sudden, generalized collateral damage that would otherwise be local, but because of the widespread multiple sites leads to severe disease and even multiple organ failure and death.




















