ADVANCE OF CORONAVIRUS IN THE HUMAN BODY

 

SARS-CoV-2 surprised us all, in fact, scientists have already had decades issuing warnings about the emergence of a new pandemic. The previous warnings had been given by SARS-CoV (cause of acute and severe respiratory syndrome) and MERS-CoV (cause of Middle East respiratory syndrome), they spread over several continents and that the latter has not yet been eradicated. The truth is that despite all the new virus surprised us all.

Despite the disorganization, health professionals and researchers were apprehended to combat the new threat in coordination before its arrival. Less than a year has passed, but thanks to global collaboration we already know enough about the new coronavirus and its impact on the human body. We begin to understand why SARS-CoV-2 causes diseases of a very different nature: some people show no symptoms, while others cough or have a fever. Most seriously, some suffer from life-threatening pneumonia and a condition called acute respiratory distress syndrome (DRA). Today we already know that this virus, similar to SARS-CoV and MERS-CoV, causes the immune system to become desoriented and cause inflammation that will end up in the SDRA and a range of dangerous symptoms.

Today we know that in a fraction of patients with COVID-19 an unmeasured immune response is unleashed that causes damage throughout the body, with blood clots, heart injuries and even organic failure. The most severe cases require admission to intensive care units (ICU).

It was known that the immune system, when attacked, produces a series of mechanisms to counteract invading pathogens. Also, if any of the stages of this response starts out of time, it can trigger an exaggerated inflammation that damages the tissues. There is a quick emergency response and a slower but longer lasting response to viruses, bacteria, fungi, and more. The first is the "innate" response, in which some receptors on the surface and inside immune cells detect intruders and activate an elaborate signaling cascade involving proteins called cytokines. These alert neighboring cells to prepare their defenses, initiate the death of infected cells or amplify the alarm with the synthesis of other types of cytokines. The cells responsible for the innate response also attract certain leukocytes from the blood so that they mount a more lasting immunity against the pathogen. After a week or two, these members of the "adaptive" immune system are activated, reinforcing the amount of antibodies and specific T lymphocytes that will eventually neutralize or kill the invader.

In most COVID-19 patients, the innate immune system does its job as it learns to neutralize and destroy SARS-CoV-2. But in almost 5 percent of cases, the counterattack is slower and the signal cascade is disrupted, the cells of the innate response react by manufacturing too many cytokines, which contributed to exacerbating COVID-19. The most recent research indicates that, in most cases, the inflammation is not typical, although it also poses a threat to the patient's health. If you cause ARDS, the lung and other tissues will suffer lasting damage. It also involves the synthesis of fibrin, a protein that encourages clot formation. And if all this was not enough, the liquid fraction of the blood begins to leak out of the blood vessels (extravasation), which triggers respiratory failure.

All viruses manipulate cellular machinery to their advantage to reproduce. One strategy of the innate immune system is to sabotage that ability, but it appears to fail against SARS-CoV-2. In recent months, interferons, a type of cytokine that act as the first line of defense, blocking the replication of the virus within the cell, have received a great deal of attention. In theory, the rapid production of type I interferon would make it possible to contain the virus and not exceed the limits of a mild infection, but some studies indicate that it would continue to reproduce due to the delay in the immune response in the elderly or in exposed patients large amounts of the virus. In addition, the entry into the scene of interferons would end up unleashing a hyperreaction that would stimulate the massive manufacture of other cytokines, which would lead to severe inflammation and symptoms.

The results of inflammation

The cytokine storm made headlines in the severe cases of the preceding coronaviruses (SARS-CoV and MERS-CoV), so when SARS-CoV-2 appeared, the intervention of a similar mechanism was naturally seen. From the beginning of the pandemic, doctors detected a high concentration of cytokines in patients, but their quantity and the subsequent inflammatory state they caused differed from the typical storm.

These patients were shaken from within by the high concentration of cytokines that, depending on the cell that received them, had different consequences, some very harmful. Cytokines amplify inflammation and tissue injury.

There are many immune reactions that doctors study to try to understand how the body's own defensive system ends up causing a reaction that affects the lives of patients.