Question

       Based on what you have learned about antigen presentation, T cells, and viral infections, describe the process of antigen presentation of COVID-19 to CD8+T cells. Include how the virus enters the cells, is processed in the cells, and activates CD8 T cells.

Answer 1

CORONA VIRUS DISEASE 19 is a pandemic caused by Severe acute respiratory syndrome coronavirus-2. It can generally enter through the mouth or the nose. And it finally reaches the air sac called alveoli. Once the virus reaches the alveoli it attacks the cells by their spiking protein present on their surface. This protein connects with the molecules in the human cells and causing the infection. The receptor in the molecule of the surface of the cells in which the virus attaches with the spike and it goes inside and takes over the control of the entire cells.

Spike proteins play a dual role in entry by mediating receptor binding and membrane fusion. Through this fusion an internalization will occur, this was done by the large conformational change in the spike. By overtime, they modify their spikes leading to the diversity of triggers to activate their fusion.

The COVID 19 spreading have 3 main stages such as the:

1) Asymptotic stage

2) Non- severe asymptotic stage

3) Severity stage

The immunity response is mainly classified into 2 phases such as:

1) during the incubation period

2) during the severity stage

When the virus enters our cells they propagate inside our body and make multiple copies. And the next step of infection is reducing the number of white blood cells. This condition is called lymphocytopenia. They show massive destruction in the cells having high ACE2 expression, which is in the kidney and in the intestine. Then leads to the inflammation in the lungs that is mediated by the pro-inflammatory macrophages and granulocytes. Lung inflammation is one of the important cause that leading to the severity.

The patients with severe conditions are affected by cytokine release syndrome. The cytokine release by the cells causes inflammation in the lung alveoli. Interferons and interleukins have a great role in the production of cytokine. Hence the blocking of the gene producing has a beneficial effect on the patients.

The presence of certain proteins makes the T cells into different types such as CD4+ T cells, CD8+ T cells.

The CD4+ T cells help to give the information to the other immune cells the invasion of a virus or a bacteria, whereas the CD8+ T cells kill the invaded organisms by cytotoxics. But the coronavirus enters the cells hijack the cell by taking the control of cells and they may not able to send the signals. This makes the T cells stay inactive finally the virus causes the self-destruction of the T-cells and reduces their number leads to the condition called lymphocytopenia.

By reducing the number of lymphocytes leads to a massive release of cytokine and leads to the cytokine storm and then leads to the inflammation in the lungs.

This finally ended up in difficulty in breathing.And causes the acute respiratory syndrome.