Another study shows a cross-reactive T cell response to SARS-CoV-2

Using ELISpot and the growth assay, researchers respond strongly in patients infected with SARS-CoV-2, but less so in negative samples.However, there may be cross-reactive T cell responses from other humans Coronavirus..

COVID-19, a disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has spread rapidly around the world in the last decade. One of the hallmarks of the disease was the severity of symptoms, often fatal at one end, and asymptomatic patients with no symptoms at the other end. This has led to a great deal of effort to understand how the immune system responds to the virus.

To better understand this, one approach was to look at the antibodies produced by the immune system. However, the range and duration of antibodies found in infected patients varies widely.

Another approach was to examine the response of T cells, a type of white blood cell that is an important part of the immune response. Studies have reported T cell responses to the SARS-CoV-2 virus in almost all cases.

In addition, researchers are also interested in understanding whether previous exposure to other human coronaviruses affects T cell responses. Previous studies have shown a reactive response to SARS-CoV-2 in people who have previously been infected with SARS-CoV.

However, various studies have reported levels of cross-reactive immunity against human coronavirus in people not exposed to SARS-CoV-2 in the range of 0-50%.

Immune response of recovered COVID-19 patients

In a new survey published on the preprint server medRxiv*, Researchers have investigated whether the levels of T cell response differ between those with and without COVID-19, and those whose T cell response is infected with SARS-CoV-2 and other seasonal human coronaviruses. I tried to figure out if I could distinguish.

First, researchers used the ELI Spot assay to examine T cell responses in 168 and 111 negative samples with confirmed SARS-CoV-2 infection.They found that interferon-g (IFN-g), a cytokine important for immunity, was found in convalescent patients. Spike protein, And SARS-CoV-2 structural and accessory proteins.

However, there was a significant difference in the level of IFN-g response between symptomatic and asymptomatic patients, with more significant responses in patients who reported fever.

Fever suggests a more important system response to the virus, and such people may initiate a more active T cell response. This may be the result of the early immune system not being able to control the infection and requiring a larger adaptive response.

The levels of CD4 + and CD8 + are T cells Changed in different pools to test response to structural and accessory proteins. Both types of T cells were present in patients infected with SARS-CoV-2. The response to M and NP proteins was very high. They may be used as antigens when testing populations for T cell immunity after SARS-CoV-2 infection.

Previous studies have shown that antibodies to SARS-CoV-2 may be short-lived. The T cell response in this study suggests a peak T cell response 4 weeks after symptoms were seen.

T cell response in SAR-CoV-2 negative people

Of those who tested negative for SARS-CoV-2, 48 had no T cell response to spike proteins and structural and accessory proteins. However, 20 people had high levels of CD4 + and CD8 + cells, responding to the S1 and S2 subunits of the spike protein, and the authors discovered using a proliferation assay. Responses to structural and accessory proteins were either absent or weak.

Researchers also analyzed cryopreserved samples prior to COVID-19. Like the COVID-19 serum-negative samples, these samples also had an inadequate T-cell response to spike, structure, or accessory proteins, but showed a response to S1 and S2 proteins.

The response to M and NP proteins was smaller than that of COVID-19 convalescent patients. Therefore, these antigens can be used as markers of T cell response to SARS-CoV-2.

These results suggest that people retain a cross-reactive central memory response to spike proteins of other seasonal coronaviruses present in the United Kingdom. It may also be cross-reactive from other viruses.

There is a correlation between antibody testing and ELI Spot testing in SARS-CoV-2 positive patients, but there is a strong response to these spike proteins, which makes a difference in SARS-CoV-2 negative or unexposed samples. There is. sample. The author writes that further testing is needed to understand this.

Based on these results, the authors write that the ELI Spot assay can be used to identify SARS-CoV-2-specific immune responses.

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they are not peer-reviewed, guide clinical / health-related behaviors, and should not be treated as established information.