60% may already have Immunity to COVID-19

This article talks about the presence of immunity against COVID-19 in as much as 60% of the population, even if they have not been exposed to the SARS-CoV-2 virus.

There are 7 types of human coronaviruses or HCoV. Four of them are common. The 229E, NL63, OC43, and HKU1. The other two, MERS and SARS, have high mortality rates and created their own epidemics. Mercifully, those have done has gone away.

The latest one that we are all familiar with is the SARS-CoV-2, which causes the COVID-19 pandemic.

Human Coronavirus Spike Proteins

All coronaviruses have protruding spike proteins on their surfaces, which gives them the appearance of a crown or corona.

The spike protein is the one that sticks to the cells of the host. Next, the coronavirus will insert its genetic sequence into the human cells and start reproduction or replication in virus terms and start an infection.

Due to its viral entry into the cells, most vaccines against COVID-19 are directed towards the spike protein. That way, the formed antibody will prevent the adhesion of the virus to the cells.

In all human coronaviruses, the spike proteins are genetically conserved. In this sense, Conserved means that the nucleic acid or protein sequences have stayed the same during evolution. This is reported in Structural and functional properties of SARS-CoV-2 spike protein: potential antivirus drug development for COVID-19.

The SARS-CoV-2 S protein is highly conserved among all human coronaviruses (HCoVs) and is involved in receptor recognition, viral attachment, and entry into host cells. Due to its indispensable functions, it represents one of the most important targets for COVID-19 vaccine and therapeutic research.

What is the significance of the genetic conservation of the spike protein?

This means people who have been exposed to the more common human coronaviruses before may have developed an immune response towards the SARS-CoV-2 already!

The 229E, NL63, OC43, and HKU1 have always been around and are responsible for 15-30% of upper respiratory tract infections yearly.

Those exposed and survived the previous encounters/illnesses with coronavirus have developed an immune response to the coronaviruses, as evidenced in the following.

Studies that show pre-existing immunity to SARS-CoV-2

The following are the titles of the studies and the quotes from the authors. You can click on the titles to read the whole study.

Targets of T Cell Responses to SARS-CoV-2 Coronavirus in Humans with COVID-19 Disease and Unexposed Individuals

Importantly, we detected SARS-CoV-2-reactive CD4⁺ T cells in ∼40%-60% of unexposed individuals, suggesting cross-reactive T cell recognition between circulating “common cold” coronaviruses and SARS-CoV-2.

Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans

In this study published in the journal Science, the authors studied preserved blood samples taken before the COVID-19 pandemic.

They found out a preexisting immune response to SARS-CoV-2 among people who were never exposed to it.

We demonstrate a range of preexisting memory CD4⁺ T cells that are cross-reactive with comparable affinity to SARS-CoV-2 and the common cold coronaviruses human coronavirus (HCoV)-OC43, HCoV-229E, HCoV-NL63, and HCoV-HKU1.

CD4⁺ T-cells or T-helper cells are part of the adaptive immune system. They activate the cells of the innate immune system like the B-lymphocytes, cytotoxic T cells, and nonimmune cells against infections.

The presence of an adaptive immunity towards a specific pathogen means that they have encountered it before, and the “experience” has been stored in the memory of the immune system.

This memory allows a faster adaptive immune response in case the virus shows up again.

SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls

 We also detected SARS-CoV-2-specific T cells in individuals with no history of SARS, COVID-19 or contact with individuals who had SARS and/or COVID-19.

Thus, infection with betacoronaviruses induces multi-specific and long-lasting T cell immunity against the structural N protein.

T-cells are a type of white blood cells. They play a central role in the adaptive immune response. The adaptive immune response is particular to a particular pathogen. In this case, the SARS-CoV-2 virus

SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls

We showed that patients (n = 23) who recovered from SARS (the disease associated with SARS-CoV infection) possess long-lasting memory T cells that are reactive to the N protein of SARS-CoV 17 years after the outbreak of SARS in 2003; these T cells displayed robust cross-reactivity to the N protein of SARS-CoV-2.

We demonstrate the presence of S-reactive CD4⁺ T cells in 83% of COVID-19 patients, as well as in 34% of SARS-CoV-2 seronegative healthy donors (HD), albeit at lower frequencies.

Seronegative means that the individuals were tested negative for the presence of SARS-CoV-2.

In conclusion, as much as 60% of people may already have an immune response to the COVID-19 even if they have not been exposed or tested positive for it. The duration of the immunity can last as long as 17 years.

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Don’t Get Sick!

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