CD4+ Cross-Reactivity between Seasonal Coronavirus Colds and COVID-19

Posted on by Jesse Santiano, M.D.

A previous article, Antibodies to COVID-19 can Exist in the Uninfected, talked about research from the Francis Crick Institute about how the antibodies formed against seasonal coronavirus infections can protect against the new coronavirus infection COVID-19.

Aside from antibody production, the body’s adaptive immune system has other components in its armory. One of which is the CD4+ cells or the T helper cells.

T helper cells regulate the other parts of the immune system. They are like the control tower in an airport or an ambulance dispatcher. Like antibodies, they are custom-made or specific to microbes. For example, a CD4+ will work for a coronavirus but not for another virus like the flu.

A new preprint study from the Charité – Universitätsmedizin Berlin entitled,  Presence of SARS-CoV-2 reactive T cells in COVID-19 patients and healthy donors, talks about their detection of the presence of CD4+ cells against the spike protein of SARS-CoV-2 in 83% of COVID-19 patients and 34% of study subjects who never had COVID-19.

This is significant because a person has to be exposed or get sick from a particular virus before developing CD4+ for that virus.

In this study, the CD4+ reactive T-cells present in the healthy, non-COVID-19 patients most likely came from previous infections with seasonal coronaviruses. Coronaviruses are responsible for 20-30% of common colds yearly.

Whether they are common ones and the SARS-CoV-2, all coronaviruses have spikes that are glycoproteins, a glucose-protein combination.

1024px-Coronavirus_virion_structure.svg

The presence of CD4+ cells gained from previous coronavirus infections in the population may give them partial immunity against COVID-19. Partial protection can lead to mild symptoms or even asymptomatic infection.

This may also explain why children have mild symptoms and a low COVID-19 mortality rate. The frequent social interaction in the schools, daycare, and playground exposed them to other coronaviruses that developed their immunity against COVID-19.

On rare occasions, the presence of CD4+ cells can lead to a disaster and worsening of diseases. That is why more research is needed to define their role in COVID-19.

COVID-19 has a high mortality rate because it is a relatively new virus, and thus not many have immunity to it. But as months go by and more knowledge is gained, we begin to understand how previous exposure to other coronaviruses can give natural immunization against COVID-19.

Knowledge about Covid-19 is rapidly evolving. Information may update as new researches are done. Stay current by subscribing.

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