As Covid-19 waves sweep the world and vaccination rates increase, more and more people are acquiring some sort of immunity against Covid-19, either from a vaccine or from an earlier infection.
However, there are people who have neither had vaccines nor a coronavirus infection. While the simplest explanation would be that they have either been very lucky or very careful, scientific efforts are ongoing to understand this phenomenon deeply.
Scientists have zeroed in on two possible causes of some people’s natural resistance to Covid-19 — they have developed immunity for Covid-19 from earlier infections of other viruses in what’s called immune cross-reactivity or genetic mutations in some people disallow SARS-Cov-2, the virus that causes Covid-19 disease, to enter their cells.
How can earlier viral infections make you resistant to Covid-19?
At the onset, you need to understand that SARS-Cov-2, the virus that causes Covid-19 disease, is only one of the several coronaviruses. “Coronavirus” is a category of viruses which range from those that cause common cold to those causing Covid-19.
Scientists have described a theory called “immune cross-reactivity” as per which exposure to any of the common human coronaviruses may lead to immunity against other human coronaviruses.
This theory appears to be further plausible in light of an earlier study by Singapore-based researchers that showed that people with antibodies to SARS disease of 2002-04 – also caused by a coronavirus – showed a potent response to Covid-19.
Explaining immune cross-reactivity, Prof. George Kassiotis of the London-based Francis Crick Institute said that there are two parts (or sub-units) of the spike of a coronavirus – the “spike” is the protruding part of the coronavirus it uses to enter human cells.
He told Medical News Today, “The S1 sub-unit allows the virus to latch onto cells and is relatively diverse among coronaviruses, whereas the S2 sub-unit lets the virus into cells and is more similar among these viruses. Our work shows that the S2 subunit is sufficiently similar between common cold coronaviruses and SARS-CoV-2 for some antibodies to work against both.”
How can you be genetically immune to Covid-19?
Immunity to a certain disease because of a person’s genetic mutation has been known for some time now regarding other diseases such as AIDS and malaria.
Similarly, certain mutations in a person’s gene can help them be immune against Covid-19 by disallowing the virus to enter its cells.
The virus enters human cells through the ACE-2 receptor and a mutation in this receptor, according to New York University’s biology professor Neville Sanjana, can make it hard for the virus to enter.
Neville told Yahoo News, “We know that there is an entry receptor similar to the one that we have identified for SARS-CoV-2, but it’s a different gene. With HIV, the virus that causes AIDS, the entry receptor is CCR5 and we know that there are some people who naturally have a mutation that gets rid of CCR5.”
What's the significance of these genetic mutations?
While vaccines generate antibodies inside you and train your immune system against Covid-19, most medications only treat symptoms caused by the virus or work towards clearing the virus from your body.
New York University's Neville, quoted above in the story, said studies on genetic mutations blocking coronavirus infections are important to develop the next generation of treatments.
He said, “Most of the therapeutics that we have, whether remdesivir or Paxlovid, work on the virus. They target the virus. They target the viral genes. You might imagine that if you understood what the key host genes are, what we could do is maybe design other therapies that target those genes.”
Once such treatments are available, a person’s genes might be mutated in a way that coronavirus cannot enter it, making them naturally immune against Covid-19.
