Dodging the coronavirus bullet is becoming more and more complicated. A few months ago, many people could be proud of not having even had contact with SARS-CoV-2 . At least that they knew. However, the current great wave caused by the omicron variant has meant that, to a greater or lesser extent, most people have been more or less exposed. Even so, there are those who are still not infected, even having been living with infected patients. This escape from the contagion of coronavirus is a mystery to many scientists, who are already beginning to start studies in search of the causes. They are not clear yet; But, for now, it seems that having had a cold could have something to do with this mysterious protection.
It is the conclusion of a study that has just been published in Nature Communications , by a team of scientists from Imperial College in London. In their study, they point to very important soldiers of our immune army as being responsible for this cross-protection: the T lymphocytes.
These are cells that recognize a pathogen and attack it, but with the difference that they remain in our body longer than antibodies. But what does all this have to do with the cold ?
Saved by the cold
Although we know the cause of COVID-19 as THE CORONAVIRUS, the truth is that there are many coronaviruses. There are their cousins ​​ more ferocious, causing in the past the deadly epidemics of SARS and MERS . But also other much milder ones with which we are constantly in contact and that, in general, do not cause more than a cold.
It is not the same virus, but the relationship it maintains has led to the fact that, as previous studies had shown, the T lymphocytes that recognize some can also recognize others. But just because they recognize them doesn’t mean they can attack them. This is something that was not known until now, which is why these scientists have focused their research on trying to find out.
And for this, the best way was to have those people who seem to dodge again and again the contagion of the coronavirus . People who, even living with the disease, have passed without becoming infected.
Lymphocytes against the spread of coronavirus
To carry out this study, 52 people who lived with COVID-19 patients were recruited. Half of them had also become ill, while the other half avoided the contagion of coronavirus .
The study was conducted in September 2020, when most people in England had not been infected or received any of the coronavirus vaccines. Thus, if there was prior immunity, it must have been for another reason. Indeed, none of these patients had antibodies indicating prior SARS-CoV-2 infection .
People who had not been infected despite exposure had higher levels of T cells against other cold-causing coronaviruses
All of them underwent a PCR on the day of detection of the positive of their companions and also 4 and 7 days later. In addition, blood samples were taken during the first 6 days of exposure to the virus.
Thus, it was seen that those who did not get sick had higher levels of T lymphocytes in their blood directed at other coronaviruses that cause colds . There was, therefore, a cross-immunity. Your immune system picked up on SARS-CoV-2 and fought it off, so to speak, because it mistook it for a relative it had fought before.
A target for new coronavirus vaccines
The authors of this study believe that what they have discovered may even be useful for the development of new vaccines.
The causes are clear. The protein spike is that key that SARS-CoV-2 uses to infect our cells. But it is also the alarm signal that normally attracts the immune system. The antibodies generated by a first exposure or by vaccines target it, causing great pressure against the virus that can drive the evolution of mutations that escape them. It has been explained in a statement by Professor Ajit Lalvani , lead author of the study.
Proteins attacked by T cells are more conserved in different variants
The proteins targeted by T lymphocytes, on the other hand, are much less exposed. If we visualize the virus as a human being, we could say that the spike is the arms and proteins that recognize T lymphocytes the heart. Being less exposed, it is more difficult to attack them, but it is also more difficult for their mutations to prosper into new variants. In short, they are much more conserved between different variants. Even in the omicron . And that could be very useful to prevent the spread of the coronavirus with new vaccines.
In any case, it does not seem that this is still necessary, since the vaccines that we currently have, to a greater or lesser extent, protect us from becoming seriously ill with COVID-19. For this reason, the authors of this study emphasize that, although the cold can give us some protection, the safest thing is to have the complete vaccination schedule . If we add to it the cross-protection that a cold offers us, all the better, but we shouldn’t gamble on that card alone.
On the other hand, the authors of the study also acknowledge that their research has certain limitations. To begin with, it has been carried out with a very low number of participants. And, in addition, all of them were of white European ethnicity , so other geographical origins are not taken into account.
It’s just a brushstroke, yes, but it helps us to see one of the channels by which some people are avoiding the spread of coronavirus. But no, if you recently had a cold, that does not exempt you from getting vaccinated. Nor does it give you carte blanche to go through life without a mask or to lead a normal life if you have symptoms. The cold can help you, but if you are not vaccinated, you are at the mercy of the COVID-19 . We’ve already seen what it can do. The best option is not to play it.