“The gun is broken” he said, running away frustrated that each shot landed differently. After giving him a few minutes to gather his thoughts, we discussed what happened. I told him the gun is new and we still don’t know how he behaved. We should not be surprised that there are some twists that go through them but the more we hear it the better we understand how it acts. A day later, and with a lot of patience, each shot was well-collected on target.
A similar reduction in target is emerging as studies on the body’s immune responses to Covid-19 have emerged. We are still at the stage of starting to see a new gun; the shots are going down around the target and people are being frustrated by the disagreement in the scientific community. Countless questions remain:
9 antibodies protect us from reconfection? Are they very persistent after recovery or fail quickly? And what does this mean for the development of a vaccine?
These questions came up in early April as the first antibody data began to come out. After reading an early article about antibody testing, I wrote a note to my undergraduate class in an online forum that I titled “this is terrible news, tell me why.” The paper clearly showed that people who had recovered from the infection were producing antibodies against the virus, but that was not my concern. It was worrying that the antibodies peaked, but then quickly decreased in concentration – so much so that if the decline is followed linearly, within 120 to 150 days you will not have protective antibodies.
This suggested that patients who had recovered from Covid-19 could be reinfected again and become ill again. Immunity caused by antibodies that lasts from six months to a year is what we often observe with the human coronavirus that causes the common cold. If this early study were to be fully trusted, this would really be bad news.
Another article describing rapidly declining antibody levels was published in June and followed by a second report in July showing a similar result. The latest document showed that, on average, patients’ antibody levels tended to halve about 36 days after the onset of symptoms, while a small portion of those sampled decreased. much slower.
Science seemed to confirm my initial fear that immunity to antibodies would not be enough to protect recovered victims of coronavirus from reconfection.
But then science moved on. A series of publications in recent weeks on antibody responses to vaccines and an elegant serological study – an examination of antibodies in your blood – have drawn attention to our knowledge. Both Oxford and Modern vaccines have generated a strong antibody response, high or higher than that generated by mild or moderate infection with live SARS-CoV-2 virus. These vaccines are like a school for your immune system, teaching your body how to react to a virus without producing a disease. This was good news! If the level of antibodies starts higher, it possibly persists for longer than previously reported. The limitation is that we still need time to determine how long the antibodies persist – and whether they will be shown to prevent real-world virus infection.
In addition, the serological study, posted as pre-printing by a research team at Mount Sinai Hospital in New York City, clearly showed that after a mild to moderate Covid-19 infection, antibody levels decreased from their peak, then maintained a constant level for at least three months.
It also showed that this immune response was able to neutralize the virus, providing the recovered patient with a strong signal of what some level of immune protection might be. This study differed from early antibody studies in that the estimated number of patients was much larger – it included almost 20,000 patient blood samples (more than 9x the size of the largest sample). previous studies) and methods have been designed to specifically measure concentration. of the anti-virus antibodies’ spike protein that allows it to enter our cells. Although not yet peer-reviewed the comprehensive methods of the study make it the best example yet of serological research on coronavirus.
Not that the early studies were wrong, they just didn’t consider how their data was related to the battle for immunity. In battle, you aim to lock your opponent with a power of numbers and superior armament. This also applies to the response to antibodies of the immune system.
When a virus invades your body and an antibody response is needed for protection, you not only make enough antibodies to match your viral opponent, you significantly exceed the target to defeat the virus and clear it from your system. When the viral threat is removed, most of the cells that initiate the antibodies recruited in the fight are left to die for free space and resources for your body to respond to new threats, and with the death of that cell the antibody. producing is also beginning to decline. . This response to viral antibodies is observed as a rapid increase in antibody levels, followed by a sharp decrease in antibodies in the months following infection. This rapid drop in antibodies was what caught the early studies.
But, what those early studies fail to solve was that some of those antibody-altering cells can live on the bone marrow, which could potentially persist for years, snagging a virus-neutralizing antibody. So after the rapid decline in antibody levels after infection, antibody levels rise and persist as long as those antibody-raising cells are kept long-term in the bone marrow. That type of response is well known with many viral infections, and importantly, it has been well documented to occur in people who survive MERS infection.
High concentrations of antibodies are not necessarily needed to fight future infections. We just need enough antibodies to provide help to the innate immune system to stop new exposure to the virus from establishing an infection.
Given the promising results of antibody stimulation from developing Covid-19 vaccines, my confidence continues to grow that a vaccine that provides at least modest protection from symptoms of severe disease is on the horizon.
However, we must be aware that each new study on antibodies may lead to different findings, resulting in the need to rearrange our understanding – and we must keep in mind what this may mean for victims. asymptomatic Covid-19. Remember, hard, long fights help to train our immune system for future threats.
So being infected and avoiding developing symptoms of infection may not produce the protective antibodies you may need in the future to rule out future exposure. We are also likely to find differences in antibody responses between children and adults, or between men and women.
Meanwhile, conflicting results are usual in science, especially at the beginning of the study of a new subject. We should not rush to conclusions, especially in studies with few samples or with news-grabbing headlines. Each new study published helps refine our understanding and we should be aware that we are all looking for quality results, but negative results or those that do not match the current narrative all help scientists refine the focus of our understanding. .