THE ANTIBODIES neutralizing against Covid-19 persist in patients for at least eight months after diagnosis, regardless of the severity of the disease, the age of the patients or the presence of other diseases. Furthermore, their early presence is essential to successfully fight the infection: those who fail to produce them within the first fifteen days of infection are at greater risk of developing severe forms of Covid-19.
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This was supported by a research carried out by the Evolution and Viral Transmission Unit of the IRCCS San Raffaele Hospital, directed by Gabriella Scarlatti, in collaboration with researchers from the San Raffaele Diabetes Research Institute directed by Lorenzo Piemonti. A test for antibodies exploiting the skills and techniques already employed for the study of the auto-immune response underlying the type 1 diabetes. Researchers from the Center for Global Health and the Department of Infectious Diseases of the Istituto Superiore di Sanità (ISS), coordinated by Andrea Cara e Donatella Negri, taking advantage of the skills and techniques already used for the study of HIV vaccines, they worked in close contact with the group of Gabriella Scarlatti to develop a new method for the evaluation of neutralizing antibodies against Sars-CoV-2.
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The study, published today in Nature Communications, maps in an exhaustive way the evolution over time of the antibody response to Covid-19 and provides important indications both for the clinical management of the disease – through the recognition of patients at greater risk of severe forms – and for the epidemiological containment of the pandemic.
The methods of the study
The researchers followed over time 162 coronavirus positive patients, with symptoms of varying degrees, which presented themselves to the emergency room of the San Raffaele Hospital during the first wave of the pandemic in Italy. The first blood samples were collected at the time of diagnosis and date back to March-April 2020, the last at the end of November 2020.
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The patient group consisted of 67% males, with a mean age of 63 years. 57% suffered from a second disease in addition to Covid-19 at the time of diagnosis, hypertension (44%) and diabetes (24%) the most frequent. Out of 162 patients, 134 were hospitalized.
In addition to specific and neutralizing antibodies against Covid-19, the researchers also investigated the reactivation of antibodies to seasonal coronaviruses (those responsible for the classic cold) in patients with the aim of verifying their impact on the response against Sars-CoV-2 . “These antibodies partially recognize the new coronavirus and can reactivate following the infection, although they are not effective in neutralizing it,” he explains Gabriella Scarlatti, who coordinated the research. “The fear was that their expansion could slow the production of neutralizing antibodies specific to Sars-CoV-2, with negative effects on the course of the infection.”
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The results of the study
Contrary to what has emerged from previous studies, the early presence of neutralizing antibodies against Sars-CoV-2 actually correlates with better control of the virus and longer patient survival. Fortunately, this is true in most cases: 79% of enrolled patients successfully produced these antibodies within the first two weeks of the onset of symptoms. Those who did not succeed were at greater risk for severe forms of the disease, regardless of other factors such as age or health.
At the same time, the presence of neutralizing antibodies, while reducing over time, was very persistent: eight months after diagnosis there were only three patients who no longer showed positivity to the test. The persistence of these antibodies for at least eight months is independent of the age of the patients or the presence of other pathologies.
Finally, according to the data analyzed by the San Raffaele researchers, the reactivation of pre-existing antibodies for seasonal coronaviruses has no influence in delaying the production of specific antibodies to counter Covid and is not associated with a greater risk of serious COVID courses. 19.
“The study of the antibody response against Sars-CoV-2,” he explains Vito Lampasona of the Diabetes Research Institute “reveals the complexity of the interaction between the virus and the immune system, one of the elements that determines the different severity with which the disease manifests itself in the individual patient”.
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“What we have discovered has implications both in the clinical management of the disease in the individual patient and in containing the pandemic” he says Gabriella Scarlatti. “According to our results, in fact, patients unable to produce neutralizing antibodies within the first week of infection should be identified and treated early, as they are at high risk of developing severe forms of the disease. The same results, however, also give us two good news: the first is that the immune protection conferred by the infection persists for a long time; the second is that the presence of a pre-existing antibody memory for seasonal coronaviruses does not constitute an obstacle to the production of antibodies against SARS-CoV-2. The next step is to understand if these effective responses are maintained even with vaccination and especially against the new circulating variants, which we are already studying in collaboration with ISS colleagues “.
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