PRESS RELEASE N° 26/2021 Neutralizing antibodies against SARS-CoV-2 persist in the bloodstream for at least eight months after infection

ISS, 11 maggio 2021 - These are the two main results of a study carried out by the Virus Evolution and Transmission Unit of the San Raffaele Teaching and Research Hospital, headed by Gabriella Scarlatti, in collaboration with researchers from the San Raffaele Diabetes Research Institute headed by Lorenzo Piemonti, who have developed a special test for antibodies by building on the skills and techniques already used for the study of antibodies involved in the auto-immune response underlying type 1 diabetes. Researchers from the National Centre for Global Health and from the Department of Infectious Diseases of the Istituto Superiore di Sanità (ISS), coordinated respectively by Andrea Cara and Donatella Negri, by exploiting the skills and techniques already used to study HIV vaccines, worked in close contact with Gabriella Scarlatti's group to develop a new method for evaluating the neutralizing antibodies against SARS-CoV-2.

The study, published today in Nature Communications, traces a comprehensive map of how the antibody response to COVID-19 evolves over time 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.

Methods of the study

The study was carried out by following over time 162 SARS-CoV-2 positive patients having symptoms of varying severity, who came 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 were collected at the end of November 2020.

67% of the patients in the group are males, with an average 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%) being the most frequent. Out of 162 patients, 134 were hospitalized.

In addition to specific and neutralizing antibodies against SARS-CoV-2, the researchers also investigated the reactivation of antibodies to seasonal coronaviruses (those responsible for the classic cold) in these

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,” explains Gabriella Scarlatti, who coordinated the research. "Our fear was that their expansion might slow down the production of neutralizing antibodies specific to SARS-CoV-2, with negative effects on the course of the infection."

"This work represents an exciting collaborative effort", point out Andrea Cara and Donatella Negri, "which combines our interest in assessing the body’s immune response against different infectious agents with out ability to leverage the experience built up within our institutions which is focused on the development of innovative and effective immunological methods that are capable of providing quick answers".

The results of the study

Contrary to previous studies, the early presence of neutralizing antibodies against SARS-CoV-2 actually correlates with better virus control and longer patient survival. Fortunately, this is true in most cases: 79% of enrolled patients in fact successfully produced these antibodies within the first two weeks of the onset of symptoms. Those who did not 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 declining over time, was very persistent: eight months after diagnosis only three patients were no longer positive to the test. The persistence of these antibodies for at least eight months is independent of the patient’s age or presence of other pathologies.

Finally, according to the data analysed by the San Raffaele researchers, the reactivation of pre-existing antibodies to seasonal coronaviruses has no influence in delaying the production of antibodies specific to SARS-CoV-2 and is not associated with an increased risk of a serious course of COVID-19.

"The study of the antibody response against SARS-CoV-2" 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 degrees of severity with which the disease manifests itself in individual patients".

“What we have discovered has implications both for the clinical management of the disease in individual patients and for the containment of the pandemic,” 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. However, the same results also give us two good insights: the first is that the immune protection conferred by the infection persists for a long time; the second is that the presence of the memory of a pre-existing antibody for seasonal coronaviruses does not constitute an obstacle to the production of antibodies against SARS-CoV-2. The next step is to understand whether these effective responses are maintained also in the presence of the vaccine and especially if they are effective against the new circulating variants, which we are already studying in collaboration with our colleagues of the ISS".

The study was made possible thanks to the internal funding of the COVID-19 OSR-UniSR Program Project activated thanks to the 5xmille funds for the San Raffaele Hospital and funds from the Ministry of Health (COVID-2020-12371617).