Some cells of the immune system of people vaccinated against Sars-CoV-2 recognize the new Omicron variant and produce an effective response, reducing the serious consequences of the disease and hospitalizations. This was revealed by a new study by the Neuroimmunology laboratory of the Santa Lucia Irccs neurorehabilitation hospital in Rome which conducted in-depth immunological analyzes on fresh blood samples from 61 donors who had carried out different types of vaccinations.
The protocol used for the study consists in the exposure of donor T lymphocytes to the Spike protein of the original Sars-CoV-2 strain, against which the vaccines currently in use have been prepared. 100% of donors responded with activation of coronavirus-specific T lymphocytes, regardless of the type of vaccination performed previously. In parallel, T lymphocytes were exposed to mutated fragments of the Omicron variant Spike protein generating a cellular response in approximately 70% of individuals. However, this response was reduced by approximately 50%, which meant that fewer cells recognized the mutated Spike protein. In light of these data, the residual efficacy of the mRNA vaccines was then estimated by the researchers to be about 80% compared to that against the original variant.
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“Initial analyzes of antibody responses showed that vaccination and infection-induced antibodies lost much of their neutralizing power, thus being ineffective in protecting against Omicron, and this alerted scientists around the world to the potential danger of the new. variant – states Giovanna Borsellino, neuroimmunologist and director of the Laboratory of Neuroimmunology of the Santa Lucia IRCCS – antibodies, however, are only part of the tools that the immune system uses to fight infections. Cellular immunity, the analysis of which requires much more complex and non-automated systems than the dosage of antibodies, is made up of an army of blood cells trained to recognize the virus, also endowed with memory and longevity: the T lymphocytes. this work has shown that T lymphocytes also recognize the Omicron variant, albeit to a lesser extent than the original Wuhan virus against which we were vaccinated. These T lymphocytes have, chemically, a broader view of the virus than antibodies, and are able to overlook small changes in its structure, always staying on target. Rino Rappuoli’s studies on influenza vaccines have long demonstrated this. With this new variant, so dangerously different in the eyes of antibodies, it was urgent and fundamental to understand if the T lymphocytes instead had kept their gaze fixed on the virus. We first measured the cellular response to the entire Spike protein of the original Wuhan virus, which is that of the vaccine. This response was present in 100% of the donors. Then we measured the response to fragments only of the mutated regions in the Omicron variant, which was present in about 70% of the donors, and we saw that fewer T cells recognized and activated them. To understand how much the recognition or not of the mutated fragments weighed on the entire cellular response to Spike, we studied in parallel the response to the same fragments, but coming from the original Wuhan virus. With these data, we estimated that about 83% of the response and therefore of the cellular immunity towards the Spike protein is maintained, despite Omicron mutations “.
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These laboratory data confirm clinical data from around the world, with hospitalization and serious illness rates far lower than in previous waves that have swept us from unvaccinated. “These vaccines work, and even if the antibodies drop over time and don’t recognize the new variants well, the T cells remain on guard, and kill the infected cells thus disrupting the replication cycle of the virus. In addition, the T cells can help. the cells that produce the antibodies, favoring the generation of new neutralizing antibodies directed against the variants. You get infected, but you are protected from severe disease. The cellular immunity induced by these vaccines appears to be very effective and of good quality. It is important. get vaccinated, because you expose yourself – and those who cannot get vaccinated – are exposed to a potentially serious disease, largely preventable with the vaccine ”, continues Borsellino.
The study was carried out as part of a larger research project to evaluate the immune response to viruses, including Sars-CoV-2, in people with multiple sclerosis undergoing immunosuppressive and immunomodulatory therapies.
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