When it already seemed that the distrust of adenoviral vector-based vaccines had prevailed, a study reinforces the importance of their use, especially in contexts where the choice is scarce. In fact, these vaccines are capable of generating “robust and long-term responses of the immune system”.
But let’s take a step back: COVID 19 vaccines based on an adenoviral vector use a virus that has lost its replicative capacity and acts as a ‘Trojan horse’ to bring the Sars-CoV genomic segment into the human cell -2 with information on the Spike protein. Today there are two authorized in our country so far by Ema, the European Medicines Agency, and Aifa, the Italian Medicines Agency: AstraZeneca (Vaxzevria) and the single-dose Johnson & Johnson)
After the reports of rare thrombotic and embolic events related to the AstraZeneca vaccine – also on the emotional wave of avalanches of renunciations – the Ministry of Health has recommended its use over 60 years, providing for people under that age a booster with a different vaccine, with mRNA: the so-called heterologous vaccination.
But adenoviral vector vaccines have another card to play: they generate “robust and long-term responses of the immune system”. This is what emerges from a work conducted by the University of Oxford and the Cantonal Hospital of St. Gallen, in Switzerland, published in the British monthly magazine Nature Immunology.
The mechanism
Using animal models, the scientists found the ability of adenoviruses to enter fibroblastic stromal cells, elements of connective tissue with a long half-life. Localized in tissues such as the lungs, they become the place where the viral antigen ‘settles’, exposing itself in a continuous and prolonged way to the action of the immune system.
Per Massimo Andreoni – Head of the Infectious Diseases Complex Operating Unit of the Tor Vergata Polyclinic in Rome – the validity of the response of the adenoviral vector vaccines is linked to the remarkable ability to stimulate both B (antibody producing) and T cells, of which those are part of memory, which represent the memory of the immunization: “It depends on the way the antigen is presented to our body: in this way the mechanism of natural infection is simulated in the best way. A strategy surpassed only by vaccines based on a virus live attenuated, where the microorganism has lost its pathogenic characteristics “.
Development technology question. “In practice we use different vaccines, because each viral antigen prefers a specific type of presentation. Purified, based on active toxins or viruses. Up to the most recent, the mRNA one”, continues Andreoni, who is also scientific director of Simit, Italian disease society infectious and tropical. And the one with an adenoviral vector? For Andreoni, its effectiveness should not be questioned: “It represented a great achievement of medical science, demonstrating an effective and long-term immunogenic capacity. Often the response of global antibodies (humoral immunity) is evaluated, which is ‘gross’ but easily achievable, or neutralizing antibodies, more specific and indicative. For a broader vision, however, cell-mediated immunity should also be analyzed, which in viral diseases becomes the most relevant. However, these types of studies are mainly carried out for research activities , and consist in putting the vital virus in contact with the cells of an individual, highlighting their ability to block the microorganism “.
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Perspectives
“Millions of people will have received adenoviral vaccines worldwide, not just the Oxford-Astrazeneca vaccine, but the J&J vaccine as well as the Chinese and Russian versions. The ultimate goal of these vaccines is to induce long-term protection of the immune system using both antibodies and T cells, “he notes Paul Klenerman, University of Oxford, one of the lead authors of the article. And obviously we look even further: thanks to the potential of these adenoviral vector vaccines, the researchers’ goal can move towards other frontiers of medicine. “The design of new vaccines that we still desperately need for diseases such as tuberculosis, HIV, hepatitis C and cancer,” he said Burkhard Ludewig, professor at the University of Zurich and head of the Medical Research Center of the Cantonal Hospital of St. Gallen, lead author of the article.
Covid, another study confirms: mRNA vaccines prevent infection, more than 95% effective
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