What is ADE?
ADE means ‘antibody-dependent enhancenment’ is a rare phenomenon affecting some types of viruses and in Italian it means antibody-dependent enhancement. Maybe we’ve heard about it lately and got scared by hearing this weird acronym, but what is it? Do we need to worry about it?
A rare phenomenon
Fortunately, the ADE phenomenon does not concern all viruses but has only been observed in some rare cases, a known example is that of Dengue. Dengue is a virus that causes various types of disease in humans, from Dengue fever to hemorrhagic fever with an often fatal outcome.
The phenomenon of ADE is observed in healed subjects who develop a much more severe disease months or years after the primary infection in case of reinfection. The explanation lies in the fact that there are 4 versions – serotypes – of Dengue and if a subject becomes infected with two different versions it can trigger an incomplete and suboptimal immune response.
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By incomplete immune response we mean not only a low production of antibodies but also the absence of neutralizing antibodies which effectively neutralize the virus and limit the infection.
ADE is also characterized by the presence of special defective antibodies that facilitate the entry of the virus into cells, a real “pass” for the virus in our body.
It should also be remembered that the ADE phenomenon can occur not only following a reinfection, but also in the case of a suboptimal vaccination (by suboptimal vaccination we mean a vaccine unable to trigger a strong immune response and few or no neutralizing antibodies. , ed).
ADE e Sars-CoV2
To date, there are no data or evidence that the Sars-CoV2 virus can generate the phenomenon of ADE neither post reinfection nor post vaccination. After billions of vaccine administrations and thousands of cases of reinfection the ADE phenomenon would have emerged and described.
Fortunately, those vaccinated or cured in case of reinfection get sick in a milder way.
But let’s try to understand why it makes little sense to talk about ADE for Sars-CoV2.
We understand that ADE can occur when the level of neutralizing antibodies is very low and the immune response is incomplete.
Thanks to the very first studies done on neutralizing antibodies, it was immediately noticed how Sars-CoV2 is able to trigger a strong immune response and an abundant production of neutralizing antibodies against the Spike protein, the famous anti Spike IgG.
Furthermore, despite the presence of Sars-CoV2 variants, our immune system responds to various infections by triggering an excellent immune response.
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So why are we talking about ADE for Sars-CoV2?
At the beginning of the pandemic when the first laboratories began working on a potential vaccine for Sars-CoV2, one of the concerns was that the vaccine could behave like those designed a few years earlier against Sars1, the “bad cousin” of Sars-CoV2.
During the preliminary studies carried out on the anti Sars1 vaccine the phenomenon of ADE was observed in macaques and there is evidence that the subjects healed and reinfected with Sars1 developed ADE therefore more severe symptoms.
The similarity between the two viruses prompted researchers to pay particular attention to the ADE phenomenon when designing the anti Sars-CoV2 vaccine, which has been shown to be able to trigger a strong immune response in total safety.
The very rare side effects observed following the administration of vaccines have a completely different explanation and origin and cannot be linked to ADE.
TAKE HOME MESSAGES:
1) The ADE phenomenon rarely occurs for some viruses and occurs when in the event of reinfection the immune system enhances the effect of the virus
2) For Sars-CoV2 the phenomenon has NEVER been observed despite billions of vaccine administrations and reinfections
3) The very rare side effects of the vaccine are not related to the ADE phenomenon
REF:
https://www.nejm.org/doi/full/10.1056/NEJMc2108120#:~:text=Reinfections%20had%2090%25%20lower%20odds, lead%20to%20acute%20care%20hospitalization
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00298-4/fulltext
https://www.salute.gov.it/portale/nuovocoronavirus/archivioFakeNewsNuovoCoronavirus.jsp?lingua=italiano&tagId=881
https://insight.jci.org/articles/view/123158