June 16, 2021

Why is there still no vaccine against HIV when a year was enough to develop several against Covid-19?

Forty years after the first AIDS alert on June 5, 1981, there is still no vaccine against AIDS. There is no cure for AIDS: people living with HIV are forced to take treatment for life. Conversely, the researchers managed an exceptional race against time against the coronavirus. In less than a year, several vaccines against Covid-19 have been authorized. How to explain such a discrepancy?

HIV and coronavirus are in fact two very different viruses, explains Christine Rouzioux, professor emeritus in virology at the René-Descartes Faculty of Medicine (Necker Hospital), member of the National Academy of Medicine and of the National Academy of Pharmacy .

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Can you remember what HIV is? How does this virus work in the body?

HIV (human immunodeficiency virus) is a virus that infects cells of the immune system – lymphocytes. Its particularity is to integrate its genetic material into the chromosome of the cells it infects. HIV is a lentivirus which induces a slow breakdown of the immune system and gradually leads to the disease AIDS (acquired immunodeficiency syndrome). The body is then vulnerable to multiple opportunistic infections (toxoplasmosis, pneumocystosis, cryptococcosis, etc.).

As lymphocytes are cells that play an extremely important role in the immune system, they are always active. However, as soon as they are active, they produce the virus. Replication of the virus is therefore continuous.

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Antiretroviral treatments and their combination in triple therapy only make it possible to block the multiplication of the virus. These treatments – which must be taken for life – prevent the infection from progressing to AIDS but do not eliminate the infected cells and therefore eradicate the virus. Infected lymphocytes go into a dormant state and are not recognized as infected, so they cannot be eliminated. This is the major obstacle of this infection. It is also an obstacle to therapeutic vaccination.

This is the reason why there is, to date, no vaccine against AIDS?

This virus continually thwarts immune responses, it bypasses them. All of the vaccine approaches that have been tested have so far failed to make an effective vaccine, including adenovirus vaccines (which use a live virus, but rendered harmless, to carry part of a DNA’s DNA. another virus, in this case HIV, in cells to trigger an immune response).

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