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Can Moderna Repeat COVID Success with an HIV Vacccine?

The Economist September 11th 2021, pp75-76 |Science & technology|The other pandemic|”A New Hope” “A new AIDS vaccine uses the same mRNA as some covid jabs”

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With the remarkable success of vaccines for COVID-19, most of us remain unaware of the futile 30 year effort to create an effective vaccine against HIV-1, the AIDs virus. Now a better understanding of the immune system, of how HIV docks to susceptible human cells and the new mRNA vaccine technology is raising hopes for an AIDs vaccine.

“One obstacle [to creating an effective HIV vaccine] is HIV’s genetic slipperiness. The virus has a high mutation rate, which helps it adapt to evade both natural immune systems and artificial vaccines.” Several new findings are helping efforts to potentially create an effective vaccine.

The underlying immune response mechanism, that will help with an HIV vaccine, consists of two parts. First, in a process called “somatic hypermutation…[HIV exposed B lymphocytes produce]...many slightly different versions of the antibody” These proteins are called broadly neutralizing antibodies (bnabs). Their ability to broadly react with a target viral protein makes it more difficult for a mutating virus to evade destruction. Second, the most successful B cells making these anti-HIV antibodies are then triggered to multiply. As these B cells mature they, in total, make higher levels of virus-fighting antibodies. Circulating antibodies, whether naturally occurring in response to infection or from vaccines, bind to targets on microbes, including viruses, that either tag the virus for destruction or block the virus from entering an otherwise susceptible human cell.

The HIV vaccine, made by Moderna as a mRNA vaccine, is unique in that it stimulates human cells to make excess amounts of the HIV protein known as gp120. Gp120 is the HIV surface protein that specifically binds to susceptible human cells. After successful binding of HIV via gp120, HIV invades the target cells and begins the process of replicating and destroying the host cell. Gp120 made in response to the mRNA code will be “seen” as a foreign protein and therefore stimulate the immune system to make anti-gp120 antibodies. These anti-gp120 antibodies will block HIV’s ability to dock to host cells or will tag the HIV for destruction. Unlike other previously tried HIV targets, gp120 is so essential for HIV propagation that HIV mutations that change gp120 create HIV mutants that are incapable of binding and infecting host cells.

The first human trial underway in America will report findings in 2023. If successful then trials will be staged in Rwanda and South Africa where HIV accounts for nearly ⅔ of all 38,000,000 people infected with HIV in 2020.

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