Monkey Trials Offer New Hope for HIV Vaccine

MONDAY, May 11, 2020 (HealthDay News) — An experimental vaccine seems to give monkeys extended protection from an HIV-like infection — by “waking up” an arm of the immune system that vaccines normally do not.

Experts cautioned that animal research often does not pan out in humans. The decades of work toward an HIV vaccine has been a clear example. But, researchers said, this vaccine works differently, targeting two “arms” of the immune system.

And they think the work potentially has broader lessons for vaccines being developed for other viruses, including SARS-CoV-2, the virus that causes COVID-19.

“The big question will be, does this translate to humans?” said Bali Pulendran, one of the senior researchers on the study and a professor at Stanford University School of Medicine, in California.

Scientists have been trying to develop an HIV vaccine since the 1980s, with glimmers of hope followed by disappointment. The latest example is a trial in South Africa that was stopped in February, because a once-promising vaccine simply was not working.

HIV, the AIDS-causing virus, “is a very tough nut to crack, for many reasons,” Pulendran said.

For one, it attacks the immune system’s T cells, disabling the very cells needed to launch an aggressive defense. The virus also has various ways of hiding itself from detection by the immune system. For example, Pulendran explained, HIV is “shrouded in a canopy of carbohydrates,” making it hard for antibodies to recognize the virus as the enemy.

Antibodies are specialized proteins produced by the immune system that recognize foreign invaders, latch onto them and neutralize them.

Traditional vaccines work by stimulating antibody production.

But, Pulendran said, it is difficult to induce and maintain a sufficiently high level of neutralizing antibodies against HIV.

So he and his colleagues designed a regimen that stimulates not only antibody production, but cellular immunity. Cellular immunity involves the marshaling of “killer” T cells that patrol body tissues for signs of viruses, then destroy cells harboring them.

“We wanted to explore using the full armamentarium of the immune system,” Pulendran said.