In a new study, researchers found that an experimental HIV vaccine has reached an important milestone by eliciting antibodies that can neutralize a wide variety of HIV strains.
The new HIV vaccine was developed by scientists at Scripps Research and the nonprofit vaccine research organization IAVI.
About 35 million people worldwide have died of the immunodeficiency syndrome, AIDS, which is caused by HIV infection. About 38 million others are now living with HIV infection.
Antiviral drugs can keep HIV-infected people alive and reduce their ability to transmit the virus to others, but these drugs do not clear the infection and must be taken indefinitely.
Scientists have long recognized that a preventive vaccine, available at a low cost to uninfected people, will be needed to eliminate HIV as a major public health threat.
HIV’s rapid mutation rate and other mechanisms for evading immune attacks have made it an extremely difficult target for vaccine designers.
But the test developed by the team confirms that vaccination can elicit the kinds of antibodies that are needed to provide broad protection against HIV.
The test, in rabbits, showed that “broadly neutralizing” antibodies, or bnAbs, targeted at least two critical sites on the virus.
These bnAbs, as vaccine experts call them, can neutralize multiple HIV strains because they bind to critical sites on the virus that do not vary much from strain to strain.
People who are infected with HIV sometimes produce bnAbs as part of their antibody response, but infrequently and usually after the infection has been long established.
Researchers widely assume that a vaccine must elicit bnAbs to multiple sites on HIV if it is to provide robust protection against this ever-changing virus.
The chief challenge for HIV vaccine designers has been to find ways to stimulate the immune system—in most or all individuals—into making bnAbs that hit multiple vulnerable sites on the virus, in order to protect against a high proportion of HIV strains.
The promising results suggest that researchers are one step closer to developing an effective HIV vaccine—a major goal of medical science ever since the virus was identified in 1983.
The finding is an important demonstration that vaccination against HIV if done in the right way, can achieve the goal of inducing bnAbs to multiple sites on the virus.
The team of scientists are continuing to test and improve their vaccine strategy in small animal models and hope eventually to test it in monkeys and then humans.
One author of the study is Richard Wyatt, Ph.D., a professor in the Department of Immunology and Microbiology at Scripps Research.
The study is published in Immunity.
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