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Antibody cocktail may provide more help for HIV vaccine
Antibody cocktail may provide more help for HIV vaccine. An HIV-preventing antibody infusion that is being tested does not seem to stop most infections, but its success against certain strains of the virus shows that the researchers are in the right direction.
This is the inspiration from a clinical trial that tested the antibody, called VRC01, in 2,700 people at high risk of HIV infection.
Researchers have found that infusing the antibody every two months does not reduce the overall risk of HIV infection in patients.
But this strategy does prevent specific HIV strains that are susceptible to VRC01 antibodies. In a 20-month trial, it reduced people’s risk of contracting these viruses by 75%.
Lead researcher Dr. Lawrence-Corey described this result as an “important proof of concept” that the antibody approach can work. However, HIV is a terrible enemy, and a single antibody is not enough, explains Corey, a virologist and professor at the Fred Hutchinson Cancer Research Center in Seattle.
He likened this situation to HIV treatment. In the 1980s, the drug AZT was found to be effective in blocking HIV, but over time, it has little effect on rapidly mutating viruses. Subsequently, the researchers discovered that a powerful drug combination or “cocktail” can inhibit HIV for a long time. These drugs are not a cure, but they turn HIV from a mortal situation into a manageable chronic disease.
In fact, Corey said, researchers have suspected that for antibodies to effectively prevent HIV infection, a cocktail-like approach is necessary.
He said that current trials show that VRC01 infusion is safe to perform, and it provides detailed information about the effects of antibodies on different HIV strains.
Corey said trials to test antibody cocktails to prevent HIV are already underway.
Dr. Rajesh Gandhi is an infectious disease specialist at Massachusetts General Hospital in Boston and the chairman of the HIV Medical Association. He described the trial as a “groundbreaking study” in support of ongoing antibody cocktail research.
“Just like multiple drugs are needed to treat HIV, more than one antibody may be needed to prevent HIV,” said Gandhi, who did not participate in the study.
Currently, people at high risk of using HIV through sex or injecting drugs can greatly reduce this risk through a daily medication regimen called PrEP.
“So the question may be. If we have PrEP, why do we need antibodies?” Gandhi said. He explained that one of the reasons is that daily pills may be difficult to manage over time, and a long-acting alternative can make prevention easier to obtain.
In this test, antibody infusions are given every eight weeks. But these intervals may be extended, Gandhi said.
The study published in the New England Journal of Medicine on March 18 involved two. One recruits men and transgender people and men in the Americas and Europe; the other involves women in sub-Saharan Africa.
Volunteers were randomly assigned to VRC01 infusion every eight weeks for 20 months, or a placebo infusion. Antibodies are produced by the immune system to recognize and neutralize foreign invaders, such as viruses.
VRC01 is a broad-spectrum neutralizing antibody, or bNab-meaning it can prevent a series of HIV strains from infecting human cells. It is able to do this because it can recognize specific HIV proteins, which tend to remain unchanged even when the virus mutates. VRC01 was first discovered in the blood of an HIV-positive patient. Corey said it is unclear why only certain people with HIV develop bNabs.
Scientists can create laboratory-engineered versions of antibodies and produce them in large quantities, which is what they did for this experiment. Unfortunately, the lethality of VRC01 on the HIV strains in the test community is not as strong as the researchers estimated. The antibody completely blocked about 30% of the strains, but was not strong enough against 70% of the strains. If antibody cocktails prove to be effective, a big question is whether they will be superior to daily pills. Both Corey and Gandhi said that they may try to reduce the frequency of use as much as possible-for example, twice a year.
They say the same is true in less developed countries. Especially for women, Corey said that treatment in the clinic can be less stigma than taking medicine every day.
Antibody infusion is different from vaccine. The vaccine trains the immune system to recognize specific viruses and installs its own response should the intruder be encountered.
But Corey and Gandhi say that findings like these can inform ongoing HIV vaccine development, for example, indicating the level of antibody neutralization required to prevent infection.
(source:internet, reference only)