Scientists develop vaccine that may hinder HIV virus

Monday October 19 2015

Scores of HIV vaccines have been developed in

Scores of HIV vaccines have been developed in the past but scientists believe they may have made a breakthrough with the latest “full-length single chain” vaccine.  

By Agencies

Anew Aids vaccine trial is about to begin in the US, and this one is a little different — the vaccine has been developed over the past 15 years by Robert Gallo.
Dr Gallo co-discovered HIV as the cause of Aids, then went on to pioneer the blood test that detects the virus.
Now, 31 years later, his team at the University Of Maryland School Of Medicine’s Institute of Human Virology is beginning human trials this month on a potentially revolutionary HIV vaccine.

While many other vaccines target specific strains of HIV, the treatment that the institute has developed takes a different approach. It attempts to block the virus before it can invade the body’s T-cells (a central component of the body’s immune system) and mutate, at which point it becomes invisible to the body’s immune system and much harder to treat. Should it prove successful, this vaccine would offer protection against a large class of viruses collectively known as “HIV-1.”
The phase I trial will involve 60 volunteers and will test the safety and immune responses of the vaccine, so we won’t know for a while whether it will be more effective than the other more than 100 Aids vaccines that have been tried over the past 30 years.

Though there have been some promising vaccine candidates in the past, the challenge with HIV/Aids is that HIV directly infects white blood cells called T-cells, so it literally turns our immune system against us.
That means that once the virus has entered a T-cell, it’s invisible to the immune system.
The only chance we have to prevent infection, is to trigger antibodies against the HIV surface proteins before that happens — something that has been equally difficult because the retrovirus can regularly change its viral envelope to hide particular surface proteins.

But Gallo and his team think they may have found a moment when the HIV surface protein, known as gp120, is vulnerable to detection: the moment the virus binds with our bodies’ T-cells.
When HIV infects a patient, it first links to the CD4 receptor on the white blood cell. It then transitions, exposing hidden parts of its viral envelope, which allow it to bind to a second receptor called CCR5. Once HIV is attached to both these T-cell receptors, it can successfully infect the immune cell. And at that point, it is too late to do anything to stop it.

Known as the “full-length single chain” vaccine, Gallo’s vaccine contains the HIV surface protein gp120, engineered to link to a few portions of the CD4 receptor.
That goal is to trigger antibodies against gp120 when it’s already attached to CD4 and is in its vulnerable transitional state, effectively stopping it from attaching to the second CCR5 attachment.
Gallo said the team had taken so long to get to this point because it had been extremely thorough in its testing on monkeys, and then had to scramble for funding to develop the drug into a human-grade vaccine. &