Wednesday, October 12, 2011

A new drug passes the blood brain barrier to fight HIV

A new approach to cure HIV infection, which can cause AIDS, focuses on transporting a drug across the barrier that prevents molecules from entering the brain. Scientists have found a way to get two important features into a new drug: persuading the blood brain barrier (BBB) to open up and let the molecule in, and correspondingly kill the virus. Currently, one of the main issues in treating HIV infection is the fact that the virus can cross the BBB, while the drugs that are supposed to kill it, can not. The new drug adds to a series of new therapies that are in development to cure HIV.

The BBB restricts access to the brain to large molecules, and pathogens such as bacteria. However, in some cases viruses are able to travel across the barrier, wreaking havoc because we are unable to treat the brain infection. HIV is able to cross the BBB, because it is able to infect immune cells. These particular cells have the capability to get into the brain by a specialized mechanism, that allows them to pass. This is needed, because immune cells need to 'scan' the brain for possible pathogens. However, the immune system is not granted full access, which is why the brain developed its own set of immune cells, to help in combating infection.

In addition to a physical barrier, the BBB has a pump that actively transports molecules back into the blood that do not belong in the brain. Drugs are an example. By blocking the pump function in the BBB, scientists have found a way to get a drug into the brain. Because it has a secondary function as an HIV killing agent, it could prove to have an important function to fight a currently incurable feature of HIV infection.

The pump blocker disintegrates after it does its job by blocking the pump function. The secondary part, the virus killer, then becomes active to go after HIV. In addition, this technique might also work for other diseases in the brain, to which a targeted therapy is needed. Examples include brain tumours, or brain-specific diseases such as Alzheimer's.

Blood vessels in the brain are surrounded by a tight layer of cells, called endothelial cells. They form the wall of the blood vessel. Right behind this wall, on the brain side, are the astrocytes, a specialized form of cells that give support to neurons.  Also present are the microglia, that protect the cell against pathogens that somehow managed to get passed the BBB.

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