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December 1, 2004

Essentially "a custom-made vaccine for each patient," French vaccine shows promise in preliminary study that demonstrates promise in suppressing AIDS virus

Topics: Medicine

In what is certainly not new technology, French researchers have used patients' own dendritic cells to suppress the HIV virus, one of the possible applications for cellular immunity. The dendritic cells essentially end-up "delivering the message that these are bad guys" to the lymph nodes. It's not a new idea but it's damned good science on the part of the researchers:

French researchers reported Sunday that an AIDS vaccine designed to treat the disease, rather than prevent it, has scored an initial success by suppressing the virus for up to a year among a small group of patients who tried it.

Although the technique is cumbersome and costly, the experiment published in an online version of the British journal Nature Medicine is being touted as "the first demonstration of an efficient therapeutic vaccine against AIDS."

The vaccine was tested in Brazil on 18 volunteers who were already infected with HIV, the virus that causes AIDS, but who were not yet taking any antiviral drugs. After four months, the level of HIV in their bloodstreams had been reduced an average of 80 percent.

By the end of one year, eight patients in the group had maintained a 90 percent reduction in virus particles in their bloodstream. Four of those patients had virus levels so low that they were comparable to so-called "long-term non-progressors," a rare cohort of people infected with HIV who never seem to get sick.

Unlike a conventional vaccine, this one cannot block infection from occurring. However, if the French technique could be perfected, it has the potential to keep some HIV-infected patients healthy without their having to take the three-drug "cocktails" of toxic antiviral drugs.

Instead, a series of injections, perhaps once a year, would keep their chronic infections in check...

.......... To make a dose of vaccine, the French doctors extract from each HIV-infected patient a sample of dendritic cells -- starfish-shaped white blood cells that play a special role in the human immune system. They also take a sample of the virus from the infected blood of each patient.

In the laboratory, they separately grow uninfected dendritic cells and a batch of the virus itself. The virus is eventually killed and mixed in with the dendritic cells, whose special function then becomes vital.

The dendritic cells consume the virus, breaking it into pieces and displaying the parts on their surfaces like grisly trophies.

Doctors then inject the dendritic cells back into each patient.

Lymph nodes receive the message

Inside the body, the dendritic cells migrate to the lymph nodes, carrying their message of an invading microbe to resting banks of "killer" white blood cells. The broken bits of HIV on the dendritic cell's surface help to program these killer cells to recognize the virus -- like bloodhounds given a scent to chase. Once activated, they will seek out and destroy any cell in the human body that is infected by HIV.

It is a system of "cellular immunity" that the body routinely uses to protect itself. The AIDS virus, for reasons not fully understood, has managed to hijack the process. Dendritic cells are, in fact, one of the favored targets of living HIV, and once it ferries HIV to the lymph nodes, it then infects other white blood cells, making more copies of itself, and eventually depleting the cells.  Read More...

Blog.bioethics.net has comments on the Nature article (referred to in the above SFChronicle article)
For a nice lay review on how cancer vaccines and in general, vaccines such as dendritic cell vaccines that can treat a disease rather than just confer immunity for future exposure, go HERE...

Update: California Yankee has a post today on reports that  India will begin human trials of a new vaccine against the virus in January. He writest that human trials of vaccines against different strains of the virus are already being conducted in the United States, Europe, Africa and South America. The Indian trial will focus on sub-type C of the virus, the most common in the country.
From his post it appears that the approach being used in the HIV vaccine trials in India and elsewhere that are mentioned in article is that of immunization rather than treatment such as is the case of a dendritic-cell vaccine.

Posted by Hyscience at December 1, 2004 1:32 PM



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