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Vaccine improves survival in monkey tests.


Researchers at the U.S. National Institute of Allergy and Infectious Diseases (NIAID NIAID National Institute of Allergy and Infectious Diseases. ) reported that an experimental vaccine clearly improved the survival of monkeys after infection by SIV SIV simian immunodeficiency virus.  (simian immunodeficiency virus Simian immunodeficiency virus (SIV) is a retrovirus that is found, in numerous strains, in primates; the specific strains infecting humans are HIV-1 and HIV-2, the viruses that cause AIDS.

The origin of HIV is now generally attributed to SIV from African primates.
), a virus similar to HIV--even though it did not prevent infection, and did not much improve viral load viral load
n.
The concentration of a virus, such as HIV, in the blood.


viral load,
n a measure of the number of virus particles present in the bloodstream, expressed as copies per milliliter.
 or total T-cell count.

While the viral load and T-cell count did not predict the greater survival, something else did--measurement of memory cells (one kind of T-cells) in the first few months of infection. Memory cells make up more than half of T-cells in adults, and early in HIV HIV (Human Immunodeficiency Virus), either of two closely related retroviruses that invade T-helper lymphocytes and are responsible for AIDS. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of AIDS in the United States.  disease many of these cells are infected and eventually lost. In the monkey test, three to five times fewer of the memory cells were infected in vaccinated animals than in unvaccinated animals.

The vaccine used in this study was a simplified version of an HIV vaccine HIV vaccine AIDS As of mid-2005, there is no viable anti-HIV vaccine. See AIDS.  now in phase II human trials in the U.S. and some other countries.

Besides the possibility of a survival benefit in humans even if a vaccine fails to prevent infection, this is important for additional reasons:

* The researchers found an immune response immune response
n.
An integrated bodily response to an antigen, especially one mediated by lymphocytes and involving recognition of antigens by specific antibodies or previously sensitized lymphocytes.
 from a vaccine that did help protect the animals. A big problem in HIV vaccine research has been that while it is easy to show immune responses to HIV vaccines, it has been very hard to find "correlates of protection"--that is, responses that do any good at protecting against HIV-type viruses.

* If this result is confirmed in humans, it could give a much earlier indication of which vaccines are promising and which are not. This early information could help with another big problem in vaccine research. Since no one would deliberately infect people with HIV in order to test a vaccine, trials have to study thousands of people for years to prove that a vaccine works. Very few such studies can be done, so it is critically important to get the best candidate vaccines into these large phase III trials. An early indicator that can be measured in every patient, and is known to predict survival, would help immensely.

* The fact that the monkeys benefited even partly creates a framework for studying HIV pathogenesis (development of the disease)--and studying how vaccines might work, as well as immune-based or other new kinds of treatment for those already infected. Without the observed benefit to the animals, lots of data could still be collected, but it might be difficult or impossible to know which findings were meaningful and which were not.

For More Information

NIAID published a press release, "Monkeys Vaccinated Against SIV Survive Longer After Infection" on June 9. You can find it at http://www3.niaid.nih.gov/news/newsreleases/2006/SIVvax.htm This press release includes references to the two articles, one in Science, and the other in Journal of Experimental Medicine The Journal of Experimental Medicine is an academic journal that publishes research papers and commentaries in the biomedical area. Topics covered include immunology, inflammation, infectious disease, hematopoiesis, cancer, stem cells and vascular biology. .
COPYRIGHT 2006 John S. James
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2006, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Author:James, John S.
Publication:AIDS Treatment News
Date:Jan 1, 2006
Words:471
Previous Article:Study finds 3,000,000 years of life saved by HIV treatment in the U.S.
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