USIS Washington File - February 14, 2007
Cheryl Pellerin, USINFO Staff Writer

The National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health (NIH), is supporting the trial, which is being conducted jointly by the South African AIDS Vaccine Initiative and the HIV Vaccine Trials Network (HVTN).

"Our best hope of ending the AIDS epidemic is a safe and effective vaccine," said NIH Director Dr. Elias Zerhouni in a February 8 statement. "To achieve that goal requires the concerted effort of governments, scientists and private industry as well as participation by well-informed volunteers."

The vaccine has shown promise in smaller studies in the United States and elsewhere. The U.S. pharmaceutical firm Merck & Co. is providing the vaccine, which contains copies of only three HIV genes, not the whole virus, so it cannot infect volunteers with the disease.

It is important to note that a vaccine like this, that does not prevent infection completely, would not be a stand-alone preventive measure like the classical vaccines we have today," said Margaret Johnston, director of the Vaccine Research Program in the Division of AIDS at NIAID, in February 14 e-mail correspondence.

"Rather," she added, "it would be most effective when used with other prevention measures," such as counseling to avoid exposure to HIV and condoms.

MOVING FORWARD

In South Africa, the trial is called Phambili, which means "moving forward." Also called HVTN 503, it is a test-of-concept trial, the first such vaccine study in South Africa.

This kind of trial is designed to tell researchers whether the vaccine has the potential to protect against contracting HIV so they can decide whether to conduct a larger "efficacy," or effectiveness, trial that could make it possible for the vaccine to be licensed for public use. More than 1,800 people have received at least one injection.

In 2005, the first test-of-concept trial of the vaccine opened at sites in the United States, Canada, South America, Australia and the Caribbean - areas where a subtype of HIV called clade B predominates. That trial is ongoing.

A clade is a group of genetically related forms of HIV. Clades also are called genetic subtypes and usually have geographic distribution patterns. For example, HIV clades A and D are most common in East Africa and clade B is found in North America and Europe.

"In smaller trials," Johnston said, "it was shown that individuals who are immunized with this vaccine based on clade B have immune responses that also recognized clade C, which is the predominant clade that circulates in South Africa. The strength of the immune responses to this vaccine is higher than we have seen with previous HIV candidate vaccines."

As in the 2005 study, the main objectives of HVTN 503 are to determine whether the vaccine can prevent HIV infection or, in those who become infected, lower the amount of HIV in the blood early in the infection process, and if the clade B vaccine could also protect against the clade C subtype.

MEETING THE AIDS CHALLENGE

HIV presents several difficult and unique scientific challenges compared to other viruses for which scientists have developed preventive vaccines, Johnston said.

Within days to weeks of the initial infection, HIV inserts itself (integrates) into the DNA/genetic material of a human cell, making it virtually impossible for the immune system to recognize and eliminate all infected cells.

Second, she added, HIV is a very genetically diverse virus and because of the way it replicates, changing genetically with each replication, the immune system can't keep up with the changes and the virus escapes typical immune system surveillance mechanisms.

"The goal of a preventive vaccine," Johnston said, "is to find a way to get the immune system to recognize [certain] parts of HIV ... and to get the immune system ready to react quickly when HIV infection first occurs" to prevent or minimize the integration step.

This way, a person can avoid or delay having to take antiretroviral drugs, and virus levels are so low that a person doesn't pass the virus on to others.

INVOLVING THE COMMUNITY

Leading the trial in South Africa is Glenda Gray of the Perinatal HIV Research Unit at the University of the Witwatersrand, based at the Chris Hani Baragwanath Hospital in Soweto. Dr. James Kublin of the Fred Hutchinson Cancer Research Center in Seattle is study co-chair.

The study will recruit volunteers at five sites in South Africa - in Soweto, Cape Town, Klerksdorp, Medunsa and Durban. Gray said the study team has sought critical community endorsement of and support for the clinical trial.

"Our communities here in South Africa are faced with the burden of HIV on a daily basis," Gray said, "and the trial investigators and study team have spent years developing a rapport with the community so that together we can move forward in our quest to identify improved approaches to prevent new HIV infections."

Community members serve on advisory boards associated with sites participating in the study. Advisory board members have access to general data on vaccine immune responses and safety.

The South African Medicines Control Council, the South African Department of Agriculture and the U.S. Food and Drug Administration have reviewed the trial.

More information is available on the Web site of the HIV Vaccine Trials Network.

For additional information about U.S. and international efforts to fight the disease, see HIV/AIDS.

(USINFO is produced by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)

070214
US070202

Copyright © 2007 - US Information Agency. Reproduction of this article (other than one copy for personal reference) must be cleared through the USIA.

AEGiS is a 501(c)3, not-for-profit, tax-exempt, educational corporation. AEGiS is made possible through unrestricted grants from Boehringer Ingelheim, Bridgestone/Firestone Charitable Trust, Bristol-Myers Squibb Company, Elton John AIDS Foundation, the National Library of Medicine, Roche and Trimeris, and donations from users like you. Always watch for outdated information. This article first appeared in 2007. This material is designed to support, not replace, the relationship that exists between you and your doctor.

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 2007. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .