Hiv Vaccine Testing in Africa

Michelle Raess

The Human Body

Dr. Shirley M. Bartido

HIV Vaccine Testing in Africa

The United Nations estimates that 5.8 million people per year become infected with the immunodeficiency virus (HIV). Ninety percent of these infections occur in sub- Saharan Africa, where infected persons do not have access to antiviral therapy. Approximately 2.4 million Africans died of AIDS in 2002, and 3.5 million occurred in the region. Where in the United States $12,000-$15,000 is usually spent on treating an HIV-infected person per year, only $6 is spent annually per person in Uganda.

The only method presently available to prevent the spread of HIV in less-developed countries is counseling against the behaviors that increase the risk of infection. It's obvious that a vaccine would be more beneficial to these countries. There are several HIV vaccines in various stages of development that need to be tested to see their effectiveness. It seems reasonable to carry out such trials in less-developed countries.

Since 1984, when HIV was identified as the cause of AIDS, the development of a HIV vaccine has been a goal for the science world. Researchers have many different strategies that may lead to an effective HIV vaccine. Scientists take small parts of the HIV virus and change them in a laboratory to create synthetic copies. The experimental vaccines do not use whole or live HIV. The vaccines cannot cause HIV or AIDS. The vaccines being tested should produce either antibodies or cytotoxic T cells to fight the infection.

There are several types of experimental HIV vaccines. A peptide vaccine is made of tiny pieces of proteins from the HIV virus. The recombinant subunit protein vaccine is made of bigger pieces of proteins from the HIV virus. Examples of a recombinant subunit protein are gp120, gp140, or gp160 produced by genetic engineering. The DNA vaccine uses copies of a small number of HIV genes which are inserted into pieces of DNA called plasmids. The HIV genes will produce proteins very similar to the ones from real HIV. A live vector vaccine is made of HIV genes that have been taken out of the virus and altered. The genes are inserted into another vector, which carries them into the body's cells. The genes in turn produce proteins that are normally found on the surface of the HIV virus. This type of vaccine most resembles the HIV virus but isn't harmful. Many vaccines that are used today, like the smallpox vaccine, use this method. A vaccine combination uses any two vaccines, one after another, to create a stronger immune response. It's often referred to as "prime-boost strategy." Lastly, a virus-like vaccine (pseudovirion vaccine) is a non-infectious HIV look-alike that has one or more, but not all HIV proteins.

Although there are several types of HIV vaccines, scientists are still learning about how the vaccines might work to prevent HIV infection. An HIV vaccine may be totally successful in preventing infection, known as "sterilizing immunity." Sterilizing immunity may be possible in 100% of the population, or maybe only in certain groups. In another scenario, a preventive vaccine may not prevent primary infection, but decrease the possibility of HIV transmission from an infected person to another person. Yet another possibility is that a vaccine may slow the process of infection, so that even if a person becomes HIV infected, the vaccine helps the vaccinated individual remain healthier longer.

After an experimental vaccine has been tested in laboratory and animal studies to determine its safety and immune response, it must successfully complete three stages of testing in people before it can be licensed. The three stages of Vaccine Testing in Humans are:

I.) 20-100 participants; Primary Rationale- safety

II.) Hundreds of participants; Primary Rationale- safety & immunogenicity

III.) Thousands of participants; Primary Rationale- safety & effectiveness

A Phase I trial is the first setting where an experimental HIV vaccine is given to people. The trial would include about 20-100 HIV-negative volunteers. This trial primarily seeks information on safety, looking for any vaccine-related side effects. This is done by