HIV/AIDS Vaccine Development

Developing an HIV/AIDS Vaccine

Developing a vaccine involves using a disease-causing agent (e.g., virus, bacterium) to stimulate the immune system to launch a protective response. Once the immune system recognizes the virus or bacterium and develops antibodies to it, vaccination (injecting a person with a vaccine) establishes immunity to the infectious disease.

A vaccine that protects people from infection is called a preventative vaccine and a vaccine that prevents disease in infected people is called a therapeutic vaccine. Sometimes, two or more vaccines are combined, such as the measles, mumps, and rubella (MMR) vaccine.

In some cases, people who have been repeatedly exposed to HIV remain HIV negative or never develop AIDS. Presumably, they have developed natural immunity (i.e., their immune system recognized HIV and their immune response successfully eliminated the virus). The fact that a person can be exposed to HIV and never develop HIV/AIDS indicates that the immune system is capable of successfully responding to HIV infection.

Studies in parts of West Africa, where both HIV-1 and HIV-2 are prevalent, have shown that people who are infected with HIV-2 may be less likely to become infected with HIV-1. In these cases, HIV-2, which is weaker than HIV-1, may be acting like a vaccine and instructing the immune system to recognize and mount an immune response to the more potent HIV-1.

Vaccine Types

There are three types of vaccine:

• Subunit vaccines are made up of parts of the virus. This is the safest type of vaccine because it does not contain infectious material.
• Killed whole-virus vaccines are whole viruses that have been inactivated so that they are no longer infectious. These vaccines often cause side effects associated with infection.
• Live vaccines are made of viruses that have been weakened so that they are much less infectious. These vaccines are the least safe because they may cause rather than prevent disease, especially in people with compromised immune systems.