Human Immunodeficiency Virus 1 (HIV) is the viral infection which leads to Acquired Immune Deficiency Syndrome (AIDS). Vaccines are important tools for combating infectious diseases, but as of 2010 there is no available vaccine to combat the HIV infection and resulting AIDS disease. Tools--including educational programs and use of condoms--can be effective preventative measures against HIV/AIDS.
Prevention
Vaccines to prevent HIV infections would need to stimulate immune responses at the site of infection by priming them to recognize HIV and prevent the virus from establishing itself in the body. As HIV is most frequently transmitted by sexual intercourse, such vaccines may need to specifically target immune responses at vaginal, penile and anal sites of infection. However, as these sites of infection differ in their immunological makeup, these types of vaccines would need to be effective at each different site. In addition, other types of vaccines might be necessary to combat HIV infection that occurs via blood transfusion or injection drug use.
Reduce HIV Spread and Slow Progression to AIDS
Vaccines designed to reduce the impact of existing infections and slow disease progression might be different from those which aim to prevent infection. HIV infects virtually all types of white blood cells, but T helper (CD4) cells are the cell type most frequently infected with HIV. HIV infection results in gradual, but marked, reductions in numbers of T helper cells; these reductions are associated with opportunistic infections and disease progression to AIDS.
Vaccines which slow progression to AIDS would need to limit the ability of the virus to infect new T helper cells and other white blood cell types. Developing such vaccines would be very valuable, as those already infected with HIV could be helped. These vaccine would need to prime immune responses to destroy HIV-infected cells whenever and wherever they are encountered in the body, and would likely involve targeting the vaccine to a variety of immune responses.
Challenges
Effective vaccines could serve to prevent initial HIV infection, prevent spread of infection and slow progression to AIDS. Some HIV vaccine trial results from a Thai study, published in 2009 in "The New England Journal of Medicine," showed a 31 percent reduction in risk of infection. While this reduction is promising, a highly effective vaccine to prevent HIV infection remains elusive as of June 2010.
Developing an effective HIV/AIDS vaccine remains particularly difficult because the most effective types of immune responses for combating infection and disease are not evident. As such, it remains unclear which specific responses should be targeted by a vaccine to limit the risk of HIV infection and progression of infection to AIDS.
