HIV vaccine

An HIV vaccine may have the purpose of protecting individuals who do not have HIV from being infected with the virus (a preventive vaccine), or treating an HIV-infected person (a therapeutic vaccine). There are two approaches to an HIV vaccine: an active vaccination approach in which a vaccine aims to induce an immune response against HIV; and a passive vaccination approach in which preformed antibodies against HIV are administered. An HIV vaccine may have the purpose of protecting individuals who do not have HIV from being infected with the virus (a preventive vaccine), or treating an HIV-infected person (a therapeutic vaccine). There are two approaches to an HIV vaccine: an active vaccination approach in which a vaccine aims to induce an immune response against HIV; and a passive vaccination approach in which preformed antibodies against HIV are administered. Currently, there is no licensed HIV vaccine on the market, but multiple research projects are trying to find an effective vaccine. There is evidence from humans that a vaccine may be possible. Some, but certainly not all, HIV-infected individuals naturally produce broadly neutralizing antibodies which keep the virus suppressed and these people remain asymptomatic for decades. Potential broadly neutralizing antibodies have been cloned in the laboratory (monoclonal antibodies) and are being tested in passive vaccination clinical trials. Many trials have shown no efficacy but thus far, one HIV vaccine regimen, RV 144, has been shown to prevent HIV in some individuals in Thailand. The urgency of the search for a vaccine against HIV stems from the AIDS-related death toll of over 35 million people since 1981. In 2002, AIDS became the primary cause of death due to an infectious agent in Africa. Alternative medical treatments to a vaccine exist. For the treatment of HIV-infected individuals, Highly Active Antiretroviral Therapy (HAART) medication has been demonstrated to provide many benefits to HIV-infected individuals, including improved health, increased lifespan, control of viremia, and prevention of transmission to babies and partners. HAART must be taken lifelong without interruption to be effective, and cannot cure HIV. Options for the prevention of HIV infection in HIV-uninfected individuals include safer sex (for example abstinence, partner reduction and condom use), antiretroviral strategies (pre-exposure prophylaxis and post-exposure prophylaxis) and medical male circumcision. Vaccination has proved a powerful public health tool in vanquishing other diseases, and an HIV vaccine is generally considered as the most likely, and perhaps the only way by which the HIV pandemic can be halted. However, HIV-1 remains a challenging target for a vaccine. In 1984, after the confirmation of the etiological agent of AIDS by scientists at the U.S. National Institutes of Health and the Pasteur Institute, the United States Health and Human Services Secretary Margaret Heckler declared that a vaccine would be available within two years. However, the classical vaccination approach that is successful in the control of other viral diseases - priming the adaptive immunity to recognize the viral envelope proteins - have failed to work against HIV. Many factors make the development of an HIV vaccine different to other classic vaccines: The epitopes of the viral envelope are more variable than those of many other viruses. Furthermore, the functionally important epitopes of the gp120 protein are masked by glycosylation, trimerisation and receptor-induced conformational changes making it difficult to block with neutralizing antibodies.