Clinical Research on HIV/AIDS Vaccines

IL 1National Institute of Allergy and Infectious Diseases
National Institutes of Health
January 1997
Clinical Research on HIV/AIDS Vaccines
The National Institute of Allergy and Infectious Diseases (NIAID) conducts clinical trials of
candidate vaccines to discover which might most successfully protect people from human
immunodeficiency virus (HIV) infection (preventive vaccine) or from becoming ill after they
acquire the virus (therapeutic vaccine). (Throughout this fact sheet scientific terms common to
vaccine research have been printed in bold-faced type and defined.)
Scientists have identified important immunologic targets on HIV and on infected cells. For
example, they know that the glycoprotein 120 (gp 120) on the outer coat of the virus contains the
region that attaches to cells of the host, the CD4 binding site. Scientists also know that most
neutralizing antibodies (proteins that block a virus from infecting cells) in HIV-infected people
are directed against gp120. For these reasons, vaccines based on genetically engineered HIV
envelope proteins--gp 160 and one of its cleavage products, gp 120--have been the most wellstudied to date.
More than 40 experimental HIV vaccines have been tested in humans worldwide. Vaccine
approaches in development or in clinical trials include the following:
* subunit vaccine: a piece of the outer surface of HIV, such as gp160 or gp120, produced
by genetic engineering.
* recombinant vector vaccine: a live bacterium or virus such as vaccinia (used in the
smallpox vaccine) modified to transport into the body a gene that makes one or more HIV
proteins.
* vaccine combination: for example, use of a recombinant vector vaccine to induce cellular
immune responses followed by booster shots of a subunit vaccine to stimulate antibody
production, referred to as a prime-boost strategy.
* peptide vaccine: chemically synthesized pieces of HIV proteins (peptides) known to -
stimulate HIV-specific immunity.
* virus-like particle vaccine (pseudovirion vaccine): a non-infectious HIV look-alike that _
has one or more, but not all, HIV proteins.
~ anti-idiotype vaccine: antibodies generated against antibodies to the virus. ___~ _- LO
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* plasmid DNA vaccine (nucleic acid vaccine): direct injection of genes coding for HIV
proteins.