AIDS Vaccines 101

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Resource: AIDS Vaccines 101HDN, IAVI & AVAC*****************[Mods note: In partnership with the International AIDS Vaccine Initiative(IAVI) and the AIDS Vaccine Advocacy Coalition (AVAC), the Health & Development Networks (HDN) is pleased to introduce the first posting fromthe on-line mini-series to help inform community advocacy on "TranslatingNeed into Reality - Accelerating the Search for an AIDS Vaccine" .]*******************What types of AIDS vaccines are being developed?**Right now, there is no vaccine to protect against HIV/AIDS, but there aremany experimental vaccines in various stages of testing.The vaccines being developed against HIV fall into two possible categories:therapeutic and preventive HIV vaccines.**What is a therapeutic HIV vaccine?**A therapeutic HIV vaccine would work by starting an immune response after aperson has been infected with HIV, and therefore would be potentially usefulas a form of treatment. As with preventive vaccines, there are no currentlyavailable therapeutic HIV vaccines. There are a few therapeutic vaccinescurrently being tested in humans, however, experience in their developmentis limited even for other diseases where effective preventive vaccines arealready in widespread use (e.g., polio, measles etc).**What is a preventive AIDS vaccine?**A preventive vaccine is a substance that is introduced into the body toprevent infection or to control disease due to a certain disease-causingorganism, such as a virus, bacteria or parasite. The vaccine 'teaches' thebody how to defend itself by creating an immune response. Preventivevaccines are intended for people who have not yet been infected with theparticular organism.Preventive vaccines being tested in humans will hopefully one day protectpeople from HIV infection. Researchers have many different strategies that may lead to effectivepreventive HIV vaccines. Scientists take small parts of HIV particles or itsgenetic make-up and alter them in a laboratory to create synthetic copies toput in trial vaccines. Because they mimic small pieces of HIV's make-up, thehope is that candidate vaccines will produce either antibody- orcell-mediated immunity (e.g., cytotoxic T lymphocytes or CTLs) againstpossible real exposure to the virus in the future.THE EXPERIMENTAL VACCINES BEING TESTED DO NOT USE WHOLE, KILLED, OR LIVEHIV, AND SO THEY CANNOT CAUSE HIV INFECTION OR AIDS.**What constitutes preventive HIV vaccines?**Many of the vaccines developed using the strategies outlined below are beingtested as possible preventive vaccines.* Peptide vaccines: Made of tiny pieces of proteins from HIV virus.* Recombinant subunit protein vaccine: This uses genetically engineeredcopies of proteins that occur on the surface of the HIV viral particle.Examples of such proteins are gp120, gp140, or gp160.* Viral vector: This strategy uses a weakened virus unrelated to HIV (egvaccinia, adenovirus, canarypox) to carry genes encoding HIV proteins. Theweakened viral vector carries them into the body's cells. The genes in turnproduce proteins that are normally found on the surface of HIV.* DNA vaccine: This uses copies of a small number of HIV genes, which areinserted into pieces of circular DNA called plasmids. Similar to viralvector vaccines, the hope is that once introduced into a subject's body, theHIV-derived genes will produce proteins very similar to the ones from realHIV, stimulating an effective immune reaction.* Vaccine combination: This strategy uses combinations of two vaccines, oneafter the other, to create a stronger immune response. Often referred to as"prime-boost strategy". Combinations that have been tested include DNAvaccines with viral vector vaccines, and recombinant subunit proteinvaccines with viral vector vaccines.**Vaccines currently in large scale trials**Vaccine development is a lengthy process of testing ideas and candidateswith the goal of identifying a safe, effective vaccine that can be reliablyand affordably produced and distributed to all who need it. Like otherpharmaceutical products, HIV vaccine trials generally follow a standardthree-step pattern, with each answering a different question:* Phase I safety trials of AIDS vaccines ask: Is the vaccine safe in a smallgroup of HIV-uninfected people? * Phase II AIDS vaccine trials ask: Is this vaccine safe and does itstimulate an immune response among HIV-uninfected people?* Only then do Phase III trials, also called efficacy trials, assess whetherthe vaccine provides protection to at-risk people against subsequent HIVinfectionTrials typically include increasing numbers of people as each phase isreached, culminating in thousands of people usually participating in anefficacy trial.Currently there are a number of phase I and II trials testing safety andimmunogenicity of potential HIV vaccine products. There are also two largertrials of interest underway. A Phase III trial in populations at risk forHIV is testing the efficacy of ALVAC vCP1521 and the AIDVAX B/E vaccines.The trial is occurring at multiple sites in Thailand and has enrolled 16,000participants. Another vaccine that seems to show potential in trials so faris the adenovirus vector vaccine, which is now in phase IIb testing.**Other resources**More information about HIV vaccines and current research is available fromthe National Institute of Allergy and Infectious Diseases (NIAID), theInternational AIDS Vaccine Initiative (IAVI), the HIV Vaccine Trials Network(HVTN) or the Vaccine Research Center (VRC) listed in links below:VAX Primer: Understanding viral vectors. Why use viral vectors for AIDSvaccines? <http://www.iavireport.org/vax/primers/vaxprimer10.asp>http://www.iavireport.org/vax/primers/vaxprimer10.aspVAX Primer: Understanding vaccine trials. How are AIDS vaccines tested?<http://www.iavireport.org/vax/primers/vaxprimer05.asp>http://www.iavireport.org/vax/primers/vaxprimer05.aspVax Primer: Understanding vaccine development. How are vaccines developed?<http://www.iavireport.org/vax/primers/vaxprimer07.asp>http://www.iavireport.org/vax/primers/vaxprimer07.aspVax Primer: Understanding vaccine development. What information can clinicalresearch studies provide? <http://www.iavireport.org/vax/primers/vaxprimer13.asp>http://www.iavireport.org/vax/primers/vaxprimer13.aspAIDS Vaccine Handbook<http://www.avac.org/primer2.htm> http://www.avac.org/primer2.htmThe Global HIV/AIDS Vaccine Enterprise: Scientific Strategic Plan. <http://medicine.plosjournals.org/perlserv?request=get-document & doi=10.1371/journal.pmed.0020025>http://medicine.plosjournals.org/perlserv?request=get-document & doi=10.1371/journal.pmed.0020025Center for HIV-AIDS Vaccine Immunology (CHAVI)<http://www.chavi.org/> http://www.chavi.orgWHO-UNAIDS HIV Vaccine Initiative<http://www.who.int/vaccine_research/diseases/hiv/en/>http://www.who.int/vaccine_research/diseases/hiv/en/Project Inform: HIV Vaccines and Your Immune System<http://www.projectinform.org/fs/vaccines.html>http://www.projectinform.org/fs/vaccines.htmlNIAID Fact Sheet: Clinical Research on HIV Vaccines.<http://www.niaid.nih.gov/factsheets/clinrsch.htm>http://www.niaid.nih.gov/factsheets/clinrsch.htmVaccine Research Center<http://www.vrc.nih.gov/VRC/> http://www.vrc.nih.gov/VRC/AIDSinfo<http://aidsinfo.nih.gov/vaccines/Default.aspx?MenuItem=Vaccines>http://aidsinfo.nih.gov/vaccines/Default.aspx?MenuItem=VaccinesHIV Vaccine Trials Network<http://www.hvtn.org/> http://www.hvtn.org---------

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