Read this article in: عربي
HIV/AIDS: Milestones in vaccine research
Breakthrough in AIDS vaccine research
NAIROBI/JOHANNESBURG, 13 May 2011 (IRIN) - News of an experimental vaccine that successfully protected more than 50 percent of macaques from the monkey equivalent of HIV will give a much-needed boost to vaccine development, which has seen little progress of late.
The researchers gave 24 healthy macaques a vaccine containing a genetically modified form of the virus, called the rhesus cytomegalovirus (CMV).
The vaccine was designed to produce antigens that attack Simian Immunodeficiency Virus (SIV), the monkey equivalent of HIV. It protected 13 of the 24 macaques in the study, and remained effective for up to one year in 12 of the vaccinated monkeys.
The findings could be useful in understanding how to develop a vaccine that could protect humans from HIV and have been published in the science journal, Nature
False leads and disappointing outcomes mark the long road to developing an effective HIV vaccine. IRIN/PlusNews has compiled a list of milestones in AIDS vaccine research:
- The first clinical trial of an HIV vaccine in the United States. A Phase I safety trial enrols 138 HIV-negative volunteers and finds that the candidate vaccine has no serious side effects.
Since then, more than 50 vaccines have been tested, involving more than 10,000 human volunteers.
- US President Bill Clinton sets a goal of developing a vaccine for HIV within 10 years. "It is no longer a question of whether we can develop an AIDS vaccine; it is simply a question of when. And it cannot come a day too soon," he is reported as saying.
- researchers start recognizing that vaccines which help the body generate antibodies against HIV, the most commonly used method, will not work because the HI virus mutates too rapidly.
Research shifts to cellular immunity, in which vaccines that stimulate one particular arm of the immune system delay or prevent HIV progression and reduce transmission, even if they don't block infection.
- AIDSVAX - an experimental preventive HIV vaccine - had no noticeable effect on HIV infection rates in the 2,546 intravenous drug users in Bangkok, Thailand, who participate in the study, nor does it slow the disease's progress in volunteers who take the vaccine and later contract HIV.
- Pharmaceutical company Merck announces
that it is ending the enrolment and vaccination of volunteers in a study funded by the US National Institutes of Health (NIH) after the vaccine fails to lower the risk of HIV infection or reduce the severity of infection in volunteers who become HIV-positive during the trial.
The data comes from Phase II clinical trials in North and South America, the Caribbean and Australia, which began in December 2004. The volunteers were mostly homosexual men and sex workers considered at high risk of contracting HIV.
After 13 months, 24 cases of HIV are found in 741 people who received at least one dose of the vaccine, compared to 21 infections in the 762 volunteers who received a placebo. The vaccine also fails to reduce the amount of virus in the blood of those who become infected.
A second phase II trial of the vaccine in South Africa
is also discontinued.
- A six-year clinical trial
in Thailand yields the first evidence that an AIDS vaccine could provide some protection against HIV infection. The rate of HIV infection is 31 percent lower in trial participants given the vaccine than in those who get a placebo.
Researchers later question
the statistical significance of some of the study's findings, but experts
are confident that the RV 144 vaccine - a combination of two vaccines - could potentially be developed into a functional vaccine.
- Two powerful new
antibodies that can cripple the HI virus are discovered and described as "broadly neutralizing" because they can make a high percentage of the many types of HIV found worldwide ineffective.
These antibodies are only produced in a minority of HIV-infected individuals but are widely believed to offer the best hope for developing an AIDS vaccine that could teach the body to produce its own antibodies before exposure to the virus. Only four HIV antibodies widely agreed to be broadly neutralizing have been found.
- A Phase II randomized, controlled trial starts in 2009 with more than 1,300 US men who have sex with men testing a vaccine developed by the NIH.
The study is not expected to prevent HIV infection, but will examine whether the vaccine significantly reduces viral load in HIV-infected individuals. Results are expected in 2012.
- Kenya starts a Phase I trial
to test the safety and efficacy of an HIV vaccine candidate - a modified vaccine virus, Ankara, (MVA.HIVA) - in infants.
The UK Medical Research Council and the European and Developing Countries Clinical Trials Partnership are sponsoring the trial, which will enrol 72 infants in Kenya and Gambia, and monitor them for one year.
Scientists in the Kenyan arm of the study say so far the vaccine has not led to any adverse effects in the infants.