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« on: February 06, 2007, 03:07:31 PM »

Such work is made even more important when persons who spearhead it pass on. RIP Prof Bwayo

Second time lucky?
After the first vaccine trials failed to yield the desired results, scientists did not give up and are currently involved in more clinical trials.
7 August 2006 - Zachary Ochieng
Source: NewsfromAfrica

Kenya is once again the focus of global attention as a search for a permanent solution to the HIV/Aids pandemic gathers momentum. A team of researchers from the Kenya Aids Vaccine Initiative (Kavi)-a research institute developed in collaboration with the University of Nairobi and Oxford University-and the International Aids Vaccine Initiative (IAVI) East Africa are conducting clinical trials on a candidate vaccine designed to prevent HIV/Aids. "This marks an important step in the worldwide battle to stop the spread of HIV/Aids pandemic", health minister Charity Ngilu said at the time of the launch, adding: "Kenya is proud to be a leader in the effort to find an Aids vaccine, which would be the best solution to the global Aids crisis".

The current trials came two years after the first vaccine trial, conducted by IAVI, Oxford University and the University of Nairobi's Department of Microbiology, collapsed. In September 2004 the researchers declared that the vaccine produced had flopped after failing to elicit the expected immune response. Dr Chrispin Kambili, IAVI's regional director had noted at the time that preliminary data from 205 volunteers in clinical trials in Kenya, Uganda and the United Kingdom showed that the candidate vaccine elicited responses in only a quarter of the volunteers, with the responses not long lasting. According to set standards, the tests would have been considered successful had they elicited a positive response in at least 60 per cent of the volunteers.

In Kenya, the first research on a vaccine was spurred when a team of local researchers found out that a group of commercial sex workers in Nairobi's red- light Majengo area remained free of HIV/Aids even after presumed multiple exposure to the virus through unprotected sex. This led to the conclusion that the women had developed a form of natural immunity, and it happened that at about the same time, a team from Oxford University had stumbled upon a similar cluster in the Gambia.
 It therefore became natural that the team from Oxford collaborates with their Nairobi counterparts. But the failure of the trials did not dampen the spirit of the researchers, hence the trial of another vaccine. "We know that in the search for an Aids vaccine, many different vaccines will need to be tested. Kenyan scientists are proud to have had long term experience with this research, and to be on the forefront of promising new vaccine candidates", said an upbeat Prof Job Bwayo, the principal researcher.

The current candidate vaccine is Multiclade ABC, meaning it incorporates HIV genes from three different sub-types (A,B and C) of the virus. These are most commonly found in Africa, the Americas, Europe and parts of Asia and comprise 85 per cent of HIV infections worldwide. Unlike the previous candidate vaccine which could only produce killer T-cells and based only on sub-type A of the virus, the current candidate vaccine produces both the T-cells as well as antibodies and is expected to elicit quicker immune response. This combination produces potent specific immune cells that work against HIV. Previous studies have shown that a combination of the two have protected non-human primates against lethal challenges posed by the deadly Ebola virus.

To make it potent, the vaccine is designed to attack the virus from two levels. On one level it is expected to elicit neutralising antibodies that will disable the key two proteins - gp 120 and gp41 that enable the virus to infect a cell. But just in case some viruses are not destroyed by the antibodies thereby infecting the cell, then the second level, the cellular immune response, will come in handy. In this case, when the infected cell takes a particular form, the immune cells, especially the killer T-cells, will be alerted and respond by killing it before the virus replicates itself.

The vaccine has been developed by Dale and Betty Bumpers Vaccine Research Center (VRC) of the National Institute of Allergy and Infectious Diseases (NIAID), a division of the US National Institute of Health (NIH). The vaccine is also being tested in other countries in Africa, notably Kigali, Rwanda and Mbeya, Tanzania as well as other parts of the world. It is a preventive vaccine designed to protect uninfected people from getting HIV. It is noteworthy that in Kenya, parallel trials are also being conducted in the Rift Valley town of Kericho by the Kenya Medical Research Institute (Kemri) in collaboration with the Walter Reeds University, a research arm of the American army.

The current collaboration between Kavi and NIH is mutually beneficial in that the Kenyan team has already gathered vast experience and data while NIH has the advanced scientific equipment and personnel for the complex genetic engineering that would be employed to replicate the natural immunity. "The vaccine has been developed by NIH and our role is purely research", Prof Bwayo told this writer. Besides Prof Bwayo, other Kenyans involved in the research are Prof Ndinya Achola and Dr Walter Jaoko.

The Nairobi study is a small-scale trial, with a primary aim to evaluate the safety of the product. However, even if the vaccine trials are successful, the world will still be several years away from containing the global pandemic, given the several years that the trials will take. The trials will be conducted in three main phases.

Phase 1, which is already underway, is conducted in a small number of healthy volunteers, about 104, HIV-negative and at low risk of being infected. The aim of a Phase 1 trial is to assess the safety of the vaccine, which means how well it is tolerated. Researchers will also collect information on the effects of the vaccine on the immune system. This phase can take 2-3 years. The phase began in January, with the last volunteer being recruited in May. So far, volunteers are responding well. Phase 1 is expected to end earliest in May 2007. It involves both male and female volunteers aged between 18 and 50. "If the vaccine is found to have no side effects on the volunteers, we shall move to Phase 2A, where between 100 and 500 HIV-negative volunteers will be recruited. During this phase, scientists will find out if the vaccine is able to protect the volunteers. Tests during this stage will take between three and four years"., said Prof Bwayo. The aim of a Phase 2 trial is to acquire more information on safety and whether the candidate vaccine induces the appropriate immune response .It also determines the optimum dosage and what is the best route for administering it-whether oral or intravenous and at what intervals it should be given-six months or one year.

If the candidate vaccine is found to be promising, the trials then move to phase 2B for the proof of concept. Phase 2B trials will also prove the efficacy of the vaccine. It will involve four sites with high-risk groups, with about 3000-5000 volunteers. The sites are in Kericho, the coastal town of Kilifi and Nairobi's Majengo and Kangemi slums.

If the candidate vaccine continues to look promising then it will enter Phase 3 trials. In Phase 3 trials, the vaccine is given to a large number of volunteers, between 2,000 and 10,000 people. The main purpose of a Phase 3 trial is to find out whether the candidate vaccine protects people from getting the disease and to collect more safety information. This phase can take 5-7 years. At the end of the Phase 3 trial, if the vaccine has been shown to be safe and effective in humans, the vaccine may then be licensed for large -scale manufacture and for use in humans by national authorities. It could be in the market in the next 7-10 years.

A vaccine is a preparation that teaches the body's immune system to recognize a foreign biological substance or a micro-organism, such as a bacterium or a virus, which can cause a disease. Vaccines are designed to protect vaccinated individuals from getting disease. Vaccines save millions of lives each year and prevent many more people from getting sick. Infants and young children all around the world are immunized against infectious diseases such as tuberculosis, tetanus, poliomyelitis and measles in the first years of their life. In many countries, this is achieved through the Expanded Program of Immunization (EPI), which is directed at infants and young children. There are also vaccines for adults and these include vaccines such as tetanus, yellow fever, meningococcal, influenza, hepatitis A and B and typhoid fever.

Vaccines were developed when British physician, Dr Edward Jenner, discovered that the virus that caused cowpox (vaccinia) could provide lasting protection against smallpox (a more virulent disease of the same family) when injected into a human being. Early manufacture of vaccines included injecting tainted human blood into a large animal, such as a horse, which would not itself become infected but would develop antibodies. The blood containing antibodies would then be drawn from the horse and injected into humans. Science has developed a long way since then.

An effective AIDS vaccine, given before exposure to HIV, could help the body completely block infection, or help the body control HIV enough to prevent progression to AIDS and/or transmission to others. The development of a preventive AIDS vaccine is believed to be possible based on promising scientific evidence. An ideal preventive HIV vaccine would protect people against infection of all subtypes of HIV and against all routes of possible transmission. An ideal AIDS vaccine would also be inexpensive, easy to transport and to administer to people, and would require few booster shots.

What if, however, something goes wrong and the test subjects get infected? Prof Bwayo rules out this, saying the candidate vaccine has already been tested in the test tube as well as on mice and monkeys. Besides, the government last year published clear guidelines for research on vaccines.
As the Aids pandemic continues to decimate the global population, there is no gainsaying that preventive measures such as abstinence, faithfulness and condom use have reduced the spread of HIV infection, but have not stopped it. There is no cure for HIV/Aids and anti-retrovirals remain beyond the reach of those in developing countries. Only an effective vaccine, used together with existing prevention programs, can end the epidemic.

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