Kenya and Rwanda have partnered with the United Kingdom in a HIV/Aids vaccine trial in a fresh effort to find a cure for the disease.
Phase 1 trials, which are scheduled to kick off before the end of this month, will be conducted by scientists at the Kenya Aids Vaccine Initiative (KAVI) in Nairobi and St Stephen’s Centre in London.
The studies are funded by the International Aids Vaccine Initiative (IAVI), a non-profit organisation based in New York.
Researchers from both institutions will recruit up to 64 healthy adult volunteers aged between 18 and 50 for the trial, which is expected to take up to two years.
According to Omu Anzala the programme director of KAVI, the vaccine trials will be carried out on a virus called Sendai.
“This is the first time Sendai is being used as an Aids vaccine candidate,” said Dr Anzala.
The Sendai vector carries an immunogen (the active ingredient of a vaccine) derived from the predominant subtype of HIV that circulates in East Africa.
But what distinguishes it from the other HIV vaccine candidates is its ability to replicate within the body following delivery, and its replication within mucosal tissues.
Both HIV and Sendai affect the mucosal tissues, found in the nose and genital area, in their early stages of infection. It is for this reason that the vaccine is administered through nasal drops.
The Sendai candidate, researchers say, may target immune responses to mucosal tissues and provide an edge to the immune system when it is subsequently challenged by HIV.
“At this point, the trial’s aim is to ensure that the vaccine is safe and more effective,” said Dr Anzala.
“If we see strong immune responses, we will go into the larger second phase of testing whether the vaccine is effective in reducing transmission or lowering the load of the virus,” he added.
In May, Uganda, Kenya and Tanzania also partnered with the United States to take part in a HIV/Aids vaccine trial.
The DNA vaccine trials are being conducted by Makerere University and the US Walter Reed Army Institute of Research on 42 participants from Uganda, 20 from Kenya and Tanzania and 12 from the United States. The phase 1 is expected to run for two years, too.
Scientists say an Aids vaccine is urgently needed to control the spread of the disease. It is estimated that 33 million people in the world are living with HIV, and 7,000 people are newly infected with the virus every day.
Currently, there are over 20 vaccine trials ongoing worldwide with four more trials scheduled to start separately in four sites in Kenya, Uganda, Tanzania and Rwanda before the end of the year.
The World Health Organisation report on HIV indicates that sub-Saharan Africa alone accounted for an estimated 69 per cent of all people living with HIV and 70 per cent of all Aids deaths worldwide in 2011.
Dr Anzala said it has taken over 27 years scientists to come up with HIV vaccine candidate because the virus constantly develops different strains.
“It took scientists close to 45 years for them to develop an effective polio vaccine and the research for a malaria vaccine, which is yet to be developed, has so far taken over 100 years,” said Dr Anzala, adding that people should maintain an optimistic outlook on the future of HIV eradication by a vaccine because there is now strong scientific data to support that position.
“The aim is to develop a safe and effective vaccine for the prevention of HIV, the virus that causes Aids.”
It is estimated that the search for a HIV vaccine has so far taken up $8 billion in the past decade.
The path to create a vaccine has been set of challenges, including a 2007 trial of a vaccine produced by Merck, which appeared to make recipients increasingly susceptible to the virus.
Two years later, there was news of a successful clinical trial in Thailand called RV144, which was sponsored by the Surgeon General of the United States Army and was found to reduce HIV infections by 31 per cent.
“While the improvement was incremental, it gave the scientific community hope,” noted Dr Anzala, adding that although the vaccine reached the most advanced stage of development, phase 3, it did not show the required effectiveness standards of 60 per cent and above for it to be rolled out as a product.
“The RV144 HIV-1 vaccine trial was the first clinically validated preventative vaccine to show efficacy against HIV infection,” he added
He said that this has helped scientists to now concentrate on developing a vaccine that targets the three arms of the immune system (exposure, infection and the disease itself) as opposed to previous research that mainly targeted the cellular immune system (infection).
“Research is now focusing on developing a vaccine that broadly neutralises antibodies that latch on to regions of the virus and make it incapable of infecting healthy cells,” he said.
Antibodies are protein molecules produced by body cells to fight or neutralise foreign particles such as bacteria and viruses in the body.
A study published in the Journal of Nature Medicine in October last year cited research on these types of antibodies from the Centre for the Aids Programme of Research in South Africa.
The study followed two HIV-positive women for several years, and discovered a key change in the outer coating of the HIV virus, which allowed them to develop antibodies that could fight a large variety of HIV strains.
In another study published in the Nature Journal, researchers at the US Duke University School of Medicine in Durham, North Carolina, tracked the evolution of immune molecules in a patient as the virus mutated.
The patient was from an undisclosed African country and had been infected with HIV-1 for 136 weeks (more than two and a half years).
In the report titled “Co-evolution of a broadly neutralising HIV-1 antibody and founder virus,” the scientists observed that antibodies evolved into new forms every time the population of the virus diversified.
The mature antibody, CH103, neutralised approximately 55 per cent of HIV-1 isolates, and its co-crystal structure with the HIV-1 envelope protein revealed a new loop-based mechanism of CD4-binding-site recognition.
The latest most advanced study under way of a vaccine to prevent HIV infection was stopped by US government researchers in April after an interim look at the data showed it was unlikely to help recipients.
According to Lisa Mills, HIV research branch chief at CDC Kenya, the HVTN 505 was the only ongoing phase 3 trial of the HIV vaccine developed by the agency’s Vaccine Research Centre in the US, didn’t prevent HIV infection or reduce the amount of virus in those who became infected.
“The vaccine was developed to target the T cell,” or white cell part of the immune system, but didn’t also target the antibody part of the immune system,” said Dr Mills.