For over 20 years, Prof Pontiano Kaleebu, director of the Uganda Virus Research Institute in Entebbe, has been at the forefront of efforts to find an HIV vaccine.
In an interview with Shifa Mwesigye, Kaleebu says the vaccine is still some years away although great advances have been made. Below are the excerpts:
Is the HIV vaccine available as the media has been reporting?
There is no HIV vaccine. What we have are candidate vaccines that are being tested to see if they are good and safe. [We also need] to test them in populations to see if they can do what we require – prevent infection or slow disease progress.
Why do scientists continue the research when many vaccine trials have failed?
We need an HIV vaccine. As you know, HIV or Aids is a viral infection [and] in medical history, it has always been difficult to get treatment for viruses. Where we have succeeded, it has been by the use of vaccines. This virus is more complicated than other viruses because when you are infected, it gets inside the cell and remains there quietly. So, getting a drug to eradicate it completely will be more challenging.
How does a vaccine work?
The vaccine we are talking about is to prevent infection. You give it to someone who is HIV negative and the body produces a defence mechanism, in form of antibodies or T-cells. When a person gets exposed through high risk behaviour, the antibodies prevent any infections. We are also now talking about other vaccines that would prevent the virus spreading and progressing to AIDS.
Do the vaccines you use in trials cause HIV infections as has been insinuated?
The vaccines cannot cause HIV infection because they are not made from live or dead viruses nor those that have been manipulated. The vaccines we use are mostly made through what we call genetic engineering. They are synthetic and cannot lead to infection.
How many vaccines have been produced?
Since HIV vaccine research started in 1987, there have been more than 100 vaccine products and more than 200 trials. Many of these have been at phase I (for safety and immunogenicity). Very few have moved to the second phase and only about four have moved to phase III (efficacy trial to test on human beings).
Only one vaccine tried in Thailand about four years ago was able to show some modest effect in protection against infection in about 30% of the volunteers. That was not good enough and more research needs to be done.
How long does it take to come up with a safe vaccine?
To have an idea and develop a vaccine to the last phase takes many years. The vaccines are first tried in small animals like mice and rabbits to see how safe they are. Then you go into larger animals like chimpanzees or monkeys. That alone can take six to seven years. And then you go to the human phase I, II and III which can take another five years.
Is there hope of finding the vaccine?
I think we will because science is advancing. Recently, we have learnt that some people have antibodies that can kill the virus. So, we are now trying to design a vaccine that can produce many of these antibodies. Other scientists are studying the results of the study in Thailand that showed 30% prevention. Information from that is even leading us to design better vaccines.
How long must we wait?
Those who waited for a polio vaccine waited maybe for 70 years, while a measles vaccine took 80 years to discover. For us it’s just 20 years you are talking about. Some of the challenges are that the virus itself is complicated – it mutates, it hides. For infections where we found vaccines, when somebody gets infected with whatever micro organism, an immune response clears that infection.
But for HIV, everyone who gets infected goes down with the disease. There are very few people who recover. We don’t have a good human model to use. But we had a few we are using for a vaccine. There are people who get exposed to the virus and remain uninfected because of their immune response.
The sex workers in Kenya, discordant couples and people who get the virus but remain long without the disease. There are others who get infected and the virus is undetected, they call those elite controllers. So, we have a few unique individuals who are giving us opportunities to understand how we can design a vaccine.