There is hope for HIV/AIDS vaccine
Jan 02, 2007
WE cannot ignore the HIV problem as we embrace the new year. In spite of intensive research, scientists still have a very long way to go to find the cure for HIV/AIDS, but at least there is hope for a vaccine.
By Raphael Okello
WE cannot ignore the HIV problem as we embrace the new year. In spite of intensive research, scientists still have a very long way to go to find the cure for HIV/AIDS, but at least there is hope for a vaccine.
Dr Andrew Kambugu, the head of Clinical Services, Infectious Diseases Institute Makerere University, put hope for a cure at ‘many, many years away.’ We know that the virus can hide in tissues (for example the lymph nodes) and it has an enzyme which allows it to integrate into the infected individual’s genetic material (DNA),†he says.
“When the virus enters the DNA, it becomes very difficult to talk of a cure or eradication.â€
Kambugu explains that the only way to eradicate it from the DNA would be to kill the whole cell. Eliminating all the HIV in the body (cure) given our current technologies means killing all the cells. But since cells are responsible for keeping us alive, this really translates into killing the person!â€
That explains why, for the last 20 years, medical research has been more dedicated to finding a vaccine that will suppress the spread and development of the virus than finding a cure.
Vaccine types
There are two kinds of HIV/AIDS vaccine under research.
The first vaccine, often referred to as sterilising immunity, will help to prevent infection among people who are not yet infected with the virus. The second vaccine being researched is a therapeutic vaccine, which will specifically be administered to people already having the HIV virus.
“This would mean a person will have the HIV virus but not the disease or it will take him/her a very long time to develop the AIDS symptoms,†explained Kambugu.
Kambugu said a lot of research has been directed towards generating what is termed as neutralising antibody response. The vaccine to induce the body to produce soluble substances in the blood that destroy HIV particles that are outside the cell.
There has been limited success with this approach. But within last year, “there has been some breakthrough in the cell-mediated responses (the other arm of the immune response that complements the antibody response). For the first time, there was indication that you could programme a person’s immune cells to kill the virus.â€
Vaccines tried
Since 1987, when the first HIV vaccine was tried in US, more than 100 vaccines have been tested throughout the world.
Dr Fiona Kalinda, the senior trial physician at International AIDS Vaccine Initiative (IAVI) in Entebbe, explains that HIV vaccine trials are done in three phases. Phase I/II establish safety of the vaccine and whether it can bring immune responses. But Phase III, the definitive and final phase, which involves thousands of volunteers, establishes whether the vaccine can actually protect someone from getting the HIV virus.
So far, only two vaccines are reported to have reached Phase III trials – the AIDSVAX tried in 1998 and ALVAC-HIV currently being tried in Thailand among 16,000 HIV uninfected adult volunteers. Kalinda says results for this trial are expected in 2009.
When the AIDSDAX became the first and only candidate vaccine to reach Phase III, results from volunteers tried in Canada, USA, Thailand and Europe in early 2003, revealed that it did not work.
In 1999, the Joint Clinical Research Centre carried out the first trial in Uganda and in the whole Of Africa. The second trial in Uganda was carried out by IAVI in 2003 and the third trial was conducted by Makerere University John Hopkins University collaboration in 2004. All those Vaccine trials were Phase I trials.
Kalinda revealed that currently more than 100 HIV vaccines are in Phase I/II trials globally. In Africa, there are about 20 Phase I/II trials completed and on going. “Uganda, South Africa and Zambia have just graduated to Phase II of vaccine testing with tgAAC09 vaccine. There are 91 volunteers from the three countries – 27 from Uganda, 48 from South Africa and 16 from Zambia 16,†she said.
Challenges
The 2006 World Health Organisation report on the Global AIDS Epidemic states that scientists are using monkeys yet the virus cannot infect them with AIDS like it does in humans.
The report revealed that the HIV virus has many subtypes. The virus in USA is different from the virus in Africa and even the virus in Africa differs from one country to another.
“It is a challenge to develop one or multiple vaccines effective against all major subtypes of HIV,†she reaffirmed.
Hope not lost
Despite the challenges, Kalinda strongly believes there is hope however. The search for a vaccine is a feasible scientific project because there are mysterious biological occurrences in humans that researchers are using as reference points.
“There is an immune response among discordant couples (where one partner is HIV positive and another HIV negative). And in Gambia and Nairobi, there are cases of people constantly exposed to HIV but do not contract the virus. These can be used as a basis of research to find a vaccine,†Kalinda cited.
WE cannot ignore the HIV problem as we embrace the new year. In spite of intensive research, scientists still have a very long way to go to find the cure for HIV/AIDS, but at least there is hope for a vaccine.
Dr Andrew Kambugu, the head of Clinical Services, Infectious Diseases Institute Makerere University, put hope for a cure at ‘many, many years away.’ We know that the virus can hide in tissues (for example the lymph nodes) and it has an enzyme which allows it to integrate into the infected individual’s genetic material (DNA),†he says.
“When the virus enters the DNA, it becomes very difficult to talk of a cure or eradication.â€
Kambugu explains that the only way to eradicate it from the DNA would be to kill the whole cell. Eliminating all the HIV in the body (cure) given our current technologies means killing all the cells. But since cells are responsible for keeping us alive, this really translates into killing the person!â€
That explains why, for the last 20 years, medical research has been more dedicated to finding a vaccine that will suppress the spread and development of the virus than finding a cure.
Vaccine types
There are two kinds of HIV/AIDS vaccine under research.
The first vaccine, often referred to as sterilising immunity, will help to prevent infection among people who are not yet infected with the virus. The second vaccine being researched is a therapeutic vaccine, which will specifically be administered to people already having the HIV virus.
“This would mean a person will have the HIV virus but not the disease or it will take him/her a very long time to develop the AIDS symptoms,†explained Kambugu.
Kambugu said a lot of research has been directed towards generating what is termed as neutralising antibody response. The vaccine to induce the body to produce soluble substances in the blood that destroy HIV particles that are outside the cell.
There has been limited success with this approach. But within last year, “there has been some breakthrough in the cell-mediated responses (the other arm of the immune response that complements the antibody response). For the first time, there was indication that you could programme a person’s immune cells to kill the virus.â€
Vaccines tried
Since 1987, when the first HIV vaccine was tried in US, more than 100 vaccines have been tested throughout the world.
Dr Fiona Kalinda, the senior trial physician at International AIDS Vaccine Initiative (IAVI) in Entebbe, explains that HIV vaccine trials are done in three phases. Phase I/II establish safety of the vaccine and whether it can bring immune responses. But Phase III, the definitive and final phase, which involves thousands of volunteers, establishes whether the vaccine can actually protect someone from getting the HIV virus.
So far, only two vaccines are reported to have reached Phase III trials – the AIDSVAX tried in 1998 and ALVAC-HIV currently being tried in Thailand among 16,000 HIV uninfected adult volunteers. Kalinda says results for this trial are expected in 2009.
When the AIDSDAX became the first and only candidate vaccine to reach Phase III, results from volunteers tried in Canada, USA, Thailand and Europe in early 2003, revealed that it did not work.
In 1999, the Joint Clinical Research Centre carried out the first trial in Uganda and in the whole Of Africa. The second trial in Uganda was carried out by IAVI in 2003 and the third trial was conducted by Makerere University John Hopkins University collaboration in 2004. All those Vaccine trials were Phase I trials.
Kalinda revealed that currently more than 100 HIV vaccines are in Phase I/II trials globally. In Africa, there are about 20 Phase I/II trials completed and on going. “Uganda, South Africa and Zambia have just graduated to Phase II of vaccine testing with tgAAC09 vaccine. There are 91 volunteers from the three countries – 27 from Uganda, 48 from South Africa and 16 from Zambia 16,†she said.
Challenges
The 2006 World Health Organisation report on the Global AIDS Epidemic states that scientists are using monkeys yet the virus cannot infect them with AIDS like it does in humans.
The report revealed that the HIV virus has many subtypes. The virus in USA is different from the virus in Africa and even the virus in Africa differs from one country to another.
“It is a challenge to develop one or multiple vaccines effective against all major subtypes of HIV,†she reaffirmed.
Hope not lost
Despite the challenges, Kalinda strongly believes there is hope however. The search for a vaccine is a feasible scientific project because there are mysterious biological occurrences in humans that researchers are using as reference points.
“There is an immune response among discordant couples (where one partner is HIV positive and another HIV negative). And in Gambia and Nairobi, there are cases of people constantly exposed to HIV but do not contract the virus. These can be used as a basis of research to find a vaccine,†Kalinda cited.