Scientists strongly believe with such an ability to stop the virus from infecting new cells, these people could hold the key to developing an effective AIDS vaccine. Photo/FILE
By ARTHUR OKWEMBA
Posted Thursday, April 29 2010 at 22:13
She is HIV positive, pregnant and has lived without drugs for nine years. And scientists are watching her with keen interest because the virus in her body is undetectable.
The patient, who cannot be named for confidentiality, is now four months pregnant and doctors want to see if she can deliver a HIV-negative baby without using ARVs or Caesarean Section, the key interventions used to significantly cut-down chances of a mother transmitting the virus to her baby.
“We are doing CD4 and viral load tests in close frequencies to establish how they are before we decide how she will deliver,” says Dr Surendra Patel, an expert in infectious diseases at MP Shah Hospital. “If the viral load remains undetectable, then there will be no justification to intervene with ARVs or Caesarean Section during birth.”
Her CD4 count — immune cells used to fight infections — is 1,200 and the viral load is below 40 copies/mL, the level at which the virus is defined as undetectable. CD4 count for an HIV-negative healthy individual is over 410. The woman is one of the seven other HIV-positives who have kept the virus at undetectable levels many years after being infected.
A similar phenomenon is being studied by scientists at the Kenya Aids Vaccine Initiative, where out of the more than 200 people they have kept tabs on for several years, three may hold the key to a broadly neutralising antibody vaccine. “So far, we have isolated a few individuals who have very promising results and now they are being studied to understand how their immune system is able to neutralise the virus,” says Prof Omu Anzala, virologist and Kavi director.
This phenomenon is evident in men and women who have been screened in Nairobi. Dr Patel has monitored his patients for over five years to establish what makes them tick. They have neither used any anti-retroviral drugs nor been attacked by opportunistic infections despite living with the virus. Of the eight people, one has CD4 count of 1,800, with the viral load below 40 copies or undetectable level.
“In the next 18 months, we hope to complete the follow-up and issue a statement on our findings,” Dr Patel says. These cases are what have come to be known as the Elite Controllers — people whose immune system is able to control the HIV viral load to less than 40 copies/mL compared to over 30,000 copies/mL of HIV in a person without such antibodies.
Only five per cent of all the HIV infected people globally, are categorised as elite controllers. Kenya is one of the countries with some. They are of two types. One is the Aviramic Elite Controllers, whose viral load is always undetectable. The other is the Viramic Elite Controllers, whose viral load has stabilised at about 1,000 copies. Because of the undetectable viral load, the infected can not transmit the virus to their partners.
Scientists strongly believe with such an ability to stop the virus from infecting new cells, these people could hold the key to developing an effective AIDS vaccine. The director of the National Aids and STD Control Programme (Nascop), Dr Ibrahim Mohamed, said the government was aware of a cohort of HIV-positive people with stable CD4 count and a low viral load who may not need any intervention for now.
“There are long-term non-progressors who are able to manage the virus without our intervention with anti-retroviral drugs.” The reasons these people manage the virus without medications are varied. He thinks besides producing neutralising antibodies, the virus might have mutated to develop into a weaker virus unable to replicate, or their CD4s have receptors.
The latter are specific sites on the cell, which HIV uses to bond and infect the cells. Without them, the virus is disabled. In fact, some of the ARVs are known to interfere with this process, making it difficult for the virus to enter the cell. In 2008, Prof Anzala’s team announced that it had identified 10 Elite Controllers with powerful antibodies that neutralise the virus.
On being screened, the individuals were found to have high CD4 counts and very low viral loads — amount of HIV in the body — which was uncharacteristic of an infected person. They also had very low possibilities of transmitting the virus to another individual and progressing to Aids, the last stage of the disease where opportunistic infections reign, killing the individual if not well managed.
Of the 1,700 HIV-positive people who have been screened in Kenya, Uganda, Rwanda, South Africa, and Zambia, 170 have HIV neutralising antibodies. “What we are experiencing now is phenomenal and provides critical information of how we move forward,” says Dr Wayne Koff, of International Aids Vaccine Initiative.
Millions of shillings have been invested in research around this new phenomenon and four antibodies have been identified which can neutralise the virus. Now, the initiative is studying them to see which ones have the ability to neutralise different types of HIV strains such as A, B, C and D, also circulating in Kenya.
The Aids initiative has set aside between 30 and 50 per cent of its budget on the identification and development of a vaccine which can elicit these antibodies. They have also developed what they call Protocol G, whose sole objective is to help scientists identify elite controllers across Africa and other parts of the world.
Identifying and understanding the broadly neutralising antibodies as the most effective way of preventing HIV infection remain a most difficult aspect. Scientists admit that HIV is tricky to contain because of its HIV immune evasion mechanisms, is sexually transmitted, and has high capacity of recombination, among other factors.
Still, they believe a vaccine that produces both broadly neutralising antibodies and cellular immune response would be a most effective way to control the virus. This encouraging information has led the Aids initiative to establish Neutralising Antibody Consortium, whose responsibility is to pick-up more antibodies with the ability to prevent HIV infection.
Established in 2002, the consortium has grown from four academic institutions to 18; but to accelerate the development and testing of a viable vaccine, researchers need incentives.
— An AWC-Feature