Q&A: MSF helps develop a simple rapid HIV/AIDS viral load test (SAMBA)

The test can be used for the detection of HIV infection in children under 18 months and as a monitoring tool for adults on antiretroviral treatment (ART). In addition, the test will also help medical staff determine whether patients are taking their pills properly.

What is 'viral load' and why is it important?

Being able to measure the amount of the HIV virus in a patient's blood is important when treating HIV//AIDS, because it shows how the immune system is responding to treatment. Keeping the viral load levels in the blood undetectable for as long as possible decreases the complications of HIV disease and helps prolong life. If the viral load measurement is high, it indicates that HIV is reproducing and that the disease will progress faster than if the viral load is low.

Detecting the HIV virus in the blood is needed to diagnose HIV infection in infants under 18 months of age. Conventional HIV tests cannot be used in infants under 18 months of age, because they detect antibodies, and infant blood often carries the antibodies of the mother.

Currently, the only way to do a viral load test is by using sophisticated equipment requiring highly trained professionals. The cost of such a machine alone is more than US$20,000. In addition, a dedicated laboratory room with a constant electricity supply are needed to be able to perform the highly sensitive testing procedure that involves many steps and refrigeration of reagents during storage. Due to these constraints, viral load testing is hardly available in developing countries, and is limited to the very few existing high-tech labs.

What is SAMBA?

The SAMBA (Simple AMplification BAsed nucleic acid test) technology aims to significantly simplify current viral load tests. If successfully developed, it can be used to test viral load at district hospital level in developing countries, and therefore more widely available to resource-poor settings. SAMBA will require little equipment compared to the highly expensive machinery that today's viral load demands. Unlike currently available tests, the SAMBA test and its ingredients do not need to be refrigerated. The technology will also allow the test to be used as a point-of-care test, and provide results while the patient is waiting.

Why is a simple point of care test needed for HIV diagnosis?

Because there is no simple test available today, infants with HIV in developing countries are rarely diagnosed before they reach 18 months. This is why almost all children currently under treatment in Médecins Sans Frontières' programmes are over two years. Without treatment, half of all children infected with HIV die before their second birthday.

An alternative method called 'dry blood spot' exists that allows patients' blood drops to be placed on special filter paper, which is then transported to high-tech labs for viral load testing. This method will be used more widely in the near future and can bring improvement in the interim, until a simple point-of-care test such as SAMBA is developed. However, having to send samples to potentially far-away high-tech labs requires a functioning transport system, and can take days and even weeks for results to return. It also means that the few existing high-tech labs have to have sufficient capacity to cater for the testing needs of an entire region or country.

During HIV treatment, drug combinations often have to be changed after a certain amount of time because resistance to the drugs develops. This happens even if patients take every single tablet according to prescription. The problem is determining the right time to switch treatment to different drugs: in resource-poor settings, treatment is switched when patients start developing new symptoms or when the level of a type of white blood cell [CD4] declines.

Today, most of MSF's nearly 60,000 patients and almost all of the approximately 1.3 million people on treatment in developing countries stay on their first-line drug combination until they become sick again. At this point, however, several drug resistances may have developed and the chances of the second-line treatment working will have become very slim.

Keeping a person on a failing treatment for too long therefore means that he/she can lose all future treatment options, which is a possible scenario for the majority of patients in developing countries. In wealthy countries, a viral load test is used to help determine the optimal point at which the therapy needs to be switched.

In South Africa, in one of the few MSF projects where viral load is available, after four years of treatment, 16% of patients were shown to be failing on their first-line drug combination and need to be switched to a second-line combination.

How will SAMBA be used?

The test can be used for the detection of HIV infection in children under 18 months and as a monitoring tool for adults on antiretroviral treatment (ART). In addition, the test will also help medical staff determine whether patients are taking their pills properly. If there are irregularities, patients can be given additional support, such as enhanced adherence counseling, to help avoid resistance to drugs developing.

The need for simple monitoring tools will become increasingly urgent over the next few years as more patients start receiving antiretroviral treatment, and as those who have been receiving it for several years begin to develop resistance and need to switch to second-line drugs.

What will be MSF's role in the development of this new test?

MSF will help the development of the new test in two key ways:

  • Advise on the most appropriate detection and cut-off levels as well as the appropriate use of the test in resource-poor settings. (A report of an experts' meeting held in January 2006 is available on request.)
  • Field-validate the test in MSF projects in different phases (feasibility prototype, working prototype, clinical trial). The field-testing and trials will be carried out by Epicentre, an MSF-associated epidemiological research organisation and is estimated to cost around 1.3 million Euros.. Epicentre will prepare the trial protocols with input from an expert advisory committee.

If agreement can be reached, MSF is also willing to fund part of the developoment work at Cambridge.

How will access to the test be provided?

The test will be produced by Diagnostics for the Real World (DRW), a spinoff company based on the technologies developed at the University of Cambridge. DRW has a two-tiered pricing policy in order to provide the tests at near to manufacturing cost to low income countries.

While the manufacturing cost for the SAMBA test is not yet clear, the initial price will already be cheaper than the current cheapest test (USS$17) and cost is expected to decline once production volume increases. Importantly, equipment costs will only be a fraction of current costs.

DRW plans to carry out technology transfer to at least one manufacturer in a developing country to produce the test. The test is expected to be available within three years.

The Diagnostics Development Unit (DDU) at the University of Cambridge was set up by a group of former industry R&D scientists. These experts left a large pharmaceutical company to begin developing simple, rapid and inexpensive tests for the detection of infectious agents for developing countries. The group, led by Dr Helen Lee, has already developed a simplified Chlamydia rapid test.

Diagnostics for the Real World (DRW) was created in 2002 as a spinout company based on the technologies developed at the University of Cambridge. Although the company will strive to make a reasonable return and profit, one of its primary goals is to serve the diagnostic needs of resource-poor settings.

Médecins Sans Frontières (MSF) is a medical humanitarian organization founded in 1971. Since the 1990s, MSF has also been caring for people living with HIV/AIDS in a variety of developing countries. MSF began offering ART in its programmes in 2000, and today provides ART to over 60,000 patients in over 50 projects in a total of 29 countries. Approximately 6% of the patients in MSF's ART programmes are children.

Founded by MSF in 1987, Epicentre is an independent, Paris-based epidemiological research centre and a WHO Collaborating Centre for Research in Epidemiology and Response to Emergencies. Epicentre carries out operational research in MSF projects around the world as well as from its research base in Mbara, Uganda.