Researchers at the Stanford University School of Medicine undertook the largest study of its kind about the transmission of HIV and found that only a limited number of mutations are responsible for most cases of transmission of drug-resistant HIV. The results of the study were published online on April 7 in PLOS Medicine.
For this study, data from more than 50, 000 patients in 111 countries were taken into account. The researchers found that a small group of mutations accounted for a majority of the cases of transmission-related resistance to the HIV drugs used to treat infections in resource-limited settings. Robert Shafer, MD, professor of medicine at Stanford and principal investigator for the study said that the positive thing about the results is also that the levels of transmission of drug-resistant strains have not increased globally as much as once thought. However, the worrying aspect is that there is an overall increase in drug resistance, particular in people living in the poorest parts of the world. Shafer added that it is very likely that transmitted drug resistance will increase further and hence, there is a greater need to continue monitoring to make sure that the results of long term treatment for people are successful.
Shafer opined that since we have the knowledge of the key mutation, steps could be taken to develop an inexpensive test for diagnosing it. It can assist in determining which drugs should be given to previously untreated patients.
Since the year 2003, great efforts have been made by the international community to achieve the goal of universal antiretroviral treatment for HIV. Thanks to their effort, 11.7 million people in developing and underdeveloped countries are now receiving the lifesaving treatment. But the concern is that with wider availability of these medications, drug resistance could spread and nullify those gains.
In order to take stock of the situation, Shafer and his fellow scientists reviewed HIV sequencing data on 50,870 individuals across the globe, taken from 287 studies published between 2000 and 2013. They analyzed each virus sequence for the presence of 93 mutations previously shown to be indicators of drug resistance.
They found the overall prevalence of transmitted drug resistance was on the rise. The scientists feared that this increase could undermine confidence in the ability to treat HIV in low-income regions and potentially dissuade new patients from seeking care. To make sure that such a situation doesn't arise, the study explores the possibility of creating a simple, inexpensive test for the key resistance-related mutations. Such a test could help clinicians in pinpointing the drugs likely to be most effective for individual patients. This way the flow of drug resistance could be shut off.
Another interesting finding of the study is that the drug-resistant strains did not come from a single line of resistant viruses; in fact were distinctly different from each other. It suggests that they had been acquired independently and not as a result of a single transmission chain. This pattern is different from how others microbes behave. For example, in malaria and tuberculosis resistant strains tend to move rapidly among populations. It is also not in line with an emerging pattern of drug resistance in many upper-income countries, where 20 years of HIV treatment have spawned the spread of many highly drug-resistant strains.
Shafer opined that the strains being detected in developing and under-developed countries are quite unrelated to one another. That in turn means that they have not yet have spread their tentacles in the population, suggesting that they are likely less often transmitted among people who have never received the drugs before.