Almost 10% of children infected with HIV do not develop any signs of infections. Their immune system, however, does not react to the virus.
Infected with HIV, these children show no signs of infection. Such an exceptional case that they were baptized with a particular name: the non-progressors. This mystery for science could be used to fight the virus in the rest of the population. It was to find out that a team from the University of Oxford (United Kingdom) looked at a group of 170 young patients. The results published in Science Translational Medicine are surprising to say the least: their immune response to HIV is closer to that of monkeys than humans.
An unchanged immune system
Infection without progression to the AIDS stage (known immunodeficiency syndrome) is very rare. Only 0.3% of adults have this peculiarity. Until now, teams around the world have focused on these exceptional cases. They demonstrated a massive immune response that controls HIV replication and reduces the number of copies in the blood. But in trying to replicate these findings, the researchers hit a wall: in a normal patient, an increased immune response accelerates the progression of the disease.
In infected patients in utero, the situation is quite distinct. In 80% of cases, the untreated virus is fatal before they reach the age of two. But in 5-10% of cases, children get the virus under control without medication. Their immune system adopts a radically different strategy when it comes to HIV: it does not react, or very little. The number of copies of the virus in the blood is very high.
A response similar to that of monkeys
In fact, these young patients take the same approach as non-human primates infected with SIV: the viral load is very high but the activity of the immune system remains unchanged. The result of a long evolution of the organism. “The diseases associated with HIV are not so much linked to the virus but to the immune response which is opposed to it”, summarizes the main author of the study, Prof. Philip Goulder, interviewed over there BBC. Looking at the similarities with these African monkeys, the researchers noted a peculiarity: the CCR5 receptor, involved in immunity, is underexpressed in leukocytes. However, it is this which is used by HIV to enter the host cells.
All of these details are invaluable to teams specializing in AIDS and HIV research. Indeed, antiretroviral treatments are very effective in controlling the evolution of the virus in the body. But the immune system is constantly overheating. The underlying inflammation is bad for the brain, and cognitive decline is associated with the infection. It is also important for the organism. “Even when treatment is working, these patients continue to be exposed to unrelated diseases often associated with aging, including cardiovascular disease, cancer and dementia,” said Prof. Goulder in a statement.
Taking advantage of these exceptionally resilient children would therefore prove to be invaluable. But two experts from Emory University in the United States call for caution. “We do not know if it is clinically certain that these patients recently identified as non-progressors remain without treatment,” said Ann Chahroudi and Guido Silvestri in a comment.
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