Unique children chart new path to HIV vaccine
An extremely rare subset of HIVpositive children can live with the virus well enough to stay healthy for years. Now, the world’s largest study into how these children fend off sickness may have unlocked important clues that may influence the world’s quest for a vaccine.
When HIV infects children, it moves with a rapid viciousness. In the absence of antiretroviral treatment, most children living with HIV will become sick within a year, according to a 2016 study published in the j ournal Nature Reviews Immunology. For adults, this period can be as long as 10 years.
Without treatment, most children with HIV will die before their second birthday, according to the United Nations Children’s Fund.
But a very small proportion of chil- dren — and adults — can fend off the virus’s attacks well enough to stay healthy for years. Now, scientists may finally be closer to understanding why.
For 10 years, researchers in South Africa and the United Kingdom worked to diagnose and track about 170 of these children in Durban and Kimberley. Born about 10 years ago, they had not received the antiretroviral treatment before, during or after their birth that is needed to prevent mother-to-child transmission of HIV.
According to Oxford University lead researcher Maximilian Muenchhoff, many were only diagnosed after their mothers had fallen sick and had been diagnosed with HIV.
As part of a study recently published i n the journal Science Translational Medicine, researchers analysed samples taken from such children over the course of 10 years. Scientists found that, although these otherwise healthy children often had very high levels of HIV in their blood, the virus largely attacked a subset of white blood cells that die within days. HIV largely spared longer-lasting white blood cells, also called CD4 T cells, because they lacked a receptor on cell surfaces that HIV uses to infect cells.
Because these cells were spared, so too were children’s immune systems and that kept them healthy.
White blood cells make up part of the body’s immune system, helping to fight off invaders such as bacteria and viruses.
“The virus is replicating at high levels in the bodies of these children, but they don’t get sick, [because] they don’t lose their CD4 T cells. Kids had fully preserved immune responses,” Muenchhoff says.
The study is the first to show that many of these children also carried rare, potent types of antibodies (proteins that fight infections) that a growing body of science thinks may be key to vaccine development.
“This has huge implications for vaccine research because it looks like children in general might be able to produce stronger antibody responses than adults. Basically, it implies that it may make more sense to vaccinate children against HIV [rather than adults],” he says.
Types of these antibodies will be used in adult HIV vaccine trials slated to start in South Africa in November.
Less than 1% of adults living with HIV can control the virus for unusually long periods before becoming sick, according to a 2003 study published in the Journal of Infectious Diseases. Sometimes dubbed “elite controllers,” these adults often have relatively low levels of HIV in their blood.
The children studied as part of the recent research had very high levels of the virus in their blood but very low levels of cellular inflammation.
This kind of chronic inflammation provoked by HIV infection is thought to be linked to increased risk of some conditions such as cardiovascular disease among people living with HIV, Muenchhoff says.
He adds: “If we were able to identify the mechanisms of how this works and maybe apply it to chronic HIV-infected adults, then this could also help prevent disease.”