Between 4% and 13% of people of African origin could be carrying a particular variant that decreases the viral load
Representative photo: iStock._ Some people of African descent possess a gene variant that likely controls human immunodeficiency virus (HIV), lowering their risk of transmitting the virus and delaying the advancement of their own illness, according to a new study.
The gene in question is Chromodomain Helicase DNA Binding Protein 1 Like (CHD1L), which contains information to make proteins that allow the body to repair DNA damage.
A variant of the CHD1L gene, specifically present in the African population, has been linked to the reduced viral load (amount of HIV in the blood) of the most common and virulent type of HIV, called HIV-1 (more common and severe retrovirus compared to HIV-2), the study published in journal Nature on August 2, 2023, noted.
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“We searched for human genetic variation that associates with spontaneous control of HIV and identified a novel region in the genome that is only variable in populations of African ancestries,” Jacques Fellay, professor at EPFL’s School of Life Sciences, Switzerland and an author of the study, said in a statement.
HIV-1 affects an estimated 37.7 million people worldwide. Despite antiretroviral therapy bringing down annual HIV cases, the decline has slowed substantially since 2005, the researchers said.
In 2021, for instance, some 1.5 million people contracted the infection and 650,000 people died from AIDS-related illnesses despite improvements in treatment.
“African populations are still drastically underrepresented in human DNA studies, despite experiencing the highest burden of HIV infection,” Paul McLaren from the Public Health Agency of Canada’s National Microbiology Laboratory, joint first author, said in a statement.
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To look for new therapeutic targets, researchers from multiple institutions began looking for gene variants that are linked to the progression of the disease.
They analysed the DNA of almost 4,000 people of African ancestry living with HIV-1 and found a gene variant CHD1L on chromosome 1. People carrying this variant had a low viral load. This lowers their risk of spreading the virus and slowing the progress of their own illness.
The researchers said between 4 per cent and 13 per cent of people of African origin could be carrying this particular variant.
By studying a large sample of people of African ancestry, he added, the researchers have been able to identify a new genetic variant that only exists in this population and which is linked to lower HIV viral loads. However, they don’t yet understand how it produces lower viral loads in patients.
The team also carried out a few laboratory tests by growing cells that either had the CHD1L gene activity turned on or off. Next, they infected these cells with HIV. They found that the virus made more copies of itself when CHD1L was turned off in immune cells called macrophages.
But there was no change in T cells, another type of immune cells. Most HIV, according to the researchers, replicates in T cells. However, research has also shown that macrophages can sustain HIV replication in the absence of T cells.
“The link between HIV replication in macrophages and viral load is particularly interesting and unexpected,” Harriet Groom from the University of Cambridge noted. The researchers now hope to understand how this variant controls the viral load.
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