Scientists have taken a step closer to understanding how some rare people’s immune systems can suppress HIV.
The innate immune response mounts a fast-acting, general response against pathogens or supports the adaptive immune response, made up of antibodies and T cells that learn to fight specific pathogens after infection or vaccination
In recent years, researchers discovered that some components of the innate immune response can, under certain conditions, also be trained in response to infectious pathogens, such as HIV.
In a study recently published in the Journal of Clinical Investigation, it was shown that elite controllers, a rare subset of people whose immune system can control HIV without the use of drugs, have myeloid dendritic cells, part of the innate immune response, that display traits of a trained innate immune cell.
“Using RNA-sequencing technology, we were able to identify one long-noncoding RNA called MIR4435-2HG that was present at a higher level in elite controllers’ myeloid dendritic cells, which have enhanced immune and metabolic states,” explained Xu Yu, MD, a Core Member of the Ragon Institute of MGH, MIT and Harvard. “Our research shows that MIR4435-2HG might be an important driver of this enhanced state, indicating a trained response.”
Myeloid dendritic cells’ main role is the support of T cells, which are key to the elite controllers’ ability to control HIV infection. Since MIR4435-2HG was found to be higher only in the cells of elite controllers, Dr Yu explained, it may be part of a learned immune response to infection with HIV. Myeloid dendritic cells with elevated MIR4435-2HG also had greater levels of a protein known as RPTOR, which drives metabolism. Because of this boosted metabolism, the myeloid dendritic cells may better support the T cells controlling the HIV infection.
“We used a novel sequencing technology, called CUT&RUN, to study the DNA of these cells,” says postdoctoral fellow Ciputra Hartana, MD, Ph.D., the paper’s first author. “It allowed us to study epigenetic modifications like MIR4435-2HG, which are molecules that bind to the DNA and change how, or if, the DNA is read by the cell’s machinery.”
The team found that MIR4435-2HG’s mechanism could function by attaching to the DNA near the location of the RPTOR gene. The bound MIR4435-2HG would then prompt cellular machinery to synthesise more RPTOR protein, from the instructions in the RPTOR gene. This kind of epigenetic modification, a ‘trained’ response to HIV infection, would keep the myeloid dendritic cells in a state of heightened metabolism, providing long-term support to the T cells battling the virus.
“Myeloid dendritic cells are very rare immune cells, accounting for only 0.1-0.3% of cells found in human blood,” said Dr Yu. “We were fortunate and thankful to have access to hundreds of millions of blood cells from the many study participants who have donated their blood to support our HIV research. These donations were key to making this discovery.”
A core component of HIV cure research is to figure out exactly how elite controllers’ immune systems can keep HIV under control. By understanding how elite controllers keep the deadly virus in check, scientists could develop treatments to enable other people living with HIV to replicate the same immune response. This would take away the need for daily medication to control the virus, achieving what is known as a ‘functional cure’.
Source: Medical Xpress
Journal information: Ciputra Adijaya Hartana et al, Long noncoding RNA MIR4435-2HG enhances metabolic function of myeloid dendritic cells from HIV-1 elite controllers, Journal of Clinical Investigation (2021). DOI: 10.1172/JCI146136