Inside the arteries of a person with HIV, a small fire smolders that does not go out even with medication. That fire is inflammation, and a new study shows it is kept alive by special immune cells that process vitamin A. Researchers compared the blood of people with and without HIV. Those with HIV had more monocytes with high activity of the enzyme ALDH. Monocytes are large immune cells in the blood, and the enzyme ALDH turns vitamin A into an active form that ramps up inflammation.
The link turned out to be direct: the more monocytes with active enzyme in the blood, the thicker the fatty deposits in the heart's arteries. In people without HIV, there was no such link. The blood of patients with HIV also had more of the active form of vitamin A and of the protein that carries it. This protein also correlated with the volume of deposits.
It is now clear that the smoldering fire in the arteries of people with HIV is kept alive by monocytes with high ALDH activity and an excess of vitamin A. No drug has yet been devised that would put out this fire, but researchers already know where to look. Perhaps in the future there will be medications that calm these cells and protect the heart.
The enzyme ALDH, which turned out to be linked to atherosclerosis in people with HIV, also handles alcohol metabolism: its inactive form causes facial flushing after drinking alcohol. In this study, its activity was measured in monocytes, not in the liver, where it works on alcohol.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.