Participants were randomly assigned to receive weekly injections of the antibody or a saline placebo for eight weeks, over which time they tracked any changes in 24 symptoms associated with long COVID, which also included loss of smell and taste, muscle and joint pain, and brain fog.

The researchers originally thought that blocking CCR5 with the antibody would dampen the activity of an overactive immune system after COVID-19 infection.

"But we found just the opposite," Yang said. "Patients who improved were those who started with low CCR5 on their T cells, suggesting their immune system was less active than normal, and levels of CCR5 actually increased in people who improved. This leads to the new hypothesis that long COVID in some persons is related to the immune system being suppressed and not hyperactive , and that while blocking its activity, the antibody can stabilize CCR5 expression on the cell surface leading to upregulation of other immune receptors or functions."

The findings, the researchers write, "suggests a complex role for CCR5 in balancing inflammatory and anti-inflammatory effects, e.g. through T regulatory cells," although the results need to be confirmed in a larger, more definitive study.

https://academic.oup.com/cid/advance-article/...26/6572226