Genetic and Metabolic Markers
of BH4 Deficiency in Long COVID

Tetrahydrobiopterin (BH4) is a vitamin-like cofactor that is made in the body by a series of enzymatic steps. However, there are common mutations in the biosynthesis pathway that are associated with cofactor deficiency. BH4 is needed for metabolism of a small number of amino acids that are precursors to neurotransmitters, and deficiency leads to cognitive impairment and a wide variety of other symptoms associated with neurotransmitter imbalance. BH4 is also needed for the enzyme nitric oxide synthase, which is a major regulator of blood flow dynamics and immune cell function.

We have determined that individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome are more likely to have pathogenic variants in BH4 synthesis genes compared to the general population, and we have also identified a corroborating metabolic signature that predicts BH4 deficiency. Oxidative stress during infection can also lead to BH4 deficiency, so there are many potential routes to the same problem. We propose to test whether these genetic markers and other indicators of BH4 deficiency are also present in subjects with Long Covid. If we are successful, we will show that ME/CFS and Long Covid have a common underlying disease mechanism that includes deficiency of BH4.