Genetic and Metabolic Markers
of BH4 Deficiency in Long COVID

The study expands on a previously-awarded proposal to thoroughly explore the underlying pathophysiology of post exertional malaise (PEM), the hallmark symptom of ME/CFS.

  • Laurel Crosby, PhD
  • Ronald W. Davis, PhD
  • Ongoing recruitment of 300 volunteers with Long COVID for BH4 genotyping, and development of LIMS software for sample management.
  • Development of a simplified BH4@Home test kit for metabolomics and urine amino acids, comparing 50 cases and 50 healthy controls.
  • Finalized development of HPLC methods to get good separation of biopterin peaks for proper quantification of BH4, BH2 and biopterin species. Now testing the effects of freezer storage on analyte stability, alongside quantification of BH4/BH2 and biopterin in study specimens.
  • Design and validation of custom blood tubes with BH4 stabilizing reagents.
  • Discovery that “creatinine” is a variable metabolite in urine specimens, which means that it should not be used as an internal reference in urine.
STUDY HYPOTHESIS AND DESCRIPTION

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.

OBJECTIVES

3D illustration. Genetic test in test tube.

  • Conduct a 1-year Genotyping study on 300 individuals with Long Covid, recruited from the Patient-Led Research Collaborative and other patient registries for Long Covid.
  • Invite 50 individuals with the affected GCH1 genotypes and 50 healthy age- and gender-matched controls to participate in tests to:
  • Measure plasma metabolites for a characteristic signature of BH4 deficiency
  • Conduct a physiology assessment of BH4-dependent Vascular Reactive Index using Digital Thermal Monitoring.