Malato, JoãoSotzny, FranziskaBauer, SandraFreitag, HelmaFonseca, AndréGrabowska, Anna D.Graça, LuísCordeiro, ClaraNacul, LuísLacerda, Eliana M.Castro-Marrero, JesusScheibenbogen, CarmenWestermeier, FranciscoSepúlveda, Nuno2021-09-152021-09-152021-08http://hdl.handle.net/10400.1/17119People with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often report a high frequency of viral infections and flu-like symptoms during their disease course. Given that this reporting agrees with different immunological abnormalities and altered gene expression profiles observed in the disease, we aimed at answering whether the expression of the human angiotensin-converting enzyme 2 (ACE2), the major cell entry receptor for SARS-CoV-2, is also altered in these patients. In particular, a low expression of ACE2 could be indicative of a high risk of developing COVID-19. We then performed a meta-analysis of public data on CpG DNA methylation and gene expression of this enzyme and its homologous ACE protein in peripheral blood mononuclear cells and related subsets. We found that patients with ME/CFS have decreased methylation levels of four CpG probes in the ACE locus (cg09920557, cg19802564, cg21094739, and cg10468385) and of another probe in the promoter region of the ACE2 gene (cg08559914). We also found a decreased expression of ACE2 but not of ACE in patients when compared to healthy controls. Accordingly, in newly collected data, there was evidence for a significant higher proportion of samples with an ACE2 expression below the limit of detection in patients than healthy controls. Altogether, patients with ME/CFS can be at a higher COVID-19 risk and, if so, they should be considered a priority group for vaccination by public health authorities. To further support this conclusion, similar research is rec ommended for other human cell entry receptors and cell types, namely, those cells targeted by the virus.engMyalgic encephalomyelitis/chronic fatigueSyndromeSARS-CoV-2ACE2Gene expressionDNA methylationjournal article10.1016/j.heliyon.2021.e076652405-8440