ACE2	angiotensin-converting enzyme 2
ADEVs	astrocyte-derived EVs
AG-GIR	Autonomie Gérontologie Groupes Iso-Ressources
ATP	adenosine triphosphate
Ba	fragment of complement factor B that results from activation of the alternative pathway
B cell	B lymphocytes
BEVs	blood extracellular vesicles
C5a	complement component 5a; protein fragment released from the cleavage of complement component C5 by protease C5-convertase into C5a and C5b fragments
Ca2+	calcium ions
CMV	cytomegalovirus
CCL18	chemokine ligand 18 (PARC).
COVID-19	coronavirus disease 2019
CNS	central nervous system
CRM	rehabilitation center
CRP	C-reactive protein
CX3CR 3	CX3C motif chemokine receptor 3
DAMP	damage-associated molecular pattern
DNA	deoxyribonucleic acid
DNM1L	dynamin-1-like protein
ELISA	enzyme-linked immunosorbent assays
EV	extracellular vesicle
ESPA	European Spa Rehabilitation Association
ETC	electron transport chain
EWGSOP2	European Working Group on Sarcopenia in Older People
FHWs	first-line healthcare workers
HBMECs	human brain microvascular endothelial cells
HCs	healthy controls
HIV	human immunodeficiency virus
HLA	human leukocyte antigen
HHV-6	human herpesvirus 6
HHV-7	human herpesvirus 7
HPBMC	human peripheral blood mononuclear cells
HUVEC	human umbilical vascular endothelial cells
GLIM	Global Leadership Initiative on Malnutrition
GSH	glutathione
iC3b	protein fragment part of the complement system, produced when complement factor I cleaves C3b
Ig	immunoglobulin
IgA	immunoglobulin A
IgG	immunoglobulin G
IgM	immunoglobulin M
ICAM	intercellular adhesion molecule
ICU	intensive care unit
IFN	interferon
IFN-α	interferon alpha
IP-10	IFN-gamma-inducible protein 10 (IP-10, CXCL10)
IFN-γ	interferon-gamma
IL-1, IL-6, IL-8, IL-10, IL-12, IL-12p70, IL-15	interleukin 1, 6, 8, 10, 12, 12p70, 15, 18, 27
IL-1α	interleukin 1α
IL-1β	interleukin 1β
ITIM	immunoreceptor tyrosine-based inhibitory motif
LC	long COVID
LBP	lipopolysaccharide-binding protein
LTC	long-term care
MAVS	mitochondrial antiviral-signaling protein
ΔΨm	mitochondrial membrane potential
MPs	mitochondrial proteins
MFN2	mitofusin-2
Mo	monocyte
MR	mountain spa rehabilitation
ME/CFS	myalgic encephalomyelitis/chronic fatigue syndrome
mtDAMPs	damage-associated molecular patterns
mtDNA or mDNA	mitochondrial DNA
N	nucleoprotein
NAD+	nicotinamide adenine dinucleotide
NK	natural killer
NDEVs	neuron-derived extracellular vesicles
NIHR	National Institute for Health Research
NIH	National Institutes of Health
NF-κB	nuclear factor kappa-light-chain-enhancer of activated B cells
NLRP3	NLR family pyrin domain containing 3
NMN	nicotinamide mononucleotide
NP	neuropsychiatric manifestations
NR	nicotinamide riboside
OXPHOS	oxidative phosphorylation or electron transport-linked phosphorylation
PAMP	pathogen-associated molecular pattern
PASC	post-acute sequelae of COVID-19
PBMC	peripheral blood mononuclear cells
PCR	polymerase chain reaction
PC	post-COVID syndrome
PCC	post-COVID-19 condition
PD-1	programmed cell death protein 1
PD-L1	programmed cell death protein ligand 1
PD-L2	programmed cell death protein ligand 2
PELORA	PEnalized logistic regression analysis
PMN	polymorphonuclear
PINK1	PTEN-induced kinase 1
RPs	recovered patients
RBD	receptor binding domain
RT-qPCR	real-time quantitative reverse transcription PCR
ROS	reactive oxygen species
RBD	receptor binding domain
T cell	T lymphocytes
Tregs	regulatory T lymphocytes
RAS	renin–angiotensin system
RT-PCR	reverse transcriptase polymerase chain reaction
RNA	ribonucleic acid
S	spike protein
sRAGE	advanced glycation end product
SARS	severe acute respiratory syndrome
SAA	serum amyloid A
SARS-CoV-2	severe acute respiratory syndrome coronavirus 2
SCFAs	short-chain fatty acids
SHWs	second-line healthcare workers
SOD	superoxide dismutase
TBARS	thiobarbituric acid-reactive substances
TCA cycle	tricarboxylic acid cycle
TCC	terminal complement complex or membrane attack complex (MAC)
TIGIT	T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains
TEVs	total extracellular vesicles
Th1	T-helper 1 or T-helper type 1
Th2	T-helper 2 or T-helper type 2
Th17	T-helper 17 or T-helper type 17
TJs	tight junctions
TLR2	toll-like receptor 2
TLR4	toll-like receptor 4
TLR	toll-like receptors
TLR7	toll-like receptor 7
TMPRSS2	transmembrane serine protease 2
TMPRSS4	transmembrane serine protease 4
TNF-α	tumor necrosis factor alpha
TGF-β	transforming growth factor-β
TKI	tyrosine kinase inhibitors
US	United States
FDA	U.S. Food and Drug Administration
UK	United Kingdom
UKRI	UK Research and Innovation
VCAM-1	vascular cell adhesion molecule 1
WHO	World Health Organization
Increased	↑
Decreased	↓
Present	+
Absent/Missing	-