AAD	Antibiotic-associated diarrhea
ACE2	Angiotensin-converting enzyme 2
AMPs	Antimicrobial peptides
APCs	Antigen-presenting cells
CD	Crohn’s disease
CFS	Chalder Fatigue Scale
CFU	Colony forming unit
CNS	Central nervous system
FAO	Food and Agriculture Organization
GI	Gastrointestinal
GPR	G protein-coupled receptors
HAM-D	Hamilton Rating Scale for Depression
HDAC	Histone deacetylases
HIV	Human immunodeficiency virus
HPA	Hypothalamic–pituitary–adrenal
HSV	Human simplex virus
IBD	Inflammatory Bowel Disease
IBS	Irritable bowel syndrome
IFN	Interferon
IgA	Immunoglobulin class A
IL	Interleukin
IRF	Interferon regulatory factor
LAB	Lactic acid bacteria
LPS	Lipopolysaccharides
MV	Measles virus
NF-κB	Nuclear factor kappa B
NK	Natural killer
NLRs	NOD-like receptors
PACS	Post-acute COVID-19 syndrome
PCS	Post-COVID-19 syndrome
PGF	Placental growth factor
POTS	Postural orthostatic tachycardia syndrome
PRRs	Pattern recognition receptors
PV	Poliomyelitis virus
RBD	Receptor binding protein
S	Spike
s.l.	Sensu lato
SARS-CoV-2	Severe Acute Respiratory Syndrome Coronavirus 2
SCAFs	Short-chain fatty acids
SIP	sphingosine-1-phosphate
TJ	Tight junction
TLRs	Toll-like receptors
UC	Ulcerative colitis
VOCs	Variants of concern
VSV	Vesicular stomatitis virus
VUM	Variant under monitoring
WHO	World Health Organization
ZO	Zonula occludens