Unveiling the viral dimension: The paediatric gut virome as a key modulator of gastrointestinal metabolic, and neurodevelopmental health

Table 6 Systemic and extra-intestinal effects

Condition	Primary virome alterations (effects)	Putative biological mechanism
Obesity and insulin resistance	Reduced viral diversity; altered phage-to-bacteria ratios	Metabolic supervision: Phages modulate the abundance of SCFA-producing bacteria, influencing energy harvest and systemic lipid metabolism
Type 1 diabetes	Enteroviral persistence; altered phage communities	Molecular mimicry and priming: Enteroviruses may directly target beta cells, while phages prime the innate immune system toward pancreatic autoimmunity
Neurodevelopment (ASD/ADHD)	Distinct viral “fingerprints”; reduced phage diversity	Microglial activation: Gut-derived viral signals influence neuroinflammation and aberrant synaptic pruning during critical developmental windows
Allergy and asthma	Low infantile viral diversity; absence of “Old Friend” commensal viruses	Th2 skewing: Lack of viral-driven Th1/Treg induction prevents the correction of neonatal Th2 bias; disrupted Gut-Lung Axis signaling

ASD/ADHD: Autism spectrum disorders/attention deficit hyperactivity disorders; SCFA: Short-chain fatty acids; Th1: T-helper 1 lymphocyte; Th2: T-helper 1 lymphocyte.