Hypothesis

It's known that senescent immune cells in gut‑associated lymphoid tissue secrete SASP factors that reshape the luminal microbiome toward LPS‑rich taxa, which in turn fuels systemic inflammaging and microglial activation. We hypothesize that targeted depletion of LPS‑producing bacteria with gut‑restricted bacteriophages will interrupt this loop, reduce circulating endotoxin, lower senescence‑associated cytokine production, and restore neuroimmune homeostasis.

Rationale

Aging immune cells accumulate in Peyer’s patches and mesenteric lymph nodes, where they release IL‑6, TNF‑α and IL‑1β that alter epithelial mucus secretion and antimicrobial peptide patterns. This creates a niche favoring Enterobacteriaceae and other LPS‑rich anaerobes. Elevated LPS translocates across a compromised barrier, triggering TLR4 signaling on peripheral monocytes and brain microglia, which amplifies SASP production in a feed‑forward circuit. Breaking the microbial arm should therefore dampen the immune senescence driver.

Predictions

• Aged mice receiving oral LPS‑specific phage will show a >50 % reduction in fecal LPS‑encoding gene copies within 7 days.
• Plasma TNF‑α, IL‑6 and IL‑1β will decline to levels comparable to young controls after 2 weeks.
• Flow cytometry of splenic and cerebral CD8⁺ T cells will reveal a ≥30 % decrease in p16^INK4a^‑positive senescent cells.
• Microbiome sequencing will reveal a relative increase in butyrate‑producing Clostridia and a decrease in Proteobacteria.
• Behavioral assays (sucrose preference, forced swim) will demonstrate improved mood‑like performance correlating with cytokine reductions.

Experimental Design

• Use 20‑month‑old C57BL/6 mice (n = 12 per group). Groups: (1) phage cocktail targeting LPS‑rich Escherichia coli and Klebsiella spp.; (2) placebo saline; (3) young 3‑month‑old baseline.
• Administer phage orally daily for 14 days; confirm gut restriction by quantifying phage in blood (<10² PFU mL⁻¹).
• Collect feces, plasma, spleen, and brain tissue at days 0, 7, 14.
• Measure LPS‑encoding qPCR, cytokine ELISA, senescence markers (p16, SA‑β‑gal), microglial Iba1 activation, and conduct behavioral tests.
• Perform 16S rRNA sequencing to assess taxonomic shifts.

Potential Outcomes

If predictions hold, the data will support a model where microbiome‑targeted phage therapy ameliorates immune senescence and neuroinflammaging, suggesting a geroprotective strategy independent of senolytics. Failure to observe cytokine or senescence reductions despite microbiome shifts would falsify the hypothesis, indicating that immune senescence drives dysbiosis rather than the reverse.

Falsifiability

A clear falsification criterion: no significant change (p > 0.05) in plasma TNF‑α/IL‑6 or senescent T‑cell frequency after phage treatment despite confirmed LPS reduction would reject the proposed causal direction.