Senolytics Reshape CD8 T Cell Responses in Aged Vaccinated Mice Without Boosting Flu Protection
Dasatinib and quercetin altered influenza-specific CD8 T cell immunodominance and raised antibody levels in aged vaccinated mice, but did not improve overall flu outcomes.
Summary
Researchers tested whether the senolytic combination dasatinib and quercetin (D+Q) could enhance influenza vaccine responses in aged mice. Administered before vaccination and flu challenge, D+Q did not significantly improve antibody titers, CD4 T cell counts, weight loss protection, viral load, or lung pathology. However, D+Q treatment did meaningfully alter the CD8 T cell immunodominance hierarchy during active infection and elevated total PR8-specific serum IgG antibodies in vaccinated aged mice. These findings suggest senolytics can reshape specific immune responses during infection without translating into measurable improvements in overall flu disease outcomes, revealing nuanced immunomodulatory effects that warrant further investigation.
Detailed Summary
Older adults suffer disproportionately from influenza, accounting for roughly 90% of flu-related deaths, partly because aging impairs both natural immunity and vaccine-induced protection. The accumulation of senescent cells with age drives chronic low-grade inflammation (inflammaging) that disrupts the tissue microenvironment and degrades immune cell function across B cells, CD4 T cells, and CD8 T cells. Senolytics—drugs that selectively eliminate senescent cells—have shown promise in improving outcomes for certain infections, but their potential to boost vaccine responses in aged individuals had not previously been tested.
In this study, young (3–5 months) and aged (18–20 months) C57BL/6JN male mice received oral gavage with dasatinib (5 mg/kg) and quercetin (50 mg/kg) or vehicle prior to vaccination with influenza nucleoprotein (NP) plus alum adjuvant and a subsequent booster. Mice were then challenged with a sublethal dose of PR8 H1N1 influenza virus. Immune responses were assessed via ELISA for serum antibodies, flow cytometry with MHC II and MHC I tetramers for antigen-specific T cells, and lung histopathology and viral load measurements at multiple timepoints during infection.
D+Q treatment did not significantly improve NP-specific serum IgG titers or the total number and frequency of NP-specific splenic CD4 T cells 30 days post-vaccination in aged mice. During flu challenge, vaccinated aged mice were partially protected from weight loss compared to unvaccinated aged controls, but D+Q did not further enhance this protection. Viral load and lung pathology were similarly unaffected by senolytic treatment. Minor kinetic alterations in NP-specific CD4 T cell subsets (Tregs, Tfh, Th2, Tfr) were observed in the mediastinal lymph node of D+Q-treated vaccinated aged mice, but these did not reach significance at the frequency level and did not propagate to the lung compartment.
The most notable finding was that D+Q treatment significantly altered CD8 T cell immunodominance during active flu infection in vaccinated aged mice. The hierarchical ranking of CD8 T cell responses to different flu epitopes was reshuffled, with some subdominant epitopes becoming more prominent. Additionally, total PR8-specific serum IgG antibodies were elevated in D+Q-treated vaccinated aged mice during infection, suggesting enhanced de novo antibody responses to live virus. These changes were immunologically significant but did not translate into measurable improvements in flu disease severity or outcomes.
The study highlights that senolytic treatment can produce specific, context-dependent immunomodulatory effects in aged hosts, particularly on CD8 T cell response architecture and antibody production during active infection, without broadly rescuing age-impaired vaccine efficacy. The authors caution that the male-only mouse cohort, single vaccination antigen (NP), and sublethal challenge model may limit generalizability. Future work should explore whether these CD8 T cell and antibody shifts could be leveraged with optimized senolytic dosing schedules, different vaccine formulations, or in combination with other immune-boosting strategies.
Key Findings
- D+Q senolytic treatment prior to flu NP vaccination did not significantly improve NP-specific serum IgG or CD4 T cell responses in aged mice.
- Vaccinated aged mice were partially protected from flu-induced weight loss, but D+Q did not enhance this protection beyond vaccination alone.
- D+Q treatment altered CD8 T cell immunodominance hierarchy during active influenza infection in vaccinated aged mice.
- Total PR8-specific serum IgG antibodies were elevated in D+Q-treated vaccinated aged mice during infection, suggesting enhanced de novo responses.
- Viral load and lung pathology were unaffected by senolytic treatment, meaning overall flu outcomes were not improved.
Methodology
Young (3–5 months) and aged (18–20 months) male C57BL/6JN mice received oral D+Q or vehicle before NP+alum vaccination and booster, then were challenged with sublethal PR8 H1N1 influenza. Immune responses were measured via ELISA, MHC tetramer-based flow cytometry, viral load assays, and lung histopathology at multiple timepoints post-infection.
Study Limitations
The study used only male mice and a single viral antigen (NP), which may limit generalizability to females and whole-virus vaccine formulations used clinically. The sublethal challenge model and specific mouse strain may not fully recapitulate the immunological context of human aging and influenza disease. Mechanistic pathways driving the CD8 T cell immunodominance shift and elevated antibodies remain incompletely characterized.
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