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Immunotherapy and Immune Responses / Chemokine Receptors and Signaling · Journal article
The Journal of Immunology · July 28, 2026
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In a murine lung adenocarcinoma model, neoantigen-specific mRNA vaccination induced functionally competent CX3CR1+ effector CD8+ T cells in the spleen within one week, but these cells remained predominantly in the lung vasculature with limited infiltration into tumor tissue. This suggests that poor effector cell recruitment from the vasculature, rather than defective priming or cytotoxic capacity, may limit the anti-tumor efficacy of mRNA vaccination alone.
Controlled murine mechanistic study. Tumor-bearing mice with engineered lung adenocarcinoma; naïve recipient mice for adoptive transfer studies.. Intervention: Intramuscular neoantigen-encoding mRNA vaccination.
Strong neoantigen-specific CD8+ cell presence in spleen one week post-vaccination, predominantly CX3CR1+ short-lived effectors Vaccine-primed effector cells mainly localized to lung vasculature with limited tissue infiltration 99% of transferred neoantigen-pulsed splenocytes cleared from spleen within 20 hours in naïve mice
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These findings suggest that clinical mRNA neoantigen vaccines may prime effective CD8+ responses but encounter a recruitment barrier limiting tumor infiltration. Future clinical strategies may need to combine mRNA vaccination with interventions enhancing effector cell homing or migration into the tumor microenvironment.
Mechanistic murine study with flow cytometry and imaging endpoints identifying a potential barrier to mRNA vaccine efficacy; results are hypothesis-generating rather than definitive for clinical practice.
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These findings suggest that clinical mRNA neoantigen vaccines may prime effective CD8+ responses but encounter a recruitment barrier limiting tumor infiltration. Future clinical strategies may need to combine mRNA vaccination with interventions enhancing effector cell homing or migration into the tumor microenvironment.
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Abstract Introduction Recent clinical trials have shown that messenger RNA vaccination against neoantigens can activate long-lasting CD8+ T cells against solid tumors. However, frequent doses appear to be needed to maintain this response. It is uncertain whether vaccination alone reliably recruits effector cells into tumors, particularly when antigen expression is low. We hypothesize that mRNA vaccination primes anti-tumor CD8+ cells, but this alone is not sufficient to recruit and sustain these cells within tumors. Methods We used a murine lung adenocarcinoma model; intratracheal lentiviral Cre recombinase was used to initiate KrasG12D/+; Trp53-/- tumors expressing two neoantigens. Mice were dosed intramuscularly with neoantigen-encoding mRNA. We analyzed CD8+ cell trafficking via flow cytometry, in vivo cytotoxicity assays, ex vivo transwell assays, and immunohistochemistry. Intravenous fluorescent labeling was used to track CD8+ T cell recruitment into tumors. Results In tumor-bearing mice, we observed a strong presence of neoantigen-specific CD8+ cells in the spleen one week post-vaccination. The majority of these cells were CX3CR1+ short-lived effectors. This was not seen among other antigen-experienced CD8+ cells in the spleen. However, these vaccine-primed effector cells mainly localized to the lung vasculature with limited tissue infiltration. In naïve mice, 99% of transferred neoantigen-pulsed splenocytes were cleared from the spleen within 20 hours. Conclusion Our data suggest that mRNA vaccination activates a strong effector population capable of clearing targets presenting neoantigens. However, these cells are ineffectively recruited from the vasculature, a potential barrier to strong anti-tumor immunity. We believe this is either due to a natural progression into short-lived effector cells after priming or inadequate signaling for tissue entry. Our current work aims to explore whether introducing a pro-migratory chemokine axis in the lung may improve recruitment of vaccine-primed cells into tumors. Funding Source NIH T32 Training Grant Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)
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