MIT researchers engineered a harmless M13 bacteriophage into a nanofiber that can display cancer antigens with tunable density. By appending one or two negatively charged amino acids to the pVIII coat protein, they increased the number of antigen copies per filament, and a production‑slowing mutation allowed finer control. They also rewired the phage genome so that its single‑stranded DNA triggers the TLR9 pathway, giving the particle intrinsic adjuvant activity without external compounds. In mouse studies, the team presented the model antigen SIINFEKL at densities ranging from 6% to 70%; the 35% formulation generated the strongest CD8⁺ T‑cell response and most effectively prevented melanoma growth. A separate experiment used the colon‑tumor‑specific neoantigen ADPGK, and the high‑density vaccine markedly reduced tumor incidence. Because the system is modular, any tumor‑associated antigen can be swapped in, enabling truly personalized cancer vaccines. Funding came from the Koch Institute Frontier Research Program, the Marble Center for Cancer Nanomedicine, and the U.S. DARPA.
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