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This page is general educational information for researchers and laboratory staff. It is not medical advice and does not describe any treatment for an individual patient.
Short answer: what is a neoantigen?
A neoantigen is a new protein feature that appears on tumour cells because of mutations in tumour DNA. The immune system can see it as foreign because it is absent from normal cells. The National Cancer Institute defines it in similar terms in its Dictionary of Cancer Terms. Laboratories identify neoantigens by comparing tumour and normal sequence data, then predicting which mutated peptides a patient’s immune molecules could present.
Definition and scope
Blass and Ott (Nature Reviews Clinical Oncology, 2021) describe neoantigens (also called neoepitopes) as novel epitopes of self-antigens created by tumour mutations. They can come from point mutations, insertions and deletions, and gene fusions. In virus-driven tumours, viral proteins can also act as neoantigens.
The key property is tumour specificity. The review describes neoantigens as expressed exclusively by tumour cells, which means they may avoid the central tolerance that limits responses to normal self-proteins, and may carry a lower risk to healthy tissue.
How neoantigens are identified in practice
The same review describes the workflow used for personalised neoantigen-based vaccines. The discovery steps are the part most relevant to laboratory planning:
- Paired samples. A tumour sample and a normal sample, usually blood cells (PBMC), are compared so that somatic mutations can be called against the patient’s normal genome.
- Whole-exome sequencing of the tumour and normal samples to identify somatic mutations.
- RNA sequencing of the tumour to confirm that the mutated gene is expressed.
- HLA typing, because a peptide is presented by the patient’s own HLA molecules (HLA restriction).
- Computational prediction. Algorithms predict MHC class I binding, with moderate-to-strong predicted affinity favoured for CD8+ T-cell responses. Newer tools add antigen processing and presentation rules and mass spectrometry data.
- Prioritisation of candidate peptides for downstream use.
For vaccines, the review lists synthetic long peptides, RNA, DNA, dendritic cells and viral vectors as formulation options, often combined with checkpoint inhibitors, with CD4+ and CD8+ T-cell responses monitored afterwards. It names the cost and manufacturing time of an individualised vaccine as limitations.
Neoantigens versus tumour-associated antigens
Blass and Ott contrast neoantigens with tumour-associated antigens (TAAs), the earlier vaccine target class.
| Feature | Tumour-associated antigen (TAA) | Neoantigen |
|---|---|---|
| What it is | A self-antigen abnormally expressed or overexpressed in tumours | A novel epitope created by a tumour mutation |
| Expression | Self-antigen, so a normal protein is the target | Exclusively expressed by tumour cells |
| Tolerance | T-cell tolerance is a probable reason early TAA vaccines largely failed | May bypass central tolerance |
| Risk to healthy tissue | Not described as reduced | May be lower |
Where it matters for labs
Neoantigen work links several bench disciplines: sequencing, HLA typing, bioinformatics, peptide or RNA production, and immune monitoring. Preclinical teams often work with mouse tumour models; see the CASRAI guides to the MC38 cell line, the CT26 cell line and NSG mice. Antibody-based reagents rely on structure covered in the Fc domain of an antibody. For the wider clinical field, see what is oncology.
Common misunderstandings
- Predicted binding is not proof of immune recognition. Prediction workflows mostly score MHC binding; whether a T cell recognises the peptide is a separate question.
- Mutation burden is not neoantigen count. Tumour mutational burden is an imperfect proxy for neoantigen load and response, and clonality also matters.
- The best platform is not settled. Optimal neoantigen discovery and delivery platforms remain open questions in the literature.
FAQ
What is a neoantigen?
A new protein feature on tumour cells caused by tumour DNA mutations, absent from normal cells, which the immune system can treat as foreign (NCI Dictionary of Cancer Terms; Blass and Ott 2021).
What are the three types of immunotherapy?
The NCI does not list three; its immunotherapy page names five types: immune checkpoint inhibitors, T-cell transfer therapy, monoclonal antibodies, treatment vaccines and immune system modulators. Neoantigen-based vaccines fall under treatment vaccines, which strengthen the immune response against existing cancer cells.
Can antigens be harmful?
An antigen is a target the immune system can recognise; harm arises from the immune response rather than the antigen itself. The NCI notes that immunotherapy side effects often occur when the activated immune system also attacks healthy cells and tissues, which is why target specificity matters in neoantigen research. For personal health questions, consult a clinician.
Is immunotherapy more aggressive than chemotherapy?
The NCI immunotherapy page does not rank immunotherapy against chemotherapy, and no blanket ranking is supported here. Side effects depend on the specific treatment. Questions about a particular treatment belong with the treating team.
Sources
- Blass E, Ott PA. Advances in the development of personalized neoantigen-based therapeutic cancer vaccines. Nat Rev Clin Oncol 2021;18(4):215-229. PMC7816749 (read 2026-11-07)
- National Cancer Institute. Types of cancer treatment: Immunotherapy. cancer.gov (read 2026-11-07)
- National Cancer Institute. NCI Dictionary of Cancer Terms: neoantigen. cancer.gov (checked 2026-11-07)
