Reducing junction epitope presentation for neoantigens
Given a set of therapeutic epitopes, a cassette sequence is designed to reduce the likelihood that junction epitopes are presented in the patient. The cassette sequence is designed by taking into account presentation of junction epitopes that span the junction between a pair of therapeutic epitopes in the cassette. The cassette sequence may be designed based on a set of distance metrics each associated with a junction of the cassette. The distance metric may specify a likelihood that one or more of the junction epitopes spanning between a pair of adjacent epitopes will be presented.
1. A method of identifying a cassette sequence for a neoantigen vaccine, comprising:
obtaining, for a subject, data representing peptide sequences of each of a set of neoantigens, wherein the peptide sequence of each neoantigen comprises at least one alteration that makes it distinct from a corresponding wild-type, parental peptide sequence identified from normal cells of the subject and includes information regarding a plurality of amino acids that make up the peptide sequence and a set of positions of the amino acids in the peptide sequence;
inputting the data representing peptide sequences of the neoantigens, using a computer processor, into a machine-learned presentation model to generate a set of numerical presentation likelihoods for the set of neoantigens, each presentation likelihood in the set representing the likelihood that a corresponding neoantigen is presented by one or more MHC alleles on the surface of tumor cells of the subject, the machine-learned presentation model comprising:
a plurality of parameters identified at least based on a training data set comprising:
a label obtained by mass spectrometry measuring presence of peptides presented by at least one MHC allele in a set of MHC alleles identified as present in each sample in a set of samples;
for each of the samples, training peptide sequences including information regarding a plurality of amino acids that make up the training peptide sequences and a set of positions of the amino acids in the training peptide sequences; and
identifying, for the subject, a treatment subset of neoantigens from the set of neoantigens, the treatment subset of neoantigens comprising a predetermined number of neoantigens having presentation likelihoods above a predetermined threshold; and
identifying, for the subject, the cassette sequence comprising a sequence of concatenated therapeutic epitopes that each include the peptide sequence of a corresponding neoantigen in the treatment subset of neoantigens, wherein identifying the cassette sequence comprises:
inputting sequences of one or more junction epitopes that span junctions between one or more adjacent pairs of therapeutic epitopes into the machine-learned presentation model to determine presentation likelihoods of the one or more junction epitopes; and
selecting an ordering of the therapeutic epitopes in the cassette sequence according to presentation likelihoods of the one or more junction epitopes.
2. The method of claim 1 , wherein the one or more junction epitopes include a junction epitope overlapping with a sequence of a first therapeutic epitope and a sequence of a second therapeutic epitope concatenated after the first therapeutic epitope.
3. The method of claim 1 , wherein a linker sequence is placed between a first therapeutic epitope and a second therapeutic epitope concatenated after the first therapeutic epitope, and the one or more junction epitopes include a junction epitope overlapping with the linker sequence.
4. The method of claim 1 , wherein identifying the cassette sequence comprises:
determining, for an ordered pair of therapeutic epitopes, a set of junction epitopes that span the junction between the ordered pair of therapeutic epitopes; and
determining, for the ordered pair of therapeutic epitopes, a distance metric indicating presentation of the set of junction epitopes for the ordered pair on the one or more MHC alleles of the subject.
5. The method of claim 4 , wherein determining the distance metric comprises combining the presentation likelihoods of junction epitopes in the set of junction epitopes for the ordered pair of therapeutic epitopes.
6. The method of claim 5 , wherein combining the presentation likelihoods of junction epitopes comprises summating the presentation likelihoods of junction epitopes.
7. The method of claim 4 , further comprising determining a presentation score based on the distance metric for each ordered pair of therapeutic epitopes.
8. The method of claim 7 , wherein determining a presentation score based on the distance metric for each ordered pair of therapeutic epitopes comprises combining distance metrics for all ordered pairs of therapeutic epitopes in the cassette sequence.
9. The method of claim 1 , further comprising manufacturing or having manufactured a tumor vaccine comprising the cassette sequence.