Tethered interleukin-15 and interleukin-21

A nucleic acid comprising a nucleotide sequence encoding an amino acid sequence of Formula I:

• S1—N1-L1-C1a-L2-S2—N2-L3-C2b (Formula I),
• wherein:
• each of S1 and S2 is, independently, a signal sequence;
• one of N1 and N2 is an interleukin (IL)-21 amino acid sequence at least 90% identical to the amino acid sequence of SEQ ID NO:
• 2, and one of N1 and N2 is an IL-15 amino acid sequence at least 90% identical to the amino acid sequence of SEQ ID NO:
• 3;
• L2 is a cleavable linker sequence comprising the amino acid sequence of GDVEX1NPGP (SEQ ID NO:
• 6), wherein X1 of SEQ ID NO:
• 6 is any naturally occurring amino acid residue;
• each of C1 and C2 is, independently, a B7-1 transmembrane-intracellular amino acid sequence, a B7-2 transmembrane-intracellular amino acid sequence, a CD8α transmembrane-intracellular amino acid sequence, a B7-1 transmembrane amino acid sequence, a B7-2 transmembrane amino acid sequence, or a CD8α transmembrane amino acid sequence;
• and
• each one of a and b is 1, and
• each of L1 and L3 is, independently,
• (i) a polypeptide of Formula III:
• X1mX2nX3pX4q (Formula III), wherein:
• each of m, p, and q is, independently, 0 or 1;
• n is an integer from 20 to 65;
• X2 is a plurality of amino acid residues, each of which is independently selected from glycine and serine;
• and
• each of X1, X3, and X4 is, independently, any one naturally occurring amino acid residue;
• (ii) a polypeptide of Formula IV:
• X5rX6sX7t (Formula IV), wherein:
• s is 1;
• each of r and t is, independently, an integer from 20 to 25;
• each of X5 and X7 is, independently, a plurality of amino acid residues, each of which is, independently, selected from alanine, lysine, and glutamic acid;
• and
• X6 is any one naturally occurring amino acid residue;
• or
• iii) 10 to 30 amino acid residues selected, independently, from glycine, serine, threonine, lysine, glutamic acid, and proline.