Provided are polynucleotides and viral vectors, e.g., alphavirus or Sindbis viral vectors, encoding multiple, e.g., two or more, epitopes of at least one tumor associated antigen, in which each epitope is separated by a processing or enzyme cleavage site. The encoded epitopes may be the same or different. Also provided are polynucleotides and viral vectors, particularly, alphavirus or Sindbis viral vectors, encoding an immune checkpoint protein, or a ligand binding portion thereof. The immune checkpoint protein or ligand binding portion thereof may be fused to immunoglobulin domains, e.g., an Ig hinge domain and an Ig heavy chain constant domain. Methods of treating subjects having a cancer or tumor, e.g., a TAA-expressing tumor, with the described viral vectors are provided. Treatment of subjects with the vectors, the checkpoint inhibitor molecules and/or other immunomodulatory components, generate an anti-cancer or anti-tumor immune response resulting in increased survivability of tumored subjects and epitope spreading.