firstly, i major in cell/molecular biology and minor in biochem so i'm pretty sure i didn't just make any of the following up, although i am still on winter break so bare with me if i'm wrong. the HeLa cells are from henrietta lacks, someone who had cervical cancer a really long time ago and for whatever reason her cells are immortal so they use them for research. this vaccine takes dendritic cells, which crawl around and search for bad stuff, ingest them, and then present antigens to the appropriate cells look for cancer cells. presumably, you get this after you have the cancer. so they're going to look for something specific on cancer cells, make the vaccine so the dendritic cells find them and present antigens to other immune cells so they can attack cancer cells. thats how i think it works.