HIV evolves during a single infection, causing its surface glycoprotein to mutate repeatedly, preventing neutralizing antibodies from binding to cells.

“first of all when you're first infected with human immunodeficiency virus and it begins to reproduce itself you make an antibody response to that virus that neutralizes and kills that virus does kills it effectively efficiently but what happens is it continues to evolve during a single infection so that the the surface protein the so-called glycoprotein of that virus two which you make an antibody response to prevent the virus from binding cells continues to mutate again and again and again”