I was a bit confused until I noticed that this is only a partial sequence. A full antibody is considerably larger, and you also need to get the disulfide bonds

I was a bit confused until I noticed that this is only a partial sequence. A full antibody is considerably larger, and you also need to get the disulfide bonds formed correctly for it to work. And I don't think it is entirely clear if expressing that antibody alone is enough to defeat HIV, especially as it targets the immune system itself. If antibodies are the solution, then developing a vaccine that triggers the production of suitable antibodies is probably the better way forward.