Monkeys have it, we don't

Just think of all the monkeys that have been infected with SIV and S/HIV in the last 10 years in the effort (wholly unproductive) to find medicines for people with HIV and vaccines against the disease. Turns out that most people lack some genetic machinery (TRIM5 gene) that macaques have for fighting retriviruses like HIV.

A clue from macaques yields evidence for impaired retroviral defense genes in humans