When a normal person is exposed to HIV, it reproduces inside of them, so can then go on to expose more people, and if there’s enough of it, infect them in turn (if there’s a smaller amount, their immune system will normally be able to clean it up before it gets enough of a foothold). If someone’s lacking the receptor, then no matter how much they were exposed to, their immune system will eventually manage to remove it all without becoming infected because it can’t reproduce. If they had a ludicrously large viral load, then there’s a possibility that it could be passed on before it was destroyed, but most of the ways people get exposed to HIV aren’t enough to infect someone who’s vulnerable, let alone infect someone else via secondary exposure if there’s not been time for the infection to grow.
When a normal person is exposed to HIV, it reproduces inside of them, so can then go on to expose more people, and if there’s enough of it, infect them in turn (if there’s a smaller amount, their immune system will normally be able to clean it up before it gets enough of a foothold). If someone’s lacking the receptor, then no matter how much they were exposed to, their immune system will eventually manage to remove it all without becoming infected because it can’t reproduce. If they had a ludicrously large viral load, then there’s a possibility that it could be passed on before it was destroyed, but most of the ways people get exposed to HIV aren’t enough to infect someone who’s vulnerable, let alone infect someone else via secondary exposure if there’s not been time for the infection to grow.