Why is Alice infected with T virus in Resident Evil?

In Resident Evil 1, Alice and another man escape from the umbrella (hive). No sooner had they left the hive than people were about to mutate. Suddenly, a group of scientists from Umbrella Company came in and separated this man from Alice. That person will be turned into a nemesis by the T virus, and Alice will join the plan to turn Alice into a super monster. However, T virus seems to be ineffective in Alice, no matter how much T virus is injected (Alice has antibodies to T virus). As a result, Alice and T virus combined, and Alice did not become a monster, but evolved (gained super powers). See Resident Evil 2 for details. Give points. I have watched this movie many times, and I like his games. Please find me the background story of Resident Evil! ! !