There are two main ways to do this.
The first would be through laws. Laws could be enacted that would prohibit businesses from discriminating against workers with AIDS. They could be prohibited from asking about HIV status during interviews. Then, once a person was hired, they could be prohibited from firing a person found to have AIDS and from refusing them promotion.
The second would be through education. Firms and their employees should be educated about the idea that people with AIDS are still capable of doing their jobs. They should be educated on the ways in which HIV cannot be passed to coworkers through casual contact. This could help to reduce the desire on the part of the firm or of individuals to discriminate against workers with AIDS.