The Right to non-discrimination on grounds of disability (i.e. HIV positive) is explained in these documents:

Legally Obligating Documents
Additional (San Salvador) Protocol to the American Convention on Human Rights in the Area of Economic, Social and Cultural Rights  (18)
African (Banjul) Charter on Human and People's Rights  (3, 18(4))
Arab Charter on Human Rights  (9)
Convention on the Rights of the Child  (2(2))
European Convention for the Protection of Human Rights and Fundamental Freedoms  (14)
International Covenant Economic, Social and Cultural Rights  (2(2))
International Covenant on Civil and Political Rights  (2(1))

Standard Setting Documents
Beijing Platform for Action  (99, 108)
Cairo Programme of Action  (8.29, 8.34)
UN Special Session on HIV/AIDS (UNGASS) Declaration of Commitment  (58, 66, 96)
Universal Declaration of Human Rights  (1, 2, 6)