Before examining the potential use of cannabinoid therapy for HIV patients, it is important to recognize that most literature or research in this field is focused on treating the symptoms or side effects caused by HIV, rather than curing the disease itself.
In fact, this was what kick-started the cannabis movement a few decades ago: a group of activists fighting for using cannabis to treat AIDS-related side effects of the first approved retroviral treatment for AIDS. These symptoms include nausea/vomiting, wasting syndrome, pain, and depression. It is also necessary to note that cannabis should only be considered as an alternative therapy should the conventional methods fail.
In terms of FDA approved drugs, there are dronabinol (Marinol) and nabilone (Cesamet) and they are both approved for anti-emetic use. In addition, dronabinol is FDA approved for the treatment of anorexia associated with weight loss in patients with HIV/AIDS.
As with cannabinoid therapy in most other diseases, the result is generally mixed. A lot of it is really dependent on the specific situation the patient has, the treatment goals as well as in conjunction with other treatments. For example, in the case of HIV induced wasting syndrome, cannabis, either in the form of FDA approved drug dronabinol or natural form, appears to be effective in weight maintenance (though not necessary weight gain or gain in lean muscle mass). However, at the same time, we know that AIDS wasting syndrome has largely disappeared thanks to the advancement in HAART therapy. Finally, cannabis is effective in treating pain (including neuropathies caused by HIV) as well as managing depression (providing the right dosage, etc).