This section is from the "Health and Survival in the 21st Century" book, by Ross Horne.
"My own research, which was published this summer in Perspectives in Biology and Medicine, suggests what these other causes of acquired immunosuppression may be. Briefly summarized, all of the following agents had been demonstrated to be immunosuppressive prior to the discovery of HIV, and all are highly associated with one or more AIDS risk groups: immunological response to semen following anal intercourse; the use of recreational drugs such as the nitrites ('poppers' and 'snappers'); chronic antibiotic use (often associated with promiscuity); opiate drugs; multiple transfusions; anesthetics; malnutrition (whether caused by 'gay bowel syndrome', drug use, poverty, or anorexia nervosa); multiple, concurrent infections by diverse microbes; and infection by specific viruses such as cytomegalovirus, Epstein-Barr virus, and hepatitis-B virus (all of which are as highly associated with AIDS as is HIV).
"Several of these agents, including cytomegalovirus, hepatitis-B virus, opiate drugs, and repeated blood transfusions, are known to cause the same sort of T-cell abnormalities that are found in AIDS, and which are usually attributed (perhaps inaccurately) to HIV infection. The other agents cause a wider spectrum of immunosuppressive responses, and probably explain why more than simply T-cells are non-functional in AIDS patients. Every AIDS patient has several of these immunosuppressive agents at work in his or her system in addition to, and sometimes in the absence of, HIV. We cannot, therefore, logically conclude that HIV is the sole or even the main cause of immunosuppression in AIDS.