Does HIV cause AIDS?
Despite the overwhelming evidence that HIV is the causative agent of AIDS, there are still many things that we do not know about the virus. Some people say that all that is necessary for AIDS is an HIV infection. Others invoke co-factors. A small but influential minority say that HIV is an unjustly maligned by-stander that is found in many immunocompromised states but is not the cause of the disease. The most outspoken of these are Drs Peter Duesberg and Kary Mullis.
The following are the arguments raised by those who believe that HIV does not cause AIDS:
i) HIV is not in semen.
It is actually found to a high degree in most investigations.ii) Viruses work exponentially to produce new virions and disease. This statement confuses virus in a cell, where this is true, with disease in individual. There are numerous examples of slow progressive viral diseases.
iii) Viruses do not cause disease when neutralizing antibody is present.
This is not true. There are examples of diseases which progress in spite of the presence of antibody.iv) Fewer than 1 in 10,000 T4 cells infected. The number is lower than originally stated but this is a problem.
v) Few hemophiliacs get AIDS. They die of immune suppression by therapeutic blood proteins. HIV positive hemophiliacs get immune suppression but HIV negative ones do not.
vi) Transfusion of HIV contaminated blood not been shown to give AIDS.
In a Mexican study of 39 patients given HIV+ blood, AIDS occurred in 3% of the recipients within 12 months, 50% after 29 months, 75% after 36 months, 100% after 48 months. The mean survival time after AIDS onset was 9 months.i) HIV does not fulfill Koch's postulates.
Postulate 1: An infectious agent occurs in each case of a disease in sufficient amounts to cause pathology.
It is said that there are many cases of AIDS without HIV, although it is to be expected that there would be other causes of immune suppression. There is the problem of the majority of uninfected T4 cells.Postulate 2: A specific infectious agent is not found in other diseases.
This was later abandoned by Koch when it was found that one agent can cause more than one specific disease.Postulate 3: After isolation and culture, the infectious agent can induce the disease in another individual.
In the case of HIV which only causes disease in humans, this is difficult to do as there is naturally a lack of volunteers. In the case of SIV, cloned virus does induce disease in healthy monkeys. This has now, in fact, been done with HIV as the result of the accidental infection of laboratory workers with cloned HIV.With regard to Koch's postulates, Duesberg has argued that the following criteria must be met to show that HIV causes AIDS
1. The microorganism must be found in all cases of the disease.
2. It must be isolated from the host and grown in pure culture.
3. It must reproduce the original disease when introduced into a susceptible host.
4. It must be found in the experimental host so infected.It is now apparent that:
1. Virtually all AIDS patients are HIV-infected
2. HIV can be isolated from virtually all AIDS patients, as well as in almost all seropositive individuals
with both early- and late-stage disease
3. Health care and laboratory workers accidentally infected with concentrated purified HIV have developed AIDS
4. HIV has been isolated from many of these individuals
It should also be noted that:
1. HIV has always preceded AIDS in a population.
2. HIV is the single common factor between AIDS sufferers who are gay San Franciscans, African female heterosexuals, hemophiliacs, children, intravenous drug users.
3. Within any risk group virtually only the HIV+ individuals get AIDS. It could be argued that all members of these groups are subject to immunosuppression but this is not the case with wives of hemophiliacs?
4. There is a better correlation between HIV and AIDS than between cigarettes and lung cancer.
Summary of the abundant evidence that HIV is the causative agent of AIDS:
1. Before the appearance of HIV, AIDS-like syndromes were rare, today they are common in HIV infected people
2. AIDS and HIV are invariably linked in time, place and population group
3. The main risk factors for AIDS are sexual contact, transfusions, IV drugs, hemophilia. These have existed for years but only after the appearance of HIV, has AIDS been observed in these populations
4. Infection by HIV is the ONLY factor that predicts that a person will develop AIDS
5. Numerous serosurveys show that AIDS is common in populations with anti-HIV antibodies but is rare in populations with a low seroprevalence of anti-HIV antibodies
6. Cohort studies show that severe immunosuppression and AIDS-defining illnesses occur exclusively in individuals that are HIV-infected
7. Persistently low CD4 counts are extraordinarily rare in the absence of HIV or another known cause of immunosuppression
8. Nearly everyone with AIDS has anti-HIV antibodies
9. HIV can be detected in nearly everyone with AIDS
10. HIV does fulfil Koch's postulates
11. New born infants with no behavioral risks develop AIDS if HIV infected
12. An HIV-infected twin will develop AIDS, while the uninfected twin does not
13. Since the appearance of HIV, mortality has increased dramatically among hemophiliacs
14) Studies of transfusion-acquired AIDS has repeatedly led to discovery of HIV in recipient as well as donor
15. Sex partners of HIV-infected hemophiliacs and transfusion patients acquire the virus and AIDS without other risk factors
16. HIV infects and kills CD4+ T cells in vitro and in vivo
17. HIV damages CD4 precursor cells
18. Body viral (HIV) load correlates with progression to AIDS
19. HIV is similar in its genome and morphology to other lentiviruses that often cause immunodeficiency, slow wasting disorders, neurodegeneration and death
20. Baboons develop AIDS after inoculation with HIV-2 that also causes AIDS in humans
21. Asian monkeys develop AIDS after inoculation with simian immunodeficiency virus
Clearly, the correlations between HIV and AIDS are very striking indeed.
Links to many other pages discussing the HIV and AIDS connect can be found here, here
Fact sheet from NIH here
Return to the HIV lecture notes
Return to the Department of Microbiology and Immunology Site Guide
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