AIDS and the "Selenium-CD4 T Cell Tailspin" The Geography of a Pandemic
Townsend Letter for Doctors & Patients - december 2000: 94-99
Abstract: AIDS involves slow but relentless declines in serum selenium and CD4 T-cells, both of which are independent predictors of mortality. This relationship between selenium and the immune system is one of positive feedback, in which a decline in either of these two variables causes further depression of the other. Termed the "selenium-CD4 T Cell Tailspin" by the author, this feedback loop plays a crucial role in both the diffusion of HIV-1 and the associated development of AIDS. Manipulating this tailspin opens new avenues for both prevention and treatment.
Except from page 94-95:
In 'Reducing Cancer Mortality: A Geographical Perspective', this author presented evidence to suggest that, after smoking and alcohol had been accounted for, global cancer mortality was determined largely by environmental levels of selenium, calcium, mercury and the application of road salt. Landscapes of longevity were thought to have elevated selenium and calcium and depressed mercury in their food chains.
Senegal was shown to have such an ideal environment for cancer prevention. This West African country is essentially a dessicated Cretaceous and early Eocene Sea. Because of this, calcium phosphate, mined for use in fertilizers, is the country's principal mineral product. It is derived from selenium-enriched phosphorites.
Since only 1 to 3% of its precipitation provides runoff, Senegal's population is almost enterily dependent on groundwater, which Furon described as the world's hardest (containing the most calcium and magnesium). Since Senegal is an equatorial country, no road salts is used. This author argued, therefore, that Senegal has the world's lowest cancer incidence, because it has the ideal environment for the operation of the human immune system.
This information is relevant here because the population of Senegal is showing a very similar ability to resist HIN-1 infection. To illustrate, HIV-1 prevalence figures for Africa, last updated on August 19, 1999 are available from the Harvard AIDS Institute's web page.
These indicate that HIV-1 prevalence has reached 25.84% in Zimbabwe, 25.10% in Botswana, 19.07% in Zambia, 12.91% in South Africa, 10.06% in Côte d'Ivore, 9.42% in Tanzania, 9.31% in Ethiopia and 4.35% in the DR of Congo. In contrast, despite the fact that the overall prevalence of HIV-1 in Sub-Saharan Africa is 8.0% that in Senegal is recorded at only 1.77%. This abnormally low HIV-1 prevalence rate occurs in Senegal despite the fact that neighboring countries have elevated mortality from AIDS. While other highly unlikely social explanations have been made for the depressed HIV-1 prevalence rate in Senegal, it seems far more probable that a food chain that provides a constant elevated supply of selenium is highly protective against both cancer and HIV-1.
To illustrate, during the period 1989 to 1996, the levels of HIV infection estimated in four sentinel urban regions of Senegal remained stable at around 1.2% in pregnant women and at 3% in male patients with sexually transmitted diseases. This stability was achieved despite the fact that in 1997, 33% of Sengalese men aged 15 to 49 reported having sex with non-regular partners and a third of those who did so were not using a condom. Clearly, HIV-1 infection is almost static in Senegal, despite widespread sexual activity.
Elsewhere in Sub-Saharan Africa such behavious has driven the AIDS pandemic, suggesting that in Senegal, elevated selenium is highly protective against HIV-1 infection.
Given the fact that AIDS is extremely common in those countries in Africa, such as Zaire, which are known to have very deficient selenium soils, the reverse appears to be true. Indeed the recently published Selenium World Atlas used the incidence of HIV-positive populations as a surrogate measure of selenium deficiency in Africa, since knowledge of actual soil levels of this trace element is quite scarce. This argument by analogy was made on the advice of E.W. Taylor from the University of Georgia who was the first to recognize that the spread of HIV-1 in Africa was occurring most rapidly in selenium deficient regions. In addition Karposi's sarcoma has long been endemic in such selenium depleted regions of Sub-Saharan Africa. It is now known to occur to individuals who are both selenium deficient and who test positive for human herpesvirus 8 (HHV-8). Myxoedematous cretinism, known to involve a lack of both iodine and selenium, is also common in Nothern Zaire.
Insights into the probable future of the AIDS pandemic can be gained from the Chinese "Disease Belt". This huge region of selenium deficiency crosses China from northseast to southwest. It is mainly characterized by temperate forests and forest-steppe soils. Within this belt, soils typically contains <0.13 ppm selenium and, as a consequence, the average daily dietary intake of this element is <10 micrograms. In the most selenium deficient areas, intake can be less than half this amount. For comparison, estimated average daily selenium intake in Canada and the United States is 170 micrograms. It is not too surprising that this Chinese region, the largest and most densely population selenium deficiency belt on earth, is already badly affected by a virus which encodes a Se-dependent GPx module, namely the coxsackievirus B3. A virulent form of this virus is responsible for endemic Keshan deisease, a cardiomyopathy which is restricted to the low selenium belt just described. This juvenile cardiomyopathy apparently occurs when selenium deficient individuals are infected by the coxsackievirus B3. Animal experiments have shown that nutritional selenium deficiency appears to drive changes in the genome of this virus, which may make the pathogen more virulent. Depleted selenium nutritional status appears, therefore, to promote mutations which accellerate the local prevalence of Keshan disease.
It seems likely that at least some of the genetic variety seen in HIV-1 and HIV-2 may be caused by a similar process.
Numerous Chinese Keshan prevention programs are currently underway. These include the addition of selenium to fertilizers and to animal foodstuff. They have demonstrated that Keshan disease can be prevented by an increase in dietary selenium. It is also of interest that, despite that Keshan disease has been endemic in China for many years, it has not spread significantly beyond the belt of extreme selenium deficiency.
Unfortunately, however, once HIV-1 becomes firmly established in this region, it is to be expected that very elevated mortality from AIDS will rapidly occur, on a scale far greater than that seen in the African Sub-Sahara.
The geographical evidence, therefore, appears to suggest that selenium abundance in the local food chain prevents, or severely inhibits, the "selenium-CD4 T cell lymphocyte tailspin, restricting the diffusion of viruses, such as HIV-1 and virulent coxsackievirus B3, that encodes GPx modules. Conversely, in selenium deficient regions, such viruses diffuse with great rapidity.
Bibliography on Foster HD: