TreatmentUpdate43: Vol. 4, No. 3, July, 1993
Sean Hosein

Working independently of each other, two research teams of virologists in the USA have made some interesting discoveries about the lymph nodes of people with HIV infection. As well, scientists, who study the immune system have made important advances in understanding how HIV infection can damage the immune system.We now report their findings in point form:

* Throughout the course of HIV infection, most of the virus is located in lymph nodes/organs/tissue (including bone marrow, spleen, thymus gland, tonsils, appendix, intestines, lungs and skin).

* Most CD4+ cells and macrophages in lymph nodes/ organs are infected with HIV. As CD4+ cells are concentrated in those areas it is no surprise that a deficiency of these cells occurs. This finding does not mean that direct infection by HIV of CD4+ cells is the only way those cells are destroyed. There is evidence that CD4+ cells are attacked by the immune system. As well, CD4+ cells are just one part of the immune system and there may be other parts that are involved in the immunodeficiency in AIDS.

* The gradual destruction of lymph nodes/organs probably reduces the body's ability to contain HIV infection. There are between 500 and 1000 lymph nodes in the body. Although researchers have documented the presence of damaged lymph nodes, they do not know if all the lymph nodes are severely damaged in people with AIDS.

* HIV replication continues in the lymph nodes/organs even when patients are symptom-free. Thus, there really is no such thing as a "latency period" in people with HIV infection.

* Cells of the immune system taken from the blood do not provide a correct "picture" of HIV replication in the body.

* As the production and spread of HIV is increased when the entire immune system becomes "activated" it is probably important that other infections be treated and/or suppressed. Thus preventative, intermittent doses of antibiotics, which can restrict the spread of various infections, may help delay the decline of the immune system. One problem with this is that some drugs are toxic to the immune system in general and T-cells in particular. Patients and their doctors will have to carefully weigh the risks and benefits of these drugs.

* Finally, and perhaps most important of all, under constant attack by HIV, the immune system changes its response. Understanding how and why this shift happens appears to be critical if an "effective" therapy for HIV infection is to be made. But the immune system does not always "lose" the fight against the virus. In the next section we report on work which suggests that there are people who can encounter and survive HIV infection.

REFERENCES:

1. Panteleo G, Graziosi C, Demarest JF, Butini L, et al. HIV infection is active and progressive in lymphoid tissue during the clinically latent stage of disease. Nature 1993;362:355-358.

2. Embretson J, Zupancic M, Ribas JL, et al. Massive covert infection of helper T lymphocytes and macrophages by HIV during the incubation period of AIDS. Nature 1993;362:359-362.

3. Shearer GM and Clenci M. T helper cell immune dysfunction in asymptomatic, HIV-1-seropositive individuals:the role of Th1->Th2 cross-regulation. Chemical Immunology 1992;54:2143.

4. Gougeon M-L, Colizzi V, Dalgleish A and Montagnier L. New concepts in AIDS pathogenesis. AIDS Research and Human Retroviruses 1993;9(3):287-289.

5 . Castenholz A. Architecture of the lymph node with regard to its function. Current Topics in Pathology 1990;84(part 1):1-32.

930701
CATI4302

Copyright © 1993 - TreatmentUpdate. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Editor, The Canadian AIDS Treatment Information Exchange, 555 Richmond St. West, Suite 505, Box 1104, Toronto, ON, M5V 3B1 • Phone: 416-203-7122 • Toll Free: 1-800-263-1638 • Fax: 416-203-8284  http://www.catie.ca