A multicenter proficiency trial of gene amplification (PCR) for the detection of HIV-1

Article Abstract:

The polymerase chain reaction (PCR), a technique used to analyze genetic material, can be used to detect extremely small amounts of the human immunodeficiency virus type-1 (HIV-1). In fact, by analyzing DNA, PCR can detect the presence of the virus in individuals who do not seem to be infected, as indicated by the negative results of blood tests used to identify antibodies to HIV-1 (seronegative individuals). The sensitivity, specificity and accuracy of PCR testing were analyzed in five laboratories which were experienced in PCR techniques. All the laboratories used the same blood samples, which were obtained from 105 HIV-1 seronegative individuals who did not have any of the risk factors for HIV infection, such as homosexuality, hemophilia, intravenous drug use, and prostitution, and from 99 homosexual or bisexual men who were seropositive (that is, tested positive for antibody to HIV). The average sensitivity (being able to detect the presence of the virus) was 99 percent, with the range of sensitivity among the five laboratories ranging from 98 to 100 percent. The average specificity (the validity of detection) was 95 percent, with a range of 90 to 100 percent. The percentage of false-positive results (detected as positive, but really negative) was 2 percent, and the percentage false-negatives (detected as negative, but really positive) was 0.8 percent. Approximately 3 percent of the cases were misclassified due to laboratory error, such as specimen mix-up or carrying over results from one specimen to another. This study demonstrates that the PCR test had low specificity rates and high rates of false-negative results in some laboratories. Uniform results were not obtained in laboratories experienced in PCR techniques. The authors conclude that standardization of PCR testing must be achieved before this technique can be used as a routine test to determine the presence of HIV-1. Until then, PCR results should be interpreted with caution. (Consumer Summary produced by Reliance Medical Information, Inc.)

Testing, HIV (Viruses), HIV, Genetic aspects, Polymerase chain reaction, Biochemical variation, Genetic variation

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AIDS as immune system activation. II. The panergic imnesia hypothesis

Article Abstract:

The objective of AIDS research is to understand how the human immunodeficiency virus (HIV) causes deterioration of the immune system. A decline in the number of helper T lymphocytes is seen, which leads to defective cell-mediated immune responses. This allows opportunistic infections to develop. It is known that the virus enters into cells via the binding of a protein in the outer layer of the virus, known as gp120, to a molecule, known as CD4, on T lymphocytes and other immune cells. This process kills the T lymphocytes, which leads to impaired immunity. However, there are other theories concerning how the interaction of the virus and the T cells causes disease. One of these theories is the panergic imnesia hypothesis, which states that the interaction causes generalized stimulation of T cells, disrupting critical immunologic regulatory mechanisms and leading to impaired immunity. The uncontrolled lymphocyte stimulation is called panergy. Clinical symptoms of panergy include an autoimmune response, (an immune response to normal components of cells), lymphadenopathy (hyperimmune reaction in the lymph nodes), and high levels of immunoglobulin, or antibody molecules, in the blood. The immune system cannot respond to other stimuli because the activated T cells cannot be activated further. The state of chronic activation interferes with the development of memory cells (imnesia), leading to a loss in the total number of cells. It is felt that therapeutic strategies should include: those that avoid immune stimulation; inhibition of factors which stimulate the immune system; blockage of gp120 from binding to CD4; and inhibition of the signal that is generated by CD4. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, T cells, AIDS (Disease), Immunodeficiency, Immunologic memory

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Expression of CD69 after in vitro stimulation: a rapid method for quantitating impaired lymphocyte responses in HIV-infected individuals

Article Abstract:

Low levels of CD69 antigen expression in T lymphocytes, following stimulation, may be an indicator of immunologic problems in HIV-positive people. Researchers analyzed the levels of CD69 expression in T lymphocytes isolated from the blood of 25 HIV-positive and 12 HIV-negative people. The numbers and percentages of certain kinds of T lymphocytes expressing CD69 before stimulation were similar in HIV-positive and HIV-negative people. However, the percentage of certain kinds of T lymphocytes that expressed CD69 after stimulation was higher in HIV-negative people than in HIV-positive people. The factors used to stimulate the lymphocytes were antigens from different viruses, including the gp120 HIV antigen, and chemicals that trigger cell division. The gp120 antigen reduced expression of CD69 in certain T cells from HIV-negative people.

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