Abstract

PIP: At this time, the evaluation of individuals suspected of having an injection with the Acquired Immune Deficiency Syndrome (AIDS) virus is a rapidly evolving area of science. As the testing procedures for detecting antibodies to the virus become more routine, it will become more important to understand the impact the infection has had on the host's immune system. Currently, the enzyme-linked immunosorbent assay (ELISA) is the standard method for sensitive screening for antibodies to the AIDS virus. This test lacks specificity, and, in view of the impact of a positive antibody test, confirmation of the result with Western blot analysis or radio-immunoprecipitation assay is essential a positive ELISA test occurs in the absence of an appropriate clinical setting. Viral isolation also may be helpful in individuals who are seronegative for the virus but who have the clinical diseases. The ELISA is the most commonly used test for screening sera for the presence of antibodies to HTLV-III/LAV. All the available kits take advantage of the fact that certain cell lines have been developed which allow for the growth of the virus without killing the cell. Supernatants or purified virus from these infected cells then are used as the material adhered to the solid phase for the ELISA. Consequently, in addition to placing viral proteins and nucleic acids on the plate, one also is adhering cell antigens. The sensitivity of such tests is good, ranging from 92-95%, whereas, depending upon the test population, the specificity may be as low as 30%. One common formula used for presenting data generated from such ELISA tests and for making the cutoff between negative and positive is to develop a ratio between the sample and the negative control and use that ratio to score samples as negative, borderline, or positive. The specificity of the Western blot technique stems from the fact that it takes the entire virus, reduces it to a variety of protein fragments electrophoretically, and then looks for antibodies directed toward any or all fragments.