Experiment Table CD4+ T lymphocyte counts and viral RNA Results Tetramer Staining Results Neutralizing Antibody Assays Results Viral Sequencing Results Peptide-binding Assays Results ELISPOT assays Results Conclusion   Navigation Home Methods Results Conclusion Quiz Links

CD4+ T lymphocyte counts and viral RNA   Purpose: To measure the condition of the immune system and the amount of viral replication at different points of time. Synopsis: Researchers measure the levels of CD4 T-lymphocytes, the specific cells of the immune system that are infected by the HIV (or SHIV) virus, in the blood as an indicator of patient health and disease progression. Additionally, since HIV can be latent and demonstrate periods of little productivity, measurements of Viral RNA levels are taken to determine how much the virus is actively replicating. How would you be able to tell whether a low CD4 count was caused by viral destruction or lack of stimulation of the immune system? Answer Presence of high amounts of viral RNA would indicate widespread destruction of T-cells Samples for SHIV RNA counts can be taken at the same time. PROCEDURE: CD4 Counts: CD4 Cells were labeled with anti-CD4 antibodies that are tagged with a molecule that fluoresces at a specific wavelength. Using a flow cytometer, these tags can be quickly and easily detected and quantified giving the number of cells present. Branched DNA Amplification: The levels of viral RNA were measured by Branched DNA amplification. This procedure transduces an RNA concentration into a quantifiable visual product displaying the amount of original viral RNA present.   1. The Viral RNA is bound to HIV specific probes in the wells of a microtiter plate.     2. The bound RNA is amplified using branched DNA. Branched DNA specific oligonucleotides linked with an enzyme (alkaline phosphatase in this experiment) are bound.   Why would the researchers wish to go through the additional step of amplifying the RNA? Answer The researchers need significant amounts of genetic material to generate a detectable signal. After amplification they can quantify the original RNA level by looking at the amount of signal. 3. The enzyme substrate is added and an insoluble colored product is produced and can be used for determining the original RNA level (see Fig. 2).       Would you expect the level of viral RNA to be inversely or directly proportional to level of CD4? Answer Inversely, the population of the virus directly harms the CD4 while the CD4 leads an immune response against the virus   NEXT