Challenge Biomedical Science – Immunology

1. Challenge Biomedical Science – Immunology HIV HIV stands for Human Immunodeficiency Virus. HIV is the virus that causes AIDS (Acquired Immune Deficiency Syndrome). HIV attacks the immune system's soldiers - the helper T cells or CD4 cells. When your immune system loses too many CD4 cells, you are less able to fight off infections and common infections can become life threatening. A person is diagnosed with AIDS when he or she has less than 200 CD4 cells and/or one of 21 AIDS-defining infections. HIV can be controlled and managed by drug therapy. South Africa In South Africa it is estimated that 29.1% of pregnant women were living with HIV in 2006. People in South Africa can have HIV voluntary counseling and testing. (VCT) The number of VCT sites in South Africa has increased significantly in recent years. The ELISA test, or the enzyme immunoassay (EIA),is the first screening test commonly used to detect HIV antibodies. In your pack you will have the tools to carry out an ELISA test on a female, pregnant, South African. Follow the instructions in order to carry out an ELISA test on her serum.

2. Challenge Biomedical Science – Immunology Decision Time What is the result? Negative Low positive High Positive Dilemma Breastfeeding provides all of the nutrients needed during the first few months of life and helps to protect against common childhood illnesses. Breastfed babies are less likely to become ill than those given replacement foods. But breast feeding can transmit HIV. Breastfeeding for two or more years can double the rate of mother-to-child transmission to around 40% The most effective way to prevent mother-to-child transmission of HIV involves a long course of antiretroviral drugs and avoidance of breastfeeding, which reduces the risk to below 2%. (Findings from one study of pregnant, HIV positive women in Africa) In some cases formula milk is handed out freely to mothers in the developing world but this itself creates a stigma from society, as she is then clearly labelled as having HIV. Mothers in developing countries with little access to the drugs or formula milk then face the dilemma of the dangers of not breastfeeding against the threat of HIV transmission. What do you think this mother should do? Discuss.

3. Challenge Biomedical Science – Immunology ELISA Test You will need: Glass bead coated with HIV antigen Patient serum containing antibodies Enzyme which attaches to the antibodies Chromogen which changes colour when enzyme attaches to antibodies If the patient’s serum contains HIV antibodies they will attach to the antigens on the glass bead, the enzyme will attach to the human antibodies and the Chromogen will change colour, producing a positive result. • What to do. • Put on goggles, apron and gloves. • Use the tweezers to add a glass bead to the well. • Use the pipette to add 2 drops of water to the well. • Add 2 drops of Jan’s serum and wait 3 minutes. • Add 2 drops of enzyme and wait 3 minutes • Add 2 drops of chromogen • Compare to control results below Negative Low positive High Positive