Question

identify a human protein that is current used to diagnose a disease. Write a short paragraph describing the target disease and how the diagnostic protein is assayed (ELISA, microarray, etc.). The disease is your choice.

Answer 1

For the above question, let us consider the protein [ enzyme] used to diagnose and detect the presence of AIDS virus in a person. This is done by ELISA test. Now, what is an ELISA test?

ELISA test, also known as enzyme linked immuno absorbant assay is a test that detects and measures antibodies related to certain infectious conditions in a person's blood. Antibodies are proteins that our body produces in response to certain harmful substances called antigens. ELISA test is used to diagnose a number of diseases like Lyme disease, pernicious anaemia, syphhilis, squamous cell caecinoma etc.

Here, we will study about the cause , means of spread and symptom of AIDS and also its detection by ELISA test. --

* AIDS is caused by Human Immunodeficiency Virus [HIV].

* HIV belongs to the group 'retrevirus'. It has RNA genome enclosed in a protein envelope.

* Transmission of HIV occurs through blood transfusion[ or any sort of blood contact] from an infected person, sexual contact with an infected person or from an infected mother to her unborn child through placenta.

* After getting into the body of a healthy person , the virus enters the macrophages.

* Here, RNA is replicated to form viral DNA by the enzyme reverse transcriptase.

* The viral DNA now gets incorporated into the host cell DNA and directs the infected cells to produce more viruses.  

* The macrophages continue to produce virus particles.

* The virus particles enter helperT-lymphocytes in the blood where they continue to replicate and produce viral progenies.

* Thus the number of helper T-lymphocytes continuously decreases in the body of the infected person.

* With the decrease in T-cells, the immunity also decreases . The person is unable to produce any immune response even against common bacteria, parasitic protozoa or fungi. Thus , any disease can take an aggressive form which can even cause the person's death.

How does ELISA test help to detect AIDS virus ?

  The ELISA test involves taking a sample of a person's blood. The blood sample is taken from the upper arm or any part of the body with the help of a sterilised needle.

The blood sample is sent to the laboratory for analysis. In the lab, the blood sample is mixed with the AIDS virus.

If the sample blood contains antibodies to the antigen, the two will bind together. This is checked by adding an enzyme to the above sample and the reaction of the blood and the antigen is observed. If the sample changes colour, the test is positive for the presence of HIV.

Further tests are done on the person to confirm the findings of the ELISA test. These tests include--

* Other antibody test-- This checks for the presence of antibody in the blood, saliva and urine.

* Antigen or antibody tese - This checks for both the presence of the virus and its antibodies, making it highly accurate for early detection of the disease.

* NATs-- This test is used to detect HIV between 7 to 28 days following a high risk exposure. This test is the most accurate for recent exposure. However, it is very expensive so is only used in situations where exoosure has occurred. It becomes important in high risk exposure cases because in some cases , the carriers of HIV do not show any symptoms of AIDS.