The Immune system is made up of a large network of cells that work together to combat infections. Helper T Lymphocytes are a particular type of immune cell that expresses a molecule called the Cluster Determinant 4 (CD4). Helper T lymphocytes are hence commonly known as CD4 cells. The Human Immunodeficiency Virus (HIV) selectively targets CD 4 cells and uses them as hosts for viral replication. As the virus replicates, it destroys its host cell as it releases new copies of the virus. Therefore, as the viral load (which is a measure of the amount of virus present in the body) increases and the host CD 4 cells will decrease.
During the early stages of a HIV infection, viral replication occurs at a very fast rate at the expense of CD 4 host cells. A vicious cycle occurs, wherein an increase in HIV viral load attracts more CD4 cells which get infected and become hosts to further increase the viral load. Within the first few weeks of a HIV infection, the CD 4 count falls precipitously. Such a sharp fall in CD4 cells is the hallmark of a HIV infection.
Upon diagnosis of HIV, it is crucial that the patient’s CD 4 and viral load are measured. The CD 4 count allows the medical team to determine the state of the immune system and plan the appropriate treatment. If the CD 4 count is below 200 units, the diagnosis of Acquired Immunodeficiency Syndrome (AIDS) is established. AIDS is a serious complication of HIV infection and can be fatal, therefore, if the patient is diagnosed with AIDS he/she requires immediate medical attention in a hospital.The viral load will give an indication of how fast the virus is replicating. Current medication used to treat HIV infection targets different parts of viral replication and interfere in the process of new viruses being produced. Therefore, a fall in viral load after commencing medication is an indicator that the medication is working.
People Living With HIV
For People Living with HIV (PLHIV), the main goal of therapy is to increase CD4 cell numbers and decrease the viral load to an undetectable level. Monitoring these 2 parameters will guide the treatment regime. In general viral load is measured 2 weeks after starting medications for HIV, then at 4 to 8 week intervals. The expected fall in viral load should be to approximately < 500 copies/ml by week 8 – 16 and < 50 copies /ml by week 16- 24. CD 4 recovery is slower, the first CD4 test is done 3 months after commencing treatment and every 6 months after. In general, a CD 4 count > 300 cell/uL with a low viral load is a good level to ensure that PLHIV does not encounter any opportunistic infections.
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CD 4 and Viral load measurements are essential parameters in guiding the medical therapy for PLHIV. Regular check of these parameters ensure that PLHIV are able to maintain an active lifestyle and avoid any infections that may occur due to a lowered immunity.