An Introduction to HIV and AIDS
HIV stands for Human Immunodeficiency Virus, whilst AIDS stands for Acquired Immunodeficiency Syndrome. HIV and AIDS are not the same thing, and not all cases of HIV lead to AIDS.
(source: American Psychological Association)
There are two types of HIV: HIV-1 and HIV-2, but the predominant virus is HIV-1. When people talk about HIV, they tend to be referring to HIV-1, as HIV-2 is a relatively uncommon strain which is concentrated in West Africa and a few other countries. It is also less infectious, and has a slower progression cycle.
The life cycle of HIV
When HIV enters our body, it gradually destroys the immune system by attacking CD4 cells, commonly known as T4-helper cells - a type of white blood cell that plays an instrumental role in protecting the body from infections caused by pathogens. The CD4 cells send signals to other immune cells such as the CD8-killer cells, which start to engulf and destroy foreign particles that have the potential of weakening our immune system.
The word ‘attacking’ involves the attachment (binding) of HIV to the receptors situated on the surface of the CD4 cells. After a successful attachment, ‘fusion’ occurs, which is the joining of the CD4 cell membrane and the viral envelope of the HIV, enabling the HIV to enter CD4 cells.
Consequently, reverse transcription begins inside the CD4 cells, whereby the HIV releases an enzyme known as ‘reverse transcriptase’, converting its genetic material from HIV RNA into HIV DNA. This conversion allows the HIV to enter the CD4 nucleus and merge with the host cell’s genetic material - its DNA.
Inside the nucleus of the CD4 cell, the enzyme ‘integrase’ (released by the HIV) allows it to insert its viral DNA into the DNA of the cell. Once the integration of the two genetic materials is complete, HIV exploits the machinery of the CD4 cells and replicates itself into long chains of HIV protein.
The newly formed HIV protein and HIV RNA move towards the surface of the CD4 cell and assembles itself into non-infectious HIV (immature). The new HIV then exits the host cell and releases ‘protease enzyme’, which breaks down the long protein chains that make up the non-infectious virus, allowing smaller viruses to combine into an infectious (mature) virus. This last stage of the life cycle is known as ‘budding’.
The four main stages of HIV
Stage one: ‘Primary Infection’
This stage can last for a few weeks. People may experience flu-like illnesses, and around 20% of those who consult their doctors about the seriousness of their symptoms are usually dismissed and are not diagnosed with the possibility of being HIV positive. During this period of ‘seroconversion’, there are vast amounts of HIV in the peripheral blood (blood circulating around the body), leading to the immune response of producing HIV antibodies and cytotoxic lymphocytes. However, the downside for those who get an HIV antibody test before the end of this stage is that their result may not come out as positive.
Stage two: ‘Clinically Asymptomatic’
This stage lasts for an average of ten years. The body is free from obvious symptoms (hence the word asymptomatic), and the level of HIV in the peripheral blood is at very low levels. However, the person is still infectious and if an antibody test is conducted at this stage, the result will come out as positive. It is clear to say that HIV is not dormant, as it is active in the lymph nodes (glands which are a part of the lymph system; an integral component of the immune system). During this stage, a test is available to measure the amount of HIV that escapes the lymph nodes. It is known as the 'viral load test', and measures the HIV's RNA.
Stage three: ‘Symptomatic HIV Infection’
This is when the immune system becomes damaged by HIV, as the lymph nodes and tissues become ‘burnt out’ and the HIV mutates, becoming stronger and more varied; thus, an increasing number of CD4 cells are being destroyed. In addition, the immune system fails to combat the HIV efficiently due to the loss of CD4 cells, causing symptoms to develop. Although most symptoms are ‘mild’, the deteriorating immune system allows for opportunistic infections to develop, and in some cases, cancer. Symptomatic HIV infection is usually the result of opportunistic infections and cancers that could have been prevented if the immune system worked normally to combat foreign particles. Such infections are often illustrated by multi-system diseases such as tuberculosis (respiratory system), cytomegalovirus (central nervous system) and Kaposi’s sarcoma (skin). Although treatment for infections and cancer can be carried out, its underlying cause is still HIV, which continues to destroy the immune system. Unless the treatment can slow down its activity, the symptoms will inevitably worsen.
Stage four: Progression from HIV to AIDS
This occurs when the immunosuppression worsens, meaning that the illness becomes more severe. Eventually, the person will be diagnosed with AIDS. The main symptoms of AIDS include meningitis, retinitis, pneumocystis pneumonia and chronic diarrhoea.
At present, AIDS diagnosis differs from country to country. For example, in the USA, a person with an extremely low count of CD4 cells in their blood can be diagnosed with AIDS, whilst a person can be diagnosed with AIDS if they develop numerous opportunistic infections or cancer in countries like Moldova. However, it is still possible for someone to be severely ill with HIV and not be diagnosed with AIDS. We will be publishing another article soon with further information regarding the differences in AIDS diagnosis, misconceptions of and treatment for HIV.
Mint is from Bangkok but currently attends high school in the UK. She is interested in medicine and global health, and aspires to become a doctor. Over the summer, Mint visited both public and private hospitals, which led her to do some research on the corruption within the healthcare system in Thailand as well as the UK. She also started an HIV Awareness Project in conjunction with local hospitals and health centres, which aims to educate the youth about HIV, as it remains a taboo subject in many countries. In her free time, Mint also enjoys playing golf and tennis.
