What is HIV?

Human immunodeficiency virus (HIV)

Human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system. It destroys certain white blood cells (CD4-T cells) that are crucial for the body's immune system and leads to the weakening of the body’s ability to fight infections.

In the absence of HIV infection, CD4-T cells play a critical role in identifying and eliminating various harmful agents such as bacteria, viruses, and other pathogens that infiltrate cells and induce illnesses. Generally, HIV attaches itself to CD4-T cells and infiltrates then destroys them, leading to increased HIV production, as the virus can only replicate within living cells.

While there is no cure for HIV, antiretroviral therapy (ART) has been highly effective in slowing down the progression of the virus, preventing the development of acquired immunodeficiency syndrome (AIDS), and allowing people living with HIV (PLHIV) to lead a healthy life with proper virus management and medical care.

In infants and children, HIV transmission can occur before or during birth, during breastfeeding, or through HIV-contaminated blood transfusions or injections. The infection might rapidly advance to AIDS because of the lack of a fully developed immune system.

There is no cure for HIV but there is a treatment called antiretroviral therapy or ART that can slow or prevent HIV from advancing from one stage to the next.

What is AIDS?

Acquired immunodeficiency syndrome (AIDS) is the advanced stage of HIV infection.

It is when the CD4-T cell count falls to a very low level, below 200 cells per milliliter of blood. AIDS is characterized by a severely weakened immune system, which makes the person highly vulnerable to a wide range of opportunistic infections and certain cancers. Nowadays, with effective HIV treatment, these types of infections are less common.

How does HIV attack the immune system?

1. Binding:

HIV targets CD4 T-cells and attaches to their receptors.

2. Fusion and entry:

HIV fuses with the cell membrane, allowing the virus to enter the CD4 T-cell. Once inside, the viral RNA and enzymes are released into the host cell.

The viral RNA carries the instructions that lead the virus to replicate and produce new virus particles that infect other cells.

3. Reverse transcription:

HIV contains RNA as its genetic material. Inside the host cell, the viral enzyme ‘reverse transcriptase’ converts the viral RNA into DNA.

4. Integration:

The DNA of the virus is integrated into the CD4 T-cell DNA with the help of the viral enzyme integrase. The integrated DNA becomes part of the host cell's genetic material.

5. Replication:

The cell then produces viral proteins and new viral particles using the CD4 T-cell machinery.

6. Assembly and budding:

New immature HIV formed by the newly synthesized HIV proteins and RNA move to the periphery of the CD4 T-cell. Once pushed out of the CD4 T-cell, an enzyme called protease is released and leads to mature and infectious versions of HIV.

7. Infection of other cells:

The newly released virus particles can go on to infect other CD4 T-cells, continuing the cycle of infection and destruction. As HIV replicates and destroys CD4 T-cells, the body's immune system becomes progressively weaker. Over time, this leads to immunodeficiency, making the person more susceptible to various infections and diseases.

The final stage of HIV infection is known as acquired immunodeficiency syndrome (AIDS), characterized by severe immune system damage and the development of opportunistic infections (infections that are more frequent and severe in individuals with compromised immune systems).

Sometimes, it is hard to recognize a new HIV infection because its symptoms are similar to other common viruses like COVID-19, flu, or mononucleosis.

Stages of HIV infection

Acute HIV: also called primary HIV infection, occurs 2-4 weeks after exposure, and is accompanied by a burst of HIV replications resulting in a high viral load and making it highly contagious. Therefore, the viral load can be detected before the antibodies. Most patients will experience flu-like symptoms: fever, lymphadenopathy (swollen lymph nodes), pharyngitis, skin rash, myalgia (muscle pain), and arthralgia (joint pain).
Chronic HIV: also called asymptomatic stage or clinical latency. During this stage, a person with HIV usually does not experience symptoms. Despite the absence of symptoms, the virus continues to replicate at lower levels and if antiretroviral drugs are not used, it can gradually harm the immune system. HIV remains contagious at this stage. The progression to AIDS takes 10 years or more.
AIDS: Acquired immunodeficiency syndrome is the final, most severe stage of HIV infection. The immune system is severely damaged and the CD4 count falls below 200/mm3 (normal CD4 count is around 500 to 1500/mm³), and the viral load is significantly high which makes the virus easily transmissible. Individuals with AIDS are highly susceptible to potentially life-threatening diseases that would not typically affect someone with a healthy immune system. These are called opportunistic infections (pneumonia, salmonella, tuberculosis…) or opportunistic cancers.
If you have HIV symptoms and this test is negative, you should do a test that includes both HIV 1 and 2.

Types of HIV

HIV has two primary types: HIV-1 and HIV-2. They both have similar clinical symptoms and progress to AIDS if left untreated.

HIV-1 was discovered first and is believed to have originated from non-human primates, particularly chimpanzees, and was transmitted to humans after exposure to chimpanzees’ blood. It is the most common: around 95% of PLHIV have HIV-1.

HIV-2 came from viruses found in the sooty mangabey monkey and was transmitted to humans the same way as HIV-1, through hunters after exposure to the blood of these monkeys. It remains largely found in West Africa. People with HIV-2 often have a lower viral load and a slower decline in CD4 T-cells. HIV-2 tends to develop more slowly to AIDS than HIV-1.

HIV-1 and HIV-2 are genetically different, which means they have different antigens.

There is a diagnostic test that is developed only to detect HIV-1.

If you have HIV symptoms and this test is negative, you should do a test that includes both HIV 1 and 2.

Antiretroviral therapy (ART) has been developed to manage both types of HIV, although treatment strategies may vary depending on the specific type and subtype of the virus involved.

Written by:

Lena Mhanna | Sexual health educator, nurse

Lena Mhanna, a passionate sexual health educator, with a bachelor's degree in Nursing Science is on a mission to break taboos, provide knowledge and empower individuals to enhance their sexual health and well-being.