Antiretroviral therapy (ART) has transformed HIV from a terminal diagnosis into a manageable chronic condition. These medications do not cure HIV, but they control the virus, allowing people with HIV to live long and healthy lives. The development of ART has changed the course of the HIV epidemic. By taking a daily combination of these medicines, people with HIV can maintain their health and prevent transmission, which has become the standard of care for managing the infection.
How Anti-HIV Medications Stop the Virus
To understand how anti-HIV drugs work, it helps to know what the virus does inside the body. HIV’s goal is to replicate by taking over immune cells called CD4 cells. The process, known as the HIV life cycle, begins when the virus enters a CD4 cell. Once inside, HIV uses an enzyme called reverse transcriptase to convert its genetic material, RNA, into DNA.
This viral DNA is then inserted into the CD4 cell’s DNA using another enzyme, integrase. The cell’s machinery is then hijacked to produce the building blocks for new HIV particles. These components are assembled into immature viruses that bud from the cell. In a final step, an enzyme called protease cuts protein chains in the immature virus, allowing it to mature into an infectious form.
Anti-HIV medications interrupt this sequence. By targeting distinct stages of the HIV life cycle, these drugs prevent the virus from completing its replication process. This intervention stops the production of new virus particles, halting the progression of the infection.
Classes of Anti-HIV Drugs
Several classes of anti-HIV drugs exist, each targeting a different step in the virus’s replication cycle. This variety allows for a multi-pronged attack by inhibiting the enzymes HIV needs to multiply.
Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs) work by providing faulty building blocks during reverse transcription, which terminates the construction of the viral DNA chain. Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) also target this stage but work by binding directly to the reverse transcriptase enzyme, preventing it from functioning.
Integrase Inhibitors (INSTIs) block the integrase enzyme, preventing the virus’s DNA from being inserted into the host cell’s DNA. Protease Inhibitors (PIs) interfere with the final stage by blocking the protease enzyme. This action prevents immature virus particles from being assembled into mature, infectious HIV.
Entry Inhibitors work by preventing HIV from entering CD4 cells. This class includes attachment, post-attachment, and fusion inhibitors, which interfere with the virus binding to and merging with the cell membrane.
Treatment Regimens and Goals
Modern HIV treatment, known as antiretroviral therapy (ART), uses a combination of drugs from different classes. This strategy involves taking at least two, and often three, different medications. This approach attacks the viral life cycle at multiple points, making it much harder for the virus to develop resistance.
The primary objective of ART is to reduce the amount of HIV in the body, or viral load, to an undetectable level. Successful treatment lowers the viral load to where standard tests cannot detect it. Maintaining an undetectable viral load allows the immune system to recover, protecting the body from opportunistic infections.
An undetectable viral load has another benefit: a person with HIV who maintains it through consistent treatment has effectively no risk of transmitting the virus to a sexual partner. This concept is known as “Undetectable = Untransmittable” (U=U). This principle highlights the power of ART to preserve individual health and halt the spread of the virus.
Using Anti-HIV Drugs for Prevention
The medications used to treat HIV are also effective for prevention and are a tool in public health efforts to stop the virus’s spread. The two main prevention strategies are Pre-Exposure Prophylaxis (PrEP) and Post-Exposure Prophylaxis (PEP).
PrEP is for HIV-negative people who have a higher risk of exposure. It involves taking an anti-HIV medication as a daily pill or a long-acting injection to build up protection. When taken consistently, PrEP is effective at preventing HIV infection.
PEP is an emergency measure used after a potential HIV exposure. It involves a 28-day course of anti-HIV drugs to prevent the virus from establishing an infection. For PEP to be effective, it must be started within 72 hours of the possible exposure and is often used after unprotected sex or needlestick injuries.