HIV virus

Human Immunodeficiency Virus (HIV)

The Human Immunodeficiency Virus (HIV) is a lentivirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype.

Virology

HIV is a member of the genus Lentivirus, part of the family Retroviridae. Lentiviruses are transmitted as single-stranded, positive-sense, enveloped RNA viruses. Upon entry into the target cell, the viral RNA genome is converted into double-stranded DNA by a virally encoded reverse transcriptase that is transported along with the viral genome in the virus particle. The resulting viral DNA is then integrated into the cellular DNA by a virally encoded integrase and host co-factors. Once integrated, the virus may become latent, allowing the virus and its host cell to avoid detection by the immune system.

Transmission

HIV is transmitted via the exchange of a variety of body fluids from infected individuals, such as blood, breast milk, semen, and vaginal secretions. Transmission can occur during unprotected sexual intercourse, contaminated blood transfusions, hypodermic needles, and from mother to child during pregnancy, delivery, or breastfeeding.

Pathogenesis

HIV primarily infects vital cells in the human immune system such as CD4+ T cells, macrophages, and dendritic cells. HIV infection leads to low levels of CD4+ T cells through a number of mechanisms, including apoptosis of uninfected bystander cells, direct viral killing of infected cells, and killing of infected CD4+ T cells by CD8+ cytotoxic T lymphocytes that recognize infected cells.

Clinical Manifestations

The clinical course of HIV infection is divided into three stages:

Acute Infection

This stage is characterized by a high level of virus in the blood and a decrease in the number of CD4+ T cells. Symptoms are often flu-like and may include fever, headache, rash, and swollen lymph nodes.

Clinical Latency

During this stage, the virus is active but reproduces at very low levels. People may not have any symptoms or only mild ones. This stage can last for several years.

AIDS

AIDS is the final stage of HIV infection, where the immune system is severely damaged. People with AIDS have a high viral load and very low CD4+ T cell counts, making them vulnerable to opportunistic infections and certain cancers.

Diagnosis

HIV infection is diagnosed using serological tests that detect antibodies to HIV, as well as tests that detect the virus itself, such as PCR tests that detect viral RNA.

Treatment

HIV infection is treated with antiretroviral therapy (ART), which involves a combination of at least three antiretroviral drugs. ART does not cure HIV infection but controls viral replication, allowing the immune system to recover and function properly.

Prevention

Preventive measures include safe sex practices, needle exchange programs, and pre-exposure prophylaxis (PrEP) for high-risk individuals. Mother-to-child transmission can be reduced by treating the mother with ART during pregnancy and delivery, and treating the infant after birth.

Research

Research is ongoing to develop a vaccine for HIV, as well as to find a cure. Studies are also focused on understanding the virus's mechanisms of infection and latency.

See Also

• Acquired Immunodeficiency Syndrome
• Antiretroviral Therapy
• Opportunistic Infections