Microbiology
Summary
HIV (human immunodeficiency virus), a member of the Retroviridae family, is a positive-sense RNA virus with a diploid genome. There are two types of HIV: HIV-1 and HIV-2, with HIV-1 being the most prevalent worldwide. The HIV virion consists of a conical capsid made of p24 subunits (capsid protein) and a protective shell of p17 subunits (matrix protein). The virion's envelope includes gp41 and gp120 glycoproteins.
HIV can be transmitted sexually, through blood (e.g., blood transfusions or sharing needles), and vertically from mother to child. HIV targets white blood cells, specifically those with the CD4 determinant, including helper T-cells and macrophages. The disease progression is marked initially by an acute phase with flu-like symptoms, followed by a long asymptomatic period known as clinical latency, which lasts 8-10 years. If left untreated, HIV infection leads to AIDS (acquired immunodeficiency syndrome). The diagnosis of AIDS is based on CD4 counts <200< strong=""> or the presence of an AIDS-defining illness, often characteristic syndromes or opportunistic infections resulting from immunosuppression. HIV testing starts with a fourth-generation test to detect HIV-1, HIV-2, and the p24 antigen, followed by an antibody differentiation immunoassay. For early detection during the serologic window, nucleic acid testing (NAT) is employed to detect HIV RNA.
Lesson Outline
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FAQs
The human immunodeficiency virus (HIV) is a part of the Retroviridae family. More specifically, it belongs to the Lentivirus genus. There are two types of HIV, known as HIV-1 and HIV-2. These are retroviruses that they use an enzyme called reverse transcriptase to replicate their RNA into DNA within a host cell.
HIV infection, if left untreated, can lead to AIDS (acquired immunodeficiency syndrome). HIV infects and destroys CD4 cells (a type of white blood cell), which the immune system needs to fight infections. AIDS is the final stage of HIV infection and is diagnosed when the number of CD4 cells falls below a certain level or if certain opportunistic infections or cancers occur.
The CD4 T-cell count is significant in HIV infections as it is a critical measurement of immune system health. These cells are a type of white blood cell that HIV specifically targets and destroys. A healthy person typically has a CD4 count between 500 and 1,500 cells per cubic millimeter of blood. A count below 200 or the occurrence of certain diseases is an indicator of the progression to AIDS in a person with HIV.
The reverse transcriptase enzyme plays a crucial role in the life cycle of HIV. After HIV's genetic material enters a host cell, the virus uses its reverse transcriptase to convert its RNA into DNA. This DNA is then integrated into the host cell's genetic material where it may remain dormant or immediately initiate the production of new HIV particles.
'Immunocompromised' refers to a weakened immune system. In the context of HIV, because the virus targets and destroys CD4 T cells, it compromises the body's ability to fight off infections and disease. Over time, as the number of CD4 T cells decreases, the individual becomes increasingly immunocompromised, eventually leading to AIDS if not treated.
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