HIV Replication Cycle
Depending on the ages of your students, you may want to examine the HIV life cycle in more detail. Use the “HIV Replication Cycle” sheet as a guide. Following are the steps involved in HIV infection of a cell.
Attachment and entry. The HIV virus bumps into a CD4+ white blood cell, attaches to it, and injects the capsid and its contents into the cell
Reverse transcriptase. Once inside the cell, HIV genetic material (in the form of RNA) is converted into a form that is compatible with the cell’s genetic information (DNA). In cells, DNA usually is used to produce new RNA through a process called transcription. When RNA is used as a template to produce DNA, as is the case with HIV infection, the process is referred to as “reverse” transcription.
Integration. The newly formed viral DNA moves into the cell nucleus, where it is spliced into the cell’s human DNA. The HIV genetic material may remain dormant or inactive for many years. In this state, HIV is able to “hide” from the immune system and is unaffected by antiviral treatments.
Transcription and translation. The viral DNA becomes active and directs the cell’s machinery to produce the virus components: viral RNA, viral envelope and capsid. This activation can occur many years after initial infection with HIV, and is not yet completely understood.
Assembly and release. The viral particle is assembled, fuses to the cell membrane and is released by “budding” off the surface of the cell. During the budding process, the new particle wraps itself in part of the host cell’s membrane to create the viral envelope. The new virus particles now circulate within the body and are able to invade other cells.
Viruses cannot live, grow and reproduce on their own. Instead, they must invade cells of living organisms and force these cells to produce more viruses. This invasion of healthy cells is how viruses cause disease.
HIV is one of a handful of viruses known to reverse the normal pathway through which genetic information is transmitted within cells. Usually, DNA is used to produce RNA, which then directs the assembly of proteins in cells. HIV, however, is able to use its own RNA as a template to produce viral DNA that can be spliced into the DNA of the human host cell.
Keywords: AIDS | blood | capsid | disease | DNA | epidemic | epidemiologist | epidemiology | HIV/AIDS | illness | immune system | infection | microbe | microbiology | microscope | pandemic | pathogen | replication cycle | retrovirus | RNA | SEM TEM | T-cell | viral assembly | virion | virus | white blood cell | HIV
- Vogt, G., and Moreno, N. (2012) The Science of HIV/AIDS Teacher’s Guide. Baylor College of Medicine: Houston. ISBN: 978-1-888997-62-0
- Illustration by G.L. Vogt and M.S. Young © Baylor College of Medicine.
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