- The reproductive cycle of HIV begins when the virus attaches and fuses with the plasma membrane of a cell. HIV entry into the cell requires CD4, a molecule on the surface of helper T cells, and some macrophages and B cells. Other coreceptors for the HIV virus include fusin and CCR5. - Once the virus enters the cell, the viral protein reverse transcriptase begins synthesizing DNA from the viral RNA strand, which eventually gives rise to a segment of double stranded DNA.

- The double stranded viral DNA then enters the nucleus and inserts into the host cell’s genome. The DNA then directs the synthesis of mRNA that encodes viral proteins. - The mRNA exits the nucleus and enters the cytoplasm, where it will direct the synthesis of viral proteins. - The viral proteins will then assemble with the mRNA and bud off of the host cell as new virus particles. - The chart to the left shows the timeline of an HIV infection. In the first year of an HIV infection, the virus concentration in the blood peaks sharply and then rapidly declines due to an immune response. Notice that at the same time, the concentration of T cells and HIV antibodies in the blood has increased. - During the period when virus concentration is low, the virus continues to replicate itself in the lymphatic system. As the lymphatic system breaks down, the virus concentration increases in the blood. At the same time, the T cell concentration in the blood decreases as T cells are depleted. - During the final stages of an HIV infection (AIDS), the T cell concentration reaches an all time low while the virus continues to replicate.

What is the role of reverse transcriptase in a retrovirus?

- Reverse transcriptase is used to catalyze the synthesis of DNA from RNA.

12.10.1 HIV: An Attack on the Immune System Flashcards by Irina Soloshenko

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12.10.1 HIV: An Attack on the Immune System Flashcards

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