HIV
6.6 Understand how Mycobacterium tuberculosis (TB) and Human Immunodeficiency Virus (HIV)
infect human cells, causing a sequence of symptoms that may result in death.
HIV
• The human immunodeficiency virus (HIV) infects and destroys T helper cells, which act as a host
cell for the virus.
• HIV is spread through infected bodily fluids.
• Infection of a new host occurs when these fluids come into contact with muscosal surfaces or
damaged tissue, or are injected into the bloodstream.
Replication
• Viruses can only reproduce inside the cells of the organism it has infected, as they lack the enzymes
are ribosomes necessary to produce proteins).
• HIV replicates inside the T helper cells of the host.
• The HIV genome consists of two identical, single-stranded RNA molecules.
Process:
1. The attachment protein attaches to a receptor molecule on the cell membrane of the host T helper
cell.
2. The capsid is released into the cell, where it uncoats and releases the RNA into the cell’s cytoplasm.
3. Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral
RNA template.
4. From this, a double-stranded DNA molecule is made.
5. The DNA molecule is inserted into the host’s DNA using another virus enzyme, integrase.
6. Host cell enzymes are used to make viral proteins from the viral DNA.
7. The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other
cell.
Acute Phase & Latency Period
• During the initial infection period, HIV replicates rapidly and the infected person may experience
severe flu-like symptoms.
• After this period, HIV replication drops to a lower level (the latency period).
• During the latency period (which can last for years), the infected person won’t experience any
symptoms).
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