Cells: Cell Recognition & the Immune System - HIV Flashcards

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1
Q

What is HIV?

A
  • HIV stands for human immunodeficiency virus
  • It is a virus that affects the human immune system
  • It eventually leads to AIDS
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2
Q

What is AIDS?

A
  • AIDS stands for acquired immune deficiency syndrome
  • AIDS is a condition where the immune system deteriorates and eventually fails
  • Makes people more vunerable to other infections
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3
Q

Describe the structure of HIV

A

• Core

  • Contains genetic material (RNA)
  • Contains some molecules (e.g enzyme reverse transcriptase - needed for virus replication)

• Outer layers

  • Has an outer coating of protein called a capsid
  • Has an extra outer layer called the lipid envelope -made of membrane taken from material surrounding the host cell
  • Sticking out the envelope are copies of attachment proteins that help HIV attach to the host helper T-cell
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4
Q

How does HIV infect cells and replicate?

A

• Invasion of cells

  • HIV attaches to the helper T cells
  • The T cells have receptor molecules that bind to the attachment proteins of HIV
  • The HIV enters and releases RNA into the cell

• Transcription of RNA

  • The reverse transcriptase transcribes the viral RNA into DNA
  • The viral DNA made is called a provirus
  • The viral DNA (provirus) is spliced into the host cell DNA
  • The host cell is now ready to make copies of the virus
  • Cells experience period of latency

• Replication

  • Host cell enzymes make viral proteins from viral DNA
  • These assemble into new viruses, which burst out of the cell, destroying it

• Further infection

  • Viruses infect more T cells and destroy them
  • The immune system is more and more compromised
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5
Q

What term is used to describe the dormancy of cells infected with HIV?

A

• Period of latency

  • HIV replication drops and cells become dormant
  • The viral DNA awaits a chemical signal to prompt the host cell to produce new virus
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6
Q

Describe the symptoms people have during initial infection of HIV and during the period of latency

A
  • During the initial infection period, the infected person may experience severe flu-like symptoms
  • After this, the latency period begins and the infected person won’t experience any symptoms
  • This is because HIV replication drops and cells become dormant
  • The latency period can last years
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7
Q

When are people classed as having AIDS?

A
  • People with HIV are classed as having AIDS when:
  • Symptoms of their failing immune system start to appear
  • Or when their T cell count drops below a certain level
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8
Q

How does HIV cause the symptoms of AIDS?

A
  • HIV kills T cells which are required for the specific immune response
  • Without these, there is no response to pathogens and no immunological memory
  • The body cannot fight infection with pathogens
  • As AIDS progresses, the number of immune system cells decreases further and patients become susceptible to more serious infections
  • Death is not directly from HIV, but is from secondary infections – most commonly TB and pneumonia
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9
Q

Why are antibiotics ineffective against viruses?

A
  • Antibiotics kill bacteria, not viruses
  • This is because many antibiotics work by preventing bacteria from making cells walls
  • Without this the bacterial cell cannot control the entry and exit of water and will therefore burst
  • Viruses don’t have a cell wall and are reproduced within a host cell so they are unaffected by antibiotics
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10
Q

Suggest possible treatments for HIV

A
  • Use antibodies that target the antigens of HIV before it enters T cells
  • Use enzyme inhibitors to block the reverse transcriptase, therefore preventing reverse transcription and viral replication
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