Introduction to HIV Virus

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Introduction to HIV Virus
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What is HIV?

• Human Immunodeficiency Virus
• Composed of 9 genes
• Bacteria typically have 5000 genes
• Humans have 20,000-25,000 genes

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Structure of HIV

• 2 identical copies of single strands of RNA
• Surrounded by viral Envelope of fatty material
• On viral envelope are 72 spikes composed of
  proteins gp120 and gp 41

gpglycoprotein number is molecular weight
(daltons)
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• Beneath is a viral matrix composed of protein p17
• RNA is surrounded by a capsid of protein p24

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• Also contains 3 enyzmes needed for HIV
  replication
• Reverse transcriptase
• Integrase
• Protease

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HIV Infection and Replication
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Entry

• HIV Spikes (Ligand) g120/41
• Must Attach to at least two Receptors on Helper
  T-lymphocytes
• CD4
• 7-transmembrane receptor
• HIV Ligand is the Key to Unlock the Receptor on
  the CD4 T cell

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• Releases contents into CD4 or Helper T-Cell

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Reverse Transcription and Integration

• HIV enzyme reverse transcriptase converts viral
  RNA to DNA
• Makes copying errors
• Leads to variations in HIV
• New viral DNA is spliced into human DNA by HIV
  enzyme integrase

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Transcription and Translation

• Viral DNA lies dormant until T-cell is activated
• Human DNA with viral DNA (provirus) now makes
  messenger RNA (human and viral)
• Translated at ribosomes to make new HIV proteins

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Assembly

• New long Viral polypeptide chain is chopped up
  into smaller pieces by protease
• Creating new enzymes and viral coat proteins

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Budding and Maturation

• Assembles all viral components
• Buds from host cell
• Takes a piece of the host plasma membrane

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Effect on Immune System

• Activates Helper T-Cell The General
• Secretes Cytokines which
• Activate macrophages, cytotoxic or killer
  T-cells, and natural killer cells
• Control maturation and induction of
  antibody-producing B cells
• Secrete colony stimulating factors for more white
  blood cells

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1st Stage of Infection -Primary

• Rapid viral replication
• Patient exhibits flu-like symptoms
• Undergoing Seroconversion
• B-cells making antibodies
• Patient is infectious but will not test for
  HIV

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2nd Stage of Infection-Clinical Latency

• Strong immune defense to that particular variant
  of HIV
• Reduced number of viruses
• Lasts 2 weeks -20 years
• Patient still infectious
• Will test for HIV

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3rd Stage of InfectionAIDS

• Virus has mutated
• T-cells and B-cells are activating against all
  the different variants of HIV
• Helper T-cells are dying
• Bone marrow cant make new cells fast enough
• Immune System is overloaded and compromised

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• Normal count 800-1200 cells/ul
• If CD4 T cell count drops below 200 cells /ul
• patient has AIDS
• patient is susceptible to opportunistic
  infections.

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Types of Drugs Used on HIV

• Reverse Transcriptase Inhibitors
• AZT blocks recoding of viral RNA into DNA
• Protease Inhibitors
• Blocks protease that cleaves viral polypeptide
  into functional enzymes
• Best regimen is cocktail of both types of drugs

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The End