Retroviruses Flashcards
What Are Retroviruses?
Family of Enveloped (+) Sense ssRNA Viruses That Replicate by Converting RNA into DNA.
Viral RNA Integrated Into Host Genome, Mediated by Reverse Transcriptase.
Describe The Retrovirus Genome.
- Diploid RNA
- Encode at Least 3 Genes (gag, pol + env)
- RNAs Joined together near 5’ ends by H
Bonds
Discuss Retroviral Proteins.
Protease (PR): Encoded by pro Gene
- Needed for Virus Maturation (So It Becomes
Infectious) - Encoded Separately/As part of Gag/Gag-Pro-
Pol Polyprotein
Group Specific Antigen (gag):
Processed into (Proteolytically):
- Matrix
- Capsid
- Nucleocapsid
Envelope Protein (env):
- Mediates Viral Entry Into Host Cells
- Encodes Surface Glycoprotein and
Transmembrane Protein
What Are The Stages of The Retroviral Replication Cycle?
- Attachment
- Penetration
- Synthesis
- Assembly
- Release
How Do Viruses Penetrate Host Cells?
Via Fusion With Plasma Membrane Or Endocytosis
What Is Human Immunodeficiency Virus (HIV)
A lentivirus (Slowly Replicating Virus) that causes Acquired immunodeficiency Syndrome (AIDS)
How Is HIV Transmitted?
- Sexual Behaviors
- Blood
- Semen
- Vaginal Fluids
- Pre-seminal Fluids
- Rectal Fluids
- Breast Milk
What is Stage 1 Of The HIV Life Cycle?
Attachment:
HIV gp120 binds To CD4 Receptors on T Helper Cells, Macrophages and Dendritic Cells
Co-Receptors needed for HIV infection:
- CXCR4
- CCR5
What Happens In Stage 2 Of HIV Life Cycle?
Fusion:
Viral Envelope Fuses With Cell Membrane (gp41)
Contents Released Into Cell
What Happens In Stage 3 of HIV Life Cycle?
Replication:
- Viral RNA converted into DNA - By Reverse
Transcriptase - Viral DNA Inserted Into Host Cell
Chromosome - By Integrase - Integrated Viral DNA Can remain Latent
(Provirus) - Viral DNA Transcribed, RNA Translated
- Viral Proteins Produced, Viral Genome
Replicated
What Happens In Stage 4 Of HIV Life Cycle?
Assembly:
New HIV Virions + Viral Proteins Produced using Host Cell’s Metabolic Machinery
