Viruses
description
Transcript of Viruses
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VIRUSES
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Lytic vs. Lysogenic
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Vaccines• First made was in 1700’s- fight smallpox• Help prevent viral infections, but they cannot cure most
viral infection • Some recently-developed drugs do combat some viruses,
mostly by interfering with viral nucleic acid synthesis.• AZT interferes with reverse transcriptase of HIV.• Acyclovir inhibits herpes virus DNA synthesis.
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WHAT IS HIV??• “Human Immunodeficiency Virus”• A unique type of virus (a retrovirus)• Invades the helper T cells in the body of the host• Preventable, managable but not curable
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WHAT IS AIDS ???• “Acquired Immunodeficiency Syndrome”• HIV is the virus that causes AIDS• Disease limits the body’s ability to fight infection due to reduced helper T cells.
• Patients predisposed to multiple opportunistic infections leading to death.
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Stage 1 - Primary• Short, flu-like illness - occurs one to six weeks after infection
• Mild symptoms• Infected person can infect other people
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Stage 2 - Asymptomatic• Lasts for an average of ten years • This stage is free from symptoms• There may be swollen glands• The level of HIV in the blood drops to low levels
• HIV antibodies are detectable in the blood
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Stage 3 - Symptomatic
• The immune system deteriorates • Opportunistic infections and cancers start to appear.
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Stage 4 - HIV AIDS
• The immune system weakens too much as CD4 cells decrease in number.
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Opportunistic Infections associated with AIDS• Bacterial infections
• Tuberculosis (TB)• Herpes Simplex• Herpes Zoster• Vaginal candidiasis• Hairy leukoplakia• Kaposi’s sarcoma
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Opportunistic Infections associated with AIDS
• Pneumocystic carinii• Toxoplasmosis• Cryptococcosis• Coccidiodomycosis• Cryptosporiosis• Non hodgkin’s lymphoma
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HAART = highly active anti-retroviral treatment
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Transduction
• Definition: Gene transfer from a donor to a recipient by way of a bacteriophage
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Transduction
• Types of transduction– Generalized - Transduction in which
potentially any donor bacterial gene can be transferred
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Generalized Transduction
• Release of phage
• Phage replication and degradation of host DNA• Assembly of phages particles
• Infection of recipient• Legitimate recombination
• Infection of Donor
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Transduction• Types of transduction
• Generalized - Transduction in which potentially any dornor bacterial gene can be transferred.
– Specialized - Transduction in which only certain donor genes can be transferred
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Specialized TransductionLysogenic Phage
• Excision of the prophage
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bio
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bio
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gal
• Replication and release of phage
• Infection of the recipient
• Lysogenization of the recipient– Legitimate
recombination also possible
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Transposable Genetic Elements• Definition: Segments of DNA that are able to move from
one location to another• Properties
• “Random” movement• Not capable of self replication• Transposition mediated by site-specific recombination
• Transposase
• Transposition may be accompanied by duplication