VIRUSES. Lytic vs. Lysogenic Vaccines First made was in 1700’s- fight smallpox Help prevent viral...
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Transcript of VIRUSES. Lytic vs. Lysogenic Vaccines First made was in 1700’s- fight smallpox Help prevent viral...
VIRUSES
Lytic vs. Lysogenic
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.
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
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.
Stage 1 - Primary• Short, flu-like illness - occurs one to six weeks after infection
• Mild symptoms
• Infected person can infect other people
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
Stage 3 - Symptomatic
• The immune system deteriorates
• Opportunistic infections and cancers start to appear.
Stage 4 - HIV AIDS
• The immune system weakens too much as CD4 cells decrease in number.
Opportunistic Infections associated with AIDS• Bacterial infections
• Tuberculosis (TB)• Herpes Simplex• Herpes Zoster• Vaginal candidiasis• Hairy leukoplakia• Kaposi’s sarcoma
Opportunistic Infections associated with AIDS
• Pneumocystic carinii• Toxoplasmosis• Cryptococcosis• Coccidiodomycosis• Cryptosporiosis• Non hodgkin’s lymphoma
HAART = highly active anti-retroviral treatment
Transduction
• Definition: Gene transfer from a donor to a recipient by way of a bacteriophage
Transduction
• Types of transduction– Generalized - Transduction in which
potentially any donor bacterial gene can be transferred
Generalized Transduction
• Release of phage
• Phage replication and degradation of host DNA• Assembly of phages particles
• Infection of recipient• Legitimate recombination
• Infection of Donor
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
Specialized TransductionLysogenic Phage
• Excision of the prophage
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• Replication and release of phage
• Infection of the recipient
• Lysogenization of the recipient– Legitimate
recombination also possible
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