Transcript Virus 2
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 • Infection of Donor • Phage replication and degradation of host DNA • Assembly of phages particles • Release of phage • Infection of recipient • Legitimate recombination 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 Transduction Lysogenic Phage • Excision of the prophage • Replication and release of phage • Infection of the recipient • Lysogenization of the recipient – Legitimate recombination also possible bio gal gal gal bio gal bio bio bio 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