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 Transduction Lysogenic Phage Excision of the prophage gal bio gal bio gal bio gal bio gal 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