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Viruses Ch 19 – Lecture Monday 12/2/13
Tuesday: Lab Quiz: Protists and FungiWednesday: Lecture Quiz on Fungi
Thursday: LAB Exam* Bring book and notes
Importance of Viruses
1. Agent of diseases2. Vector of gene in biotechnology– 30% of human DNA is viral
3. Agent of evolution or mutation
Smallpox viral disease
• Infectious variola virus cause maculopapular rash• Transmission via respiratory droplets• Cause macropuplar rash (not itchy) with permanent scarring• Transmission via respiratory droplets• Humans are the only known host• Eradicated 1979• Russia and US have smallpox samples• Can be used as a bioweapon• Death occurs in 30% of cases due to respiratory
complications
Chicken pox and shingles
• Varicella zoster virus• Virus dwell in sensory nerves• Symptoms include rashes, fever, and general
malaise• Adult form: shingles
Rabies (hydrophia)
• Viral need treatment in 3 days• Zoonotic disease (spread by animals) that
cause encephalitis resulting in violence, madness, and hydrophobia
• Virus causes nervous damage• Delirium, coma, death• Bats are likely rabies vectors
Herpes I
• Herpes I cause sores and blisters
Herpes II
• Cause genital blisters• Mild and asymptomic in healthy adults• Can be transmitted to newborn
AIDS
• HIV targets specific cells. HIV kills white blood cells with CD4 antigen, primarily T helper cells
• T-helper cells are crucial in the activation of other white blood cells
• T helper cells are generals. They organize immune strategy.
• Death from AIDS is due to opportunistic infections– TB, PDP, Kaposi Sarcoma, toxoplasmosis
AIDS v HIV
• HIV positive:• AIDS: T cell count is below 200 micro-liter
Common cold, influenza, SARS, Hanta virus
• Cause respiratory problems
Hepatitis A
• Liver inflammation• Transmitted primarily contaminated water or
food• Infection occurs during childhood• Cause liver damage• Vaccine available
Hepatitis B
• Blood transfusion/exchange• Vaccine vacation • Can lead to liver cirrhosis (hardening) and
caner
Hepatitis C
• Transmitted via blood exchange• Most cases are asymptomatic• Can progress to liver cirrhosis and cancer req
requiring liver transplant• No effective vaccine available
Warts and cervical cancer
• Caused HPV• Can lead to cervical, ovarian, genital, and anal
cancers• We all have had it• Can transmit by casual contact • Vaccine available for 70% of cases called
Gardasil. You have to get it before you get sexually active.
Ebola & Marbug
• Mortality is as high as 90%• Cause shock due to loss of vascular integrity
and loss of coagulation• Endemic and sporadic
Structure of Viruses
• Viruses are NOT cells. • Viruses are obligate intracellular parasites. They are
active or reproduce only when inside host cells• Viruses consist of nucleic acid enclosed in capsid
(protein coat) and membranous envelope. • Each virus has a host range, a limit number of host
cells that it can inflect. – Herpes will attack only nerve cells, not muscle cells– H1N1 can go from one species to another
• Viruses are smaller and simpler than bacteria,.
All viruses
• 1. Have RNA or DNA• All viruses have protein shells or capsids.
Viral genomes
• All viruses have double or single RNA or DNA. It can’t be both DNA and RNA. It is one or the other.
capsid
• Protein shell that encloses the viral genome• Functions: attachment to host cell protection
of genome• Capsid of some virus is used as a vaccine to
induce immunity– BHV, HPV, and polio vaccines
Membranes (some viruses)
• Some viruses have membranous envelopes that surround the capsid which helped them infect host cells
• Viruses acquire membranes from host cells. • Host cell membranes allow viruses to escape
detection by host white blood cells.• exocytosis
spikes
• Some viruses have spikes protruding from their envelope (glycoprotein)
• Spikes help viruses attach to host cells• H (hemagluttin) N (neuranidase) H1N1: spikes
are made of proteins H and N.
Bacteriophages: viruses that infect bacteria
• Two types: lytic and lysogenic
Lytic (virulent phage)
• Upon entrance, virus directs host cell to synthesize more virus copies.
• Capsid stays out. Only DNA or RNA goes inside the host.
• Lytic cycle terminates in death of host cell. • Virulent phage: a phase that reproduces only
by lytic cycle• Virus only injects the genome into host cells,
not capsid
Lysogenic
• Viral DNA is incorporated into the host DNA• Virus knows when host cell will die• Prophage: integrated viral DNA• Every time host divides, virus genome also gets
copied and viral genome is passed on to daughter cells.
• Temperate phage: uses both lytic and lysogenic cycles. HIV is temperate
• Does NOT kill host cell immediately