Viruses, Protists) Part Ii

Part II, Viruses and their Allies • Noncellular infectious agent • Consists of protein wrapped around a nucleic acid core • Cannot reproduce itself; can only be reproduced using a host cell

Viral Body Plans • Genetic material is DNA or RNA • Coat is protein

Helical virus

Polyhedral virus

Complex virus (bacteriophage)

Enveloped Virus (HIV)

lipid envelope; proteins span the envelope, line its inner surface, spike out above it

viral coat (proteins)

Viral Multiplication - Basic Steps • Virus attaches to host cell • Whole virus or genetic material enters host • Viral DNA or RNA directs host to make viral genetic material and protein • Viral nucleic acids and proteins are assembled • New viral particles are released from cell

Lytic Pathway Refer to text for graphic

Lysis

Assembly

Assembly Virus injects genetic material

Production of viral components

Lysogenic Pathway (Refer to text forLatent graphic) period extends the cycle

Viral DNA becomes part of host chromosome for a time

Viral material integrated

Viral material passed on

Video: Virus Reproduction

• http://www.med.sc.edu:85/movies/phageh.mov

Replication of an Enveloped Virus Refer to text for graphic.

Transcription of viral genes DNA replication

Assembly

Translation Proteins

Answer 14 • 14. Viruses are composed of an outer protein coat with an interior core of nucleic acid.

Answer 15 • 15. HIV is a(n) enveloped (or RNA) virus.

Answer 16 • 16. Identify this type of virus. helical

Answer 17 • 17. Identify this type of virus. complex

Answer 18 • 18. Name the two modes of viral replication. Lytic and lysogenic

Question 19 • 19. Of the two modes which one may have a long “latent” (resting) period?

Answer 19 • 19. Of the two modes which one may have a long “latent” (resting) period? • lysogenic

Food and Water Borne Viruses • • • •

Norwalk and Norwalk-like viruses Polio hepatitis A (HA) Massive virus discovered in water tower

Norwalk and Norwalk-like viruses • • • • •

small round structured viruses (SRSVs) strand RNA single structural protein viral gastroenteritis self-limiting, mild, and characterized by nausea, vomiting, diarrhea, and abdominal pain.

Massive Virus Discovered in Water Tower “The largest virus ever discovered has been found in a water-cooling tower in Bradford, England. It was lurking inside single-celled organisms called amoebae, but its discoverers believe that it may also be capable of infecting humans. “

http://www.newscientist.com/news/news.jsp?id=ns99993559

Photo from the New Scientist girth of 400 nanometers (visible with a good light microscope) 900 genes

Polio • Small water-food borne RNA virus • In about 1% of the infected population, the virus attacks and kills motor neurons • This results in various degrees of paralysis

http://www.rednova.com/news/stories/2/2003/04/29/story004.html

Polio’s Effects

http://cha.state.md.us/edcp/html/polio.html

http://www.bret.org.uk/nec2.htm

Hepatitis A (HA) Symptoms • • • • • • •

fatigue jaundice abdominal pain loss of appetite nausea diarrhea fever

Persons at Risk • Household contacts of infected persons • Sex contacts of infected persons • Persons, especially children, living in areas with increased rates of hepatitis A during the baseline period from 1987-1997. • Persons traveling to countries where hepatitis A is common • Men who have sex with men • Injecting and non-injecting drug users

Average reported cases of hepatitis A per 100,000 population*, 1987-1997

Red> 20

The HA World

TRANSMISSION • “HAV is found in the stool (feces) of persons with hepatitis A.  • HAV is usually spread from person to person by putting something in the mouth (even though it may look clean) that has been contaminated with the stool of a person with hepatitis A. ”

Prevention • “Hepatitis A vaccine is the best protection. • Short-term protection against hepatitis A is available from immune globulin. It can be given before and within 2 weeks after coming in contact with HAV.  • Always wash your hands with soap and water after using the bathroom, changing a diaper, and before preparing and eating food.”

Vaccination • “Travelers to areas with increased rates of hepatitis A • Men who have sex with men • Injecting and non-injecting drug users • Persons with clotting-factor disorders (e.g. hemophilia) • Persons with chronic liver disease • Children living in areas with increased rates of hepatitis A during the baseline period from 19871997.” http://www.cdc.gov/ncidod/diseases/hepatitis/a/fact.htm

Outback chain acquires ChiChi's

LOUISVILLE, Ky. (AP) — Chi-Chi's, the chain of Mexican restaurants, may have served its last chimichanga.     Outback Steakhouse Inc. this week closed on its $42.5 million deal for the rights to 76 restaurants in the Chi-Chi's chain, which was beleaguered by bankruptcy and a hepatitis outbreak.

http://www.washtimes.com/business/20040922-091157-9257r.htm

Cervical Cancer and Human Papilloma Virus • “Q:  I was surprised recently to learn that cancer of the cervix may be caused by a virus. I had never heard this before and would like more information. • A:  Cancer of the cervix should probably be reclassified as a sexually transmitted disease. More than 95% of all cases can be attributed to three types of human papilloma virus (HPV). This is the virus that causes genital warts. “ • (From: http://healthlink.mcw.edu/article/951329620.html

Cervical Cancer and HPV

Yes, cervical cancer is infectious.

Answer 20 • 20. Hepatitis A infects which organ? • liver

Answer 21 • 21. Which water born virus may attack and kill motor neurons (nerves)? • polio

Viroids • Smaller than viruses • Strands or circles of RNA • No protein-coding genes • No protein coat • Cause many plant diseases

PSTV • Most known viroids cause diseases in plants. • The first viroid was discovered in 1971, by Diener. It's called the potato spindle tuber virus (PSTV), • Contains a single loop of RNA • Relies wholly on enzymes all ready in the host cell http://math.ucr.edu/home/baez/subcellular.html#Viroids

“Vegetable MD Online” • Cornell University Ag School

http://vegetablemdonline.ppath.cornell.edu/Images/Potatoes/PotatoViruses/PotatoVirusfs1.jpg

Prions • Small proteins • Linked to human diseases – Kuru – Creutzfeldt-Jakob disease (CJD)

• Animal diseases – Scrapie in sheep – Bovine spongiform encephalopathy (mad cow disease)

BSE (Mad Cow Disease) There is a disease similar to BSE called Creutzfeldt-Jacob Disease (CJD) that is found in people.

Fore tribes of Papua, New Guinea….Kuru…. “the trembling with fear” Creutzfeldt• “The real breakthrough for understanding

Jakob disease occurred in 1957 with the discovery of a curious degenerative brain disease of cannibals. Certain Fore tribes of Papua, New Guinea were inflicted with a disease called Kuru - the trembling with fear. This disease manifested itself as a fatal disease with an onset and duration that lasted usually 1 year. To date there have been 2500+ cases reported in these relatively small villages with an occurrence of at least 1% of the population. It was prevalent in women and children but rarely affected adult males. The terminal stage of this brain disease was marked by total dementia, muteness, inability to move, ataxia ( jerkiness of the muscles ), dysarthria, dysphagia and death.”

http://psyweb.com/Mdisord/jsp/CJdisease.jsp

Kuru was determined to be linked to the ritual cannibalism…. • “Kuru was determined to be linked to the ritual cannibalism that was practiced by these tribes. The brains of the elders were ritually prepared and eaten by the women and children, but seldom by the men. This endocannibalism was outlawed by the authorities of New Guinea and now the disease is slowly disappearing. There are still cases appearing due to the extreme incubation periods of the disease -exceeding 30 years in some instances.” http://psyweb.com/Mdisord/jsp/CJdisease.jsp

Warnings Sent to Emory Brain Patients • ATLANTA Oct. 1, 2004 — Emory University officials sent warning letters to more than 500 surgery patients at the school's medical center after a brain surgery patient tested positive for a fatal disease similar to the human version of mad cow disease. Chances of infection are very low, said Dr. William Bornstein, chief quality officer for Emory Healthcare. "By using modern sterilization, this has never been transmitted," he said. http://abcnews.go.com/wire/Living/ap20041001_1791.html

Answer 22 • 22. Viroids are “naked” strands or circles of RNA.

Answer 23 • 23. Viroids are known to only infect plants.

Answer 24 • 24. Prions are composed exclusively of proteins.

Answer 25 • 25. Mad cow disease is a disease that is caused by a prion. It is found in farm animals and there is a human form.

The End of Part II