VIRUSES Learning objectives Key examples overall structure who

VIRUSES Learning objectives: - Key examples -overall structure -who viruses infect -Replication -Vaccinations -Anti-viral treatments

Current news: Latest emerging (Oct 2015)virus: _____ • Why is it a concern? : Babies born to infected mothers have microcephaly (small heads and brain development problems) • Symptoms in adults: Rash, fever, joint pain, pink eye • Transmitted: by mosquito bites, • sex and blood transfusions • First identified: Uganda (1947) • Vaccine: None • Treatment: None

Viruses cause a variety of diseases or illnesses • • • warts or cervical cancer (papilloma virus) colds (adenovirus or rhinovirus) tumors cold sores or genital sores (herpes 1 or 2) smallpox chicken pox diarrhea polio rabies influenza (“the flu”) AIDS (HIV) mononucleosis (“mono”) or cancer (Epstein-Barr virus)

Viruses are …. A. Protein coats that contain DNA or RNA B. Simple eukaryotic cells C. Simple prokaryotic cells D. alive

What are viruses? • Non-living infectious particles • Do not have cells or metabolism • About 100 x smaller than bacteria (>1000 x smaller than eukaryote cells)

Viruses are not exactly living organisms.

The genetic material in all viruses is ___ A. DNA B. RNA C. Protein D. Capsid E. DNA or RNA

Viruses infect a wide range of organisms but most are host and tissue specific

Viruses use the surface proteins to bind to cells and enter them VIRUS nucleic acid proteins HOST CELL

Viruses bind to specific protein shapes. This limits the tissues or species they can infect. Common Cold Virus human nerve cell (NOT INFECTED) human lung cell (INFECTED) horse lung cell (NOT INFECTED)

What’s in a Flu name? H: Hemagglutinin (16 versions) Allows virus to enter a cell N: Neuroaminidase (9 versions) Allows virus to leave a cell Viral infection (very specific tissues are infected) 1. common cold virus infects respiratory tissue (lungs, nose, and throat) 2. Polio virus infects nerve tissue 3. HIV infects white blood cells

Role of pigs in virus transmission Viruses that infect birds don’t bind well to glycoproteins in human cells, making it difficult for bird viruses to infect humans. However, the cells of pigs have glycoproteins that allow both human viruses and bird viruses to bind to them. Thus, a pig cell can be infected by a human virus and a bird virus at the same time.

If the bird flu virus can enter a pig cell, then the pig cell must have ____ that allow the bird flu virus to enter the cell. A. Cell membrane B. Capsid C. Glycoproteins D. All of the above

Current news: Research to continue on modified bird flu virus Science: Jan 23, 2013 • Stopped Research on genetically modified bird flu virus in Jan 2012 because Genetically modified bird flu virus will have the ability to be transferred airborne from mammals to mammals

Viruses infect plants • how they get infected – injury – inheritance Genetically-engineered crops Have viral resistance capabilities : tomatoes, squash, cucumbers, papayas, etc Effects

Viral replication Replication depends on the type of virus Types of viruses: • DNA virus • Retrovirus

Role of Reverse transcriptase • Normal cells (no reverse transcriptase) • DNA • RNA • Protein • Virus with Reverse trancriptase (Retroviruses) • RNA Reverse transcriptase • DNA • RNA • Protein Reverse transcriptase: helps make _____ from ____

HIV replication Structure of a HIV virus

Which of the below statements is correct? A. All viruses are retroviruses B. All DNA viruses are retroviruses C. All RNA viruses are retroviruses D. All retroviruses are RNA viruses E. Retroviruses lack both RNA and DNA

Reverse transcriptase is ____ A. present in viral DNA B. present in host DNA C. present in viral RNA D. present in both viral and host DNA

. Prevention: Vaccines 2. Treatments: Antiviral agents Nigeria : Almost “Polio free” The country saw its last case of polio in 2014. Only Nigeria, _______ and ______ remain on the WHO’s list of polio-endemic countries.

Vaccines containing… 1. Killed (inactivated) viruses 2. Live (Weakened or Attenuated) viruses Advantage Killed virus Attenuated virus Disadvantage

Current news Zmapp proteins attack the Ebola virus by binding to it and preventing it from entering the host cells.

Antiviral Agents • block entry into cell • block replication (AZT blocks reverse transcriptase) • block viral protein production (protease inhibitors) • block viral release New antiviral agents (new strategy) 1. Trigger suicide of infected human cells 2. Amp up human defenses 3. Target host cell protein making machinery to inhibit virus maturation Take Home Message: Targeting the host cell rather than the virus http: //www. metacafe. com/watch/2673927/hiv_re plication_life_cycle_3 d_medical_animation/

Viruses that have ___ as their genetic material make vaccination futile. A. Glycoproteins B. Reverse transcriptase C. DNA D. RNA

Why do flu viruses change quickly? DNA vs. RNA viruses DNA viruses are more stable than RNA viruses

Influenza is an RNA virus. Why do you need to get vaccinated for influenza every year? A. Because the vaccination elicits a weak immune response. B. Because the number of viral particles increases every year, overwhelming the immune response. C. Because different strains of influenza are present each flu season. D. Both B and C

New (or “emerging”) viruses come from… • genetic changes (in DNA or RNA): – mutations (copying errors) • exposure to another infected species – avian flu outbreaks (Asian ducks) – hantavirus outbreaks (mice) • travel of humans into new areas (Example: Zika virus!!)

Beneficial viruses? ? ? 1. Viral infection in tulip 2. Genetic engineering 3. Gene therapy 4. To get rid of antibiotic resistant bacteria 5. Virotherapy: Tumor specific oncolytic viruses 6. Genetically modified viruses to make batteries

Viruses and Prions do not fall into any domain Viruses What are prions? Normal Protein Prions Prion: Misfolded prote

Prions and diseases • Prions: proteins (no DNA or RNA) Examples: Scrapie (Sheep) mad cow disease (BSE) Chronic wasting disease (deer, elk, moose) In Humans: - Creutzfeldt-Jakob disease (CJD) - Kuru

Normal Protein Prion: Misfolded protein How can you get infected by prions? 1. Eating contaminated meat 2. Having the mutation 3. Spontaneous change How do prions replicate?