module 18

Define a bacteriophage.

Define a bacteriophage.

A bacteria virus. Viruses that infect bacteria

Define a virus and give some general characteristics. 

 

Infect every known organism

Phages are determined by receptor specificity

Small

What is the basic viral structure (what are the components) and what makes up each component?

Always have nucleic acid-DNA or RNA

Always have protein capsid- protein coat that surrounds the nucleic acid

May contain an envelope around capsid- made up of lipids, proteins and carbohydrates

Describe the difference between the old and new taxonomic system for viruses.

1. Old

   1. Based on symptoms (humans had) or similar morphologies

   2. Problems

            i.     May cause more than one disease state

           ii.     Look the same but dramatically different in actions

2. New

   1. Nucleic acid

   2. Strategy for replication

   3. Morphology

   4. Classification is new and changing

   5. Viral species

               i.     Same genetic info

     ii.     Same host range

                  iii.     No specific epitet-use common name

 

What are the major steps for lytic bacteriophage infection also describe these?

 

1. Attachment-phage attaches to host cell wall

2. Penetration- penetrates cell via phage lysozyme and injects DNA

3. Biosynthesis-phage DNA directs synthesis of viral components by host cell-eclipse period-parts made

4. Maturation- components assembled into virions

5. Release-cell lyses (phage lysozyme) and virions released- blows up

What is the difference between the lytic and lysogenic pathway in bacteriophage replication? 

1. Same

   1. Attachment and penetration- cell wall and inject

2. Different

   1. Can then continue with lytic cycle or DNA sometimes integrates with bacterial DNA- called prophage

                                                  i.     Reproduce normally (divide)- prophage genes repressed

                                                ii.     Phage conversion can happen

                                              iii.     Occasionally, viral DNA excises from bacterial DNA and then continues with lytic cycle

What is a prophage?

When DNA integrates with bacterial DNA

 

What are some of the animal viruses life cycles?

 

1. Lytic

2. Persistent infection- not completely cleared

   1. Latent- virus remains in host for long periods without producing disease- repressed state- reactivates- chicken pox

   2. Chronic- small amounts of virus always found- slow- HIV

What does a dsDNA virus do for biosynthesis/assembly?

Follow the normal genetic flow of info

DNA-RNA-Protein

What does a ssDNA virus do for biosynthesis/assembly (different from dsDNA virus)?

Make a single strand double stranded using enzyme and then follows normal genetic flow of information

ss-ds-DNA-RNA-Protein

What does a +ssRNA virus do for biosynthesis/assembly?

Like mRNA, first finds ribosomes and makes proteins, make capsid, make enzyme to make more. No DNA ever

RNA-Protein

What does a -ssRNA virus do for biosynthesis/assembly (different from +ssRNA virus)?

Change special RNA to mRNA then make protein

Special RNA-mRNA-Protein

How does attachment, penetration, maturation and release steps differ between bacteriophage and animal viruses?  Which type of virus does uncoating?

1. Attachment

   1. Use a receptor on the plasma membrane of host cell

   2. No tails- attachment sites over whole surface of virus

2. Penetration

   1. Endocytosis- plasma membrane folds inward to form vesicle which virus is in-loses the envelop

   2. Fusion- envelop fuses with plasma membrane and releases capsid

3. Uncoating-enzymatic removal of proteins-animal

4. Maturation and release

   1. lysis-nonenveloped

   2. Budding-enveloped, push against plasma membrane-surrounds and free, take plasma membrane with

 

Is there any similarity on the release step (option) between bacteriophage and animal viruses? What is it?

Yes, they both can perform lysis. The difference is for animal cells, it's only for nonenveloped

 

What are some antiviral drugs which interfere with DNA and RNA synthesis (be able to describe these)? 

Nucleoside analogs-2 parts: sugar and nitrogenous base

1. Interferes with DNA and RNA synthesis

2. Examples

   1. Acyclovir

         i.     Herpesvirus, shingles treatment

       ii.     Activity- virus-infected cells use drug in place of norma; nucleoside which leads to DNA synthesis issues

     iii.     Administered orally, topically, or injected

        iv.     Destroys virus factory

2. Ribavirin

      i.     Hepatitis C and respiratory syncytial virus

ii.     Induces high mutation rate of RNA virus

2. Zidovudine (AZT)

      i.     HIV treatment

      ii.     Competitive analog blocks synthesis by reverse transcriptase- HIV brings reverse transcriptase-humans don’t have

iii.     Fairly toxic

What is an antiviral drug which is a reverse transcriptase inhibitor?

1. Nevirapine

   1. HIV treatment

   2. Enzyme inhibitor-virus enzyme, not human

   3. Inactivates transcriptase

What are some antiviral drugs which are protease inhibitors?  Integrase inhibitor?

1. Indinavir and saquinavir

   1. HIV treatment

   2. Protease inhibitor

2. Raltegravir and elvitegravir

   1. Integrase inhibitors-integrates into DNA

What is a fusion inhibitor drug?

1. Enfuviritide

   1. Stops HIV fusion-can bind but cant enter

What are exit inhibitor drugs?

1. Olsetamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab)

   1. Prevent influenza virus release

   2. Can come in but cant leave

What is an interferon and how do they function?

1. Natural product of the immune system which stimulate cells to produce antiviral proteins

2. Alpha-interferon

3. Hepatitis C treatment

What is a prion and what are some characteristics?

1. Proteinaceous infectious particle

2. Causes rare neurodegenerative disorders

   1. Diseases with long incubation periods

Always fatal (progressive)- when signs and symptoms show, too late

What does the prion cause to form in the body?

Rare neurodegenerative disorders

How does a prion “work” to cause these changes in the body?

1. Mode of action

   1. Can induce abnormal folding of normal cellular prion proteins in the brain- when proteins go bad cells die don’t replenish in the brain

   2. Causes large vacuoles in the brain- spongiform encephalopathy

List three ways that prions are transmitted.

1. Transmission

   1. Eating central nervous system from an infected animal

   2. Transplanting nerve tissue

   3. Contaminated surgical instruments- hard to degrade via enzymes of heating

What is a viroid and what do they cause?

1. Short pieces of naked circular RNA- 300 to 400 nucleotides long, no protein coat

2. Causes plant disease