Lecture 3

Question 1

What are the main steps involved within the transmission of DNA viruses?

Answer 1

1. Attachment protein on the surface of the virus and a complementary protein receptor on the surface of the cell (attachment protein will be located either on the capsid (or for the enveloped viruses, in the envelope)
2. Penetration- for enveloped viruses this involves the fusion of the cell wall with that of the protein or engulfment of the virus. For non- enveloped viruses this involves engulfment of virus by the cell or the virus may directly penetrate cell membrane
3. Uncoating- events that occur after penetration that release the viral genome
4. Same as five
5. Early transcription and translation- formation of mRNA from the virus DNA and subsequent production of early viral proteins. Early codes proteins are very important for the next step in the viral process being DNA synthesis (DNA  nucleus  mRNA goes back to the cytoplasm  rise to viral proteins  then go back into nucleus where they are needed for further transcription)
6. Viral DNA synthesis
7. Same as 8
8. Occurring after DNA synthesis has started this is involved with making late mRNA’s that are involved with making structural proteins
9. Assembly of virons- after the synthesis of DNA and proteins these are packaged together to continue the virus
10. Release- progeny virions are released by autolysis of the cell. Method used by most DNA viruses

Question 2

What are the main steps involved in the transmission of RNA viruses?

Answer 2

• Main difference to note is that early and late transcription will not be required with positive types because + senses RNA will already have the bases ready to go in the correct order
• Negative sense DNA will require the negative sense intravirion polymerase

Question 3

What are the main steps involved in the transmission of retroviruses?

Answer 3

1. Change DNA to RNA
2. Via enzymes change it to double stranded DNA and you will now have a complete helix
3. It will then cut apart the chromosomes and it will stick itself in
4. Now we have a mutant cell that contains all of our DNA, but it also contains HIV that is relatively well hidden and hence has the ability to escape the detection of the immune system

Question 4

How do antiviral drugs work?

Answer 4

• Main goals of these specific drugs is to block virus attachment to the host cell and to block unique virus enzymes
• Immunoglobins are effectively purified neutralised antibodies. We are able to give these to somebody and it will neutralise the virus
• Neuraminidase inhibitor stops that flu particle leaving the cell. Useful to know that these are only helpful preventatively