Virology (2) Flashcards
(17 cards)
What is the classification of Herpes simplex virus?
1) Baltimore - Group I dsDNA, Herpes simplex Type I and Type 2
2) ICTV - Simplexvirus humanalpha1; Simplexvirus humanalpha2
How many capsid glycoproteins does HSV have?
1) 12 gA-gL
2) Uses gB, gC, gD, gH and gL to attach to receptive host cell
3) Herpes envelope fuses with host cell membrane with involvement of gB
What happens when the virion of HSV enters the host cell?
1) Enters cytoplasm
2) Is transported to nucleus where particle uncoats
3) Linear ds viral DNA closes into circular form
How does the viral mRNA use host cell enzymes?
1) Immediate early - regulatory proteins for next phases
2) Delayed early - DNA polymerase and other enzymes (e.g., thymidine kinase)
3) Late - structural proteins for new virus particles
What happens in the ‘delayed early’ and ‘late’ stages of HSV replication?
1) Genomes and proteins for new (progeny) virus particles are being made
2) ‘Late’ stage - viral DNA polymerase is going around circular genome repeatedly - makes many copies
3) Also known as rolling circle replication
How does the HSV have a lipid envelope?
Nucleocapsids bud out of host cell membrane and acquire lipid material for envelope
How common is Herpes simplex infection?
1) HSV 1 - at least 3,700mil people infected, around 67% global population
2) HSV 2 - >400mil infected, around 19.5mil new cases each year (0.5% global population)
How do you diagnose HSV in a lab?
1) Vesicle swabs/samples of vesicle fluid/ CSF
2) PCR - target gene where there is a difference in sequence between 2 species - e.g., DNA polymerase, gpB, gpD (glycoproteins involved in attachment to host cell)
How is HSV treated?
1) Acyclovir
2) Zovirax
What is the classification of Influenza virus?
1) Baltimore - Group V negative sense ssRNA, Influenza virus type A, B, C and D
2) ICTV - Influenza A virus
What is the structure of Influenza virus?
1) Genome comprises 8 segments of RNA of varying lengths
2) Each 1 contains codes for specific proteins e.g., Haemagglutinin glycoprotein (HA) on segment 4/ Neuraminidase (NA) coded for on segment 6
How does Influenza use HA and NA?
1) HA attaches to sialic acid component of host cell receptors (respiratory epithelial cells)
2) NA acts as enzyme to bind to and then cleave sialic acid molecule from host cell glycoprotein
How does Influenza replicate once virus particles are released from host cell?
1) Viral membrane components absorbed into host membrane, aided by HA
2) Nucleocapsid is released into host cell cytoplasm
3) Migrates to nucleus and uses its own RNA polymerase to transcribe +ve sense RNA molecules
4) Viral mRNAs move back to cytoplasm
Why is nucleic acid replication not always accurate?
1) Mammalian cells have complex processes to correct errors in DNA replication but RNA replication does not need to be as strictly controlled
2) Errors in replication of RNA viruses inside host cells are not always corrected
What is antigenic drift in Influenza?
1) Could mean progeny virus not viable
2) Could give rise to new ‘strain’ of virus
3) New strains of influenza A virus regularly arise through antigenic drift
How does Influenza get diagnosed?
1) Point of care test
2) PCR
What is the treatment for Influenza?
1) Usually no specific treatment - paracetamol, fluids and bed rest
2) Sometimes antivirals used - anti-RNA virus drugs e.g., oseltamivir, zanamivir
3) Secondary infections can lead to bacterial pneumonia –> antibiotics
