Influenza lecture Flashcards
viruses are made up of
nucleic acid, protein coat, lipid envelope and vila proteins
virus basics
only replicate once host cell is infected
nucleic acid
either RNA or DNA
shape of virus
helical or isosahedral
lipid envelope
originates from host cells
stages of viral replication
1) virus enter cell by pinocytosis
2) virus sheds coat
3) replication of viral nucleic acid
4) synthesis of viral protein of capsid
5) assembly of new virion
6) release of new virion
what part of the virus facilities entry of the virus into the host cell
hem agglutinin- binding to sialic acid
what facilitates the release of the virus from infected host cell
Neuraminidase
viruses are classified based on
size, shape, type of nucleic acid in genome
and who they produce mRNA
how host cell synthesise protein
DNA is converted to complementary strand RNA in nucleus
mRNA moves out into cytoplasm where it attaches to a ribosome
mRNA acts as a template- amino acid binds to
non-sense RNA virus
1) replicating virus- nonsense RNA (viral RNA polymerase. RNA to RNA)
2) RNA
3) Ribosome produces caps protein from ribosome
sense RNA virus
1) Replicating virus- sense RNA
2) viral RNS polymerase (RNA to RNA)
3) RNA
4) RNA polymerase (RNA to RNA)
5) Ribosome produces caps protein from ribosome
sense RNA virus
cant act as RNA template
sense RNA virus cant act as RNA template
1) replicating virus. Sense RN that can not act as an RNA template
2) viral reverse transcriptase (RNA to DNA)
3) DNA
4) host RNA polymerase (DNA to RNA)
5) RNA - ribosome - capsid protein
Baltimore classification
virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc..) and their method of replication.
how many groups in baltimore system
7
viral enzyme shave
low proof reading ability
mutations least likely in
Group 1- DNA -due to the host having proof reading machinery already
why are mutations more likely in other groups
more steps- mutations more liekly
types of genomic shift
drive and shift
drift
point mutations, make small changes
shift
Antigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains.
happened when a genome is segmented. when pandemic occur- completely changes antigens
- unrecognisable
example of a virus that has undergone genetic shift
H3H2 influenza virus
- mixture of H3 avian virus and H2N3 human virus
how virus which aren’t dangerous to humans becomes dangerous
- Type of influenza which infects a birds cannot infect a human, however the type of influenza virus that effects birds or humans, can both infect pigs. Therefor if we have a pig infected with both avian and human influenza, a type of new influenza (genomic shift), which can infect humans can be produced
ham agglutinin is an antigen that is variable between subtypes ?
true
genomic drift implies new vaccine is required
false-antigens will still be similar so same vaccine may work
if virus are very small and cannot be visualised under a microscope what could be used for them to be detected
- ELISA
- PCR looking for viral DNA
- RT-PCR looking for RNA virus
can only use ELISA
when the body has started producing antibodies at day 5
when the patient has just started reporting symptoms look at
site of infection e.g. nose or pharynx
look for antibodies in
the blood
throat swabs form patients convalescing 9recovering) from an infection are the most useful sample for oral testing?
false - better off looking for antibodies
the plaque assay
used to measure virus time
to performa a plaque assa
o 10-fold dilutions of a virus stock are prepared, and 0.1 ml aliquots are inoculated onto susceptible cell monolayers.
o After an incubation period, to allow virus to attach to cells, the monolayers are covered with a nutrient medium containing a substance, usually agar, that causes the formation of a gel.
o When the plates are incubated, the original infected cells release viral progeny. The spread of the new viruses is restricted to neighbouring cells by the gel.
o Consequently, each infectious particle produces a circular zone of infected cells called a plaque.
o Consequently, each infectious particle produces a circular zone of infected cells called a plaque.
o Eventually the plaque becomes large enough to be visible to the naked eye. Dyes that stain living cells are often used to enhance the contrast between the living cells and the plaques.
why may plaque assay not be best
takes a bout a fortnight to get results back-not best if an outbreak
what is a positive result with qualitative RT-PCR
an increase in fluorescence
qPCR
- Quantitative reverse transcription polymerase chain reaction, is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule during the PCR, i.e. in real-time, and not at its end, as in conventional PCR.
hameagglutination assay
quick way of measuring the amount of virus in a sample
- only works with viruses which bid to RBC
assays rely on the fact
we can see what happens with RBC with the naked eye
in a tube of blood..
abc will sink to the bottom of the tube due to gravity
if we mix the right quantity of virus with the right quantity of rbc
then shield at the bottom of the tube will form
why will a shield at the bottom of the of the tube form
due to the virus binding to sialic acid, causing cross linking between abc, forming a lattice and spreading to fit the bottom of the tube
qRT-PCR can be used to distinguish diff influenza subtypes?
True- use PCR to look for virus, can tailor it so we have primers which pick out speicifc subtypes e.g. H1, H2 or H3
when thinking if PCR can determine if specific dna is there
think specific primers
Anti-N ELISA tests for exposure to a virus or vaccine
Yes- my body has seen this virus or through a vaccination and has produced anti bodies against it
if virus is present
shield will be formed instead of button
the hameaglgutination INHIBITION test produces a (antibody present)
a button since the reaction steps the virus from binding so abc fall as a button- no lattice formed
viral detection in clinical samples
- Genomic techniques
- Antibodies against them
- Cell culture
- Hameagglutination
- Plaque assays
- ELISA
sample for hamealgutination assays must be taken
at acute stage- symptoms
-second serum taken during convalescent stage- when antibodies ar eliekly to be present
why in hameglutination inhibition assay is a button a positive result
since antibody has captured the virus so abc has fallen to the bottom as a button
example of how haemagglutiantion assays can be used
- When john was acutely ill there were not many antibodies against H1 or H3
- However when he was recovering he had many positive button results for wells with antibodies against H1, but few positive results for H3 antigens
- Therefor he is likely to have suffered an infection from an H1 virus
