Iih L9 Viruses

Front 1

Immune response to viruses

type 1 IFN...

Back 1

type 1 interferons limit the infection within tissues

e.g.

IFN alpha

IFN beta

Innate lymphocytes: NK cells, gamma-delta T cells

Adaptive immune response CD4 and CD8 T cells recognise and destroy viruses, resolve acute infection, immuno-surveillance for latent infections e.g. HSV

Front 2

Viruses are

Back 2

obligate

intracellular

parasites

Front 3

Viruses

features unique to viruses...

Back 3

no metabolic activity outside of host close

virion (virus particle) made of nucleic acid genome protected by a capsid, surrounded by an envelope

Front 4

Classifying viruses

Questions to ask?

Back 4

according to genome

Is the genome DNA?

is the genome double stranded?

is the RNA genome sense?

dose it use reverse transcriptase enzyme?

Front 5

what is ambisense?

example of an ambisense virus?

Back 5

Ambisense virus - RNA genome is sense and antisense

Lassa fever

Front 6

DNA vs RNA viruses

Back 6

I II VII are DNA

rest are RNA

Front 7

Baltimore classification of Viruses:

Class I

examples?

Back 7

ds DNA virus

HSV, adenovirus

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Baltimore classification of Viruses:

Class II

Back 8

ssDNA virus

Parvovirus

Front 9

Baltimore classification of Viruses:

Class III

examples?

Back 9

dsRNA virus

Retroviruses, Bluetongue

Front 10

Baltimore classification of Viruses:

Class IV

examples?

Back 10

sense RNA virus

HCV, Polio, Yellow fever

Front 11

Baltimore classification of Viruses:

Class V

examples?

Back 11

Antisense RNA virus

Influenza, Ebola, Measles

Front 12

Baltimore classification of Viruses:

Class VI

examples?

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RNA reverse transcribing virus

HIV, HTLV-1 (retrovirus)

Front 13

Retroviruses

why is it different to central DNA dogma?

Back 13

central dogma

DNA → RNA → protein

but retroviruses

RNA → DNA → RNA → protein

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Baltimore classification of Viruses:

Class VII

examples?

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DNA reverse transcribing virus

HBV

Front 15

Virus

Back 15

capsid

icosahedral virus - adenovirus

helical virus - Ebola

Front 16

Replication

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Viruses only replicate wen they infect a host cell

capsid is partially disassembled

virus directs cell to synthesise viral components

Front 17

Viral components

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3 types

1. essential replication factors - for genome synthesis

2. subunits assembled for new capsid and virioins

3. Copies of viral genome - packaged in new capsids

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Eclipse phase

which phase in "life cycle" of virus?

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during this new components are made, infectious virus cannot be recovered

Front 19

Virus release phase

which phase in "life cycle" of virus?

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viral genome has replicated

→ viral proteins synthesised progeny virus can be assembled

new viruses may be released by budding/cell lysis

Front 20

Virus receptors

where are they?

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outside of the virus has receptors

if the receptor is highly specific can be human restricted e.g. polio binds to decay accelerating factor (DAF) in humans

if receptor is not very specific can infect different species e.g. swine flu

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extent of damage to host

cytopathic virus?

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cytopathic viruses - completely destroy target cell by cell lysis

e.g. non-enveloped viruses polio, adenovirus

viruses affect cells in a minor way show chronic infections

some viruses show latency, virus does not replicate but stays quiescent for long periods

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identifying viruses in the laboratory

ELISA methods

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viruses don't grow in cultures

ELISA based methods

Enzyme Linked ImmunoSorbent Assay

identify by antigens

or by detecting antibodies to the virus

as long as the virus is common and known this is quick cheap and effective

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identifying viruses in the laboratory

PCR

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PCR

using primers specific for suspected pathogen in array with several other candidates

rapid diagnostic assay

used when ELISA can't detect viruses

can be used for unknown viruses

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Types of virus infections

acute infection?

persistent infection smouldering?

persistent infection latent?

persistent infection slow?

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Acute infection e.g. Rhinovirus, Influenza

Persistent infection, smouldering e.g. Lymphocytic choriomeningitis

Persistent infection, latent e.g. HSV

blue line - level of virus in the orhganism

red bar - when symptoms are seen

Persistent infection, slow e.g. Measles, HIV