intro to viruses Flashcards by Monica Palumbo

virus

nucleic acid enclosed in a protein coat

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metabolically inert

must invade a host in order to replicate

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virus enzymes

may carry their own enzymes or use host cell enzymes

utilise host cell ribosomes and organelles

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virus envelope

some viruses have this 
made of host cell lipid bilayer membrane, acquired when progeny bud out of the host m membranes 
eg 
nuclear membrane 
membrane of endoplasmic reticulum 
membrane of Golgi apparatus 
outer plasma membrane

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capsid

protein shell

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capsomeres

protein components of capsid

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virus unit

virion

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glycoproteins on enveloped viruses

enveloped viruses express virally encoded glycoproteins on the surface of the envelope
there perform important functions related to virulence, such as adhesion to the host cell

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3 shapes of viruses

plyhedral
helical
complex

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polyhedral viruses

many sides
capsomeres are triangle shaped
usually 20 sides - icosahedral

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helical viruses

capsomeres arranged in a helix around a helical genome

may have filamentous shapes

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glycoproteins on influenza

haemaglutinin

neuraminidase

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complex shaped viruses

pox virus

bacteriophage - infect bacteria

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sense positive

if nucleotide sequence is the same as that of an RNA (mRNA) transcript that can be translated into amino acid sequence

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acute infection

detectable
gets cleared
recovery or death

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latent infection

virus may not be detecatable
not cleared
periodic reactivation and illness
not actively replicating

chronic infection

virus is detectable
may be cleared eventually
fluctuating illness

slow infection

virus is detectable
virus is not cleared
end stage illness

latent virus example

herpes viruses 
varicella zoster virus 
EBV
cytomegalovirus 
Human T lymphotrophic

chronic viral infection example

Hepatitis B and C
HIV
human papilloma virus

Hep B virus

Hepatitis B core antigen - HBcAg
Hepatitis B surface antigen - HBsAg
Hepatitis B ‘e’ antigen (uncertain role) - HBeAg
has envelope and DNA polymerase

Hep antigens

blood tests for antibodies against Hep B antigens

surface antigen is found in the blood in three forms in a person with active infection

Hep B core antigen

stays inside the liver - not detectable in blood

Hep B chronic infection

people who don’t clear the virus
surface antigen persists in the blood - if found for longer than 6 months this is indicative of chronic Hep B
surface antibody is never detected

Hep B e antigen

can persist | means the patient is highly infectious to other people

outcomes of chronic hep B infection

persistant viral replication in the liver many patients remain symptom free carriers others experience chronic hepatitis and liver damage cirrhosis liver failure death a small percentage of those with chronic infection will develop hepatocellular carcinoma

subacute sclerosing panencaphalitis

SSPE | defective forms of the measles virus

progressive rubella pan encephalitis

rubella virus

prion diseases

classified as slow viruses but not caused by viruses

prion disease examples

Creutzfeldt-Jakob disease variant creutzfelt jakob disease fatal familial insomnia Kuru

oncogenic viruses

only a minority of people infected with a potentially oncogenic virus will develop cancer

hepatocellular carcinoma

HBC, HCV | other conditions causing fatty liver and/or cirrhosis will increase the risk

cervical carcinoma

HPV high risk types 15 strains/200 cause cervical carcinoma Gardasil 9 vaccine covers the main 9 strains

oropharyngeal cancer

many cases causes by HPV | other risk factors are smoking, chewing tobacco and excess alcohol

nasopharyngeal carcinoma

caused by EBV

burkitt's lymphoma

caused by EBV B cell non Hodgkin childhood cancer in endemic regions strong epidemiological links to infection with falciparum malaria and HIV infection

kaposi's sarcoma

HHV-8 | became common during the aids epidemic

adult T cell lymphoma

HTLV-1 very high incidence of infection in aboriginal and Torres straight islander people 1 in 20 of those with the infection will develop cancer

Merkel cell carcinoma

MCPyV - uncommon aggressive cancer seen in elderly and immunocompromised propensity to metastatsise cofactors are UV exposure and pale skin