Virus Basics Flashcards
Replication patterns of DNA and RNA viruses
DNA: replicate in nucleus
RNA in cytoplasm
Exceptions:
Small pox and molluscum contagiosum DNA viruses in cytoplasm
Influenza and retrovirus RNA viruses in nucleus
Viral structure
small genome
symmetric form
nucleocapsid - bind to host
enveloped - as bud off
- lipid bilayer - more likely to dessicate, less stabile
- spread by droplets, parenterally or sexually
nonenveloped can withstand harsh environments
nonenveloped RNA viruses
“my Real Heavy Picture of California was Ruined w/o an envelope”
Reovirus
Hepevirus
Picornavirus
Calicivirus
non-enveloped DNA
“PaPa and Aunt Poly Didn’t have an envelope”
Parvovirus
Papilloma virus
Adenovirus
Polyomavirus
Virus ploidy
all are haploid except retrovirus has 2 copies of ssDNA
Viral reassortment
RNA viruses, segmented genome
2 viruses infect same cell –> exchange genetic segments
Influenza viruses –> new types o virus –> limited epidemics or world wide pandemics
Viral recombination
2 different viruses infect same cell - similar type or strains
genes exchange from 2 different chromosomes
offspring unlike parent viruses
Need DNA phase - like retroviruses
Viral complementation
2 viruses infect same cell
1 mutation –> nonfunctional protein
If second virus makes protein, allows both to replicate, but no mix of genetics
progeny still has defect
Phenotypic mixing
2 viruses, same cell
progeny w/ surface antigens from one or both viruses
can alter which tissue type it can infect
genetic material not changed
change good only for 1 generation
DNA viruses
“HAPPy HiPPo Dung”
Herpes virus Adenovirus Parvovirus Papillomavirus Hepadnavirus Polyomavirus Poxvirus
Linear dsDNA
replicate in nucleus
icosahedral shape
exceptions: Parvovirus - ssDNA Papillomavirus - circular Polyomavirus - circular Hepadnavirus - circular
RNA viruses
+ sense ssRNA
-serves as mRNA –> immediate translocation
Retrovirus Togavirus Flavivirus Coronavirus Hepevirus Calicivirus Picornavirus
-sense has to be transcribed to + sense; must bring viral transcriptase
dsRNA need to supply own polymerase
Naked viral genome infectivity
dsDNA infectious
+ sense ssRNA infectious
Live attenuated vaccines
healthy patients
caution in immunocompromised
- -> subclinical infection –> long lasting immune response
- humoral and cell mediated
Small pox Yellow fever Chicken pox MMR Sabin polio (oral) Herpes zoster (shingles) Intranasal flue (flumist) rotavirus
live attenuated vaccines contraindicated in CD4 less than 200
Chicken pox
MMR
Killed virus vaccines
Formed from whole, killed viruses
may need boosters
injectable influenza
Rabies
Hep A
Salk polio - injectable
