Virology: Baltimore classifications Flashcards
1
Q
DNA viruses
A
- Enveloped (dsDNA)
- Pox
- Herpes
- Hepadna
- Naked capsid (dsDNA)
- polyoma
- papilloma
- adeno
- parvo
2
Q
RNA viruses
A
- RNA
- Naked
- Picorna
- Calici
- Enveloped
- Toga
- Flavi
- Corona
- Naked
- RNA
- RNA
- Enveloped
- Rhabdo
- Filo
- Orthomyxo
- Paramyxo
- Bunya
- Arena
- Enveloped
- RNA
- +/- RNA
- double capsid
- reo
- RNA via DNA
- Retro (enveloped)
- RNA via DNA
3
Q
Baltimore classification of viruses: Class I
A
- Class I: dsDNA
- Papilloma, polyoma, herpes, adeno, pox
- some can transform cells
- host enzymes transcrobe IE or E mRNA
- E-proteins: replicate parental DNA & late (L) mRNA;
- L-proteins: assemble into capsids
- Capsids: incorporate the viral DNA to make mature virus
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/528/a_image_thumb.jpg?1659431597)
4
Q
Class II
A
Class II: ssDNA
- very small (parvum=small), circo- or parvo-virus (linear so susceptible to DNAses)
- replication occurs in nucleus
- form a (-) strand -> template for (+) strand
- require cell enzymes
- mRNA translated into viral proteins
- NOTE: no immediate early or early proteins
- viral proteins: make up capsids
- viral DNA is encapsidated in progeny virus
- Parvovirus can only replicate when cells are actively replicating
- icosahedral, non-enveloped
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/532/a_image_thumb.jpg?1659431597)
5
Q
Class III
A
Class III: ds RNA Virus
- dsRNA: cannot function as mRNA; class III must package an RNAP to make mRNA after infection of host cell
- genomes segmented
- RNA-dependent RNAP in virion
- Ex. Reo-, Birnaviruses, rotavirus
- ds RNA -> transcribed to viral mRNA (v-mRNA) by virus-associated RNA-dependent RNAP
- v-mRNA: translated to structural and non-structural proteins:
- viral proteins to form immature capsid
- mRNA packaged into immature capsid, then copied w/in capsid to form ds RNA
- Rotaviruses, members of Reoviridae
- acute gastro in infants and young children
- icosahedral
- 11 dsRNA segments
- RNA replication: concurrent w packaging of genome segments
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/542/a_image_thumb.jpg?1659431597)
6
Q
Class IV
A
Class IV: (+) sense RNA viruses
- Divided into IVa & IVb
- always infectious w/o viral proteins
- ends of genomes often modified w caps
- Ex. Picorna-, toga-, corona-, flaviviruses, dengue
IVa
- polyprotein: post-translational cleavage make multiple viral proteins
- non-structural proteins: transcribe parental (+) RNA into (-) RNA whih in turn is transcribed to (+) RNA
- Structural proteins: make up capsids, incorporate viral RNA - progeny virus
IVb
- stuctural proteins (not one polypeptide)
- parental RNA transcribed into (-) RNA by viral non-structural proteins
- ss (-) RNA -> transcribed into (+) RNA (many copies)
- Capsid incorporates the (+) RNA, other viral proteins -> progency virus
IV: Picornaviruses
- naked, small, icosahedral
- genome is mRNA (naked genome is suffcient for infection)
- virus replicates in cytoplasm, most are cytolytic
- v-RNA: translated into polyprotein; cleaved into enzymatic & structural proteins
- include poliovirus, hepA, rhino- and enteroviruses
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/543/a_image_thumb.jpg?1659431597)
7
Q
Class V
A
Class V: ss (-) sense RNA viruses
- virus-associated, premade polymerase reads (-) RNA
- segmentation common
- genome by virus-specfic polymerase (premade); reads (-) RNA -> forms (+) RNA
- assembly of capsid -> incorporation of genomic RNA and viral proteins, including the virus RNAP -> progeny virus
- Ex. Filiviruses, Orthomyxo-, Bunya- (Hantavirus), Paramyxo-viruses
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/544/a_image_thumb.jpg?1659431597)
8
Q
Class VI
A
Class VI: ss (+) sense RNA viruses (RT)
- 2 copies of +ve strand RNA (not ds); premade RT generates ds provirus
- retroviruses (HIV)
- Provirus: integrates into host genome, template for synthesis of viral mRNA
- Viral mRNA: viral non-structural and viral structural proteins
- not directly infectious on its own
- Non-structural proteins: may be RT and other polymerases
- Structural proteins: assemble into the capsid
- Mature virion: the capsid incorporates viral genome AND the nucleoproteins including RT -> progeny virus
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/545/a_image_thumb.jpg?1659431598)
9
Q
Class VII
A
Class VII: ds DNA viruses, ssRNA intermediate, RT
- Ex. Hepadnaviruses including HBV
- VII: partially ds DNA virus comes in w its own RT
- core is stripped of nucleic acids
- fills in gaps
- ds supercoiled DNA
- pre-genomic RNA
- structural proteins made and then assemble into a capsid
- pre-genomic RNA goes into capsid; this is ss
- maturation: RT makes a RNA-DNA hybrid in capsid
- RNAase activity digests RNA
- DNA polymerase activity makes the partially dsDNA
- comes out of Golgi and goes out of cell
- VII: HBV
- enveloped virion w partially ds circular DNA genome
- replication is thru a circular RNA intermediate
- virus encodes and carries RT
- HBV has a strict tissue tropism to liver
- HBV genome can integrate into host chromosome
![](https://s3.amazonaws.com/brainscape-prod/system/cm/110/676/546/a_image_thumb.jpg?1659431598)