DNA Viruses I Flashcards
Key Concepts in DNA Viruses
-transcription and replication in nucleus (not poxvirus)
-host RNA polymerase transcribes mRNA (not poxvirus)
-viral or host DNA polymerase replicates genome
Size:
-parvo- BK virus
-papova- Warts, cancer
-adeno- colds, keratitis
-Hepadna- Hep B
-Herpes- cold sores,
-Irido
-Baculo
-Pox
Steps in DNA Virus Replication
1) Recognition of the target cell
2) Attachment
3) Entry: Penetration of Fusion
4) Uncoating
5) Transcription of mRNA-> Host RNA polymerase
6) Protein synthesis
7) Replication of the genome -> host or viral DNA polymerase
8) Assembly of virions
9) Egress: lysis, budding ,exocytosis
Use of Host RNA for mRNA for transcription
- DNA viruses use the host RNA Pol for transcription of mRNA
- RNA Pol II and transcription factors (X, Y) recognize viral promoters
- X,Y= proteins that enhance viral transcription
Transcription factors
- both cellular and viral factors regulate transcription by host RNA Pol
- Viral TFs are important virulence factors and may even be essential proteins
Genome synthesis- use of host DNA polymerase
- some viruses genomes are recognized by the host DNA Pol complex
- these viruses do not encode their own polymerase (small genomes)
- parvovirus: Adeno-associated virus 2
Genome synthesis- use of viral DNA polymerase
- large DNA viruses encode their own polymerase and accessory proteins
- examples: Herpesvirus, Adenovirus
Origin of Diversity in DNA viruses
- recombination between and within genomes
- DNA polymerases have higher fidelity than RDRP
- mutations occur ~1 in 10^5-6 nucleotides
- DNA viruses are genetically more stable than RNA viruses
What DNA viruses are the most common causes of disease?
- Adenovirus
- Papillomavirus
- Herpesvirus
Adenovirus Diseases
Respiratory:
- a bad cold with a fever
- pharyngoconjunctival fever
- laryngitis and cough
- pneumonia
Other sites:
- acute hemorrhagic cystitis
- epidemic keratoconjunctivitis
- gastoenteritis
Adenovirus Epidemiology
- Transmission:
- aerosol, fecal-oral objects
- poorly chlorinated swimming pools
Susceptible populations: children, military recruits
Sites of Outbreak:
-daycare, swim clubs, boot camp
Adenovirus Life Cycle
- adenovirus fiber protein binds to cell receptor
- entry is by endocytosis
- endosome acidification causes fibers to lyse the vesicle
- capsid traffics to nucleus and DNA genome uncoats through the nuclear pore
- genome replicates in nucleus
- host RNA Pol II makes mRNA
- gene expression phases: immediate early, early, late
- genome replication by viral DNA Pol
- capsid assembly in nucleus
- virions egress by lysis
Adenovirus Diagnosis and Treatment
Match the diagnostic test to the patient sample: culture, antigen detection, PCR, Serology
Treat immunocompromised patients with cidofovir- reserved for the most dire cases, cidofovir is nephotoxic
Adenovirus Prevention: Vaccine
- used only for military personnel
- reinstated for use in late 2011
- incidence for Ad4 infections plummeted
Human Papilloma Virus Diseases
- most commonly diagnosted STI in the US
- epithelial Diseases: Verruca vulgaris (common warts), Verruca planaris (plantar warts), Condyloma acuminata (genital warts)
Malignancies: Head and neck cancer, cervical cancer, penile cancer
HPV Tissue Tropism: Differentiated Epithelial Cells
- It infects the basal lamina
- limited amplification of episomal papillomavirus DNA
- there is then maintenance replication till it gets to the surface
- then productive replication of virus
