Virology 575: Lecture 4

Classical system, disease-based classification, Baltimore system

Rhinovirus, Family: Picornaviridae, Genus: Enteroviruses

RNA viruses, infect gastrointestinal tract, spread to other areas of body (nervous system)

Complete viral particle

Proteins of the shell, protect genome from damage, is pseudo-stable (needs to be stable outside of the cell and able to release genetic material outside cell). very specific/highly evolved proteins

Repeating patterns, because there is not room for many proteins

• Helical: Sheet rolled up
• Icosahedral: made up of only a few types of proteins, looks like d20 generally

Visualizing viral proteins

A simple repetitive one.

• Disease (antivirals and vaccines)
• Vectors for foreign gene expression
• Models for regulation of gene expression
• Models for oncogenesis
• Models for latency

an organism/cells that permit completion of a viral multiplication cycle

A host that does not permit completion of a viral multiplication cycle. Infection does not occur: host lacks some required factor/anti-viral mechanism

Results in production of infectious virus progeny. Infected host may survive

Viral infection is initiated but stalls/is terminated. Host usually survives

Low level infection wherein virus-specific multiplication is difficult to detect and symptoms are absent or inapparent to the host.

Condition in which virus is present and multiplying. The host is a constant source of infectious virus

Virus goes dormant but can alternate between periods of active multiplication. Reactivation from latency can result in disease and shedding of infectious virus.

Latent infections

• Small viruses express early genes all at same time and late genes all at same time
• Large viruses express immediate early genes (regulatory) and delayed early genes (replication) and late genes all at once

At a transcriptional level

Host transcription factors and RNA polymerase

Transcriptional activators and repressors

multiple

host or viral encoded transcription factors

• Post-processing: splicing, methylation, poly-adenelation
• These are all things that viral RNA do not need to do, so this inhibits host protein production but not viral protein production

• Families: Polyomaviridae, Adenoviridae, Papillomaviridae
• Examples: SV40, polyomavirus, adenovirus, papilloma virus

• use host transcription and DNA synthesis machinery
• RNA splicing generates multiple virus proteins
• has capacity to cause tumors
• causes mild disease in humans

They need to use host machinery so they force the cell into S phase where it is available.

Some non-permissive hosts can allow the S phase stimulators but not the replication and cell death that would stop permissive host cells from causing uncontrolled growth

• Closed circular dsDNA
• Encodes 6 proteins: T-antigens and capsid proteins
• Needs host transcriptional and replication factors
• Early and late phases
• Large T antigen controls host cell cycle

See Lecture 4

• Intermediate sized DNA virus, linear dsDNA
• Virion is non-enveloped w/ icosahedral symmetry
• Acute respiratory infections, conjunctivitis, gastroenteritis
• Oncogenic (not in humans)

• Expresses: E1A/B/2/3/4 (Early), IX and IVa2 (delayed early), L1/2/3/4/5 (late)
• All are encoded by splicing and use of overlapping codes

• Viral DNA replication
• turn-on major late promoter
• alter splicing and polyadenylation
• transport viral and cellular RNA

Immediate Early gene (EA1)