DNA Viruses I- Saviola Flashcards
What are the characteristics of Poxviridae? What members of this genus cause disease in humans?
o Large brick-shaped complex particles.
o Replication and transcription of DNA much like for cellular DNA but uses mainly virus-coded enzymes because it occurs in the cytoplasm.
o Predilection for epidermal cells.
o Has a dumbbell-shape core and complex membrane.
o Members that cause disease in humans: Variola (smallpox), Vaccinia, Molluscum contagiosum (benign epidermal tumors)
What are the characteristics of Variola (smallpox)?
- Only known host is humans.
- Extinct in 1979.
- Transmission thru inhalation and replicates in upper respiratory tract.
- Rash forms on extremities and face (centrifugal pattern). All at the same stage of development.
- Two strains: variola major and minor.
What are the characteristics of Vaccinia?
- Vaccinia virus is the basis for the modern smallpox vaccine. May be from horse pox virus (originally thought to be cow pox). The FDA says it may be associated with myocarditis and/ pericarditis in those individuals vaccinated for the first time.
- Experimental viral vaccines have been made using vaccinia virus with genes for other virus surface antigens spliced in.
What are the characteristics of Molluscum contagiosum (benign epidermal tumors)?
especially in people infected with HIV and children.
• Transmission via direct contact or fomites.
• Affects the basal cell layer and replicates.
• Lesions are smooth, firm, shiny and flesh colored w/ umbilicated centers.
What are the characteristics of Herpesviridae?
o Enveloped icosahedral nucleocapsids.
o Most maintain a latent or chronic infection and can be reactivated.
o Disease causing members:
1. Alpha Herpes viruses: Herpes simplex 1 (HSV-1), Herpes simplex type 2 (HSV-2)
2. Varicella (chicken pox)
3. Herpes zoster (shingles)
4. Gamma Herpes Viruses: Epstein-Barr Virus (EBV)
What does Herpes Simplex Virus 1 (HSV-1) cause? What are its characteristics?
Causes: fever blisters, keratoconjunctovitis, severe encephalitis
Most primary infections are subclinical, followed by latency in the ganglia of the sensory nerves innervating the affected area, from which can later be activated.
What does Herpes Simplex Virus 2 (HSV-2) cause? What are its characteristics?
Causes: genital infections, perinatal infections
Primary infection is also followed by latency in sacral ganglia from which it can be reactivated.
•Moves via the microtubules and enters the nucleus.
•When it is reactivated, it buds off of the nuclear membrane.
What are the characteristics of Varicella (chicken pox)? What does it cause?
• Primarily a childhood disease.
• Transmission via respiratory route.
• Primary replication in the lymph nodes and a primary viremia.
• Replication in the spleen and liver and a secondary viremia.
Causes a distinctive rash.
• Becomes latent w/n the ganglia of neurons.
What is Herpes Zoster (shingles)?
- Reactivation of latent virus from posterior root of ganglia or cranial nerve roots.
- Skin eruptions occurs in areas innervated by these.
What is Varicella-Zoster (VZV)?
- Live attenuated virus vaccine (Varivax) for chickenpox or ProQuad for measles, mumps, rubella and varicella.
- Zostavax = live attenuated vaccine for shingles.
What are the characteristics of Epstein-Barr Virus (EBV)? What does it cause? How is it transmitted? What is the pathogenesis? What is the heterophile?
individuals remain infected for life and often shed virus in saliva.
Asymptomatic in very young children.
Causes: Infectious mononucleosis- U.S. and elsewhere, disease in children and young adults, transmitted by saliva. Susceptible cells are oropharyngeal epithelial cells, B-lymphocytes and some other lymphocytes. EBV infects B cells and acts as a B-cell mitogen. The virus’ proteins activate B-cell growth and also prevent apoptosis. In vivo, B-cell proliferation occurs and is indicated by spurious production of an IgM antibody, termed the heterophile antibody.
