DNA Viruses Flashcards
These are the smallest of the DNA viruses, has linear (-) ssDNA and presents as childhood infection, fever and rash. What is this?
Parvovirus - genome encodes only 2 proteins; only replicates in dividing cells
Describe how HPV viral proteins disrupt the host cell cycle.
- E6 binds p53 so there is no cellular apoptosis
2. E7 binds Rb so txn is no longer inhibited, resulting in prolonged DNA replication
Why is HPV associated with cervical cancer? Describe the mechanism.
HPV expresses early genes that make viral proteins (E6 and E7) that causes constant cellular proliferation. This can increase the risk of malignancy resulting in genital and cervical cancers.
Describe the transmission, features and Dx of: Smallpox virus
Tsm: respiratory or fomites;
Cx: fever, malaise;
Dx: progressive pox rash with live virus in vesicular fluid
The rash presents with lesions that are the SAME STAGE
Describe the viruses, spread, latency and effects of: Alpha Herpes subfamily
- VZV, HSV 1 and 2
- rapid spread
- latent @ sensory ganglia
- destroy infected cells (cold sores)
Describe the viruses, spread, latency and effects of: Beta Herpes subfamily
- CMV, HHV6, HHV7
- Slow infectivity
- latent @ monocytes
- LARGE infected cells
Describe the viruses, spread, latency and effects of: Gamma Herpes subfamily
- EBV, HHV8
- infection specific to T or B-cells
- latent @ lymph tissue
- Associated with lymphomas
List 5 ways in which Herpes Viruses can evade the immune system.
- Inhibit cytokine activity
- Decrease MHC class I
- Inhibit interferon activity
- Block apoptosis
- Hinder macrophage activation
What are 2 main defenders of our immune system that can activate against the Herpes virus?
- NK cells kill infected cells that do not have MHC 1 on cell surface.
- CD8’s recognize viral glycoproteins on infected cell surfaces
What viral substance prevents the cell from coming out of latency?
Infect Cell Protein O hybridizes to ICPO Gene to inhibit infection during latency. This is an example of a viral latency-associated transcript (LAT).
What is the relationship between Varicella and Zoster, in regards to alpha-viruses?
Varicella (chicken pox) in young people is the SAME VIRUS as Zoster (Shingles) in older people. The latter is the recurrent form of Chicken pox.
Rash is systemic and presents as DIFFERENT STAGED ULCERS
Compare and contrast Chicken pox from Herpes viruses.
- HSV is localized and presents as painful lesions, latent in one ganglion;
- Chicken pox is SYSTEMIC and presents as itching lesions, latency in multiple nerves
Describe the Dx, spread, latency and effects of: Cytomegalovirus (CMV)
Dx: cytomegaly (large multinucleate giant cells);
Tsm: infected body fluids, slow infectivity;
Latency @ neutrophils and monocytes;
Cx: asymptomatic in kids, mononucleosis-like disease
Describe the Dx, spread, latency and effects of: Epstein-Barr virus
Dx: virus transforms B-cell cultures (no inclusion bodies nor cytopathic effects)
Tsm: kissing, respiratory secretions;
Latency @ B-cells;
Cx: Infectious Mononucleosis and associated w/ human tumors
Explain the relationship between Burkitt’s Lymphoma and M. falciparum.
Burkitts Lymphoma and Malaria are in the same endemic area. M. falciparum suppresses CTLs and stimulates c-myc gene to translocate. This increases B-cell proliferation to increase the amount of EBV infectivity in a patient. It’s also associated with EBV in African endemic regions.
Describe the 2 ways to diagnose EBV.
- Heterophile antibodies = made by infected B cells agglutinate RBCs
- Serology from anti-viral capsid (early infection), anti-EBV nuclear Ag (later infection)
When looking at the serology to diagnose EBV, how can a clinician differentiate between early and late infections?
Early infections are indicated by HIGH IgM titers in the Anti-VCA titer. Later infections are indicated by the HIGH IgG showing a past infection from Anti-EBVNA titer.
Describe the transmission, features and Dx of: Molluscum contagiusum virus
Tsm: respiratory droplets, scratching the itch inoculates other lesions;
Cx: dimpled lesions on trunk and arms, self-limiting and common warts in teens;
Dx: a Pox virus with a dumbell-shaped core on EM
Describe the transmission, latency, features, Dx and Tx of: Alpha Herpes viruses
Tsm: RAPID infectivity @ respiratory mouth, sexual contact;
Latency: HSV 1 @ trigeminal ganglia; HSV 2 @ sacral ganglia
Cx: HSV 1 = cold mouth sores + encephalitis, HSV 2 = genital lesions + aseptic meningitis;
Dx: intra-NUCLEAR inclusion (Cowdry) bodies, tegument btw envelope and viral capsid, PCR test
Tx: Acyclovir or Valcyclovir for breakouts
Describe the transmission, latency, features, Dx and Tx of: Cytomegalovirus (CMV)
Tsm: Slow infectivity, infected body fluids (blood, sex, saliva), Beta-Herpes;
Latency @ neutrophils + monocytes;
Cx: CMV = mono-like disease, salivary gland disease, Blue-berry muffin rash, jaundice, sensorineural hearing loss @ congenital;
Dx: Cytomegaly, calcification in brain, Owl-eye inclusion bodies TORCHES;
Tx: Gangcyclovir
Describe the transmission, latency, features, Dx and Tx of: Epstein-Barr Virus (EBV)
Tsm: infection @ T or B cells via respiratory secretions, “Kissing Disease”;
Latency @ lymph tissue, Gamma-Herpes;
Cx: infectious mononucleosis (sore throat, lymphadenopathy, fatigue), fever, splenomegaly;
Dx: Reactive (Downy) T-cells = atypical lymphocytosis, Heterophile ABs = latent B-cells, serology
Tx: Supportive therapy, avoid contact sports (splenic rupture risk)
What type of cancer is EBV associated with. Explain it’s association.
B-cell lymphomas in the immunosuppressed. Hodgkin’s lymphoma (cells look like owl’s eyes). African Burkitt Lymphoma (large jaw lesion and swelling).
Describe the transmission, latency, features, Dx and Tx of: Varicella Zoster Virus
Tsm: Respiratory droplets
Latency @ MULTIPLE Dorsal sensory ganglia, Alpha-Herpes;
Cx: SYSTEMIC Vesicular “dew drops on the rose” rash (similar to HSV), “Chickenpox = Varicella, Herpes Zoster = Shingles”;
Dx: Tzank smear + rash appearing at same stage
Tx: Acyclovir + Live, attenuated vaccine for children
How does the Smallpox rash differ from the Alpha herpes (VZV) rash?
Smallpox presents as a LOCALIZED rash that occurs ALL at the SAME STAGE; whereas, Varicella-Zoster presents with SYSTEMIC lesions at DIFFERENT stages of healing.
What virion makes Herpes Viruses unique from other DNA viruses?
Tegument - protein filled space btw capsid and envelope
Which virus infection develops as Progressive Multifocal Leukoencephalopathy (PML) in AIDS patients?
Human Polyoma virus JC
What is the DNA-virus related illness is characterized by a fever and rash in children? What is the cause of the rash?
Fifths Disease (Erythema infectiosum) = Slapped Cheek illness from Parvovirus B-19 infection; Cause = inflammation initiated by complexes of antibody and viral antigens
What is the cause of red cell deficiency in Parvovirus B-19 infection?
Viral infection/destruction of red cell precursors.
What 4 factors played a crucial role in the eradication of smallpox?
- No asymptomatic carriers
- Lack of vector or reservoir
- Single serotype
- Long-lasting immunity by vaccination
What is unique about the viral replication of Poxviruses?
This is the LARGEST of the DNA viruses that transcribes its viral genes in the cytoplasm
