HemeOnc Viruses

Question 1

Cause of Dengue Hemorrhagic Fever

Answer 1

Infection with the Dengue virus causes severe myalgias and joint pain (breakbone fever). However there are 4 serotypes to the virus. If a patient is infected a second time with a different serotype, the virus benefits from “Antibody-dependent enhancement” increasing its virulence. This causes the hemorrhagic fever.

Question 2

What is unique about the EBV envelope?

Answer 2

Unlike most viruses, EBV (along with all herpes viruses) obtains its envelope from the nuclear membrane of the host cell instead of the cell membrane.

Question 3

Receptor that EBV binds and its two main locations.

Answer 3

CD21

• B lymphocytes
• oropharyngeal epithelial cells

Question 4

Why doesn’t EBV lead to cancer with every infection?

Answer 4

Patient’s infected B cells are controlled by CD8 T cells. Only an immunocompromised host with lowered T cell count can progress to cancer.

Question 5

If CD8 T cells kill replicating B cells that are infected with EBV, how does the virus keep the B cells from being lysed to ensure its own survival?

Answer 5

EBV secretes an analogue of IL-10 (BCRF-1) which decreases the activity of the B cell and inhibits the T cell response.

Question 6

How can EBV mono be differentiated from CMV mono?

Answer 6

EBV activated B cells produce an IgM Ab that can be detected on blood test called a “heterophile” Ab.

In both CMV and EBV there are atypical appearing T lymphocytes called “Downey Cells”

Question 7

Main 3 symptoms of infective mononucleosis.

Answer 7

Fever
Pharyngitis
Splenomegaly (big risk of splenic rupture so athletes are restricted from play for at least a year)

Question 8

Why don’t you risk treating EBV patients with antibiotics?

Answer 8

Often this condition is confused with strep throat. If it is actually EBV mono, the risk of adverse reaction to any treatment could cause increased morbidity in the patient. The infected B cells are massively producing Abs that have a chance of cross reacting with any administered drug.

Question 9

Common manifestation in AIDS patients infected with EBV.

Answer 9

Hairy Oral Leukoplakia

• loss of CD4 cells leads to funtionless CD8 cells
• white plaques (keratosis or keratin production in epithelial cells that normally don’t produce it) form on the oral mucosa similar to thrush presentation

Question 10

What two other microbes contribute to an EBV infection progressing to Burkitt Lymphoma?

Answer 10

1. Malaria (Plasmodia sp.)
2. HIV

(Malaria is more common)

Question 11

CMV prevents the cell mediated immunity of the host from killing infected cells by what 3 mechanisms?

Answer 11

1. Downregulates expression of MHC I to CD8 cells
2. Interferes with MHC II expression to CD4 cells
3. A viral protein blocks NK cell attack (NK cells normally back up CD8 cells by attacking cells without any MHC I presentation)

Question 12

Most common neonatal disease caused by CMV.

Answer 12

Blueberry Muffin baby

• vertical transmission thru placenta or ascension from cervix
• leads to low birth weight, rash, jaundice, and/or hearing loss

Question 13

Most common complication of CMV infection in AIDS patients.

Answer 13

Retinitis

Question 14

Main histology characteristic of CMV.

Answer 14

Owl’s Eye Inclusion