Microbiology

Question 1

Epstein-Barr virus

Answer 1

Icosahedral, enveloped, double-stranded DNA virus
Uses CD21 as receptor, transmitted via saliva
Infectious mononucleosis
Later on, polyclonal and monoclonal B-cell lymphomas and oral hairy leukoplakia

Question 2

Mechanism of EBV

Answer 2

Proliferation/activation of CD8+ T cells - kill B cells and limit proliferation of B cells
T-cell response is required for controlling infection but also contributes to clinical disease
Latency in memory B cells

Question 3

When does EBV reactivate?

Answer 3

When memory B-cell hosting latent virus is activated

Question 4

How does EBV cause cancer?

Answer 4

In absence of T cells, EBV can immortalize B cells

IL-10 analogue inhibits TH1 response, stimulates B-cell growth

Question 5

What does B cell activation cause?

Answer 5

Production of an IgM antibody (heterophile Ab) to the Paul-Bunnell antigen
Overall immune response - mono
Lack of effective immune control - lymphoma, hairy cell leukoplakia

Question 6

What cancers can be caused by EBV?

Answer 6

Burkitt Lymphoma
B cell lymphoma
Hodgkin lymphoma
Nasopharyngeal carcinoma
X-linked lymphoproliferative disease

Question 7

Symptoms of mono

Answer 7

4-6 wk incubation
Fever, fatigue, lymphadenopathy, exudative pharyngitis, splenomegaly
May have erythematous rash

Question 8

Complications of mono

Answer 8

Laryngeal obstruction, splenic rupture, neurological complications (Meningioencephalitis, Guillain-Barre)

Question 9

Hairy oral leukoplakia

Answer 9

Opportunistic EBV infection in AIDS patients
Infection of epithelial cells
Characterized by lesions of the mouth

Question 10

Diagnosis of EBV

Answer 10

Blood counts - lymphocytosis w/ more than 10% atypical lymphocytes
Heterphile antibody test most common

Question 11

EBNAs

Answer 11

EBV Nuclear Antigens - first to appear, seen in all infected and transformed cells
Anti-EBNA develops late in infection

Question 12

What does presence of Anti-EBNA suggest?

Answer 12

Past EBV infection
Reactivated EBV
Burkitt’s Lymphoma
Nasopharyngeal Carcinoma

Question 13

Cytomegalovirus

Answer 13

Double-stranded linear DNA virus
Lymphotrophic virus - only replicates in human cells
Latent infection in mononuclear lymphocytes

Question 14

How does CMV replicate?

Answer 14

Activation of transcription factors, NF-kB, and SP1

Replicates in kidney and secretory glands

Question 15

Pathology of CMV infection

Answer 15

Suppression of cell-mediated immunity allows recurrence and severe disease
Prevents antigen presentation to CD8 and CD4 T cells; viral protein blocks NK cell attack

Question 16

Neonatal CMV

Answer 16

Most common viral cause of congenital disease
Fetus infected via blood (primary infection) or by virus ascending from cervix (recurrence)
Low birth weight, thrombocytopenia, microcephaly, jaundice, hepatosplenomegaly, Blueberry muffin rash

Question 17

What is special about CMV mono?

Answer 17

Heterophile antibody isn’t present

Question 18

CMV in Immunocompromised patients

Answer 18

Pneumonia (can be fatal if not treated)

Question 19

CMV in AIDS patients

Answer 19

Retinitis, colitis, esophagitis

Diarrhea, weight loss, anorexia, fever

Question 20

CMV in organ transplants

Answer 20

Often reactivated in recipients due to immunosuppression

Responsible for most kidney transplant failures

Question 21

Diagnosis of CMV

Answer 21

Owl’s eye inclusion
ELISA, PCR
Seroconversion good marker for primary infection

Question 22

Treatment of CMV

Answer 22

Ganciclovir (Drug of choice)

Cidofovir, Foscarnet