Lecture 4

Question 1

Paramyxovirus causes what major diseases

Answer 1

Mumps + Measles

Question 2

HN (hemagglutinin-neuraminidase) associate with

Answer 2

Mumps

Question 3

H (hemagglutinin) – binds surface receptors, no N
associate with

Answer 3

Measles

Question 4

Togaviruses properties

Answer 4

Enveloped virus
Icosahedral capsid
ssRNA(+) virus
2 glycoprotein spikes – E1 and E2
Replicates in cytoplasm

Infects upper respiratory tract
Spread via viremia to lymphoid tissue, skin and other organs
Causes Rubella (also known as German measles)

Question 5

Mumps virus

Answer 5

Highly contagious, lytic infection
Spread by viremia
2◦ infection of parotid gland; characterized by painful swelling
CNS infection in 50% of patients

Question 6

Measles Virus

Answer 6

Highly contagious
Primary infection in epithelial cells
Secondary infection in lymphocytes & monocytes
Spread systemically through lymphatic system
Rash due to T cells targeting skin blood vessel endothelial cells

Question 7

Enteroviruses contain

Answer 7

Poliovirus
Coxsackie A virus
Coxsackie B virus
Echovirus
Enterovirus

Question 8

enteroviruses properties

Answer 8

no envelope
icosahedral capsid
small, ssRNA (+) viruses
linear mRNA genome
replicated & assembled in the cytoplasm
large family of viruses
very resistant to harsh conditions
enteroviruses (tolerate wide pH range)
transmitted by fecal-oral route
Lytic virus with specific tissue tropism

Question 9

Enterovirus time course

Answer 9

6-12 days
*rash, ferbrile illness

Question 10

T/F: Enteroviruses can survive harsh environments

Answer 10

TRUE

Question 11

HERPESVIRUSES: PROPERTIES

Answer 11

Viral-glycoprotein rich envelope
Icosadeltahedral capsid
dsDNA viruses
Linear genome
3 subfamilies
Based on gene structure, site of latent infection
Replicated & assembled in the nucleus
Common infection, usually benign and asymptomatic but can be serious especially in immunocompromised individuals
Significant morbidity in eye, brain & disseminated infections
Some herpesviruses have highly specific tissue tropism
Released by lysis, exocytosis or cell-cell bridges

Question 12

3 subfamilies of herpesviruses are

Answer 12

Alpha
Herpes simplex type 1 (HSV-1)
Herpes simplex type 2 (HSV-2)
Varicella-Zoster virus (VZV) – HHV-3

Beta
Cytomegalovirus (CMV) – HHV-4
Human Herpesvirus 6 & HHV-7

Gamma
Epstein-Barr Virus (EBV) – HHV-5
Kaposi’s Sarcoma-related Virus (HHV-8)

Question 13

Herpes Virus life cycle slide 32 ig know it

Question 14

Herpes simplex viruses

Answer 14

HSV-1 & HSV-2 (alphaherpesvirinae)

Genome encodes ~80 proteins
2 main groups

Viral replication
Viral DNA polymerase
Scavenging enzymes (create deoxyribonucleotides)

Other proteins
Attachment glycoproteins
Immune escape proteins

Question 15

HSV infections properties

Answer 15

Lytic – fibroblasts & epithelial cells

Latent – non-dividing cells (neurons)
Non-permissive cells
Early & late genes not expressed
latency-associated transcripts (LATs)
micro-RNAs that inhibit gene expression
Persist in sensory neurons (ex. trigeminal neurons)

Avoid host immune response, asymptomatic
Block TAP, express Fc & complement receptors

Reactivation
Systemic infection, fever, stress, sun exposure

Question 16

HSV-1 syndromes

Answer 16

Mucocutaneous lesions (cold sore, fever blister)
Pharyngitis
Eczema herpeticum
Encephalitis

Question 17

HSV-2 syndromes

Answer 17

Genital herpes (sacral ganglion)
Neonatal HSV (often fatal – cell-mediated immunity not fully developed)

Question 18

VARICELLA-ZOSTER VIRUS

Answer 18

VSV (Chicken pox virus) – HHV-3
Alphaherpesvirinae subfamily

Primary infection – chickenpox
Epithelial cells, fibroblasts, T cells

Recurrent infection – herpes zoster (shingles)
Neurons

Establishes a latent, recurrent, neuronal infection

Dorsal root or cranial nerve ganglia

Primary route of transmission – inhalation

Replicates in mucosal epithelium, cell-cell spread (synctium formation)

Spread by viremia to skin producing lesions (pox)

Question 19

EPSTEIN-BARR VIRUS

Answer 19

EBV (gammaherpesvirinae subfamily) – HHV-4

3 infection outcomes:

Primary infection (productive, lytic)
Binds CR2 receptor expressed on selected epithelial cells and B cells (B cell parasite)
Early & late genes transcribed & translated

Latent infection in memory B cells – recurrence once B cell is activated (no early or late gene expression)

Immortalization of B cells
B cell lymphomas (African Burkitt lymphoma)
Nasopharyngeal carcinomas

Question 20

EPSTEIN-BARR virus pt 2

Answer 20

Infectious mononucleosis (“kissing disease”)

Transmission through shedding virus
Proliferation & activation of B cells results in massive activation of T cells

T-cell-mediated immunity critical for controlling infection
Contributes to symptoms of infectious mononucleosis
lymphocytosis (increases in mononuclear cells)
swelling of lymph tissue
malaise

Question 21

CYTOMEGALOVIRUS

Answer 21

CMV (betaherpesvirinae subfamily) – HHV-5

large genome, lots of proteins produced
dsDNA virus but harbors mRNA transcripts in capsid

Permissive cells
fibroblasts, epithelial cells, granulocytes, macrophages

Latent infection (non-permissive cells)
monocytes, lymphocytes, bone marrow stromal cells
Slow replication favors latent infections
Reactivated in immunocompromised individuals

Asymptomatic shedding of virus in body fluids
saliva, tears, urine, breast milk, semen

Question 22

HERPESVIRUSES

Answer 22

HHV-6 (Roseola, herpes lymphotrophic virus)
nearly everyone seropositive by adulthood
replicates in salivary glands
high fever followed by neck & trunk rash
latent infection in lymphocytes (CD4+ T cells in particular) & monocytes
productive infection upon T cell activation

Question 23

Herpes virus pt 2

Answer 23

HHV-8 (Kaposi Sarcoma-related virus)
similar to EBV (gammaherpesvirinae)
rare B cell lymphoma

Opportunistic infection in AIDS patients

HHV-8 proteins
IL-6 homologue – promotes growth
Bcl-2 analog – prevents apoptosis