Mechanisms of viral infection pathogenesis

Question 1

What are the three patterns of viral infections?

Answer 1

→acute infection
→latent, reactivating infection
→persistent infection

Question 2

Give examples of acute infections

Answer 2

→common cold
→measles
→ebola
→small pox

Question 3

How many human herpes viruses are there?

Answer 3

→8

Question 4

What is HHV8?

Answer 4

→Kaposi sarcoma

Question 5

What is HHV3?

Answer 5

→chicken pox

Question 6

What is HHV4?

Answer 6

→EBV

Question 7

What is HHV5?

Answer 7

→cytomegalovirus

Question 8

What is HHV1 in infants?

Answer 8

→Primary Gingivostomatitis

Question 9

What is HHV1 brought under control?

Answer 9

→cold sore

Question 10

Describe the primary infection of herpes simplex and VZV

Answer 10

→ herpes infection causes mild pharyngitis fever
→VZV infection causes chicken pox
→virus transits up to peripheral nerve using microtubules to neuronal nucleus
→lies latent
→amplification using cells mcachinery

Question 11

Describe the recurrence of VZV and herpes

Answer 11

→age and X-irradiation or local injury activates VZ virus in neuron
→fever, sunlight to face, menstruation activates herpes
→virus transits down peripheral nerve
→causes shingles in VZV
→ causes cold sore

Question 12

Which viruses are persistent in presence of active immune response?

Answer 12

→HIV- retrovirus
→HCV-flavivirus
→measles

Question 13

What is flavivirus

Answer 13

→positive,
→single-stranded,
→enveloped RNA viruses

Question 14

What can be caused by measles shed virus years after acute infection?

Answer 14

→encephalitis

Question 15

What is congenital rubella?

Answer 15

→if infected in utero, virus is seen as self, baby is born immunotolerant and virus continues to replicate (and cause damage) in neonatal tissues

Question 16

How does rubella infect pregnant women?

Answer 16

→infect the placenta

→viral replication can infect all foetal organs

Question 17

What is a hallmark of rubella in foetal rubella infection?

Answer 17

→infection that persists throughout foetal life

→shedding of virus up to 2 years after birth

Question 18

What percentage of poliovirus infections are asymptomatic?

Answer 18

→90%

Question 19

What is a requirement of inapparent infections?

Answer 19

→viruses be non-cytopathic

Question 20

What are zoonotic infections?

Answer 20

→virus from one species to another

Question 21

What does Ebola virus target?

Answer 21

→Vascular Endothelial Cells

Question 22

What damage does Influenza A virus cause?

Answer 22

→targets lung epithelia

Question 23

What does RSV(Respiratory syncytial virus) induce?

Answer 23

→syncytia in lung epithelia

→Nuclei are inactive as a result

Question 24

Describe the course of illness of Hep C

Answer 24

→acute infection
→chronic infection
→fibrosis
→cancer or cirrhosis

Question 25

How can you differentiate between Hep C infected hepatocytes and healthy cells?

Answer 25

→by staining

Question 26

Describe the immunopathology response to Hep C

Answer 26

→extensive liver infiltration of leukocytes →infiltration of CD8+ cells →Liver has a lot of CD8+

Question 27

What is HCV persistence associated with?

Answer 27

→generation of HCV variants that are not recognised by CD8+ cells

Question 28

What type of viral infection is Dengue fever?

Answer 28

→mosquito-borne infection

Question 29

How many serotypes of Dengue are there?

Answer 29

→4 | →have the same clinical manifestations

Question 30

What are the symptoms of dengue virus?

Answer 30

``` →acute fever →severe abdominal pain →headache →plasma leakage skin rash vomiting ```

Question 31

What can happen as a result of severe dengue?

Answer 31

→dengue shock syndrome (DSS), | →hemorrhage

Question 32

What is the greatest risk of severe dengue?

Answer 32

→previous infection with a different serotype | →Antibodies formed in response to a dengue infection are not cross-protective against other subtypes of the virus

Question 33

What is antibody dependent enhancement in dengue?

Answer 33

→preexisting antibodies from a primary dengue virus infection bind to an infecting DENV particle during a subsequent infection with a different dengue serotype. →The antibodies from the primary infection cannot neutralize the virus → Ab–virus complex attaches to receptors called Fcγ receptors (FcγR) on circulating monocytes → antibodies help the virus infect monocytes more efficiently.

Question 34

Describe RSV immunopathology

Answer 34

→RSV infections in early life show unbalanced Th1/Th2 responses →depresses inflammatory cytokine production, CD8+ responses and IgG production →clearance is slow →enhances IgE production, leading to allergy/asthma on re-exposure by activating eosinophils

Question 35

What are the symptoms of influenza?

Answer 35

→Fever, often prolonged →Neurological (headache, malaise) →Myalgia- sore muscles

Question 36

Why are there different vaccines for influenza?

Answer 36

→Influenza changes its amino acids on H1N1 which are required for binding to receptors →antibodies against those amino acids

Question 37

What is pandemic flu?

Answer 37

→strain of influenza virus that causes much more morbidity and mortality →every 20-40 years

Question 38

Why can be pandemic flu?

Answer 38

virus has changed it’s surface proteins (H and N) →there is no widespread immunity

Question 39

What is antigenic shift?

Answer 39

→major change in a flu A virus, resulting in new HA and/or new HA and NA proteins in flu viruses that infect humans →eg swine flu

Question 40

What does outcome of infection depend on?

Answer 40

→what you are you infected by, →whether you’ve seen it (or anything like it) before, →the state of your immune system

Question 41

What is antigenic dift?

Answer 41

→small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus, HA (hemagglutinin) and NA (neuraminidase)