WK 8- INFECTION AND IMMUNITY

Question 1

What does virulence mean

Answer 1

degree of pathogenicity- highly virulent= more significant pathogen

Question 2

What are opportunistic pathogens

Answer 2

Microorganisms that cause a disease in a compromised host rather than a healthy (non-compromised) host

Question 3

How can flora and environmental bacteria be present but not create an infection

Answer 3

Infection will only occur if the bacteria breaches the surface/membrane and enters the body

Question 4

What are the 3 factors that determine whether or not a pathogen can cause a disease

Answer 4

1. route of entry
2. number of infectious bacteria
3. status of host defence (eg. if commensal flora or if immunocompromised)

Question 5

What are the 4 species of pathogens and give a common example of each

Answer 5

Bacteria (neisseria meningitidis), Viruses (HIV), Protozoans (malaria), Metazoans (helminths)

Question 6

Out of the 4 types of pathogens, which has the highest rate/ability of mutation

Answer 6

Viruses, follows by protozoans

Question 7

What is a niche and how does it impact on immune response

Answer 7

Niche is the place in which a pathogen is most likely to survive and thrive-> the niche determines the bodys immune-> eg. if the organism’s niche is within the cell, the immune response cannot contain antibodies/complement as they cannot penetrate the cell

Question 8

What is the adaptive immune response to extracellular bacteria

Answer 8

Primary response is humoral immunity-> antibodies

-Antibodies will eliminate bacteria & neutralise toxins

Question 9

What is the innate immune response to extracellular bacteria

Answer 9

Primary response is complement activation->
- (LPS) activate the alternative pathway
–Phagocytosis
–Inflammatory response initiated by PAMPs (e.g. LPS, LTA, DNA, flagellin)

Question 10

What is the adaptive immune response towards intracellular bacteria

Answer 10

Primary response is cell mediated immunity
-Th cell derived signals – CD40L & IFN- γ help macrophage to kill phagocytosed bacteria (vesicular microbe)
–CTLs (CD8) induce lysis of infected cells (cytoplasmic microbes)

Question 11

What are the innate immune responses towards intracellular bacteria

Answer 11

Aim is to kill the infected cell

• NK cells promote phagocytosis and killing
• Direct stimulation by bacteria to produce IFN-γ-> macrophage activatin

Question 12

What is the smallest type of infected particle

Answer 12

virus

Question 13

True or false- viral genetic material can be RNA or DNA

Answer 13

true

Question 14

What are the 5 types of viral infetions

Answer 14

1. Acute
2. Subclinical
3. Latent
4. Chronic
5. Oncogenic

Question 15

Describe acute viral infection

Answer 15

Release of virus causes lysis of host cells (lytic)

-Well defined recognisable symptoms→e.g. influenza, measles

Question 16

Describe latent viral infection

Answer 16

Virus remains dormant in host cells, reactivated at later stage→ e.g. herpes viruses HSV 1&2, varicella zoster virus (chickenpox+shingles)

Question 17

Describe chronic viral infection

Answer 17

Virus remains in host > low level viral production and shedding
-No disease symptoms, unaware they are carriers→ e.g. Hep B, Hep C, HIV

Question 18

Describe oncogenic viral infection

Answer 18

Cause tumours→ e.g. HPV, Hep B, EBV

Question 19

Describe subclinical viral infection

Answer 19

No recognisable clinical signs, general malaise, slight fever, lymphadenopathy→ e.g. Rubella, EBV

Question 20

What are the 9 different ways in which a virus can be spread

Answer 20

1. Saliva- EBV
2. Mechanical trauma- Cowpox
3. Bite-Rabies
4. Injection- Hep B
5. Generalized infection- Chickenpox
6. Localised resp infection- Influenza
7. Sexual intercourse- HIV
8. Transplacental- Rubella
9. Faecal-oral- Hep A

Question 21

What is a defensin and how does it work- what immune response does it belong to

Answer 21

Innate- they are small cysteine-rich cationic proteins released by neutrophils and macrophages-> increase membrane permeability of pathogens (aid in destruction)

Question 22

What innate immune responses are developed against viruses

Answer 22

• Acts via Lysozyme, antiviral-cytokines (interferons) and NK cells-> these produce IFN-g, carry out ADCC, cause phagocytosis and cell death
• also release defensins
• activation of the complement pathways (alternative and classical)-> create MAC

Question 23

What adaptive immune responses are developed against viruses

Answer 23

• Ag specific immunity, antibodies, cell mediated killing, memory cells
• -> Antibodies act to neutralisation extracellular virus, aid in phagocytosis and opsonisation and promote cytotoxicity and complement activation

Question 24

What innate immune responses occur with extracellular protozoa

Answer 24

phagocytosis, complement activation

Question 25

What antibody responses occur with extracellular protozoa

Answer 25

opsonisation, complement activation, ADCC

Question 26

What antibody responses occur with intracellular protozoa

Answer 26

neutralisation to block entry to host cells

Question 27

What T cell responses occur with intracellular protozoa

Answer 27

Th1 cytokines to activate macrophages, Cytotoxic lymphocytes (CTL’s) kill infected cells

Question 28

What T cell responses occur with extracellular protozoa

Answer 28

Th2 cytokines for antibody response, ADCC

Question 29

What are examples of intracellular protazoa

Answer 29

malaria, leishmaniasis, toxoplasmosis

Question 30

What are examples of intracellular protazoa

Answer 30

amoebiasis, trypanosomiasis, giardiasis

Question 31

What are the 3 T cell receptors involved in HIV transmission

Answer 31

CD4 receptor, and 2 co-receptors (CCR5 or CXCR4)

Question 32

What is the major viral receptor involved in HIV transmission

Answer 32

Gp120

Question 33

How can meningococcal result in organ failure/death/disability

Answer 33

Infiltration of pathogen through mucosa causes cytokine activation→ raises TNF-α, IL-1, IL-6→ cause sepsis and can create endothelial damage and capillary leakage (causes the purpuric rash, shock, DIC, thrombolytic events)→ combination of poor tissue perfusion and coagulopathy leads to multiple organ failure and necrosis of extremities (dry necrosis)→ can lead to death or permanent disability

Question 34

What is the most important virulence factor in neisseria meningitides

Answer 34

Most important virulence factor is the presence of an outer polysaccharide capsule→ the capsule contributes to survival through inhibition of phagocytosis, but also in mitigating meningococcus’ susceptibility to drying

Question 35

What are the 3 cell types infected in HIV

Answer 35

CD4 T cells, macrophages and DCs