WK 8- INFECTION AND IMMUNITY Flashcards
What does virulence mean
degree of pathogenicity- highly virulent= more significant pathogen
What are opportunistic pathogens
Microorganisms that cause a disease in a compromised host rather than a healthy (non-compromised) host
How can flora and environmental bacteria be present but not create an infection
Infection will only occur if the bacteria breaches the surface/membrane and enters the body
What are the 3 factors that determine whether or not a pathogen can cause a disease
- route of entry
- number of infectious bacteria
- status of host defence (eg. if commensal flora or if immunocompromised)
What are the 4 species of pathogens and give a common example of each
Bacteria (neisseria meningitidis), Viruses (HIV), Protozoans (malaria), Metazoans (helminths)
Out of the 4 types of pathogens, which has the highest rate/ability of mutation
Viruses, follows by protozoans
What is a niche and how does it impact on immune response
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
What is the adaptive immune response to extracellular bacteria
Primary response is humoral immunity-> antibodies
-Antibodies will eliminate bacteria & neutralise toxins
What is the innate immune response to extracellular bacteria
Primary response is complement activation->
- (LPS) activate the alternative pathway
–Phagocytosis
–Inflammatory response initiated by PAMPs (e.g. LPS, LTA, DNA, flagellin)
What is the adaptive immune response towards intracellular bacteria
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)
What are the innate immune responses towards intracellular bacteria
Aim is to kill the infected cell
- NK cells promote phagocytosis and killing
- Direct stimulation by bacteria to produce IFN-γ-> macrophage activatin
What is the smallest type of infected particle
virus
True or false- viral genetic material can be RNA or DNA
true
What are the 5 types of viral infetions
- Acute
- Subclinical
- Latent
- Chronic
- Oncogenic
Describe acute viral infection
Release of virus causes lysis of host cells (lytic)
-Well defined recognisable symptoms→e.g. influenza, measles
Describe latent viral infection
Virus remains dormant in host cells, reactivated at later stage→ e.g. herpes viruses HSV 1&2, varicella zoster virus (chickenpox+shingles)
Describe chronic viral infection
Virus remains in host > low level viral production and shedding
-No disease symptoms, unaware they are carriers→ e.g. Hep B, Hep C, HIV
Describe oncogenic viral infection
Cause tumours→ e.g. HPV, Hep B, EBV
Describe subclinical viral infection
No recognisable clinical signs, general malaise, slight fever, lymphadenopathy→ e.g. Rubella, EBV
What are the 9 different ways in which a virus can be spread
- Saliva- EBV
- Mechanical trauma- Cowpox
- Bite-Rabies
- Injection- Hep B
- Generalized infection- Chickenpox
- Localised resp infection- Influenza
- Sexual intercourse- HIV
- Transplacental- Rubella
- Faecal-oral- Hep A
What is a defensin and how does it work- what immune response does it belong to
Innate- they are small cysteine-rich cationic proteins released by neutrophils and macrophages-> increase membrane permeability of pathogens (aid in destruction)
What innate immune responses are developed against viruses
- 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
What adaptive immune responses are developed against viruses
- 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
What innate immune responses occur with extracellular protozoa
phagocytosis, complement activation
What antibody responses occur with extracellular protozoa
opsonisation, complement activation, ADCC
What antibody responses occur with intracellular protozoa
neutralisation to block entry to host cells
What T cell responses occur with intracellular protozoa
Th1 cytokines to activate macrophages, Cytotoxic lymphocytes (CTL’s) kill infected cells
What T cell responses occur with extracellular protozoa
Th2 cytokines for antibody response, ADCC
What are examples of intracellular protazoa
malaria, leishmaniasis, toxoplasmosis
What are examples of intracellular protazoa
amoebiasis, trypanosomiasis, giardiasis
What are the 3 T cell receptors involved in HIV transmission
CD4 receptor, and 2 co-receptors (CCR5 or CXCR4)
What is the major viral receptor involved in HIV transmission
Gp120
How can meningococcal result in organ failure/death/disability
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
What is the most important virulence factor in neisseria meningitides
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
What are the 3 cell types infected in HIV
CD4 T cells, macrophages and DCs
