Viral Pathogenesis and Host Resp Flashcards
Tissue Tropism
the likeliness of a virus to infect tissues and not others; aka tissue specificity.
Which virus is hardier, enveloped ones, or non-enveloped ones?
□ Enveloped viruses: fragile and sensitive
- thus needs to be transmitted via close contact
□ Non-enveloped: hardier, can withstand stresses
- thus often transmitted via- viral associated objects or fomites ( objects) and use respiratory or fecal/ oral routes.
acute local disease (ie: common cold)
- incubation period
- virus shedding and transmission
- host responses
- likelihood of re-infection
- incubation period: short
- virus shedding and transmission: many serotypes are rapidly mutating, resulting in short lived immunity
- host responses: secretory IgA
- likelihood of re-infection: common
acute systemic disease (ie: measles)
- incubation period
- virus shedding and transmission
- host responses
- likelihood of re-infection
- incubation period: long
- virus shedding and transmission: primary infxn in epithelium but can result in 2nd replication sites
- host responses: secretory IgA and serum IgG
- likelihood of re-infection: low
Types of viral diseases
Examples
- Acute local: common cold
- Acute systemic: Smallpox, measles
- Chronic: rubella in neonate
- Latent: VZV in nerves
- Slow/Progressive: AIDS
Effects of viruses on infected cells:
- CPE (Cytopathic effects)
- Syncytia
- Growth
- Apoptosis
CPE (Cytopathic effects)
any detectable morphological changes or inclusion bodies in host cell.
- Direct cell damage: *think what things virus can interfere with in the cytoplasm
- Indirect cell damage: integration of viral genome→ induction of mutations in host genome →inflammation and host immune response.
Explain the interferon response and “anti-viral state”.
When the host cell is infected (bound) with the virus, it induces IFNs (interferes with viral infection of neighboring cells) which induces the anti-viral state.
When a host cell is infected with a virus, what factors does it induce? What does that do?
IFNs → antiviral state
- results in some blockade of cell division, reduction of cell metabolism, increase in NK activity including IFNg production, ¬ expression of APC, and may lead to apoptosis and more.
What two ways are IFNs activated by viruses?
- facilitated by dsRNA (virus)
2. TLRs and RLHs (retinoic acid inducible gene- like helicases)
What does innate response to viruses depend on?
TLRs and Helicases (RLHs)
non specific, but immediate
Type I IFNS and Type II IFNS
- what do they each consist of?
- Are they apart of innate or adaptive responses?
Q
Type I IFNS: alpha and beta
Type II IFNS: gamma
- Both are innate
What produces:
Type I IFNS
Type II IFNS
Type I IFNs (IFN alpha and beta) produced by most infected cells within hours of infection
Type II IFNs (IFN gamma) produced by T cells and NK cells, (more restricted)
IFNs induce the antiviral state how? (mechanism)
IFNs bind to specific receptors on cells → signal through JAK/State pathway and control Type I and Type II genes → induce transcription of genes = antiviral state.
IFNs induce the antiviral state how? (mechanism)
IFNs can involve mediators such as PKR and OAS when activating the antiviral state. What do each of them do?
□ PKR (protein kinase): phosphorylate and inactivate translation (tln) initiation factor to decrease protein synthesis
□ OAS: activates a cellular ribonuclease that degrades mRNA
2 types of viral Adaptive Responses
- humoral
2. cell mediated
Humoral Response:
Ab produced during primary virus infections are usually of lower affinity. It is not until later that they bind with higher affinity, most Ab being IgM (unswitched).
§ BIG PICTURE: humoral response is important for recognition of virions.
Which Ig inhibits fusion of enveloped viruses with host membranes
IgG
Cell-Mediated Response:
CTLs lyse/clear virus-infected cells
NK and macrophages kill infected cells directly or by Ab-dependent cell-mediated cytotoxicity (ADCC)
Between Th1 and Th2 which one “skews” toward humoral response and which towards cell-mediated?
Q
Th1 differentiation skews towards cell-mediated immunity and inflammation
Th2 differentiation skews toward humoral response
Compare antibodies produced in primary and secondary responses.
- 1° response: Abs are usually of lower affinity than those produced later.
- 2° Response: Already has Abs of greater affinity and there is a faster increase in that AB both due to immunological memory.
List and describe major cell types involved in anti-viral responses.
- Mononuclear phagocytes: phagocytosis, release of inflammatory mediators, Ag presentation
- DC: APC, stimulate B cell diff and prof, modulator of development of adaptive immune response, secrete antoviral and immunoregulatory cytokines.
- NK cells- serve to contain infection while
CTL cells are produced by adaptive immune response which can then clear infection. - Granulocytes- PMNs, basophils, and eosinophils
Which Ig inhibits virion/host attachment, neutralizes toxins and enzymes
IgA
