Exam 3 Week 2 Flashcards
- Identify the virus structure of Influenza virus?
- family
- stranded ness
- nuclei acid
- sense/polarity
- capsid type
- envelop or not
- What are the respective hosts of the various influenza types?
* which type is linked to pandemics and why?
- Orthomyxoviridae - Influenza type A, B, C
A. Ss RNA; negative sense (-) RNA. Segmented. Type A and B has 8 segments and type C has 6 segments
B. Helical nucleocapsid; composed of RNA + NP, PB1, PB2, PA
C. Envelope contains 2 glycoproteins - H and N
D. 9 structural + 2 non structural proteins (NS); the 9 are H, N, PB1, PB1-F2, PB2, PA, M1, M2, NP
**Remember every helical nucleocapsid must have an envelope
2. Hosts Type A - human, swine, avine, equine Type B - human only Type C - human only **Type A is linked to pandemics because of antigenic SHIFT - major mutation due to mix of human and animal resortment
What factors limit effectiveness of an influenza vaccine
- Antigenic drift ; H and N varies anitgenically due to point mutation
- antigenic drift leads to epidemics; existing ab in human
population from previous infections by influenza virus may
not efficiently neutralize virus.
**You make vaccine based on prediction of what strains of type A would be in the environment
What relationship do specific structural components of the intact influenza virion have to the pathogenesis of the disease? (3)
Antigens (influenza virus)
- Nucleocapsid and “M” protein
- Hemagglutinin antigen; detected by hemagglutination, neutralization and C-fixation
- H and N are both strain specific Antigens; influenza type A, Hong Kong strain
**H and N are major antigens. H is most important antigen
Describe the process of the following in influenza virus
- Replication
- Viral transcription/ Viral protein translation
- Viral genome replication
- Replication (nucleus)
- attach virus particle to cell surface receptor
- Hemagglutinin of virus binds to sialic acid containing receptors.
- Hemagglutinin initiate fusion between the virus envelop and the vacuole membrane - Viral transcription/ viral protein translation
- Transcription (nucleus); (-) RNA serve as template for (+) RNA **diagram. Primer for RNA dependnet RNA polymerase (PB2PB1PA) is m7g (cap structure)
- Translation (cytoplasm always); MP protein and other proteins come together and form the structural proteins - Viral genome replication
- Production of new viral genome; RNA polymerase copy (-) RNA to (+) RNA. A negative RNA with multiple (+) RNA is called REPLICATIVE INTERMEDIATE
- newly synthesized viral genomic RNAs then transported out of nucleus to the cytoplasm
- What factors are involved in the genetic variation exhibited by the influenza A virus?
- What is the clinical significance of this genetic variation?
- Antigenic shift
- Pandemic (world wide infection spread); due to antigenic shift. Human virus has hemagglutinin from pig.
- H major antigenic variation due to reassortment between
human and animal influenza virus- “ antigenic shift” -
responsible for pandemic which occur about every 10
years, exchange RNA segments between animal influenza
virus and human influenza virus; N protein antigenicity
can also be changed as a result of reassortment of the N
gene. - As a result of shift, presentation of entirely new
antigens to population with no immunity - yields acute
respiratory disease, no neutralization of virus by pre-
existing antibodies
- What structural components of the influenza virion are involved in inducing protective immunity of the infected host?
- Role of secretory IgA in resolving/modifying influenza infections
- A. Major antigen for immunity = H, 11 H subtypes change in H
affects antigenicity most, additive effect if N also
changes
B. N antigenicity is also important, 8 N subtypes. 2 functions of Neuroaminidase;
- important in budding (viral release) of progeny virus
- lowers viscosity of mucus in vivo during infections
- B. H & N varies antigenically due to point mutation -
“antigenic drift”
C. antigenic drift leads to epidemics; existing ab in human
population from previous infections by influenza virus may
not efficiently neutralize virus.
*** “Antigenic Sin”: with each new infection with influenza A
an individual responds with the strongest antibody against
the 1st subtype, which infected that individual
- Describe general classification of retrovirus
- A. Ss RNA ; diploid 35S genome joined by tRNA
B. Complex capsid; helical nucleocapsid (house reverse transcriptase) with icosahedral/cylindrical outer shell
C. Envelop
**RNA dependent - DNA polymerase is the reverse transcriptase
Describe structure of retrovirus
- Enzymatic complex
- Envelope
- RNA genome content ; chronic leukemia vs acute leukemia/sarcoma
- Enzymatic complex
- RNA dependent - DNA polymerase (reverse transcriptase)
- DNA polymerase and RNAse
- H and integrate; encoded by pol gene
- PRO gene encodes protease. Either part of pol or adjacent to it - Envelope; cell membrane derived via building
- 3 envelope proteins (ENV)
- 4 internal capsid proteins (GAG gene) - RNA Genome = GAG - Pol - Env - ONC (+-)
I) chronic leukemia; lack onco gene
II) Acute leukemia/sarcoma; have oncogene but no envelop. ***exception is Ross sarcoma which has full complement of genes
** HIV ; GAG - Pol - ENV plus other encoding region
Short description of major retroviridae
- subfamily
• Retrovirus is the family that has subfamily;
i) oncovirinae - tumor virus
II) lentivirinae - slow virus (AIDS)
iii) spumavirinae - non oncogenic and looks like soap sods (foamy virus or syncytial virus)
** Oncornavirinae classified as type B, C, D based on host range, antigenicity, virus morphology (location of core relative to virus structure)
Role of RNA-dependent DNA polymerase (reverse
transcriptase)and other viral enzymes in viral replication.
• Replication; occur both in cytoplasm and nucleus. (+) RNA to (-) DNA to (+-) DNA - provirus - integrate integrate provirus into cellular DNA. There is an LTR (long terminal repeat) structure at the ends of the provirus - formed during transition from RNA to DNA. LTR has regulatory regions (TATA enhancers) within it. DNA dependent DNA polymerase converts ssDNA to DsDNA (provirus)
- 35s mRNA - GAG or GAGpol polyprotein
- 28s Env polyprotein (has to be proteolytically cleaved)
- 21s ONC protein (acute leukemia/sarcoma virus)
Describe process of replication of retrovirus
A. Location
B. General scheme
C. Provirus formation
***describe integration process
Replication
A. Cytoplasm + nucleus
B. General scheme= (+) RNA to (-) DNA to (+-) DNA - provirus
—> integration provirus DNA at many sites within chromosomal DNA; Provirus integration is INTEGRASE MEDIATED
C. Provirus formation takes place in cytoplasm which is then
transported to the nucleus where integration occurs
D. the conversion of genomic RNA to proviral DNA produces a
long terminal repeat (LTRs) which are located at each end of the provirus; LTR has regulatory regions within it
Retrovirus
- Transcription results
- Translation
- Transcription from provirus yield two or three mRNAs
- 35s mRNA
- 28s mRNA
- 21s mRNA - Translation fo mRNAs
- 35s mRNA GAG or GAG -Pol polyprotein; Gag mRNA
predominates
- 28s Env polyprotein; polyprotein proteolytically cleaved
into smaller proteins
- 21s ONC protein; present in acute leukemia/ sarcoma virus
- Proteolytic cleavage of polyprotein precursors to yield
actual viral proteins, viral proteases encoded by PRO gene involved in specific cleavage
DNA evidence RNA tumor virus
Unlike DNA tumor viruses, which transform cells or cause a lytic infection with virus production, retroviruses can transform cells and produce progeny virus, Also cause tumors in vivo
Avian subgroup of retrovirus
Differentiate between chronic leukemia and acute leukemia - sarcoma
A. Chronic leukemia virus;
- In vitro - no transformation (no onco gene).
- In vivo - leukemia in animals after long latent period (activate protooncogenes in the cell).
- No defective envelop
B. Acute leukemia - sarcoma;
- In vitro - transform cells but no virus is produced (SRC/oncogene present). **Rous sarcoma virus is the exception in that it produce virus
- In vivo - cause sarcoma.
- Usually defective (no envelope) so need helper virus
that will supply the missing envelope for replication
Retrovirus
1. Differentiate protooncogenes vs oncogene
- Identify modes of protooncogens (4)
- A. Oncogenes; found in different species. v- onc (viral oncogene)
B. Protooncogenes are also called c - onc and they serve a purpose (normal cell genes)
• C- onc (protooncogenes); find equivalence in v- onc (viral oncogene). **They come together and can form point mutations overtime.
- Modes of protooncogenes activation; normally repressor gene keep then in check.
I) mutation in repressor gene (caused by chemical carcinogen); protooncogene no longer repressed
II) insert leukemia provirus right next to protooncogene. LTR of leukemia virus “turns on” expression of protooncogenes or endogenous virus
III) translocation of c onc (protooncogene)from normal position of chromosome to position on another chromosome. Place protooncogene under influence of an enhancer or promoter which activates transcription of protooncogenes e.g burkitt lymphoma myc translocated to position under control of Ig enhancer
IV) Sarcoma or acute leukemia introduce provirus (oncogene) into cell DNA , this will “overdose” the cell with the oncogene protein. Some oncogene products may appear as fused proteisn e.g gag -myc
Retrovirus
- Functions of transforming proteins encoded by protooncogene - diverse
- most are kinases that can phosphorylate a lot of other enzymes.
Retrovirus
Give examples of antioncogenes
- RETINOBLASTOMA gene(Wilms tumor) ; born with one allele mutation and later develop second allele mutation.
- Normally Rb protein is phosphorylated-dephosphorylated
during cell cycle
- Alterations of Rb protein may alter its interaction with
controls of the cell cycle - DNA tumor virus (Adenovirus)
- Products of DNA tumor viruses, eg. EIA of adeno, or E7 of HPV-16, bind to Rb protein which may in turn alter the
control of the cell cycle
** So far retinoblastomas, Wilm’s tumors, colorectal cancers,
lung cancers and breast cancers require loss or mutation of suppressor genes in their development
Identify the following and Identify 3 components
- oxygenated products of poly unsaturated long-chain FA. Eikosi is Greek for 20. 20 carbon FA precursors
**Give examples of a potent vasoconstrictor vs a relatively inactive one
**identify activity of prostaglandin types from most to least
- Eicosanoids
- prostaglandins (PGs); PGD2, PGE2, PGF2alpha, PGI2
- leukotrienes (LTs); LTC4, LTD4, LTE4
- thromboxanes (TXs); TXA2
• TXA2 is a vasoconstrictor (platelet aggregator).
- TXA3 is relatively inactive
- *Eicosanoids are derived from FA precursors that are esterified to membrane phospholipid such as;
- Dihomo-y-linolenic acid
- Arachidonic acid
- eicosapentaenoic acid
**Activity of prostaglandin PGI2 > PGI1 and PGI3
What is the most abundant and most important precursor of Eicosanoids
- synthesized from?
- how many C? Double bonds?
- what enzyme release this product from complex phospholipids (what 2 pathways)
- half life?
ARACHIDONIC ACID; made in liver from linoleic acid (essential FA)
- Linoleic acid is derived from dietary constituents - vegetable oil (sunflower oil)
- Arachidonic acid = Eicosa
- 20 C and 4 double bonds
- PHOSPHOLIPASE release arachdonic acid from complex phospholipids in different ways (diagram slide) - linear (Lipoxygenase and PGH synthase COX 1 and 2) vs cyclic pathways (PGH synthase, epoxygenase - CYP, free radicals)
• A lot of these prostaglandins have VERY SHORT HALF LIFE.
- Describe the cyclooxygenase (Prostaglandin G/H synthase) pathway
- Describe 2 options for metabolism
- Cyclooxygenase pathway aka prostaglandin G/H synthase;
- from Arachidonic acid; form PGG2 (C15 hydroperoxide) and
- PGH2 (C15 hydroxyl group)
* which are both UNSTABLE. The number comes from original/substrate fatty acid (2 - arachnidonic acid)
**PGH2 - PGE2 (PGE synthetase), PGD2, PGI2, TXA2
2. Metabolism
(i) Hydration or
(ii) Oxidation of the15-hydroxyl gp to ketone
by prostaglandin 15-OH dehydrogenase, followed by Δ13 reduction, beta-oxidation and ω-oxidation
- Identify product of cyclooxygenase
- 3 types
- half life
- receptor?
- major effects? (4)
- other targets
- PROSTANOIDS
A. prostacyclin, prostaglandins and thromboxanes.
B. Short half life. (Paracrine or autocirne)
C. cell surface receptors GPCR - activate G proteins; increase cAMP and decrease intracellular calcium. EP2, EP4, IP, DP or EPI, FP, TP - increase intracellular calcium
D. Major effects is on 4 types of smooth muscle
- vascular
- GI
- airway
- reproductive
E. Other targets; platelets, monocytes, kidneys, CNS, sensory nerve endings, endocrine organs, and the eye (this may probably involve smooth muscle)
Differentiate COX 1 vs COX 2 vs COX 3
- location
- what inhibit COX 1 and COX 2 (2) - side effects
- what selectively inhibit COX 2
- what is major source of vascular Prostanoids
- COX 1 (constitutive/ housekeeping - protect GI tract stomach mucusa from gastric acid by increasing stomach mucus)
- found in endothelial cells, stomach and kidney - COX 2 (inducible); involved in inflammation. **COX 2 is major source of vascular prostanoids in endothelial cells
- elevated by inflammation and cytokines (constitutively expressed in brain and kidney) - COX 3 ; new isoform
• Aspirin inhibit both COX1 and COX2
• 60% homologous between COX 1 and COX 2 but different functions
• NSAIDS/Aspirin (COX 1 and 2 inhibitors) adverse effect; GI ulcers/bleeding. Block acid production from parietal cell and also mucus production?
- New generation (Coxibs) inhibit COX-2 more selectively
Identify 4 types of Prostanoids
- PGI2 - prostacyclin
- PGE2 - prostaglandin
- TXA2 - Thromboxanes
- PGF2a - Prostaglandin F2alpha
Identify the effects of Prostacyclin - PGI2 on the following
- Vascular
- Airway
- GI
- Renal
- Reproductive
- Pain
- Fever
- Eye
- Receptors
Prostacyclin - PGI2
- Vascular; *INHIBITS PLATELET AGGREGATION by all agonist(thrombin, ADP, TXA2)
- relax vascular smooth muscle
- powerful vasodilator - Airway
- relax respiratory smooth muscle
- powerful bronchodilator - GI ; *INHIBITS GASTRIC ACID SECRETION, INCREASE MUCUS SECRETION
- protects GI tract - Renal
- increase GFR and renal blood flow
- increase water and sodium excretion
- stimulate renin release - Reproductive ;
- relaxes uterine muscle - Pain; *INDUCES PAIN
- Fever; N/A
- Eye ; N/A
- Receptors ; IP (Gs - increase cAMP)