Virology Flashcards

Question

IFNα and IFNβ

Answer 1

Virus detected by TLR nuclear factor kappa B (NF-κB), activated and cause transcription of IFN-a/b Secrted and bind to IFN receptor Causes JAK STAT pathway, to activate interferon stimulated gene factor 3 (ISGF-3) Binds to interferon stimulated response element (ISRE) and make antiviral proteins like protein kinase R (PKR) Mx Can stop protein synthesis

Answer 2

stopping activation of the PRR-induced signalling cascades soluble proteins to bind IFNs and stop them from binding to receptor, Vaccina makes B18 protein to bind IFN inhibiting the JAK-STAT signalling targetting the ISG proteins directly

Answer 3

PAMP detection can cause death by blocking the action of caspases or targeting Bcl-2 family pro-apoptotic proteins at the mitochondria

Answer 4

chemo-attractant cytokines that recruit leukocytes produce more IFNs or cytokines to activate T cells and macrophages to fight the infection.

Answer 5

Promote inflammatory response,with IL-1, IL-12, IL-18 IFN-γ activates cytotxic T cell herpesviruses and poxviruses secret proteins to block them Epstein-Barr virus expresses a viral cytokine (vIL-10) to cause TH2 response instead of TH1 Wekaer cytotoxic response, instead mor B cells which EB replicates in

Answer 6

If viral infected cell expresses antigen on MHC NK cell can kill If MHC removed by virus, missing self response so can kill, antigen independent

Answer 7

bind to and neutralise virus particles diminish spread by free virions Mucosal IgA is important in preventing infection by viruses that enter by the respiratory system. Cytotoxic T lymphocytes DEstroy virus infected cells Herpes evasion Block generation of peptides by the proteasome Block transport of peptides into endoplasmic reticulum-HSV Destroy class I MHC molecules-HCMV Retain class I MHC molecules intracellularly-vzv

Answer 8

Latency. Hide from the immune system Express Fc receptors on cells and virions. The Fc region of antibodies are bound to viral Fc receptor so not available to bind host Fc receptors. Antigenic variation: influenza, HIV and hepatitis C virus

Answer 9

Virus dose High doses may overwhelm the local innate response and cause disease. Route of entry variola virus (smallpox) dangerous if enters by respiratory tract but less by dermal Age and sex Varicella-zoster virus (VZV) , mild as child, dangerous as adult Hepatitis B virus (HBV) has a high chance of chronic infection(cancerous) early in life, acute later on Worse for males, higher chance of chronic infection Physiological state Stress and immunological deficiency

Answer 10

Superficial infections: Virus replication occurs in the epithelium at the initial infection site, no spread acute infections with a short incubation period and of short duration. influenza Systemic infections- spreads by various routes (lymphatics, bloodstream, nerves) More severe measles

Answer 11

Temperature- Rhinoviruses (common cold) grow well at 32 ºC but not at 37 ºC and so replicate well only in upper respiratory tract epithelium Budding site apical or basal Influenza apical so into airways If basal may be systemic

Answer 12

Acute infections: The virus is cleared after an acute infection. Variola, influenza Persistent (chronic) infections virus is detectable in the host for years, or even lifelong. HIV and hepatitis C virus almost always establish persistence. Hepatitis B virus 90% acute 10% chronic ,90% of infected male neonates become infected chronically. Latent (persistent) infection primary infection but reappears (reactivates), years later, to cause a recurrence of disease. All herpesviruses establish latency and are not cleared.

Answer 13

Varicella zoster virus acute disease is chickenpox varicella virus genome resides in neurones of sensory ganglia and may cause shingles (zoster). some cells are permissive for productive infection, while others are non-permissive A stimulus may cause a non permissive cell to allow replication eg The differentiation of a latently-infected monocyte to a macrophage results in production of HCMV, acute in macrophage Varicella and HSV-acute in mucosla epithelium, latent in sensory neuron Epstein-Barr virus- acute in B cell, latent in memory B cell

Answer 14

Virion stability Enveloped viruses are less stable The lipid envelope is fragile and can be disrupted easily Since the envelope contains the virus attachment protein(s), loss of the envelope results in loss of infectivity Spread by clos contact small non-enveloped viruses are very stable outside the host and can be transmitted over long distances

Answer 15

Acute infection short so high quantities of virus made, shed in high conc persistent virus make less virus but shed repeatedly over a long period, lower conc

Answer 16

population size Measles virus is physically unstable and survives for only a short time outside host, after intial infection long immunity, no non human hosts so disapperas so no one to infect Yellow fever virus and rabies virus infect multiple hosts zoonotic infections are very hard to eliminate due to animal reservoir

Answer 17

The average number of infections produced by each infected host R > 1 = the epidemic is expanding, R < 1 = the epidemic is declining

Answer 18

Congenital infection (transplacental infections) rubella, HIV, human cytomegalovirus Perinatal: infection during birth or from breast milk HSV,Human cytomegalovirus Hepatitis B virus Germ line transmission Retrovirus as provirus can be inherited as endogenous retroviruses. Can reactivate

Answer 19

MOst virus cause little disease as have co evolved with host, harmful if in abnormal host Foot and mouth disease virus Cost 8 billiion as killed many sheep and cow Myxoma harmless poxvirus to South America rabbits, fatal to European rabbits Yellow fever flavivirus, female mosquito Aedes aegypti. Infects humans and primates

Answer 20

-ve ssRNA, helical capsid lipid membrane haemaglutinin HA (agglutinates RBC) neuraminidase NA M2 ion channel RNA-dependent RNA polymerase pre packaged replicates in nucleus 4 types, A,B,C,D, A causes most disease natural Reservoir in birds Many HA and NA variants, diverse transmitted via aerosol and inhaled virions, infects respiratory epithelial cells HA trimer, HA1 binds sialic acid. Endocytosis, HA2 has a hydrophobic fusion peptide so in acidic conditions fuses viral membrane and endosome membrane At low pH M2 ion intakes H+ intp core, promotes uncoating amantadine and rimantidine inhibit M2

Answer 21

After entry the nucleocapsid is transported into the nucleus viral RdRp transcribes -ssRNA into mRNA Viral mRNA obtains 5' cap by cap snatching host mRNA so still needs host RNA pol II More +ssRNA made and used to make -ssRNA for new virions by viral RdRp New nucleocaspid leaves by budding Needs neuraminidase to cleave sialic acid or viral HA would bind to same cell or agglutinate together Tamiflu-siacilic acid analogue, inhibits NA, virus agglutinates and sticks to cell Antigenic drift HA protein changes over time as mutations due to error prone RNA pol change amino acids, slow, gradual Antigenic shift If a cell is infected with 2 viruses, human and avian, during reassembly virus can pick up RNA from both parents If human virus picks up avian HA, dangerous as can replicate in humans and escape immunity, pandemic

Answer 22

Sialic acid galactose with 2-3 and 2-6 linkage human virus prefers 2-6, avian 2-3 The PB2 subunit of RNA pol influences replication E627 to K627 causes better replication in humans for avian flu non-structural protein 1 (NS1) confers resistance to interferons, avian NS1 not great in humans so needs to adapt Antigenic shift mostly occurs in pigs, swine flu

Answer 23

picornavirus +ve ssRNA icosahedron capsid Transmits by fecal matter infects epithelial cells of the oropharynx or intestine Can spread via blood to liver, virions in bile into faeces Acute, causes jaundice asymptomatic in children, adults develop acute hepatitis, fever, jaundice,diar Vaccine Live attenuated vaccine Inactivated virus Like polio expresses protein by cleaving polyprotein

Answer 24

hepadnavirus DNA virus, reverse transcription Acute and chronic hepatitic and liver cancer icosahedral capsid lipid envelope Australia antigen surface protein (HBsAg) small DNA genome, uses 4 overlapping reading frames HBsAg binds hepatocytes, target for anitbody and used in vaccine Reversivirus Uses reverse transcriptase to makes it genome but does not integrate its DNA into host genome, No latency, packages DNA not RNA Hard to grow in culture Transmission Infected mother to child infected blood product Needles Acute infection with jaundice Chronic- virus not cleared, high HBsAg, liver disease and leads to hepatocellular carcinoma Males and young children mor likely to develop chronic Prevention Scrren blood products Vaccination uses yeast to make HBsAg and purify

Answer 25

flavivirus icosahedral capsid lipid envelope E1, E2 glycoprotein +ve ssRNA Huge diversity, hard to make vaccine Acute and chronic infection, 70% chronic liver cirrhosis then cancer Screen blood products Treatment Interferons Drugs to target proteases and RNA pol Effective drugs availabe but expensive HCV RNA virus, hard to make vaccine so drugs used, HBV DNA virus, vaccine used

Answer 26

infectious proteins transmissible spongiform encephalopathies (TSEs) chronic, progressive neurodegenerative diseases Scrapie in sheep. Kuru in the Fore tribes in Papua New Guinea, transmitted by cannibalism. Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD) in humans. Bovine spongiform encephalopathy (BSE) in cattle (also called mad cow disease) Found by infecting primate with kuru, no bacteria or virus, irradtion destroying nucleic acid had no effect, was a protein

Answer 27

PrP alpha helical, GPI-anchored, cell surface glycoprotein Highly conserved Found in CNS PrP can form PrPSc(scrapie) a beta sheet, stable and hard to digest Catalyses normal protein to misfold Can spontaneously form

Answer 28

feeding cattle with meat and bone meal ) infected with prions, from scrapie-infected sheep

Answer 29

like BSE in that: * the disease had florid plaques in the cerebellum, like BSE prions in primates * the PrP glycoform typing showed the same pattern as BSE Transmitted by eating infected BSE meat

Answer 30

No adaptive immune response Monoclonal antibodies can distinguish bio assay, infect mice

Answer 31

Prominant surface spike like corona nucleocapsid lipid envelope +ve ssRNA 30kb genome, big for RNA RNA pol has proof reading nsp14 exonuclease Still more mutation than DNA viruses If 2 Cov infect same cell can recombination Spike protein trimer, binds cells via angiotensin converting enzyme II (ACE-2) and causes fusion From horseshoe bats related to pangolins asymptomatic, or cause severe acute respiratory syndrome (SARS) 0.3% fatality rate, higher when older,obese,lung conditions Social distancing person protective eq hygiene Quarantine Dexamethasone:lowere lung inflammation Remdesivir-inhibit viral RdRp monoclona antibody against spike Use several drugs to avoid res mRNA vaccine

Answer 32

HIV latent, spread lots before AIDS recog From primates retrovirus + ssRNA, like mRNA with 5'cap and polyA tail genome diploid, has tRNA to prime reverse transcriptase Inserted into host genome by integrase Provirus has long terminal repeats at each end regulatory and evasion proteins made intially tat and rev switch so capsid and env made later Vpu-block NF-Kb signalling transmitted by sex, needles, blood education, anti retroviral therapy, screen blood gp120 binds CD4 on T/macrophages as well as co recptor CCR5, CXCR4(Tcell) Intitially infects CCR5 but as immunodeficiency develops infects T cells Polymorphism of CCR5, deletion so non functional, decreases risk in caucasian

Answer 33

Intially provirus heavily spliced, makes small proteins like tat and rev, later less splicing, bigger proteins Leaves by budding goes on for lonf periods LAtent if provirus not transcribed, reservoir Initial infection, CD8 T cell kill infected CD4 T cell Later virus goes asymptomatic, comes back later, less TH cells to maintain toxic T cells, immunodeficiency Opportunistic infection can kill Rapid progerssors and long term, long term can control virus for a long time No vaccine due to error prone reverse transcriptase, rapid variation Azidothymidine- thymidine analogue, incoroporated by RT, terminates chain better substrate for HIV pol than DNA pol ritonavir-inhibit HIV protease so polyprotein not cleaved Fusion or integrase inhibitors HIV becomes drug resitance quickly, Highly active anti-retroviral therapy (HAART) where multiple drugs given at once.

Answer 34

Quarantine, slaughter surveilance hygiene vector control Screen blood Vacines

Answer 35

acyclovir for herpes simplex virus phosphorylated by HSV thymidine kinase, but not cellular kinases, incoporates into viral DNA by HSV DNA pol and terminates chain

Answer 36

Variola, 40% Initialy variolation, material from patient who survived smallpox rubbed into arm Vaccination by using cow pox Eradication possible due to no animal reservoir no latent infection easily recognizable symptoms no antigenic variation Vaccine effective, cheap, heat stable, easy to administer Rinderpest also eradicated by vaccination

Answer 37

Live vaccines. Attenuated mutants or related virus Self replicating-cheap Virus may revert to virulence, danger to immunocompromised, needs cold storage Dead vaccine inactivated whole virus Or subunit of virus safe may require mutliple shots to become immune Passive Give antibodies from animal serum or monoclonal antibodies Maternal antibodies in breast milk immedtaie protection serum sickness short lived Rational attenuation-delete virulence genes Live recombinant virus-Put antigen into safer virus, rabies glycoprotein in vaccina Virus-like particles-capsid can be virus like Nucleic acid immunization-mRNA encoding antigen