L7 Viruses

Question 1

LO2: gen sig of genom composit, env, and replic strat for classif and detec virs.

Answer 1

-diag most infec by detec genom eg PCR.
-cont na core surr by capsid, somet surr by env. bind host R and endoc or x mem via coated pits or fuse host mem if env. transl and assemb then lysis if non env, budd if env.
-nucleocapsid- prot coat enclose and protec genet mater. multip capsomer monom. can make vacc or detec ab. poss inv in host cell att esp non env. icosahedral or helical.
-bactphage t4- LOT phage. transf drug resis and carry some prot enab infec.
-req for infec and replic- R can bind vir ligand on env, or capsid. HIV gp120 binds CD4R and CXCR4 coR on Th. or CCR5 on mac. ebola gp bind chol transporter in targ cells.
HIV 2x ssRNA, rev transc, ma prots, capsid, lip bilay with host prot and gps.
also cell needs cellul mach for replic. host range= can infec and replic in. if replic=productive and host cell is permissive.

Question 2

Baltimore classif: based on rel btw vir genome and mRNA used for transl dur genome exp.

Answer 2

• exploit ev molec niche of cellul orgs. biochem feats allow targ drug/vacc and underst rap evol.
• dsDNA to mRNA.
• pos ssRNA to mRNA or neg ssRNA.
• neg ssRNA to mRNA.
• dsRNA to mRNA.
• pos ssRNA to dsDNA to mRNA.
• pos ssDNA to dsDNA to mRNA.
• neg ssRNA to dsDNA to mRNA.

Question 3

medicine uses na type and env main classif:

diff agents treat r vs dna and env gen more suscep to disinfec/heat.

Answer 3

DNA:
-env- hep B, herpesvir, smallpox.
-non env- papillomavir(latency, warts, cervic, CA).
RNA:
-env- rubella, rotav, HIV, ortho+paramyxo (influ, measles, mumps), corona (colds, SARS, MERS).
-non env- picorna (polio, hep a, colds).

Question 4

eff of virs on host cell:

Answer 4

• death often on rel.
• cytopath effs- visib due to replic eg inclus bods site of active synth.
• syncitia form- multinuc giant cells by PM fus.
• chrom dam.
• inhib host cell prot/R/DNA synth.
• CA- if vir integs all/part genome to host dna. only rna retrov can cause CA. bring in/ turn on cell oncogs=uncontr prolif. inaccess to tx, DNA edit fut. many dna virs can cause CA but us in non permiss cell. us inactive TS prots that keep cell from going through cyc. prolif.

Question 5

ebola:

Answer 5

• haemorr, disord clott, integ BV.
  -env gp ligs bind Rs and coRs. gp proteolysis, mem fus and rel rna. ma-nucleoprot disass, transcriptase/replicase, genome, capsids.
  can prod dozens prots, some targ to surf and alt interacs surr cells and imm sys. can aff nuc proc. some ent nuc for proc.
  -imm resp- direc infec mac, neutroph, NK. neur dgran. mac sig casc =inflamm and endoth leak. imm reac=dam host. lot tx contr imm resp. comprom imm sys= alt symp and reac and rap growth rate.
  -ebola zoonosis. anim reserv, primate suscep less symp. bod fluid contact.
  -infec mac and dendrit cells. infec heaptocs and adren cortic =necrosis.
  -ebola decr eff imm resp, incr unprod inflamm=coag fail=haemorr. specif imm resp alt meth diag.

Question 6

org no, time symps-

Answer 6

-incub period time for dam suffic to cause symps.
can get asymp infec. org no decr spont or due to tx.
can get recurr infec. latent infec- not elim, no symps, not infectious, can reactiv, classic imm comprom.

Question 7

INFEC:

Answer 7

-bact and virs:
can be lytic, latent, acute, subacute, chromic.
can be acq from hum or env: dir contact eg sex, vertic transm. env eg aerosols, fecal oral, inoc.
have char incub period.
can be detec by genome directed na amplif eg pcr, cell cult, or tiss specim. also recog by detec specif vir direc imm resp.
-just vir-
can spread via nerves to NS and via blood to organs.
curtailed in host prim through cell med imm.
diag by cell cult, embryonated eggs, or anims and immunocytochem strain and id vir partics/ag’s in specimen.

Question 8

LO1: comp props bact and vir vs euk.

Answer 8

-vir smallest. virs can egg histol eg inclus bods. cytop effs in cell cult.
-living or not? 18-350nm. EM req. oblig intracell- no genes for metab. may have prots proc ns. no genes for prot synth. may/not encod enzs for na synth.
R or DNA. RNA less stable. no small ions or polysaccs, gp by host enz. env cont lip, non env dont. non env diffic destr.
-DNA vir eg pox, herpes, adeno.
rev transc- hepadna, retro.
RNA- filo, rhabdo, corona, picorna.
diff shapes, recog help tx.
non env- adeno, papilloma, parvo, morbilli.
env-herpes, parainflu, unfu, pox.
-bact log expans. virs ent cell, div v fast, burst. gen 3 orders more.
-R or DNA. ss or ds. lin/circ/nicked. unseg or seg eg influ allow reass.
ssRNA pos sense- genomic RNA serves as mRNA.
neg sense- not direc transl eg ebola.